HULL MATERIALS....3D Printing. Croatian Motion.

[Lester]

Google translate

I have to protect Robert! I was unofficially involved.
Unfortunately, I was unable to convey my point of view well enough and met with massive resistance.

The problem with the infill is not a problem as any boat that does not use solidly printed parts for the hull is simply illegal. It doesn't matter whether a new definition or rule is made. This is the case with a laminated hull and also with a wooden hull. The printed hull is no exception! How and whether this is to be checked does not matter, because even with a laminated hull I cannot see every point.
And there, too, I could partially work with foam blowing agent in the resin and create a honeycomb-like structure that no one would see!
Many laminated boats are also illegally produced if I take the rule very hard. Because often a mixture of resin + thixo + microbubbles is used for gluing! These are small hollow glass spheres ...
It's just about fair play.
The crucial point is the filament and it will break your neck when the restrictions really come.
There were statements about PLA that it works. It doesn't work! After a year at the latest, the hull is so brittle that it can no longer be used. In cold water, it will burst upon light contact. Heavy hits in an obtuse angle and high speed make it burst! I am writing here with over 5 years of experience. With over 50 ranking regattas, international championships and participation in the world championship with printed hulls.
It really only works nylon in the long run. Unfortunately, nylon alone cannot be printed without distortion, which is why a glass fiber content is essential. This can be used to print hulls that hold the weight, or need some weight correction.
The glass fiber content also does not give the connection any additional stability. It is only used for printability.

With PLA, PETG, or ABS you can print and test prototypes, but boats suitable for competition, which really can withstand the harsh conditions over the long term, are not possible with them. At least not with a competitive envelope weight.
At the moment, 3D printing is still in its infancy, even if many companies convey that anything is possible. The pure technology is mature and available cheaply. Unfortunately, filament development is still lagging behind, as too little is being developed for technical applications.

One more important thing:
3D printing in the area of ​​IOM hulls should be limited to FDM.
First of all, all other techniques are useless and it also makes rule finding much easier.

[Robert Grubisa]

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.


RG: Of course that you can now built such a hull with moulding technique. I tried to give you an example for 3D printed boat which is now "threatening" our usal way of making boats

[...] 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.

RG: I disagree with you on this point. Honeycombed structure is just that honeycombed structure. One example is here and it is prohibited for use on IOM hulls: https://www.easycomposites.co.uk/honeycomb-cores Why such 3D printed structure should be 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.

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.

RG: I answered above. Honeycombed structures are not permitted for any construction techniques. Or, we should allow it for all building techniques which I believe is not a good idea for IOM hulls.

Robert Grubiša
CRO 68

[Juan Marcos Egea]

Hi Lester, Robert,

Thank you Lester for the article. Could be interesting to include a column in the "Laws of physics.xlsx" with the numbers of a honeycomb nylon core and S-glass skins (if the formulation of the excel allows that), and compare results. In my opinion, the discussion about infill or no infill is about don´t allow professional builders to take advantage of using the best material (fiber glass-epoxy) in combination with materials manufactured by additive technologies. If there is nothing to worry about for me is OK to allow infill.

[Lester]

Honeycombed structures are not permitted for any construction techniques.

Hi Robert

Yes, understood, honeycombing, foaming, etc currently not permitted. My question earlier was,

"whether we wish to permit 3D printing where “infill” is less than 100%, that is, honeycombing."

So I am asking about permitting honeycombed thermoplastic materials (only), and keeping the prohibition on honeycombing (with the other exception of elastomeric) in all other permitted materials.

[Lester]

Could be interesting to include a column in the "Laws of physics.xlsx" with the numbers of a honeycomb nylon core and S-glass skins (if the formulation of the excel allows that), and compare results.

Hi Juan

Yes, I have accepted the challenge to "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". This is absolutely non-trivial (smile), it may take a little while....

[Torsten Kass]

I now don't understand the discussion about honeycomb printing ...
It is clear that honeycomb printing or reduced infill are not allowed! Just because we want to print hulls, we cannot expect, and certainly not demand, a special status. Right now we are having issues with the durability of our filaments, but that is our problem, not the class problem. There are plenty of other ways to build hulls, we can't ask for a special status.
So stay with the topic.
In my opinion there is only one point that should be negotiated and determined:
Allow all filaments as long as they do not contain carbon.

The point infill is clearly ... massive prints. Everything else contradicts the class rules.


Google-Translator...

[Antonio Campos]

My piece of thought:

I do a lot of 3D printing, I started longtime ago, but mainly for parts, as the hull I did print was not competitve.

In my view, the rules are perfect as they are, except a clarification/rewriting is needed with regard to Honeycombed materials.

