IOMICA Forum

Posted: **20 Nov 2020, 17:04**

Let's all have a discussion in the correct place, the IOMICA forum, and not Facebook or secret emails, yes, an open discussion with even luddites included.

My understanding is that most want to embrace the new 3D Printing technology but the wording of the recent Croatian motion was not to everyones taste and it failed to gain the sufficient two thirds majority to get passed.

There were a lot of views on the recent Facebook thread but let's kill two birds with one stone, come to an agreed wording to get the motion passed and inject a bit of life in this IOMICA forum.

Posted: **20 Nov 2020, 18:01**

Excellent plan, lets slaughter the entire avian population while we're about it (just kidding folks, just kidding).... My suggestion, Graham, is that you post the text of a motion that you think would get traction, and we all throw stones. Then, after a while, post a version which you think has been beaten into shape, rinse and repeat.

Posted: **20 Nov 2020, 21:08**

You know, the first thing I'd like to see happen on this forum is to hear from actual home builders who are using 3D printing and see what they think needs to be modified in the current rules. I've always believed that change should come from the bottom up.

Posted: **20 Nov 2020, 23:21**

I will start by saying that I am not knowledgeable abut 3D printing, but it seems to me that there are three elements to proposing a materials rule change for the class.

First, a proposal for 3D printing should only apply to class rule D2.1(8) and not attempt to change the rest of the rule D2.1 relating to hull materials which have stood the test of time.

Second, the proposal to change D2.1(8) needs to clarify which thermoplastics and additives should or should not be permitted. As I understand it, there are several chemical designations for 3D thermoplastics – and there are many additives that may change the properties of the finished item. The challenge is to list those products and additives that make sense, and eliminate those products that due to cost or complexity or properties would give an unfair advantage over other thermoplastics or traditional hull materials. I understand that it may be difficult to establish the additives, and once a hull is built, difficult to confirm its materials base.

Third, is the concept of techniques such as ‘infill’ or internal lattice structures – do these need to be spelled out? There are no qualifiers for construction in wood or fiberglass, for example, a wooden hull may be planked, or formed from double diagonal veneers – or even bread and butter. But does the printing method and internal structure of 3D printing need any permissions (eg honeycomb), or bans?

So a new rule proposal may look like
2D.1
(8) Thermoplastic, which may be molded, containing only permitted materials
8.1 for a 3D printed hull, any PLA (or abc) based thermoplastic with any additives (except -x,y,z) are permitted.
8.2 there are no restriction on infill nor any internal reinforcements.

John

Posted: **21 Nov 2020, 00:15**

Lester, would love to re-write the proposal so we could all send it through the mixer but my knowledge of 3D printing is limited, hopefully not for long though.

The feeling I got was that the folks that were against the Croatian proposal wanted a better written proposal that was more of a 'closed' allowance to materials than an 'open' allowance.

Does this mean that we should actually name the brands of filament allowed within the proposal?

I do follow the fantastic FB 3D printed boats page and would love to hear from some of the home builders on this site to see what they would like, as the whole point of this proposal was to encourage and help the home builders as the new 3D printed boats will take over from the woodies as skills are lost and found in other areas for the home build.

I will try and reach out to some of these 3D home builders, as we all should do, go and have a look at these fantastic printed boats that the likes of Juan M Egea, Gabriel Le Duc, Torsten Kass, Thierry Vangent, Zachari Chan, Damian Ackroyd, Mike Cooke and many more are producing and lets listen to there views, as has been proven by the vote, this minority should have a voice that is heard and then we can move forwards and get more competitive home builds on the water.

Posted: **22 Nov 2020, 01:31**

That is a great idea Graham. Perhaps this rule change should not only be crafted by 3D printing home builders but also only apply to home builders and not to boats sold and produced by commercial builders.

Posted: **22 Nov 2020, 10:38**

Hello, I am a french IOM sailor, home designer and 3d builder. I can share my "small" experience if you want.
I had printed 3 iom boats.
I noticed that using infill print does not give me waterproof boat and I waste a lot of printing time. So my futur boats will be only vase mode printed. But I think that building technic is out of scope of actual class rule.

Build boats are sailing but if I compare with classical glass fiber hull they are heavier (maybe 100-200gr heavier hull).
Concerning materials, based on the experiment of selvyn Holland (australian guy) I use PLA+, quite similar to classical PLA.
For sure there are lots of variants in available materials : ABS, PLA, PETG, PLA with carbon fiber, ASA... with each one its propertie (mechanical, thermal resistance, water resistance...).
I can suggest you to have a look at this comparison table :
https://www.simplify3d.com/support/mate ... ies-table/

You will notice that PETG (polyethylene) could be a good candidate but people having tried it gave bad feedback.
If you look at carbone fiber pla, you can notice that it has a better stiffness but it is less robust. So if we imagine reduce the hull thickness to save weight it will not be enought robust. More over its density is higher than classical PLA.

My conclusion is that Man should no be affraid by the use of a 3d printed revolutionary material which will allow to win the IOM wolrd championship, it does not exist yet. The 3d printed boat will be at best as competitive as classical glass fiber one, but never better at the time I am writing. Lots of tests have not been done yet.
Maybe for longer hull (M class) the carbon fiber added filament will help getting enougth stiffness but not reduce weight.
The big advantages of 3d printed hull are COST saving, time to build and building accessibility.

Regards,
Sébastien LEFEBVRE

Posted: **22 Nov 2020, 10:53**

Let me put my views on this:

It would be impossible to police clauses that specified materials that cant be used in 3D printing, and the list of materials is constantly growing. You know what the base product is (PLA, PLA+, PTEG etc) but what materials give it that additional property, and more to the point, when you buy it, how do you know what’s in it.

Infill should be allowed, after all, the main rule does not specify how many layers of fibre can be used, or even the weave or type.

