Foam Hull

[Jamestj]

Can I build a hull out of expanded polystyrene and still comply with the class rules?
If the hull was strenghthend with a space frame of thin wall alluminium tubing is this still permitted?

Please help, many thanks

[edmorales]

can it handle the load of the standing rigging? as well as the stress from the sheets to the sail winch servo

[Jamestj]

Hi Ed.

I understand from Fred who replied to another of my questions that expanded polystyrene is a foam material so I could not use it. I should have read the rules! When reinforced with aluminium tubing, foam would certainly take the load of the rigging.

Anyone out there, - is it allowable to use a thin walled aluminium tubing space frame to reinforce a GRP hull? If it is, why does't anyone use this method of construction. It works well in formula 1 racing cars.

Many thanks

[awallin]

Hi Ed.
Anyone out there, - is it allowable to use a thin walled aluminium tubing space frame to reinforce a GRP hull? If it is, why does't anyone use this method of construction. It works well in formula 1 racing cars.
Many thanks

both metal and GRP are permitted for the hull. a combination is also permitted.

I think the reason nobody uses this is that if you really wanted to save weight with this kind of construction the GRP shell needs to be very very thin and thus fragile. I think this kind of construction could hold up to the forces encountered while sailing but it would be very fragile to handle on land + even at international events collisions do happen

[Muzza]

Maybe the Class Rules section is the wrong place to continue this thread, but I too have been pondering the idea of using a space frame - either alloy or laminated light ply, to accept and spread the rig loads in a light hull. It brings to mind Ron Holland's "Imp" (and IOR 40 footer back in 1977) which used the spaceframe concept succesfully.

I note Anders comment re fragility of the hull, which may well be correct. It would be a neat experiment though.

[Arvin S.]

Maybe the Class Rules section is the wrong place to continue this thread, but I too have been pondering the idea of using a space frame - either alloy or laminated light ply, to accept and spread the rig loads in a light hull. It brings to mind Ron Holland's

Murray,

On the contrary I think it is "the best" place to discuss what you guys are talking about It is the best place to learn and to ask and to help out with questions about our class.

I couldn't find anything on the rules (I just scanned it) against metal or aluminum in the hull, and from what you described I imagine that you are going to use the frame as a "bulkhead" to reinforce the area around the "chainplates" where the shrouds are and maybe even support a deck stepped mast. If this is the case I think this is all legal.

As for James' question about Polysterene, I think that if you shape the foam like a surfboard then fiberglass it, and then melt the foam with acetone that would become class legal. You don't want the foam anyway coz it will just add weight. The nice thing about IOM which might not be too nice with your experiments James is that the minimum weight requirements makes all boats virtually equal when it comes to weight, coz even if you had a paper thin fiberglass hull, you will still have to bring it up to minimum weight when all is installed, adding corrector weights if necessary.

TTFN
aRvin

[Jamestj]

If I ran into something, the 2kg lead bulb would keep on moving and crack open the hull. If I had a section of thin walled aluminium tube connecting front bulkhead and keel it would prevent this. Similar bracing connecting standing rigging would let me run it nice and tight so that wind in sails will have negligible effect on the bend in the sail.

Built robots but never built a yacht before. Am I solving a problem that doesn't exist?

[awallin]

If I ran into something, the 2kg lead bulb would keep on moving and crack open the hull. If I had a section of thin walled aluminium tube connecting front bulkhead and keel it would prevent this. Similar bracing connecting standing rigging would let me run it nice and tight so that wind in sails will have negligible effect on the bend in the sail.
Built robots but never built a yacht before. Am I solving a problem that doesn't exist?

I don't think many people design for crashes where the hull stops dead and the bulb would be free to move. at most waters the bulb will hit the bottom first and you have no problem with strength of the keelbox as long as it is of similar or stronger GRP than the hull.