The honeycombed materials that were regarded when the rules were written were expensive hi-tech panels for the aeronautic/spacial industry that have nothing to do with 3D printing. When trying to read how the rules contemplate 3d printing, somebody thought that it would apply to infill with hexagonal structure between surface layers, as the infill may have this design (but also square, triangular, concentric). This interpretation of hexagonal infill as honeycombed material is debatable, and in my view the rules should say that hexagonal infill is NOT considered a honeycombed material.

I think it is important to point for this debate that everybody is thinking only about 3d printing with thermoplastics, but to have a complete debate, you should be aware that a new 3d printing technology is becoming very popular, which is with photoactive resins. Again, as these are resins, an authorised material, it is allowed and the rules do not need to be modified.

Coming back to thermoplastics, the rules are clear that thermoplastics including carbon fibers are excluded. That is OK, for me, (although carbon is not that expensive anymore, either in as a thermoplastic component or as a classic resin based build), the class does not need to change this rule.

Other thermoplastics with glass fibers poweder are also available, and are also permitted materials, so again no need to change the rules.

I am not aware of any thermoplastic that is terribly expensive that provides a significant advantage, they are all cheaper than a fiberglass approach, and actually are not very competitive, at best slightly less than a fiberglass hull.

Also the measurement process at regattas will not be able to analyze what kind of plastic is used, so it is not practical. In fact the same applies to things like the mast alloy. It is useless to specify what aluminium alloys are allowed, as neither the sailor nor the official can test it or identify it (go find the alloy identification of an aluminium tube!). It is generally a bad idea to forbid things that cannot be reasonably tested at measurement.

As some colleagues have pointed, no 3d printed hulls have shown any real competitveness so far, so the idea of limting the materials specifically to prevent a problem that does not exist is not a good one as of today. Also, as some have pointed, the rules now prescribe materials, but not manufacturing processes, so 3d printing (a process) should not be treated differently than, for instance, vacuumed glass-reinforced resin construction or any other.

In summary: keep rules as they are except clarify that 3d printed hexagonal infill is not a honeycomb material .

Hope this helps.
Antonio

[Robert Grubisa]

Other thermoplastics with glass fibers poweder are also available, and are also permitted materials, so again no need to change the rules.

In summary: keep rules as they are except clarify that 3d printed hexagonal infill is not a honeycomb material .

Hope this helps.
Antonio

Hi Antonio,

Thermoplastic with glass fibres are prohibited according to the latest interpretation:

http://iomclass.org/doc-files/Technical ... 230620.pdf

CRO proposal has not been voted, so you can not use glass fibres in thermoplastic for 3D printing.

Regards

Robert Grubiša
CRO 68

[Hiljoball]

The question of allowing glass fibre as an allowed material for thermoplastics could be achieved by a motion to reword D.2.1(a)(3) which says
(3) Resin, which may be coloured and/or reinforced with glass fibres,

but if it were changed around such as
(3) Glass fibre. which may be bonded with resin, which may be couloured.

then glass fibre becomes a permitted material in thermoplastics as stated in (8) and eliminates the problem caused by the interpretation.

However I suspect that does not fully address the issues of additives for thermoplastics. What kind of additives are used in thermoplastics? Are all additives in a thermoplastic product listed on the box? Are there any additives that should not be permitted within the spirit of the current IOM rules - eg no carbon fibre or Kevlar strands ? These issues should be addressed by adding clauses to (8).

John

[Robert Grubisa]

The question of allowing glass fibre as an allowed material for thermoplastics could be achieved by a motion to reword D.2.1(a)(3) which says
(3) Resin, which may be coloured and/or reinforced with glass fibres,

but if it were changed around such as
(3) Glass fibre. which may be bonded with resin, which may be couloured.

then glass fibre becomes a permitted material in thermoplastics as stated in (8) and eliminates the problem caused by the interpretation.

However I suspect that does not fully address the issues of additives for thermoplastics. What kind of additives are used in thermoplastics? Are all additives in a thermoplastic product listed on the box? Are there any additives that should not be permitted within the spirit of the current IOM rules - eg no carbon fibre or Kevlar strands ? These issues should be addressed by adding clauses to (8).

John

John,

Your proposal is not solving following items, related to the "classic" moulded boats. According to the current IOM Class Rules:

a) Gel coat is not listed. Is it permitted?
b) Coloured pigment is not listed. Is it permitted?
c) Is a filler made of resins with some filler (micro balloons) permitted? Is it adhesive or not?

CRO proposal is solving the above mentioned issues.

Asking for interpretation from any NCA for items under a) and c) could be asked. CRO NCA wanted to avoid such a situation but...