The general IOM rule should not be changed from what it currently says, it works!

There should be an additional section or appendix on 3D printing.

Understanding the rule should be simple to everyone.

The base materials used in 3D printing are classified as thermoplastics. Thermoplastics are a plastic polymer which becomes soft and mouldable when hot and when cool returns to a hard condition. They can contain many different additives to achieve rigidity, weight and accuracy.

With so much discussion this all needs coordinating properly otherwise we will just go round in circles. I propose that specific questions should be asked and taken to conclusion. The most simplest to start with would be:

When a hull is 3D printed, infill may be used.

Chris.

Posted: **22 Nov 2020, 11:47**

Hallo, ich bin der Neue...

Leider muss ich in deutsch schreiben, da mein Englisch nicht gut genug ist. Ich verstehe 95 Prozent, ich kann es lesen...nur...es ist nicht meine Muttersprache.
Um kurz meinen Hintergrund zu beleuchten:
Ich bin seit meiner Kindheit Modellbauer, vor allem Modellflieger. Es gibt nur sehr wenige Fertigungsmethoden im Modellbau, die mir fremd sind...Sinterdruck ist so eine Methode. Sonst habe ich eigentlich alles durch. Holzbau, GFK/CFK in allen möglichen Fertigungsverfahren, Drehen, Fräsen und natürlich auch der 3D-Druck.
Seit ca. 6 Jahren bin ich dem Druck verfallen. Diese Methode ermöglicht mir, innerhalb sehr kurzer Zeit kostengünstige Boote zu entwerfen und auf das Wasser zu bringen.
Ich muss auch zugeben, dass ich extrem viel Zeit und Geld rausgeworfen habe! Selten mit dem gewünschten Erfolg, aber dafür habe ich wohl die meiste Erfahrung in Bezug auf Filamente und ihre Eigenschaften.

Kommen wir aber zu Thema:
IOM und 3D-Druck ist ein ganz schwieriges Thema, aber eigentlich auch nicht!
Wenn wir uns ganz dumm stellen, sind für IOM Hulls 3 Materialien erlaubt: Holz, Glasfaser und Thermoplastischer Kunststoff.
Auch Kombinationen sind erlaubt! Ich darf Holzrümpfe innen und aussen mit Glas belegen. Ich könnte auch einen tiefgezogenen, oder geblasenen ABS-Rumpf mit Glas belegen.
Bei diesen Kunststoff-Rümpfen habe ich keine Ahnung welche Zusatzstoffe der Hersteller verwendet...sind aber erlaubt.
Ich brauche also gar keine neue Regel, oder irgendwelche Definitionen, denn die Fertigungsmethode ist nicht begrenzt!
Spielt aber keine Rolle, da irgend jemand es zu einem Problem gemacht hat und sich nun das technische Komitee damit ärgern muss.

Meine persönliche Einschätzung der Lage ist relativ einfach:
Derzeit gibt es kein -KEIN - Filament, das die extremen Anforderungen unserer Wettbewerbsboote stand hält.
Das einzige Filament, das einen sicheren Betrieb unserer Boote halbwegs zulässt, ist Nylon + Glas - wenn es richtig gedruckt wird!
PLA und seine Ableger sind temperaturempfindlich und verspröden bei Kälte. PETG reagiert nicht ganz so empfindlich auf höhere Temperaturen, aber kann Schläge nicht ertragen. Bei einer harten Kollision kann ich Löcher und Layerrisse garantieren. ABS und ASA sind da etwas besser, aber die Layerhaftung reicht nicht aus. Jedenfalls ist es für den Normal-Anwender kaum zu schaffen.
Was bleibt da noch? Leider nicht viel...
Jede Einschränkung in Bezug auf erlaubte Filamente tötet den Einsatz des Drucks in dieser Klasse! Wenn die Entwicklung der Filamente übergangen wird, haben wir verloren, denn derzeit haben wir nur ein brauchbares Filament!
Denn seien wir doch mal ehrlich...alle derzeit gebauten und gesegelten Boote haben den rauen Regattabetrieb nie gesehen. In der deutschen Rangliste gibt es ein gedrucktes Boot...das segelt mein "Testfahrer" und nächstes Jahr kommen vielleicht zwei Boote dazu. Damit dürfte Deutschland schon die größte Flotte von gedruckten IOM auf Regatten haben...

Es gibt nur eine Einschränkung für die Filamente - kein Carbon - Ende der Ansage.

Das ist meine persönliche Einschätzung der Lage.

Posted: **22 Nov 2020, 12:51**

I'm not sure about the motivation for the rule change, it appears that the rules have been changed to stop 3D printed boats obtaining a competitive advantage through the construction techniques and materials that they can use. This would be ok IF the 3D printed boats were obtaining a competitive advantage but I don't think that this is the case. With the current generation of 3D printers and materials that they are able to print I don't think that it is possible to build a boat that is stronger or lighter than traditionally manufactured boat. The exact opposite is the case. 3D printed boats tend to be heavier for the same strength or weaker for the same weight. Similarly I don't think that the motivation of banning honey combing and non solid infill in 3D printed structures is positive and simply serves to make 3D printed boats heavier. I certainly am no expert but I have printed four boats to completion and for my printer in order for the boats to be strong enough to stand up to the contacts that happened in IOM racing I am struggling to build them to the weight limit. I would build them lighter but the water I sail on if the boat sinks it is highly likely that I will never get it back.

I think that any rule changes that discourage the use of 3D printing to construct IOM boats is negative and only goes to discourage home builders from making boats and entering the sport.

