Hi all,

I'm just starting down the route of building a large oven for use of prepregs etc but for the time being I need to epoxy wet lay projects such as this and for that matter I'm not sure I would even be able to get hold of a low temp cure prepreg from the materials I need to use.

The project is small sidecar fairing much like an F2 Racing Sidecar only a kart sized one that is raced on kart tracks. Its about 1.5m long and has a fair amount of shape. Top end speeds are 60-70mph on larger kart circuits. There tends to be a some body contact and your average polyester/gelcoat fairing tends to look crap after only a few meetings due to the cracking nature of the gelcoat as the bodywork flexes and takes knocks from the other tricycle bumper cars! 

The bodywork needs to have some flex and 'give' at the extremities whilst being fairly sturdy around the middle part and mounting points. I guess the nearest other subject would be a white water racing kayak or similar. I will achieve this by use of multiple materials (Glass, Diolen, Carbon) where appropriate. I know I cant expect something that gets abused like this to look great forever or last forever but keeping it looking fresh for as long as possible would be preferable.

Sorry if that was all a bit long winded but once people have quizzed me about my intended use I would have ended up writing it all in the end anyway.

So...... I want a black surface finish, dont want to paint it and dont want carbon on the outer skin (looks great but is dangerous in a heavy accident). First thought it to use black Diolen for an all over first ply. I will never get this layup to stay down everywhere so will bag it, being a fairly big job I know that I'll end up with dry bits/air bubbles here and there no matter how careful I am partly due to not being able to get a coat of resin to stay on the released mould first. I have some GC50 epoxy compatible clear gelcoat but after doing some tests I'm sure it will de-laminate/crack after some impacts.

Next thoughts are to use fumed silica to spray some thickened resin onto the mould surface as a thin epoxy gelcoat which will most likely end up looking milky? Then I'm thinking maybe just add black pigment as well as the silica or will this go grey rather than black?

Any got any experience with this or have any thoughts or ideas how else I could achieve a decent looking but hardy  black surface on my mobile battering ram?



My mould and pattern

Sorry for the delay in replying, its a bit hectic round here.

Thanks for your thoughts and opinions guys, you make some very interesting points, some of which have crossed my mind also, some that hadn't. Agreed, keeping in mind that once in varying layups the performance of the reinforcement changes somewhat and I reckon they'll be a lot less in some places than others. One thing for sure is that I can never expect a component that 100% ticks all the boxes but the nearer I can get to that the better. To some degree it's going to have to be best guestimation for now and an element of ip-dip dog s**t. I like a bit of R & D and if I end up building a few fairings on the way to get the best recipe then so be it. It's all a good learning exercise, I'll be doing some more test pieces and going for the main lay up asap. I've left it too late to order some extra materials I was going to play with so I'll just  dive in and make 'something' as a starting point from what I've got. I have black and white diolen, glass and various carbon cloths. No pigment. I will either have a punt later today or maybe order a few more bits monday if I dont progress is that far today. I need to get on though as time is short and the clock is ticking.  

I have toyed with the idea of a removable nose and I reckon it's a great idea, it will also aid the transport situation as well so definitely on the cards but probably not for this first one, grafting repair sections in could be done if needed. I would prefer to break bodywork than bend the mounts on the chassis.

One thing I'm finding pretty annoying is that on a couple test pieces there has been alot of air entrapment within the black diolen I fancied as a top ply. This has been on a piece with a decent result on surrounding glass and carbon  areas. The glass is a loose plain weave 200g, carbon tight plain weave 120g and the diolen is a reasonably loose twill 200g. I wonder if its something to do with diolens polyester based fibre?

Sun exposure will probably be less than 20hrs per year so the gloss finish dulling is not a biggy for me. Are your boat hulls painted Fasta?