CRO proposal is stating that glass fibres are permitted. So every existing boat and future boats made of epoxy, vinylester , polyester or some other resin reinforced with glass fibres are permitted. If you want to 3D print an IOM hull, filament with glass fibres is Ok.

So if you buying glass cloth and it is declared as glass cloth you are on the safe side. Same is valid for printing filament. If the builder decide to use some other fibres for the reinforcement than he/she has to check the modulus of elasticity of such material. Such data can be published on the IOM ICA website and you will find such data for various materials which somebody may assume to use for IOM hull building.

Something like table here (scroll to "Approximate values"):

https://en.wikipedia.org/wiki/Young's_modulus

So, according to the CRO proposal, carbon, Kevlar and alike fibres are not permitted in accordance within the spirit of the current IOM rules.

Do we know any other component/constituent part, material, etc which we want to prohibit due to the "spirit of the current IOM rules" which is not covered by the CRO proposal?

Regards

Robert Grubiša
CRO 68

[Torsten Kass]

Hello John,
most manufacturers have detailed lists of additives as PDF. Can be found on the dealer website.

I just think it's unfair to ask for something like that. There are no regulations for resins. I can use any epoxy, polyester, or phenol. I can use hollow glass and there is no question about the treatment of the glass fibers.
Will I be asked whether I mixed in thixo, cotton flakes or microbubbles? Will I be asked if I am using foam blowing agents? No...

[Torsten Kass]

Robert,
you did it just right. Nothing is fixed and everyone can cheat. With clear definitions, even the inexperienced laminator will be able to achieve equivalent results and we print enthusiasts are not doomed to failure now.
I currently can't sail my 2 year old IOM ... glass in filament. Although I was able to achieve podium places with it.

[Torsten Kass]

There is still basalt and metal in filaments. They don't conform to the class rules either. There is also wood in the filament, but it should conform to the class.

[Hiljoball]

Hi Robert,
You wrote


Your proposal is not solving following items, related to the "classic" moulded boats. According to the current IOM Class Rules:

a) Gel coat is not listed. Is it permitted?
b) Coloured pigment is not listed. Is it permitted?
c) Is a filler made of resins with some filler (micro balloons) permitted? Is it adhesive or not?

These items are not an issue - they are resolved.
The technical ruling
http://www.iomclass.org/doc-files/Techn ... -IOM-4.pdf
answered these questions - and even though the rulings have expired, the logic behind them still stands - and if you were to ask the question again, there is no reason to assume that you would get a different answer. The rulings are still on file for reference.

The normal process, when an item is found to be compliant, is that there is no reason to change a class rule. So the wording did not change.

John

[Robert Grubisa]

Hi Robert,
You wrote


Your proposal is not solving following items, related to the "classic" moulded boats. According to the current IOM Class Rules:

a) Gel coat is not listed. Is it permitted?
b) Coloured pigment is not listed. Is it permitted?
c) Is a filler made of resins with some filler (micro balloons) permitted? Is it adhesive or not?

These items are not an issue - they are resolved.
The technical ruling
http://www.iomclass.org/doc-files/Techn ... -IOM-4.pdf
answered these questions - and even though the rulings have expired, the logic behind them still stands - and if you were to ask the question again, there is no reason to assume that you would get a different answer. The rulings are still on file for reference.

The normal process, when an item is found to be compliant, is that there is no reason to change a class rule. So the wording did not change.

John

Hi John,

The document which you mentioned has been made in 2003 and it is obsolete as you indicated. The snag is a fact that in that year IOM Class Rules explicitly allowed gel coat.

D.2.1(b) In glass fibre reinforced plastic:
(1) an external gel coat is optional and may be pigmented

After GBR proposal to delete mentioned rule which has been voted on the IOM ICA AGM 2012 and implemented in the Class Rules 2013, pigmented or unpigmented gel coat are not in the IOM Class Rules. I am sure that this was not the intention of the GBR friends, but it is like that. So your cited document from 2003 is not covering the current edition of the IOM Class Rules problem with gel coat. You may find more about that here:

http://iomclass.org/doc-files/Technical ... 100417.pdf

Please go to page 26.

CRO proposal solved this snag as well.

Regards

Robert Grubiša
CRO 68

[Hiljoball]

HI Robert,

Thanks for the reference to the rule change, however, it is still not an issue, as gelcoat is a type of resin (permitted) and resin may be coloured. The other references such as use of fillers still apply.

John

[Antonio Campos]

Thank you, Robert, noted. I understand though that out of this discussion glass infilled thermoplastics may be allowed, and that is part of this debate.