Posted: **22 Nov 2020, 13:06**

Torsten Kass wrote: ↑
22 Nov 2020, 11:47
Courtesy of Google Translate:

Hello, I'm the new one ...: D
Unfortunately, I have to write in German because my English is not good enough. I understand 95 percent, I can read it ... just ... it's not my mother tongue.
To briefly illuminate my background:
I have been a model builder since my childhood, especially a model pilot. There are very few production methods in model making that are alien to me ... Sinter printing is such a method. Otherwise, I've actually been through everything. Timber construction, GRP / CFRP in all possible manufacturing processes, turning, milling and of course 3D printing.
I've been under pressure for about 6 years. This method enables me to design inexpensive boats and get them out onto the water in a very short time.
I also have to admit that I wasted a lot of time and money! Rarely with the desired success, but I probably have the most experience with filaments and their properties.

But let's get to the topic:
IOM and 3D printing is a very difficult topic, but actually not!
If we act really stupid, IOM Hulls can use 3 materials: wood, fiberglass and thermoplastic.
Combinations are also allowed! I am allowed to cover wooden hulls inside and outside with glass. I could also cover a deep-drawn or blown ABS hull with glass.
With these plastic hulls I have no idea which additives the manufacturer uses ... but are allowed.
So I don't need a new rule or any definitions, because the manufacturing method is not limited!
It doesn't matter, though, as someone made it a problem and the technical committee has to be annoyed with it.

My personal assessment of the situation is relatively simple:
There is currently no - NO - filament that can withstand the extreme demands of our competition boats.
The only filament that allows our boats to operate safely is nylon + glass - if it's printed correctly!
PLA and its offshoots are sensitive to temperature and become brittle in the cold. PETG is not quite as sensitive to higher temperatures, but cannot take blows. In the event of a hard collision, I can guarantee holes and layer cracks. ABS and ASA are a little better, but the layer adhesion is not enough. In any case, it is hardly manageable for normal users.
What's left? Unfortunately not much...
Any restriction on allowed filaments kills the use of printing in this class! If the development of the filaments is skipped, we have lost, because currently we only have one usable filament!
Because let's be honest ... none of the boats currently built and sailed have ever seen the rough regattas. There is a printed boat in the German ranking list ... my "test driver" sails that and next year maybe two boats will be added. This means that Germany should already have the largest fleet of printed IOMs on regattas ...

There is only one limitation for the filaments - no carbon - end of the announcement. : P

That is my personal assessment of the situation.

Posted: **22 Nov 2020, 15:38**

Hallo Chris, mir hat es einen 2mm-PLA Rumpf durchgeschlagen. Kein Layer-Schaden, sondern ein Loch. B-Rigg an der Grenze und ganz stumpfer Winkel.
Ist aber nicht wichtig.
Wichtig ist die Tatsache, dass die Entwicklung der Filamente noch Zeit braucht und diese Zeit sollte uns gegeben werden.
Ich halte es auch für wichtig, das alle fest verklebten Einbauteile massiv gedruckt sind. Generell sind Waben und Ähnliches bei fest verklebten Teilen nicht erlaubt und an diese Regel sollten wir uns halten. Bei richtig konstruierten Teilen ist Infill auch nicht nötig. Das bekomme ich durch Formgebung und Perimeter-Anzahl besser und leichter hin.

@Lester
Danke für die gute Übersetzung!

Posted: **22 Nov 2020, 15:57**

Torsten Kass wrote: ↑
22 Nov 2020, 15:38
Google translate:

Hello Chris, a 2mm PLA fuselage hit me. No layer damage, just a hole. B-rig at the limit and very obtuse angle.
But it is not important.
The important thing is that the development of the filaments still takes time and this time should be given to us.
I also think it's important that all firmly glued built-in parts are solidly printed. In general, honeycombs and the like are not allowed on firmly glued parts and we should adhere to this rule. In the case of correctly constructed parts, infill is also not necessary. I can do this better and more easily through the shape and number of perimeters.

@Lester
Thanks for the good translation!

Posted: **22 Nov 2020, 20:13**

Hola a todos, perdon que escriba en Castellano pero es la lengua del pais donde naci y creci (Argentina) y por lo tanto la mas facil para mi.

En mi humilde opinión, y teniendo en cuenta lo que he podido probar por el momento, no es interesante utilizar PLA Carbono por ejemplo, de hecho no aporta ninguna rigidez adicional como para, por ejemplo reducir los espesores y aligerar el casco ya que no son fibras de carbono continuas sino polvo de carbono o filamentos demasiado pequeños, a mi solo me dio cascos mas blandos con una adhesión entre capas peor.

Por el momento hago mis cascos en PLA +, como la gran mayoria, con lo que obtengo las mejores adherencias entre capas y rigidez, que en mi opinión es lo más importante en un casco 3d ya que no disponemos de ninguna fibra continua de refuerzo en ninguna direccion, que en lo que a mi respecta seria lo mas importante a la hora de hacer un casco funcional y durable y que lamentablemente por ahora no veo como se podria hacer esto en una impresora 3D, aparte de luego estratificarlo con fibra de vidrio y epoxi, cosa que he probado y da mucho trabajo para un resultado mediocre en cuanto a peso final...

Probé PETG pero en mi opinión es demasiado frágil en caso de impacto, y el ABS demasiado complicados para imprimir piezas grandes debido a los efectos de deformación o tensiones internas a medida que se enfría.

En mi opinión no deben temer el uso de materiales prohibidos en la construcción 3D, ya que no aportan ninguna continuidad en las fibras de carbono, kevlar u otro material de alto modulo.

En cuanto a los aditivos que puedan agregarse en los plasticos no creo tampoco que sea algo para alarmarse, lo unico que hacen es cambiar las caracteristicas del plastico ( plasticidad, adhesion, temperatura de fusion, etc, etc.) y forman parte del propio plastico.

Yo pienso que tendria sentido poner restricciones en los filamentos con materiales prohibidos si estos fueran con filamentos de carbono o Kevlar continuos y pudieramos imprimirlos en en las direcciones que nos convengan para formar una estructura resistente, pero no es el caso!