As for supporting the attachment points for shrouds and the forestay/jib, that is done in most boats.

take a look at this for how it looks like on an Italiko:
http://el-servo.physics.helsinki.fi/per ... ltrunk.jpg

most boats also have either a alu-tube, wood, or dyneema lines that run from the jib attachment point to the bottom of the hull for support. If I remember correctly the TS2 does not have this but it has a piece of wood running all the way under the foredeck(in an "I-beam" configuration)

[spaldi01]

I’d like to challenge your idea of building a foam IOM

Foam is a good material to work with but the rules state that the hull may not be constructed out expanded foamed or a honeycombed material. Therefore a foam hull would not be allowed. However if it were the volume of an IOM is about 0.02m3 (guess) and the density of foam is at least 20Kg/m3 so the weight of a hull constructed out of the foam would be at least 400g before anything else is added. Using traditional construction methods it is already possible to build a completed hull around this weight.

Aluminium can be used without restriction and would be better than wood because it has a higher strength for a given weight. I would suggest that wood is however used more widely because it is easier to work with than metal and in many instances it is good enough

To be successful an IOM needs to be fairly tough. After all you don’t want to travel 100 miles to race to suffer equipment failure in the first race and go home. Using some ultra light construction technique you may be able to save 100g in hull weight which will enable you put a 100g corrector weight at the bottom of the hull. This will increase the righting moment by less than 1% which is good but if the cost is a fragile hull its not IMHO worth paying.

A long time ago I remember seeing photo of a beautiful 36/600 constructed of solaflex (model aircraft wing covering material) stretched over a very light wooden frame. This technique could be used to construct a very light hull using permitted materials although the hull shape would be somewhat dictated by the construction technique

Have you also considered making a foam plug covering the plug in glass fibre then removing the foam afterwards. It would be possible to make a hull very quickly using this method allowing you to explore your ideas.

Keep up the good work

Chris

[fred]

http://www.bleu-cerise.org/vrcpassion/C ... oques1.htm


here are pics of 2 foam built ioms, with 2 different technics, both with melting foam after moulding...

Thanks to Gilles for hosting the pics on his website:

http://www.bleu-cerise.org/vrcpassion/

[Chairman]

http://www.bleu-cerise.org/vrcpassion/C ... oques1.htm

Bonjour Frederic

Merveilleux! Merci bien!

[fred]

I designed both boats, Velox with Lester's excel sheet... This boat was built in the USA, it is not my building, nor my pics...

Vermine is a all by myself "dining room" built boat... I failed the fin, which is a little twisted, so I must make a new fin before really testing the boat...

[Gyula]

Here are some questions from an outsider (when I started sailing I built an IOM-Little wig-, but soon I realized that our country is Naviga member, not ISAF, so I sail with it in the Naviga F5E class)

Can anybody explain me what could be the purpose to forbid the foam as building material? It is not an expensive or high tech material like kevlar or else. It is cheap, easy to work with, could be perfect for home build.
The original purpose of the class rules were to make a samaller and cheaper boat. This is why carbon masts cannot be used for example. Interesting, but a carbon fin, which is permitted, costs more than five times the price of a carbon mast...

Gyula

[Chairman]

Can anybody explain me what could be the purpose to forbid the foam as building material? It is not an expensive or high tech material like kevlar or else. It is cheap, easy to work with, could be perfect for home build.

Hi Gyula

Your question and observations deserve a careful answer. My, ah, unofficial opinions...

In a number of areas, the rules seem to prohibit something, a material, say, or a method of construction, which at first sight reasonable people would think should not be prohibited. The reason for the prohibition can often found in the fact that, erm, "unreasonable" people would be able to exploit what is permitted in an undesirable way. I put quotes around "unreasonable" people, because it is not intended to be offensive or make a judgement. It is intended instead to identify the kind of person who seeks to push the envelope, to find unexplored or unexploited areas of performance improvement, to squeeze and stretch the rules to the point where they almost, but do not quite, break. I'm probably one of these kinds of people!