In that sense, I would like to point that 3d printing with UV photoactivated resins, the growing new 3d printing technology (for instance with Elegoo Mars and Saturn printers, if you want to search and check what I am talking about) could also be filled with glass fibers and would be allowed under the present rules. I think a lot of 3d printing in the near future will be with this kind of materials and printers, as the quality is much better, and potentially the resins resistance also, and the prices are coming near the range of thermoplatic extrusion 3d printers (200-600 €)

I would like to insist that I see in the debate that you are taking for sure that all infill are Honeycomb. I have to repeat that only hexagonal infill may be interpreted as being honeycomb (with a hard interpretation, as I explained above, it could be debated if that is what the rules meant by honeycombed materials when writing the rules). So any other infill (rectangular, concentric, ...) is NOT forbidden by the honeycomb mention in the rules. I have tried to include images of such infills here, but I have not found the correct way to post images.


Also some of you interpret that infill may be forbiden by the "expanded, foamed" material words, I do not think that is the case. The thermoplastic does not foam or expands when in the infill differently from the normal printing of walls, solid or not. Some new thermoplastics are now being introduced that foam slightly (in a non perceptible manner) giving lighter parts. These are excluded by the rulle, wether in infill or in the walls, although I do not see how that would be checked at measurement.

And as some have pointed, the only way to check the infill of parts is to destruct them, so it seems that any rule specifying wether infill is allowed or what kind of infills are allowed would be impossible to be checked at championships.

Although at this point some have said that all examples of hull build are not using infill, and therefore the discussion seems theoretical and academic instead of practical, it is quite possible to use infill to reinforce parts of the construction, so it is a necessary dicussion when looking forward. I could imagine the bow or the stern being built with infill, the rest of the hull without it. And as pointed out, so far 3d printed hulls are handicapped in terms of weight, so it makes no sense to make things more difficult for them, as it is a cheap alternative to test new ideas and access the sport.

[Robert Grubisa]

Thank you, Robert, noted. I understand though that out of this discussion glass infilled thermoplastics may be allowed, and that is part of this debate.

In that sense, I would like to point that 3d printing with UV photoactivated resins, the growing new 3d printing technology (for instance with Elegoo Mars and Saturn printers, if you want to search and check what I am talking about) could also be filled with glass fibers and would be allowed under the present rules. I think a lot of 3d printing in the near future will be with this kind of materials and printers, as the quality is much better, and potentially the resins resistance also, and the prices are coming near the range of thermoplatic extrusion 3d printers (200-600 €)

I would like to insist that I see in the debate that you are taking for sure that all infill are Honeycomb. I have to repeat that only hexagonal infill may be interpreted as being honeycomb (with a hard interpretation, as I explained above, it could be debated if that is what the rules meant by honeycombed materials when writing the rules). So any other infill (rectangular, concentric, ...) is NOT forbidden by the honeycomb mention in the rules. I have tried to include images of such infills here, but I have not found the correct way to post images.


Also some of you interpret that infill may be forbiden by the "expanded, foamed" material words, I do not think that is the case. The thermoplastic does not foam or expands when in the infill differently from the normal printing of walls, solid or not. Some new thermoplastics are now being introduced that foam slightly (in a non perceptible manner) giving lighter parts. These are excluded by the rulle, wether in infill or in the walls, although I do not see how that would be checked at measurement.

And as some have pointed, the only way to check the infill of parts is to destruct them, so it seems that any rule specifying wether infill is allowed or what kind of infills are allowed would be impossible to be checked at championships.

Although at this point some have said that all examples of hull build are not using infill, and therefore the discussion seems theoretical and academic instead of practical, it is quite possible to use infill to reinforce parts of the construction, so it is a necessary dicussion when looking forward. I could imagine the bow or the stern being built with infill, the rest of the hull without it. And as pointed out, so far 3d printed hulls are handicapped in terms of weight, so it makes no sense to make things more difficult for them, as it is a cheap alternative to test new ideas and access the sport.

Hi Antonio,

If I understand correctly the way how photos could be added here, the only way is to put here the link where photo is stored on some server/provider etc. This one is from my personal Google Photo Cloud:

https://photos.app.goo.gl/U9QDiJFFfUheJ2y46

The photo is not the best one but clearly represent the infill method. Let me know if you are able to see it.

For me, all shown patterns (except 100 and 0%) are clearly some sort of honeycombed structure not permitted by the current IOM Class Rules and the CRO proposal.

If you have a problem with posting photos, send them to me on e-mail and I will post it here.

All the best

[Robert Grubisa]

HI Robert,

Thanks for the reference to the rule change, however, it is still not an issue, as gel coat is a type of resin (permitted) and resin may be coloured. The other references such as use of fillers still apply.