El tema del relleno, he hecho pruebas para imprimir cascos en sandwich y el resultado fue desastroso, agujeros por todos lados, y mucho mas pesado que un casco impreso en una sola pared en modo espiral.

Pienso tambien que las reglas actuales sobre construcciones tradicionales deberian dejarse tal cual y agregar una seccion especial solo para las construcciones en 3D.

En general comparto en gran medida lo dicho por Torsten, Chris y otros, todavia hay mucho por probar y con la tecnologia actual podremos hacer barcos prototipos rapido y a bajo coste, y tal ves servira para que gente con menos recursos puedan entrar en nuestro fascinante mundo, con un barco relativamente competitivo, pero con sus limitaciones actuales.

Muchas Gracias por vuestra comprehension.

Gabriel Le Duc

Posted: **22 Nov 2020, 20:15**

Now in Google English

Hello everyone, sorry to write in Spanish but it is the language of the country where I was born and grew up (Argentina) and therefore the easiest for me.

In my humble opinion, and taking into account what I have been able to prove at the moment, it is not interesting to use PLA Carbon for example, in fact it does not provide any additional stiffness to, for example, reduce the thickness and lighten the helmet since they are not Continuous carbon fibers but carbon dust or filaments that are too small, it only gave me softer hulls with a worse adhesion between layers.

At the moment I make my hulls in PLA +, like the vast majority, with which I obtain the best adhesion between layers and rigidity, which in my opinion is the most important thing in a 3d helmet since we do not have any continuous fiber reinforcement in no direction, which in my respect would be the most important when making a functional and durable hull and that unfortunately for now I do not see how this could be done in a 3D printer, apart from then stratifying it with fiberglass and epoxy, which I have tried and it gives a lot of work for a mediocre result in terms of final weight ...

I tried PETG but in my opinion it is too brittle on impact, and ABS too complicated to print large parts due to the effects of deformation or internal stresses as it cools.

In my opinion you should not fear the use of prohibited materials in 3D construction, as they do not provide any continuity in carbon fibers, kevlar or other high modulus material.

As for the additives that can be added to plastics, I do not think that it is something to be alarmed about, the only thing they do is change the characteristics of the plastic (plasticity, adhesion, melting temperature, etc, etc.) and they are part of the plastic itself. .

I think it would make sense to put restrictions on the filaments with prohibited materials if they were with continuous carbon or Kevlar filaments and we could print them in the directions that suit us to form a resistant structure, but it is not the case!

On the subject of filling, he tested to print sandwich hulls and the result was disastrous, holes everywhere, and much heavier than a helmet printed on a single wall in a spiral way.

I also think that the current rules on traditional constructions should be left as is and add a special section only for 3D constructions.

In general, I largely share what Torsten, Chris and others said, there is still much to test and with current technology we will be able to make prototype ships quickly and at low cost, and perhaps it will help people with fewer resources to enter our fascinating world. , with a relatively competitive boat, but with its current limitations.

Thank you very much for your understanding.

Gabriel Le Duc

Posted: **23 Nov 2020, 13:42**

Hi everybody, and thank you Graham for the initiative.

I personally like to explore the different possibilities that this technology offers; testing materials, techniques, etc. This desire to experiment and develop I think is shared by many and is conducive to creating more hobby and activity in the IOM class.

Regarding the proposal for change D2.1 limiting the elastic module of the materials to be used: it restricts the use of materials such as carbon, but it allows a fairly wide range as are all thermoplastics and fiberglass. For me it is sufficiently permissive to favour that possibility of experimenting and developing that I have talked about before, so in that aspect I think it is positive.

I understand that the spirit of the rules is to keep prices low and favour in-house manufacturing. In this context I try to think what things related to 3d technology in the near future might not be in line with that spirit of the rules. It is difficult to predict the future, however, from rcsailinglab there are already things we are working on that I don't mind sharing, in order to give one more perspective, so that we can all assess if there is anything we don't want for the IOM class.

What we see happening:
- More home-builders, more designs and more designers.
- New opportunities to explore. Example: we work together with a school to create a rc sailboat project to print for the technology teacher/lessons. We do this thinking it could be good for the kids and for the rcsailing world.

What we think may come in the future:
- Printing of the boats by companies specialized in additive technology. They could print the boat in several sections or in one piece, in PLA or in better materials, with FDM technology or with more sophisticated ones (we use FDM technology most of the time at home but there are actually more than five different additive manufacturing technologies).
- Additive manufacturing can facilitate the manufacture of boats with an interior structure, in the whole boat or in some areas.
- Composite builders can print some parts of the boat, which can lead to lower production costs.
- Composite builders could also print the core to create a sandwich laminate, either all over the hull or in some areas.

My conclusions about rules:
1. Limiting materials from the elastic module is not a perfect rule but I have no better one. As a 3d printer user it gives me enough freedom to investigate, test, develop, etc.
2. Using infill on printed boats is not expensive and anyone can do it, however it could lead to sandwich laminates with sophisticated print cores shapes. It's OK for me to avoid it.

*I do not speak fluent English, surely there are errors in the text, sorry for that.

Posted: **23 Nov 2020, 17:02**

This is all going to get very complicated. My limited experience of printing suggests that the only advantage is speed of build. Printed structures require additional reinforcement to be practical as a hull. We already allow anyone who wants to risk building an extremely fragile light epoxy glass hull, using high tech vacuum and possibly even a vac autoclave. Way, way outside the scope of an amateur builder. Whereas an amateur builder could buy a printer.
I would suggest simply adding "thermo plastic printed" to existing list of materials. The rule already covers prohibited materials anyway.
Could think of other areas for consideration to bring the class up to date though !

