Fiberglass options

I am planning on making an IOm using the german latex/rubber method. Seeing that IOM’s cannot use carbon and what not. How should the arrangement of layers work out for fiberglass? Does fiber orientation play a roll as it does with carbon fiber (not nec. on boat hulls but many other things). Just curious what weight fabric to use. Thanks for your help.
Andrew Miller

Have you thought of using a glass/nomex sandwich? Very light and stifff.
Don’t know if that’s class legal thou…

really wanted to make it carbon since I dont plan on actually sailing in IOM events, but figured that would hurt me down the road in case I got into it. Im not sure if that configuration is allowed, Ill look over the rules and in the mean time if anyone has any further knowledge feel free to add to this. Thanks in advance for the input.
Andrew Miller

There are hundreds of combinations and methods. You can either ask around and copy some one elses lay-up schedule, or strike out on your own.

Good Luck![:D]

Im relatively new and Im trying to get an idea of some of my options, can you recommend and sites, or other material that may be able to help my decision?

Do you have info on glass/nomex sandwiches, never really though of it until you mentioned it.

I would forget about any sandwich type of construction for an IOM. The rules only allow glass and resin, with the lay up being transparent except for the outer surface gell coat, or wood. NO exotics. Your best bet is to use glass woven twill and lay it up at 45 degrees to longitudinal. Twill has no bonding agents to hold the weave together and ‘moves’ over the mould. Use epoxy with this. If you try to use epoxy with fine chopped glass matt, then the strand bonding agent won’t allow the glass to ‘wet out’. Polyester resins are OK with chopped strand as the solvent deals with the bonding agent.




I can’t really pick for you, one way over another as it does come down to style, tools, time, money and money and did I mention money?

There are holes even in the IOM rules which are probably the tightest of any class going today… exotic being an indefinite term.

If you wanted a hull that was the lightest possible, and still met the “criteria” probably a divinicell core glass sandwich would be the best for weight to strength. This is a “fiberglass” hull, but it would be cost prohibitive in the first place, and the amount gained would be negligible.

Honestly, if you took the money that you would spend on the most high tech hull and super Gee-whiz everything… and just built a quality boat… the amount left over you used to take time off from work and went to the pond EVERY DAY and practiced with it… you would be MUCH faster than you would be with a Super Hi Tech boat and only a few times at the pond.

Believe me, an hour a day turns into more time each week, and then as if by magic one day you just start to under stand your boat and what makes it faster and BANG there you are.[:D]

As of right now the only money being spent would be for materials for the plug. All the carbon is left over from big boats and the vacuum bagging materials are more or less being donated. So it might actually cost more to build a hull out of something other than carbon seeing that the material would have to be bought. Thanks for the input.
Andrew Miller

Andrew -

repress your urge to use “big boat” materials - even if free surplus. In most (all ??) cases they are specified for certain scantlings as imposed by warranty, sailing and weather loads, insurance and other factors.

9 oz. glass, chopped strand mat, etc. as example are all used for big boats. These are way overkill for something 3 feet in length. Likewise, using 5.8 oz sail material for a model boat will result in stiff sails that won’t shape in a light breeze. I wouldn’t dream of using anything heavier than 4 oz. cloth - preference given to 1/2 and 3/4 oz. stuff for model boats. If you are looking for experience in laying up cloth, you can always purchase clothing fabric from a local fabric store and it will have similar layups as the exotic stuff but at 1/3 the price.

Not sure what your intended outcome is to be - but 6 oz. carbon used in a 40 foot boat is inappropriate for an IOM sized model. Remember, the heavier weight the fabric (class or carbon) the coarser the weave of the cloth. The coarser the cloth weave, the more resin needed to fill in between the fabric fibers. The more resin used, the heavier the weight of the final hull.

I don’t want to seem like I’m preaching - but why would you spend your valuable time building something too heavy and non-class legal? It’s like the guy who wants to end up with an IOM valued at $1500 but doesn’t want to spend $15 on a set of plans… just doesn’t make sense!

Dick Lemke
F-48 #US-06
MultiONE #US-06
Class 3 Landyacht #US-196

Im not sure exactly what the surplus is, but im sure it is relatively light seeing that it is for a 20ft A-class cat as well as some of the accessories, such as tillers and what not. Once I find out a final deicision would be made. I might not trying to build and “expensive” boat im trying to build a less expensive boat with what I have access to, I understand your points though.
Andrew Miller

Not sure where you are located, but here in the US only Performance Catamrans (aka Catalina) is building “production A class” cats, while Morelli & Melvin are doing semi custom stuff.

My guess is they are most likely using 4 oz to 6 oz weight carbon for hull layups and perhaps 3 layers.

1k x 1k 2.5 oz x 40 inches wide carbon cloth will run around $48.00/yard retail.

If you are “down under” then there are “production” boats being built down there - or in Europe and are probably of a similar weight of materials.

Glad you understood my point - stress and loads are a big larger on an 18 foot (not 20) cat as compared to your IOM design.

Dick Lemke
F-48 #US-06
MultiONE #US-06
Class 3 Landyacht #US-196

i have been building IOM class boats now for almost 15 years. mostly my own designs. as you can accept. most boats were not fast. others were better. what you need to understand, and i think dick pionts is out. you are building , basicly a 3 foot boat. what works on a 20 footer.does not neccasarly work on our scale. my last hull i pulled from my mold. wieghed 199 grams. and that is with deck installed. but no fin trunk. the glass i used was a 3 step system i lay down a coat of just resin. then layed in a coat of resin / 3/4 oz. then finaly a 4 oz matt. this I have been told is overkill. but so far my hulls have not broken. I too have played around using “surplus” and learned. what I would like to see, is for you to biuld one. get out in the water and see what YOU need to improve. basicly just like i did. nobody is going to laugh at you.
good luck

long live the cup and cris dickson

anything lighter than 6 oz CF is real expensive and unlikely to have been used on big boat projects.(I don’t think andrew as given us a weight of his CF cloth)
The total cost of glass for a IOM is most likely less than $20.
The pulley you will put on the stern will cost more than that.
I don’t see any "savings " here …sorry.
I wouldn’t waste my time with VAC bagging either…I have found that with care and experience I can hand layup with similar glass/resin ratios and avoid the expense and hassle of Vac bagging.


I know in my case, the “left over” carbon is not cloth. The scrap is trimmed from parts and is already cured. You might want to find out what you are getting as far as scrap. Also, I assume that if you are getting the pre-preg that you have access to the oven and the vac system as well… since without all of the above you won’t get’er done. [:-angel]

where did you find the web site for german latex building method. I am worried what I might find if I do A goggle search for it.


here is the link

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