John

Hi John,

This is one of Q&A which is questionable:
------------------
Question:
Is it permitted to use fillers and gel coats containing micro balloons?

Question details:
a) Is it permitted to use fillers that contain:
– micro balloons?
– bulking materials such as slate, talc etc?

b) Is it permitted to use epoxy gel coats that contain micro balloons?

Reference to the old interpretation issued before year 2017
Interpretation 2003-IOM-4 on the IOM CR – edition 2002

Answer:

YES – in adhesives, NO – in glass reinforced plastic.

Fillers are permitted provided they are constituent parts of permitted materials listed in IOM CR D.2.1. Fillers supplied as parts of a resin for laminating or/and gel coat are constituent parts of laminating resin and/or gel coat which are explicitly mentioned as parts of the glass fibre reinforced plastic. Another filler added by the builder to laminating resin and/or gel coat is not a constituent part of laminating resin and/or gel coat.

Fillers are a normal part of adhesives and therefore permitted.
------------------

Resins including gel coats are commonly used for the IOM hulls construction. Currently, resin is mentioned in the Class Rules while gel coat is not. Ok, we may agree that gel coat is a sort of resin. But, according to the above mentioned Q&A (originally interpretation on the Class Rules in 2003), you are not allowed to add "fillers" in laminating resins and gel coats... So, if somebody asks questions above, he should receive the same answer which we want to change because anyone involved into laminating process know that life is much easier if you may thicken the resin with some filler., if needed on particular parts of the moulding... Or in other words, how many already doing this not knowing the above Q&A or simply ignoring it

I think that this is really unnecessary restriction, and we believed that such Q&A will be deleted if CRO proposal is voted, but....

In the CRO proposal, fibres are restricted ("Not better than glass fibres") and other restrictions like above mentioned are not existing).

All the best

Robert Grubiša
CRO 68

[Lester]

I've completed a spreadsheet which calculates values of stiffness, strength, and weight to allow what-if comparisons of various materials in hull construction. I've updated the document to explain it, give some sample calculations, and suggest some conclusions. I repeat these here:

Permitting honeycombed (foamed, expanded, micro-ballooned, voided anything, etc) materials in any form of sandwich is likely to be disruptive.

Permitting solid materials in any sandwich looks perfectly safe, as safe as the current permission for wood in a sandwich.

Permitting 3D printed hulls with less than 100% infill seems perfectly safe, the weight penalties to achieve any reasonable stiffness or strength are severe.

[Robert Grubisa]

I've completed a spreadsheet which calculates values of stiffness, strength, and weight to allow what-if comparisons of various materials in hull construction. I've updated the document to explain it, give some sample calculations, and suggest some conclusions. I repeat these here:

Permitting honeycombed (foamed, expanded, micro-ballooned, voided anything, etc) materials in any form of sandwich is likely to be disruptive.

Permitting solid materials in any sandwich looks perfectly safe, as safe as the current permission for wood in a sandwich.

Permitting 3D printed hulls with less than 100% infill seems perfectly safe, the weight penalties to achieve any reasonable stiffness or strength are severe.

Hi Lester,

Thanks for files. I will go through them later.

In the meantime, could you please give your definitions of:

a) Honeycombed construction
b) Infill construction

Some photos / sketches are most welcomed

Because, I am not sure that I understand the difference between them. Infill construction on photo which I share in my post above is honeycombed (in my opinion).

Thanks

Robert Grubiša
CRO 68

[Lester]

Hi Robert

From the point of view of the rules we wish to make, I think we distinguish between solid materials, and materials with voids.

Honeycombed, foamed, expanded, micro-ballooned, infill less than 100%, all these words and concepts refer to materials with voids or ways of creating materials with voids. I do not think that we are concerned with the shape of the void, whether square, hexagonal, gyroid, and so on in this case.

Some materials with voids are accepted as 'solid', probably because we think of them as natural. For our rules, they are the woods. A nice light balsa sheet is effectively a foamed wood filament.

Voids can be introduced into materials which were originally solid or 'solid'. When this is systematic, we call the material honeycombed, foamed, expanded, micro-ballooned, printed or fused or deposited etc with infill less than 100%.

When voids are introduced accidentally, 'accidentally', non-systematically, or unintentionally, well, we are unsure at the moment. For example, it is understood that almost any pre-preg has voids; the only issue is how much. The very high quality aerospace pre-pregs are guaranteed to have less than 1% voids, but it is certain they have *some*, it cannot be 0%. The low quality cheap materials may have 5% voids. Similarly, if we make a hull with resin and fibre mat, it is certain that there are voids in the result.