Richard

Posted: **23 Nov 2020, 17:09**

Mr Graham Elliott wrote: ↑
20 Nov 2020, 17:04
Let's all have a discussion in the correct place, the IOMICA forum, and not Facebook or secret emails, yes, an open discussion with even luddites included.

My understanding is that most want to embrace the new 3D Printing technology but the wording of the recent Croatian motion was not to everyones taste and it failed to gain the sufficient two thirds majority to get passed.

There were a lot of views on the recent Facebook thread but let's kill two birds with one stone, come to an agreed wording to get the motion passed and inject a bit of life in this IOMICA forum.

Graham,

So, if I understand your intention, you want to come on agreed wording to get the motion passed on the next IOM ICA AGM. Is this correct?

It is, if not impossible, to have a wording to everyone taste. From technical point of view, I see here that only Hiljoball posted some other proposed wording which I will comment in a separate post. So it will be nice to hear snags/problems/etc in the proposed wording which is not voted.

All the best
Robert Grubiša
CRO 68

Posted: **23 Nov 2020, 17:20**

Hiljoball wrote: ↑
20 Nov 2020, 23:21

So a new rule proposal may look like
2D.1
(8) Thermoplastic, which may be molded, containing only permitted materials
8.1 for a 3D printed hull, any PLA (or abc) based thermoplastic with any additives (except -x,y,z) are permitted.
8.2 there are no restriction on infill nor any internal reinforcements.

John

John,

Construction techniques for forming a hull are unrestricted subject to the compliance with D.2.1. 3D printing is one of possible "construction techniques" and it should not be restricted. Also, there are other "aditive technologies" beside the 3D printing so listed all possible methods is simply not feasible and not easy to understand. If you want to give the "equal changes" to moulded and 3D printed boats than it is not fair if you permit honeycombed structures in 3D printed boats (infill) while you prohibit it in the moulded boats. Also, your proposal will allow to 3D print the honeycombed core and implement it to the moulded skins. Do we want this ? Personally, I don't.

All the best

Robert Grubiša
CRO 68

PS Original typo corrected.

Posted: **23 Nov 2020, 17:27**

This is the response to misleading criticism of CRO IOM CR proposal 2020 which Graham Bantock sent to the IOM ICA World Council members before the voting: (I am posting it here with his permission).

The CRO IOM NCA forwarded to me a misleading posting on Facebook that criticises the CRO proposal concerning the IOM Class Rules to the 2020 IOMICA General Assembly.
The explanation by the CRO NCA in reply neatly corrects the impression given. However, I would like to express and explain my own support (acting in several in several roles) for the CRO proposal.

As Technical Officer for the GBR NCA I convened a forum discussion about the use of printed thermoplastics in the class. This was prompted by the interpretation on the IOM class rules concerning this subject and which seems to invite subsequent questions. During the course at that discussion it was found that the number of competitors at GBR IOM ranking events and national championships has declined markedly over recent years. Over the same period the number of new boats being certified has also fallen markedly. It was also clear that the contribution made to new boats in the class by home builders was far lower than when the class started in 1988. This proportion has steadily decreased since then. As the IOM has been the most widely raced class in GBR we here should be concerned about all the possible causes of the decline. One of those is the decline of home built boats.

As a member of IOMICA’s Technical Committee I am uncomfortable with the interpretation that has been issued as it prompts subsequent questions.
There is a danger that defining thermoplastic simply by the way it behaves (softens when heated, hardens when cooled, the cycle is repeatable, melts to a liquid) will lead to all manner of ‘thermoplastic’ materials that cont in additives of all sorts that remain undetected/undetectable in
the base material.
As far as I am aware most thermoplastics printed on typical home printing machines contain bubbles of air. These may not be intended but they exist as an inevitable consequence of the process. It is stated in the interpretation that infill can* result in a honeycomb like structure and, as
honeycombing is prohibited, infill is prohibited. It seems to be accepted in the interpretation that infill may not* result in honeycombing in which case, presumably, it may be permitted. This is confusing. Even if a further interpretation were to establish that all infill is covered by the terms
‘expanded, foamed or honeycombed’ there remains the question of when a small number of random air bubbles in the print constitute infill.

IOMICA board members and the NCA representatives should be aware that an interpretation lasts for a maximum of two years. After that time it lapses. Hence, if its effect is to be enduring, the class rules need to incorporate it. The CRO proposal neatly does this, while also simplifying the
construction materials section and regularising the current bizarre situation where hulls moulded using resin may contain glass fibres but hulls that are 3D printed may not.

As a long time sailor and one of the mid-wives of the class who considers it to have provided the best competitive racing at all levels for some time, and in most of the countries that currently use it, I am naturally jealous of the class’s reputation for this. As they say about investments, past
performance is no indicator of future performance. The class will not maintain its monopoly of the best racing unless what makes the class attractive and distinct is carefully maintained and cultured in the present so that its position can be retained in the future. In 1988 the IOM class was proposed because it offered a less costly alternative to the most popular class of that time. As such it would appeal to those who did not wish to afford the higher price. Additionally, by framing the class rules in such a way that home builders (amateurs in the nicest sense) might be able to build boats equal to the best, no one was excluded from ownership. The home building skills required to plank hulls are possessed by far fewer potential IOM owners in 2020 than they were in 1988. The low cost mass production technique of vacuum forming has been made virtually redundant by 21 st century additive manufacturing techniques of which 3D printing is only one. Many who have gone through schools, colleges, universities over the last couple of decades will have developed CAD skills but may not possess traditional manual skills. The time to not only permit 3D printing, but to ensure it can compete structurally with the best professional construction standards, has already arrived.

I urge IOM sailors to embrace the proposal to modernise the construction materials section of the class rules.