On the specific issue of foam construction, a foam-built hull could offer me a number of places where my envelope-pushing could become "unintentionally" illegal, and it could not be verified what I had done. So to prevent nasty accusations of cheating, and to permit effective inspection by anyone at any time, the hull materials and construction methods are restricted accordingly.

The original purpose of the class rules were to make a smaller and cheaper boat. This is why carbon masts cannot be used for example. Interesting, but a carbon fin, which is permitted, costs more than five times the price of a carbon mast...

Yes, and this was an unfortunate "error" right at the start of the class, when it was not appreciated how much of a performance gain could be obtained by super-thin appendages. Some years ago, when the trend became apparent, RSD asked the DMs to vote on a class rule change to restrict thickness and/or materials. The change was defeated.

I put "error" in quotes as well, and for much the same reasons. It is only an error when seen with perfect hindsight. At the time, the suggestion of a 6% fin would have been greeted with incredulity -- "every one" knew it wouldn't work and could't work. I find a similar incredulity even today when I speak to full-size designers: "Your fin thickness is what? You are crazy, it can't work!"...

There is gathering interest, again, in a rule change to limit thickness. I would expect to see such a proposal to be put to the World Council, and thus to the Owners, in the not-too-distant future.

[edmorales]

decades ago,carbon fibre,mylar kevlar etc. was once exclusive for the mil, space projects, F-1 teams and sorts. but now it can be purchased readily and cheaply compared to say, 10 years ago.any chance that it will be legalized in the future?
just curious
ed

[cfwahl]

There is gathering interest, again, in a rule change to limit thickness.

Just so nobody misunderestimates the Chairman: the rule proposal referred to would limit "thinness" or (in other words) establish a minimum thickness; right, Lester?

Charles Wahl

[Chairman]

the rule proposal referred to would limit "thinness" or (in other words) establish a minimum thickness; right, Lester?

Hi Charles

Yes, exactly so. And just so no one misunderstands what is going on here, let me summarise:

It is a near certainty that the issue of fin "thinness" will be put to an owner vote by the IOMICA Technical Sub-Committee at some time in the not-too-distant future. The issue has never been decided by IOMICA. Some years ago, the RSD TC asked DMs to vote on the issue, and the idea of introducing a minimum fin thickness was defeated. Since then, a background debate on the issue has nevertheless continued, and the intention of bringing the matter to an owner vote will be to expose this debate, to make the pros and cons clear and accessible to all owners, and to then allow IOM owners to have their own say.

Questions like this reach discussion/voting stage on the World Council agenda via two main routes. One route is from the IOMICA Executive Committee and the IOMICA sub-committees, who have their ear to the ground and who raise relevant matters for action. In the last few years, the Technical Sub-Committee has been particularly busy giving official advice and seeking official interpretations. In particular, the IOMICA Technical Sub-Committee maintains a list of rule changes it thinks are worth bringing to the attention of IOM Owners and are worth voting on. In due course, the list will go to the WC and owners for voting. Any NCA is free to approach the TSC and ask that a rule change be considered for inclusion on the list, and this is the other route. Any NCA can raise matters with the Executive Committee, any IOMICA sub-committee, or in the World Council.

[Gyula]

Dear Lester

Thanks for your answer.
I brought up the foam hull question because I just finished my foam boat, which is a slightly modified a Triple Crown, but it will sail in Naviga races where the foam hull is permitted. As I wrote you some time ago, I made it on the kitchen table, with very-very low costs. The most "expensive" was the 50 gr/sqm galss cloth to cover it. Here are a few pictures photo.1, photo.2.

a foam-built hull could offer me a number of places where my envelope-pushing could become "unintentionally" illegal, and it could not be verified what I had done

I suppose one of these would be that a glass coated and painted hull couldn't be veified for material content.
Well, the same sitation occures if I build a balsa hull, (permitted? yes), cover it with glass cloth (permitted? yes), paint it (permitted? yes), and I obtained a hull that again cannot be checked for material content, even if I made only permitted things...

Gyula