[Robert Grubisa]

Hi Robert

From the point of view of the rules we wish to make, I think we distinguish between solid materials, and materials with voids.

Honeycombed, foamed, expanded, micro-ballooned, infill less than 100%, all these words and concepts refer to materials with voids or ways of creating materials with voids. I do not think that we are concerned with the shape of the void, whether square, hexagonal, gyroid, and so on in this case.

Some materials with voids are accepted as 'solid', probably because we think of them as natural. For our rules, they are the woods. A nice light balsa sheet is effectively a foamed wood filament.

Voids can be introduced into materials which were originally solid or 'solid'. When this is systematic, we call the material honeycombed, foamed, expanded, micro-ballooned, printed or fused or deposited etc with infill less than 100%.

When voids are introduced accidentally, 'accidentally', non-systematically, or unintentionally, well, we are unsure at the moment. For example, it is understood that almost any pre-preg has voids; the only issue is how much. The very high quality aerospace pre-pregs are guaranteed to have less than 1% voids, but it is certain they have *some*, it cannot be 0%. The low quality cheap materials may have 5% voids. Similarly, if we make a hull with resin and fibre mat, it is certain that there are voids in the result.

Hi Lester,

Ok. I will try to provide definitions of terms (as I understood them) appearing in the relevant IOM Class Rules dealing with hull materials.
I am not trying here to provide scientific, academic definitions of them. I hope that for IOM community following could be used:

Honeycombed:
- cellular structure that resembles a honeycomb in structure. Shape of the void is irrelevant (square, hexagonal, gyroid, and so on).

Expanded:
- materials which have a light cellular structure like expanded polystyrene and similar.

Foamed:
- solid foams like polyurethane foam, Termanto and similar materials.
-------------------------------

Can we agree on the above mentioned?

I think that we may agree that accidentally, (not 'accidentally'), non-systematically, or unintentionally voids are not falling under above mentioned definitions, so I think that we may live with them as a result of our imperfections in production.

I am still asking, is the construction shown here (regardless of building technique used) honeycombed?

https://photos.app.goo.gl/U9QDiJFFfUheJ2y46.

Why such construction need to be permitted regardless of construction techniques used?

Robert Grubiša
CRO 68

[Lester]

Honeycombed
Expanded
Foamed
Can we agree on the above mentioned?

Hi Robert

Well, OK, if the idea is to develop a list, then we could add "meshed" and possibly "bubbled". The difficulty I can see is there could be a new material in the future which is called, oh, "companiformed". Because this material is not said to be honeycombed, expanded, or foamed, it is permitted.

Instead of making such a list, can we develop a definition which more exactly expresses what we want to prohibit -- a material with voids, cells, or cavities?

Honeycombed:
- cellular structure that resembles a honeycomb in structure. Shape of the void is irrelevant (square, hexagonal, gyroid, and so on).

Perhaps, "structure of adjacent voids, cells, or cavities of any shape"

Expanded:
- materials which have a light cellular structure like expanded polystyrene and similar.

Perhaps, "structure of particularly small, light cells, cavities, or voids"

Foamed:
- solid foams like polyurethane foam, Termanto and similar materials.

As for expanded, perhaps, "structure of solid foam having particularly small, light cells, cavities, or voids"

is the construction shown here (regardless of building technique used) honeycombed?

For me, except for the 100% and 0% images, yes, all these are 'honeycombed'.

Why such construction need to be permitted regardless of construction techniques used?

Not entirely sure I understand your question. For me, except in the cases of thermoplastics and elastomers, such construction does not need to be permitted and should not be permitted. I would write CR D.1.2(b) as, "With the exception of elastomer and thermoplastic, materials shall not be: expanded, foamed, honeycombed."

To finish off the permissions for thermoplastic, I would suggest CR D.2.1(a)(8) is written, "Thermoplastic, which may (i) be coloured (ii) be moulded (iii) be 3D printed (iv) contain fibres with a modulus E no higher than 90 (v) contain only permitted materials"

I would suggest tidying up the permission for resin, D.2.1(a)(3), writing, "Resin, which may (i) be coloured (ii) contain fibres with a modulus E no higher than 90"

And then there is a separate discussion, I think, for the other things like gel coat.

[Robert Grubisa]

is the construction shown here (regardless of building technique used) honeycombed?

For me, except for the 100% and 0% images, yes, all these are 'honeycombed'.

Why such construction need to be permitted regardless of construction techniques used?

Not entirely sure I understand your question. For me, except in the cases of thermoplastics and elastomers, such construction does not need to be permitted and should not be permitted. I would write CR D.1.2(b) as, "With the exception of elastomer and thermoplastic, materials shall not be: expanded, foamed, honeycombed."