Graham Bantock

* author emphasis added
end

Posted: **23 Nov 2020, 17:32**

Reasoning for the proposed IOM Class Rule are given here for easy reference as submitted with the proposal. Maybe all interested are not aware of it:

The purpose of the proposed IOM Class Rule changes is to formulate a construction materials section of the rules having in mind the original intention of the IOM Class - to permit home built boats to compete structurally with mass produced boats and at an attractive cost – in order to enable good quality hulls to be obtained from a wider variety of sources than at present.

Currently, only a very small percentage of home-built boats now exist in the class. Those that are home built are invariably used by their owner/builders at their own club. Boats competing at the highest level come from a relatively limited number of builders. The class will be much more robust if sources of good quality hulls are available from a larger number of sources and from a larger number of designers.

The relatively small number of builders seen to provide competitive boats, relative to the number of countries where they are raced, means many hulls are imported at a cost that is large in comparison with their value. The absence of locally produced boats that are seen to be competitive works against local growth of the class. Whereas few individuals have the skills or time to create their own hulls from timber, many are now in a position to create a hull by 3D printing. Currently, according to a recent interpretation, glass fibres may be used in traditionally laminated hulls, and in structures made using additive manufacturing involving resin, but may not be used in 3D printed hulls. This is an unreasonable restriction on a low-cost method of construction which is available to many who do not possess the construction skills of earlier generations.
Proposed class rule changes are permitting the use of glass reinforced thermoplastic material used for 3D printing of the IOM hulls. Fibre materials with modulus of elasticity higher than glass are still prohibited so the boat builders using glass reinforced resin don't need to invest in new materials and building techniques.

The proposed rule is simpler to understand than the existing. It is expected that this rule changes will allow more home builders keen in 3D printing of hulls to build their own or others design. Also 3D printed prototype designs could be tested against the molded hulls before the investments in the plug and mold have been made. In addition, all sorts of gel coats, resins with pigments and other additives as well as additives to thermoplastics are clearly permitted which was not clear in the current wording of the class rules.

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Robert Grubiša
CRO 68

Posted: **23 Nov 2020, 17:33**

Juan Marcos Egea wrote: ↑
23 Nov 2020, 13:42
Hi everybody, and thank you Graham for the initiative.

I personally like to explore the different possibilities that this technology offers; testing materials, techniques, etc. This desire to experiment and develop I think is shared by many and is conducive to creating more hobby and activity in the IOM class.

Regarding the proposal for change D2.1 limiting the elastic module of the materials to be used: it restricts the use of materials such as carbon, but it allows a fairly wide range as are all thermoplastics and fiberglass. For me it is sufficiently permissive to favour that possibility of experimenting and developing that I have talked about before, so in that aspect I think it is positive.

I understand that the spirit of the rules is to keep prices low and favour in-house manufacturing. In this context I try to think what things related to 3d technology in the near future might not be in line with that spirit of the rules. It is difficult to predict the future, however, from rcsailinglab there are already things we are working on that I don't mind sharing, in order to give one more perspective, so that we can all assess if there is anything we don't want for the IOM class.

What we see happening:
- More home-builders, more designs and more designers.
- New opportunities to explore. Example: we work together with a school to create a rc sailboat project to print for the technology teacher/lessons. We do this thinking it could be good for the kids and for the rcsailing world.

What we think may come in the future:
- Printing of the boats by companies specialized in additive technology. They could print the boat in several sections or in one piece, in PLA or in better materials, with FDM technology or with more sophisticated ones (we use FDM technology most of the time at home but there are actually more than five different additive manufacturing technologies).
- Additive manufacturing can facilitate the manufacture of boats with an interior structure, in the whole boat or in some areas.
- Composite builders can print some parts of the boat, which can lead to lower production costs.
- Composite builders could also print the core to create a sandwich laminate, either all over the hull or in some areas.

My conclusions about rules:
1. Limiting materials from the elastic module is not a perfect rule but I have no better one. As a 3d printer user it gives me enough freedom to investigate, test, develop, etc.
2. Using infill on printed boats is not expensive and anyone can do it, however it could lead to sandwich laminates with sophisticated print cores shapes. It's OK for me to avoid it.

*I do not speak fluent English, surely there are errors in the text, sorry for that.

Hi Juan Marcos,

Full agreed with your post.

Thanks

Robert Grubiša

CRO 68

Posted: **23 Nov 2020, 21:11**

Yes, just using this open forum to, as I said, 'come to an agreed wording and get the motion passed'.

Seems to be working so far, an open forum where the more experienced 3D printing home builders can have a voice and not just the commercially involved or a selected few friends.

Must admit, some great posts so far from everyone, especially good to see valued posts from the home builders as we must remember, this was the target audience for the original motion, not for the commercial builder to find loopholes in the rules for commercial gain and this is why we must choose our wording of a new motion carefully and make sure it is as watertight as possible but still helps the 3D printed hulls to be as competitive as the technology and rules allow them to be.

Posted: **23 Nov 2020, 21:31**

Mr Graham Elliott wrote: ↑
23 Nov 2020, 21:11
Yes, just using this open forum to, as I said, 'come to an agreed wording and get the motion passed'.

Seems to be working so far, an open forum where the more experienced 3D printing home builders can have a voice and not just the commercially involved or a selected few friends.

Must admit, some great posts so far from everyone, especially good to see valued posts from the home builders as we must remember, this was the target audience for the original motion, not for the commercial builder to find loopholes in the rules for commercial gain and this is why we must choose our wording of a new motion carefully and make sure it is as watertight as possible but still helps the 3D printed hulls to be as competitive as the technology and rules allow them to be.

Graham,

Yes, target audience for the original CRO motion was home builders not commercial builders! It is so clear from the "reasoning for the amendment" which I posted earlier. So far, I am not aware of loopholes for commercial gain...

