Advice needed

[Streethawk!]

Well I am almost finished my foam buck for the nose cone of my Streethawk replica and the other day I had a crack at doing something in fiberglass as practise and well it turned out like a dogs dinner. I am seriously worried about fcuking up the proper Streethawk one, can anybody give me any advice that could help me, or an explanation on how to pull a female mold off the buck?

Much appriciated

[Davi]

might help to know a bit more details about what problems you had first. Also a pick of the buck to guage complexity.

One thing that's certain - the quality of the buck is EVERYTHING at this point, it needs ideally to be better than you expect the finished item to be - painted to a mirror like finish etc.

Once that's done, you'll need to work out close lines first, and stick on some fillets to create the break points, prep the buck firstly with some wax and mould release agents (if it's only small, you can use a non-silicone wax from a good furniture polishers, I tend to use between 3 and 8 coats depending on complexity, then 4 or 5 thin coats of hairspray)

Edited by Davi on Tuesday 7th August 21:35

[Streethawk!]

Ok, Here is a side shot of what I have, I put the lines in to show other people of a different forum what I have left to do.

Here is what the finished article should look like, I am only on the nose cone though lol;


Basically what happened is that I tried the fiberglass stuff on a smaller very simple shape, I got the outer mold fairly good, then a while after when it came time to pull the finished piece out it was stuck in the outer mold, I used gelcoat and all. But it just became stuck inside it ???

I am thinking of covering the buck in skimcoat and sanding that down to a perfect finish when its ready to be molded off. I will probably have to mold it in two pieces though am I right?

[Davi]

If it became stuck inside, it's most likely either poor prep work - release wax and agents are usually the first things to suffer on a "quick test" - or you didn't allow for an undercut somewhere. Once you have finished the plug I wouldn't even consider trying to set a mould until you have put a few coats of paint on it and wet sanded to a mirror finish. I wouldn't use polish on it as paint polishes tend to have silicone in them, which causes beading of the release agent (be it hair spray or "proper" release agent) just go straight to release wax.

What release stuff did you use on the test piece and how did you prep it?

Looking at it you might get away with 2 part mould, just split down the middle, but its hard to tell without having it in front of me, I reckon 3 or 4 could possibly be needed - size isn't important in deciding number of mould parts, complexity and curves are.

[Streethawk!]

Somebody who I was talking to informed me that any wax would do as release agent, including beeswax. He was probably talking BS but thats what I used. The same person told me that since its just a test piece there is no point in applying anything to it, just leave it as foam and attempt to mold from that. Im guessing thats a load of horse sht though
In regard to the fairing here are clearer pics of a genuine fairing from the show that went on ebay;


and another one;

Since on the first two pics there is only a split line down the middle I would be assuming that it was molded in 2 parts rather than 3 or 4.

Do you think that applying a few coats of paint straight onto the foam would do? The reason I am asking is that to repair bits on it I have been using spray foam which is quite porous and I doubt paint would adhere well to it. I would be thinking about using something along the lines of applying skimcoat onto it and then painting it?!?!

Thanks for your help, its very much appriciated.

Edited by Streethawk! on Wednesday 8th August 09:22

Edited by Streethawk! on Wednesday 8th August 09:23

[Davi]

Streethawk! said:

Somebody who I was talking to informed me that any wax would do as release agent, including beeswax. He was probably talking BS but thats what I used.

he's not far off the truth - you can use most waxes, but that's not the end of the matter, you need a further "agent" put on top of that for predictable results. You can use either a proper release agent which is often blue or as I say above, hairspray!! The point is both are water soluable, so when you come to release the mould if you have any problems you just dunk it in warm water, wait a bit and pop it straight out. Which comes back to why I mentioned not using a wax with silicone in it - the silicone wont let the agent or hairspray stick to it, so it just forms patchy coverage and can cause problems. Beeswax may or may not contain silicone depending on brand - I actually use a beeswax / carnuba (sp?) wax mix.

Streethawk! said:

The same person told me that since its just a test piece there is no point in applying anything to it, just leave it as foam and attempt to mold from that. Im guessing thats a load of horse sht though

yes that is horse shit. There is no point testing something unless you are going to use the same proceedure as when you do something "properly" as you'll not know what's gone right and what's gone wrong. Use any test as practice - you'll need it

Streethawk! said:

In regard to the fairing here are clearer pics of a genuine fairing from the show that went on ebay;
[snip]
Since on the first two pics there is only a split line down the middle I would be assuming that it was molded in 2 parts rather than 3 or 4.

tricky one - yes you probably could get that out of a 2 piece looking at the pics. I'd personally go for 4, splitting it also down the outer edge of the flaired section - probably unnecessary, but I hate buggering a plug and mould for the sake of an extra join...

Streethawk! said:

Do you think that applying a few coats of paint straight onto the foam would do? The reason I am asking is that to repair bits on it I have been using spray foam which is quite porous and I doubt paint would adhere well to it. I would be thinking about using something along the lines of applying skimcoat onto it and then painting it?!?!

Thanks for your help, its very much appriciated.

I'd skim then paint from the sounds of it - can't hurt to skim it, might hurt not to!

[Streethawk!]

Thanks for your help Davi, I have also been told told that there is a far easier method rather than using skim-coat and paint, You just cover the buck with a single layer of fiberglass and that forms a hard surface which can then be primed/painted after of course being surfaced. Any thoughts on that?

[Davi]

Streethawk! said:

Thanks for your help Davi, I have also been told told that there is a far easier method rather than using skim-coat and paint, You just cover the buck with a single layer of fiberglass and that forms a hard surface which can then be primed/painted after of course being surfaced. Any thoughts on that?

no problem mate.

yes that is a very good way of doing it, either with a layer of GF tissue or even just the resin (which is all bodyfiller is - resin with a load of talc as a bulking / sanding agent) depends on the complexity and quality of your "basic" buck as to whether I'd agree with it being easier. A skim can be easier to sand and take up greater depth of mistakes in one swoop, but if your buck is looking good then there isn't a lot in it - depends what you are better at working with.

One distinct advantage with laying up a layer of thin glass over it is it strengthens the buck as well - but you aren't working with the largest part in the world.

I'd say have a play around with some test pieces. Nearly all my stuff is quite old tech and passed on to me by people who... may not be quite up to date, shall we say. I've just taken what I've been taught and adapted to a style I find easiest.