To finish off the permissions for thermoplastic, I would suggest CR D.2.1(a)(8) is written, "Thermoplastic, which may (i) be coloured (ii) be moulded (iii) be 3D printed (iv) contain fibres with a modulus E no higher than 90 (v) contain only permitted materials"

I would suggest tidying up the permission for resin, D.2.1(a)(3), writing, "Resin, which may (i) be coloured (ii) contain fibres with a modulus E no higher than 90"

And then there is a separate discussion, I think, for the other things like gel coat.

Dear all,

I strongly believe that we should not list any construction techniques. They are currently unrestricted and it should be like that in the future.
We are now discussing 3D print which is just one of available additive manufacturing techniques.

I invite other which are experts in the field of additive manufacturing technologies to provide more data.

We may restrict materials but it is unreasonable to permit specific construction (in this case -> honeycombed construction as intentionally made cellular structure that resembles a honeycomb with the aim to made light and stiff construction) if they are made of particular materials using particular building technique and prohibit it if it is made of another material and other building technique.

Despite the language barriers, I hope that Forum members understand my position and reasoning for that.

Over to others to give their opinion.

Regards

Robert Grubiša
CRO 68

[Antonio Campos]

Hopefully in the following link you will see examples of non-hexagonal infill that cannot be included in the "honeycombed" definition above, as I pointed in a previous post, and are therefore allowed by the present Class Rules (but excluded by the recent interpretation issued?).

https://photos.google.com/share/AF1QipP ... VSalJNMlNR

(you can press the arrows in the sides to roll the images if you only see one image in fullscreen)

I understand there is two lines of thinking being discussed in terms of how to modify the present rules to cope with 3d printed hulls:

1) modify them so as to catch all materials with voids in the construction, the rationale being that this is the spirit of the existing material rule, rendered obsolete by the new manufactoring technology (3d printing).

(I would like to point that in this case, hollow fiberglass parts in the hull, such as servo trays or the reinforcement between shrouds attachment and keel box base in Britpops, for example, may be rendered ilegal by such modification)

2) Keep the present approach of not limiting manufacturing techniques and look at materials definitions so as to Improve the wording of the existing rule so officials are clear about what is authorized and don't need to speculate. Infill in that case would be considered a manufacturing technique and not a material property, and not be limited.

For the sake of clarity, and given that 3d printed hulls are far from being competitive as of todya in IOM, I would vote for 2, so as not to stop 3d manufacturing, which has the potential of facilitating lower cost of acces to the class and cost of prototyping of new hulls, both being consistent with the more general spirit of the Class Rules.

[Robert Grubisa]

Hopefully in the following link you will see examples of non-hexagonal infill that cannot be included in the "honeycombed" definition above, as I pointed in a previous post, and are therefore allowed by the present Class Rules (but excluded by the recent interpretation issued?).

https://photos.google.com/share/AF1QipP ... VSalJNMlNR

(you can press the arrows in the sides to roll the images if you only see one image in fullscreen)

I understand there is two lines of thinking being discussed in terms of how to modify the present rules to cope with 3d printed hulls:

1) modify them so as to catch all materials with voids in the construction, the rationale being that this is the spirit of the existing material rule, rendered obsolete by the new manufactoring technology (3d printing).

(I would like to point that in this case, hollow fiberglass parts in the hull, such as servo trays or the reinforcement between shrouds attachment and keel box base in Britpops, for example, may be rendered ilegal by such modification)

2) Keep the present approach of not limiting manufacturing techniques and look at materials definitions so as to Improve the wording of the existing rule so officials are clear about what is authorized and don't need to speculate. Infill in that case would be considered a manufacturing technique and not a material property, and not be limited.

For the sake of clarity, and given that 3d printed hulls are far from being competitive as of todya in IOM, I would vote for 2, so as not to stop 3d manufacturing, which has the potential of facilitating lower cost of acces to the class and cost of prototyping of new hulls, both being consistent with the more general spirit of the Class Rules.

Hi Antonio,

Thank you for your views. May I just comment as follows:

My understanding of the IOM Class Rule D.2.3: "Construction techniques for forming a hull are unrestricted subject to compliance with D.2.1" is that moulding, additive manufacturing technology (including 3D printing), forming under heat and pressure, plank on frame and so on are permitted. Honeycombed construction (made by infill in 3D printing or using glass made honeycombed structure glued between moulded skins) are not "construction techniques" in the sense it is used in the IOM Class Rules. Honeycombed structure is a description of the final product made using any construction technique. So, I believe that your point 2) is not valid.