Robert Grubiša
CRO 68

Posted: **23 Nov 2020, 21:47**

I was one of the members of the GBR NCA forum discussion about the use of printed thermoplastics in the IOM. I found it difficult to discuss the issues without understanding the engineering and physics behind 3D printing, in particular where and how a honeycombed 3D print might be as good as, or even better than, a conventional resin and glass fibre hull. I made a document and a spreadsheet which looks at the laws of physics, and attach them to this post. In summary:

The question
Some think that glass fibre is currently permitted in 3D printing. Not so. The recent interpretation noted, "The fact that the resin (listed in CR D.2.1(a)(3) ) may be reinforced with glass fibres means that resin may include glass fibres but does not mean that glass fibres are permitted in thermoplastic material." Hence, we begin by assuming that we wish to permit g/f reinforcement in 3D printing filament, and that the real question that needs answering is whether we wish to permit 3D printing where “infill” is less than 100%, that is, honeycombing.

Conclusions
We can 3D print a nice honeycombed (20% infill) hull in g/f nylon filament with the same stiffness and same weight as a pre-preg S-glass hull but it'll have one third the strength. So this is not going to obsolete the fleet or threaten anyone with a nice g/f hull. This is simply due to the laws of physics.

If we’d like our hull to be just as strong as pre-preg S-glass, it will be 4.3 mm thick and twice the weight. If we don’t want a honeycombed 3D print, the hull in solid (100% infill) g/f nylon 2.5 mm thick is around 40% the strength of the pre-preg S-glass and has similar stiffness at twice the weight. If we want it as strong, then it'll be 4 mm thick and three times the weight.

Posted: **23 Nov 2020, 22:54**

Yes, target audience for the original CRO motion was home builders not commercial builders! It is so clear from the "reasoning for the amendment" which I posted earlier. So far, I am not aware of loopholes for commercial gain...Robert G.

Robert, I believe your words but I feel the motion failed because there was no public discussion and I am not even sure if even one 3D home builder was included in the closed emails and closed forums to give there views, and for this reason, people did feel it was a commercially pushed motion.

Luckily, we can now solve this and move forwards with a re-write and a passed motion and look forward to getting our first competitive printed IOM's on the water.

Posted: **24 Nov 2020, 00:55**

It appears as though this discussion concerns how to allow "home builders" to use 3D technology for rapid prototyping.

Since by all accounts, a 3D printed hull will be heavier for the same strength as a conventionally constructed hull, these will probably not be competitive but more as "trial horses" for new designs and ideas that may not warrant the time/expense of traditional construction methods.

Rather than try to incorporate the ever changing iterations of 3D printing into our rules, why not consider some sort of special exemption for non-commercial builders to build these boats as they please.

Similar to the Texalium issue from years past, allow 3D construction of any sort, prohibit them from championship regattas or ranking events, but allow them to sail on equal footing in club events.

Hopefully, this will allow a flood of practical applications of 3D printing as well as numerous new designs, materials, techniques, and ideas, all of which will be good for the class.

If, after this flurry of activity, we can all agree on what 3D printing methods/infill/materials make sense, we can incorporate them into our rules in a more specific way once the initial dust settles and we start seeing these boats plying our waters on a more regular basis.

How's that for thinking outside the box?

PS. I am no longer a USA NCA officer as noted in my profile, but don't know how to update it.

Posted: **24 Nov 2020, 13:51**

Lester wrote: ↑
23 Nov 2020, 21:47

Conclusions
We can 3D print a nice honeycombed (20% infill) hull in g/f nylon filament with the same stiffness and same weight as a pre-preg S-glass hull but it'll have one third the strength. So this is not going to obsolete the fleet or threaten anyone with a nice g/f hull. This is simply due to the laws of physics.

If we’d like our hull to be just as strong as pre-preg S-glass, it will be 4.3 mm thick and twice the weight. If we don’t want a honeycombed 3D print, the hull in solid (100% infill) g/f nylon 2.5 mm thick is around 40% the strength of the pre-preg S-glass and has similar stiffness at twice the weight. If we want it as strong, then it'll be 4 mm thick and three times the weight.

Hi Lester,

Thanks for interesting article. I am not questioning the law of physics at all

but take into consideration the following assumption.

What if somebody conclude that the current "traditional"

moulded glass/epoxy hulls are simply unnecessary stiff and long-lived and that for the top results you don't need such "extra stiffness" and that the risk of collision and total loss of the boat is not so high.... And that such skipper manage to make a hull using new technologies (one of them is 3D printing). Note, building techniques are not restricted..... And that such skipper/builder produce the hull with different thickness of hull skin so the ends are lighter than the middle part of the boat. And that some XYZ commercial manufacturer is starting to advertising and selling such IOM boats as the state-of-the-art product using the latest additive manufacturing etc etc in compliance with the IOM Class Rules. Do we want that? I don't.

Therefore, the CRO proposal is allowing the same materials (as an example - glass fibres to be used in any construction techniques including 3D printing of the hulls (at the moment glass fibres are not allowed in the 3D printing filaments) but honeycombing (infill) is not allowed because if it is allowed for 3D printed boats why to prohibit it on the moulded boats? Combination of moulded and additive manufactured parts of the hull is allowed. 3D printing of honeycombed material as a core between two layers of moulded skins is the possible loophole if you allow the 3d printing with honeycombing.

Once again, the spirit of the CRO motion is to controllably allow the new emerging building techniques to be used in the IOM hull production for both commercial and amateur builders.

At the end, Lester what is your suggestion for the wording of the revised material class rule?

All the best

Robert Grubiša
CRO 68

Posted: **24 Nov 2020, 16:06**

Ich muss Robert in Schutz nehmen! Inoffiziell war ich eingebunden.
Leider konnte ich meinen Standpunkt nicht gut genug vermitteln und stieß auf massiven Wiederstand.

