I'm wondering how much carbon fibre cloth (and associatedmoulding equipment) i will need to replicate a dual hull model boat i have, itwill need to be strong enough to withstand engine vibration & waterinteraction.

Should i be using just the plain cloth or put through afew layers of your kevlar / aramid weave?ill be putting some pretty fastengines in it & don't want it to..

a) break up under stress of hitting the water or

b) allow water to seep through - is this an issue? i havenot used carbon fibre before? if it is, how many layers do i need to use toensure waterproofing while still keeping it as light as possible?

It is approximately 50cm width x 50cm length * 100mmdepth

I live in Australia and i was wondering what the shippingto here would be - i live at hope island on the gold coast (QLD) the postcodeis 4212,

Thanks in advance,

Hi Bryce,

Carbon fibre, carbon/kevlar hybrid or kevlar would all make very good reinforcements for a model boat hull. The combination you choose is really about what properties you value most highly out of: stiffness, durability (impact resistance) and appearance. For out-and-out stiffness you would go for all or the majority of the reinforcement being carbon fibre. For the most impact/damage resistant hull you would go with all or the majority being kevlar and finally you may be considering what the finished hull will look like. Generally, kevlar (being a bright yelloe weave that will fade over time to a dark yellow) is not chosen as a cosmetic finish. Carbon/kevlar hybrid (like many canoes) is an attractove finish and so to of course is carbon fibre. If you're painting the boat then the appearance of the fibre is not really a consideration.

In answer to your specific points, if made correctly there is no way that a hull made from any of these materials will break up or be damaged by the impact of the boat on water and nor is there any chance that it will leak in any way. When I talk of durability or impact reistance of kevlar then I'm thinking really of high speed impact with rocks, other boats, bouys etc; in which case the forces could be huge and enough to clean-break carbon fibre reinforcment. Kevlar is incredibly difficult to 'clean break' and as such even in the even of such an impact, although the boat may sustain damage it is very unlikely to be destroyed/sunk. For this reason it's up to you what reinforcements you use in your hull. The more kevlar, the more invincible the hull will be but for a given weight it will be slightly less stiff than a carbon hull would be.

We supply a few professional and semi-professional RC boat builders and a layup that seems to work out about right is 200g carbon, 175g kevlar and 200g carbon again. This makes for a very thin laminate which would ordinarilly be too flexible so strips of 3mm closed cell pvc are included on the flat sections of the hull, in between the first layer of carbon and kevlar (on the outside) and the second layer of carbon on the inside. 3mm closed cell foam can be shaped using a heat gun (on a high setting) and the resulting 'sandwhich' panel makes for a very stiff and lightweight hull. Another customer uses 200g carbon, 2mm lantor soric, 200g carbon for his hulls. These are 150cm racing boats running incredible electric power (some details and maybe a video coming in the future!).

It's likely that you'll want to consider vacuum bagging or resin infusion for your hulls although, depending on how demanding your requirements are (regarding strength to weight ratio and surface finish quality) wet laying and then lining with release film before pressing car sponges or something similar into the mould to create some positive pressure on the laminate may suffice.

As for what you'd need to buy and postage to Australia, for a hull the size you're talking about you'd only be looking at a square metre of 200g carbon and a square metre of 175g kevlar plus a 50x50 peice of 3mm closed cell foam. To find the postage cost of any order just add the items to your basket on the easy composites website and then click the "Carriage Costs" button on checkout page.

I hope this helps but welcome any questions. I'm sure other readers of this forum will find the information useful.

Best regards, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

I think this is a simple question, BUT. I am refurbishing a plank on frame tug, some of the planks have shrunk so i need to coat the inside of the hull with glass cloth and resin.