Regarding your item 1), I don't see how servo/winch trays or similar hull structural items with openings are not in compliance with current IOM Class Rules and CRO proposal. Opening for servo or winch is certainly not falling under "expanded, foamed, honeycombed" as stated in the current IOM Class Rules and CRO proposal.

Regards

Robert Grubiša
CRO 68

[Lester]

I strongly believe that we should not list any construction techniques. They are currently unrestricted and it should be like that. 3D print is just one of available additive manufacturing techniques.

We [should] restrict materials

Hi Robert

Hmmm, restrict materials, de-restrict construction techniques? An interesting suggestion, very attractive. In this discussion, I explore only permission for 3D printing while retaining all other existing rules to see where we can go. It is a very different discussion for me whether we can also eliminate or rephrase other rules to do with metal, wood, resin, etc etc etc.

OK, to adjust my draft for CR D.2.1(a)(8), we omit mention of construction technique and mention only the material, so it reads something like, "Thermoplastic, which may (i) be coloured (ii) contain fibres with a modulus E no higher than 90 (iii) contain only permitted materials"

I think we can keep my draft for CR D.2.1(b), which is also a rule about materials, something like, "With the exception of elastomer and thermoplastic, materials shall not be: expanded, foamed, honeycombed"

And now, the "But". Let's have some thought experiments. I take a permitted material, perhaps a thin aluminium sheet, I cut the sheet with short slits, pull the sheet apart, and bend it over a plug. I take another permitted material, perhaps a piece of bamboo, and in my workshop I chop it into fibres, throw them into a little boiling resin, stir vigorously, and then pour the result into a mould where it cools. I take another permitted material, perhaps thin strips of cedar with cross-section 1 mm x 1mm, and with incredible patience I glue these strips together using staggered spacer pieces 4 mm long at 4 mm intervals with just a micro-drop of cyano-acrylate as they lie over a plug or lie inside a mould. The materials were not and are not expanded, foamed, or honeycombed, they are perfectly solid and so permitted. I have used permitted construction techniques to take them and make something which, when skinned using other permitted materials, makes nice hulls.

This leaves me saying that I do not think we can so easily ignore construction technique and only talk about materials. In some sense, all materials have properties given to them by construction and manufacturing techniques, and the difference is only whether we purchased them already modified and called them "materials", or used our own techniques at home to modify them.

[Lester]

materials shall not be: expanded, foamed, honeycombed"

Just to be a little academic (smile), this phrase must be understood to be talking about what the material *is*, not how it is processed. We are thinking that we ignore all matters about processing, that is, construction techniques, and we focus only upon material properties, so that is how this phrase must be interpreted.

If we do not ignore matters about processing, then this phrase can be interpreted to mean two things -- what the material is, and also how it may be processed. In this case, all my thought experiments fail, because they were exactly intended to take a material and expand, foam, and honeycomb it.

[Robert Grubisa]

I strongly believe that we should not list any construction techniques. They are currently unrestricted and it should be like that. 3D print is just one of available additive manufacturing techniques.

We [should] restrict materials

Hi Robert

Hmmm, restrict materials, de-restrict construction techniques? An interesting suggestion, very attractive. In this discussion, I explore only permission for 3D printing while retaining all other existing rules to see where we can go. It is a very different discussion for me whether we can also eliminate or rephrase other rules to do with metal, wood, resin, etc etc etc.

RG: Construction techniques are unrestricted subject to the compliance with D.2.1 in the current IOM Class Rules. So we are not de-stricting construction techniques.


And now, the "But". Let's have some thought experiments. I take a permitted material, perhaps a thin aluminium sheet, I cut the sheet with short slits, pull the sheet apart, and bend it over a plug. I take another permitted material, perhaps a piece of bamboo, and in my workshop I chop it into fibres, throw them into a little boiling resin, stir vigorously, and then pour the result into a mould where it cools. I take another permitted material, perhaps thin strips of cedar with cross-section 1 mm x 1mm, and with incredible patience I glue these strips together using staggered spacer pieces 4 mm long at 4 mm intervals with just a micro-drop of cyano-acrylate as they lie over a plug or lie inside a mould. The materials were not and are not expanded, foamed, or honeycombed, they are perfectly solid and so permitted. I have used permitted construction techniques to take them and make something which, when skinned using other permitted materials, makes nice hulls.

RG: I am waiting to see such boat, and I am curios why nobody made it so far. Maybe because "incredible patience is needed" Lester, I think that the risk of a problem is very small.

In some sense, all materials have properties given to them by construction and manufacturing techniques, and the difference is only whether we purchased them already modified and called them "materials", or used our own techniques at home to modify them.

RG: Agree. Why we should be worried about that? Maybe I am missing something important here.

Robert Grubiša
CRO 68