Die Problematik mit dem Infill ist kein Problem, da jedes Boot, das nicht massiv gedruckte Teile für den Rumpf verwendet einfach illegal ist. Da ist es egal, ob eine neue Definition, oder Regel gemacht wird. Das ist bei einem laminierten Rumpf so und auch bei einem Holzrumpf. Da ist der gedruckte Rumpf keine Ausnahme! Wie und ob das zu überprüfen ist, spielt dabei keine Rolle, denn auch bei einem laminierten Rumpf kann ich nicht jede Stelle einsehen.
Und auch da könnte ich teilweise mit Schaumtreibmittel im Harz arbeiten und eine wabenartige Struktur erzeugen, die niemand sehen würde!
Auch werden viele laminierte Boote illegal produziert, wenn ich die Regel ganz hart auslege. Denn oft wird zum verkleben ein Gemisch aus Harz + Thixo+Microbubbles verwendet! Das sind kleine Hohlglaskugeln...
Da geht es einfach um Fairplay.
Der entscheidende Punkt ist das Filament und das bricht euch das Genick, wenn die Beschränkungen wirklich kommen.
Hier gab es Aussagen zu PLA, das es funktioniert. Es funktioniert nicht! Spätestens nach einem Jahr ist der Rumpf so versprödet, das dieser Rumpf nicht mehr brauchbar ist. Bei kaltem Wasser platzt er bei einem leichten Kontakt. Schwere Treffer im stumpfen Winkel und hoher Geschwindigkeit lassen ihn platzen! Ich schreibe hier mit über 5 Jahren Erfahrung. Mit über 50 Ranglistenregatten, internationale Meisterschaften und einer Weltmeisterschaftsteilnahme mit gedruckten Rümpfen.
Es funktioniert wirklich nur Nylon auf Dauer. Leider ist Nylon allein nicht verzugsfrei zu drucken, deshalb ist ein Glasfaseranteil unerlässlich. Damit lassen sich Rümpfe drucken, die das Gewicht halten, oder etwas Korrekturgewicht brauchen.
Der Glasfaseranteil gibt auch keine zusätzlich Stabilität der Verbindung. Er dient nur der Druckbarkeit.

Mit PLA, PETG, oder ABS kann man Prototypen drucken und testen, aber wettbewerbstaugliche Boote, die wirklich auf Dauer die harten Bedingungen aushalten, sind damit nicht möglich. Jedenfalls nicht mit einem konkurrenzfähigen Gewicht der Hülle.
Im Moment steckt der 3D-Druck noch in den Kinderschuhen, auch wenn viele Firmen vermitteln, das Alles möglich ist. Die reine Technik ist ausgereift und günstig verfügbar. Die Filamententwicklung hängt leider noch hinterher, da zu wenig für technische Anwendungen entwickelt wird.

Noch eine wichtige Sache:
Der 3D-Druck im Bereich IOM-Rümpfe sollte auf FDM beschränkt werden.
Erstmal sind alle anderen Techniken nicht brauchbar und ausserdem macht es die Regelfindung deutlich leichter.

Posted: **24 Nov 2020, 16:47**

Robert Grubisa wrote: ↑
24 Nov 2020, 13:51
What if [...] the hull with different thickness of hull skin [...] advertising and selling such IOM boats as the state-of-the-art?

Hi Robert

I think looking at specific scenarios is a good way to explore the issues we have.

In this case, I think a fragile super-light hull with different skin thickness etc is completely possible today with resin-glass fibre lay-up. It is still completely possible even if that risk made us decide suddenly to prohibit a resin-glass fibre lay-up, for example, and insist on only wooden hulls, and so on. This has nothing to do with 3D printing.

And XYZ suppliers are completely possible today who make misleading claims about their boats. This has nothing to do with 3D printing.

So for me, the, er, "nightmare" scenario has no relevance to help us decide for or against 3D printing an IOM hull with less than 100% infill.

Robert Grubisa wrote: ↑
24 Nov 2020, 13:51
[...] honeycombing (infill) is not allowed because if it is allowed for 3D printed boats why to prohibit it on the moulded boats?

Prohibited for moulding because the 3D printed hull is thermoplastic, whereas the moulded hull is thermoset.

I think it is a general property of a thermoplastic material that it can be melted, allowed to "freeze" into a shape, re-melted, and so on. This means that the internal bonds which make the material strong in 2D are relatively weak, and in the case of 3D printing the 3D bonds between layers are even weaker. There is no point engineering a thermoplastic to have very strong bonds, because it stops being able to be repeatedly melted and frozen and is no longer an effective or efficient *thermoplastic*.

On the other hand, a thermoset plastic such as resin makes a network of 3D bonds when it freezes, and these are relatively stronger than those in a thermoplastic when it sets. In addition, these thermoset bonds are irreversible, and the modern resins are engineered to make bonds as strong as possible, because they will never need to be broken. Hence, we know that a good epoxy resin is as strong as steel (well, the advertisements say so!) but this does not, and I think cannot, happen with a thermoplastic.

Robert Grubisa wrote: ↑
24 Nov 2020, 13:51
3D printing of honeycombed material as a core between two layers of moulded skins is the possible loophole if you allow the 3d printing with honeycombing.

I don't understand why this is a "loophole". I can see no problem to have a 3D printed thermoplastic honeycomb which is a core between two layers of glass fibre skin. Thermoplastic is much weaker than almost any other material of interest, and the only way to get strength and stiffness is to make it thick. When thick, it is heavy, so we honeycomb it. The laws of physics tell us that a honeycombed thermoplastic is somewhere between twice and four times as heavy as a thin material for equivalent strength and stiffness. But I will check this, I can construct and test a desktop model of a 3D printed honeycombed nylon sheet between two thin g/f sheets and let you know the outcome.

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