DIY Fibreglassing Advice?

Hi, I might look into getting my hands dirty soon and building some DIY fibreglass horns in the vein of the Terror Tops by James Folkes.

Has anyone got some basic advice for what products to use and how to best go about it.

I have a fair idea how to get pairs of tights to fit over a frame to get the shape I need, but more interested in how to best approach making the structure solid by embedding rope or other items or is this not really necessary if I use enough layers?

Its for a single 10" flare in my custom wedges (so please dont recommend I just buy a janaudio unit cos that wouldnt be suitable)

Thanks

Stu

Hi Stu, I'm a bitbaffled on how you plan to use the pair of tights to give you your mould shape. If you want to have a repeatable model, you will need to make up a pattern in wood or plaster, or some other solid medium. Or do You propose to lay the tights up with matting first, then use this as your mould?. Having been a laminator, mould and pattern maker,I would suggest a more solid pattern to start with. The weight of the matting will distort the tights, and you'd wind up with a soggy masswell out of shape.
I have used paper rope as a former for reinforcing,with an extra layer of matting tolay over the top of the rope, this gives a very stiff support, and does work well to hold grp flares in shape, and helps to prevent the horn from distorting with time. I did have a few 30 year old radial flares I made up, and they were still in good shape. The lay-up was 4 oz, with double overlap at the edges, andbatten formers across the top of the mouth. But this was after making a solid pattern first.(Paper rope was actually used for formers as reinforcement of the decks of allTyne Canoes back around the 70's).
If you made up some cardboard forms and covered them with thick pvc sheet, sealed the edges with selotape, you could at a pinch use this for a mould.
As you said, the process is extremely messy!. Barrier cream, thick rubber glovesand loads of polythene sheetspring to mind!.
Do you plan on forming the driver mounting as part of the flare?. Loads more complicated if you wish to do this.
If you want a good surface finish you will need to use gel coat as a first layer, before laying the matting on with lay-up resin.A metal laminating roller wouldbe an advantage for removing air bubbles from the matting.
If you're close to yeovil, or southhampton, you'll be able to getthe above locally. If you need a bit more help, tell me what your plans are, I'll help if I can.If you're close to shaftesbury, we could meet up. PMme for details.
Enjoy the rich smell of polyester resins and catalyst, and above all, avoid ingesting the catalyst, it's bleach about 50 times more concentrated than domestos, and if you leave some on a rag, it's liable to spontaneously combust!.
Happy Building!.

Stu, Here's my bit. If you have a shape, you could start off with a wooden main frame that has your throat size and exit mouth, and of course the length you require. Using body filler, you can then develop your shape and measure as you go, this method teaches you quite a lot about shape versus response. All A.S.S. horns have been done like this since '75.
when this is done you can then mould your pattern from it, knowing that it already works.

Simonr - see this thread

www.speakerplans.com/forum/forum_posts.asp?TID=9422

Hi Stu, Very interesting method, and would work very well structurally, but as Tony pointed out, if you haven't tested a prototype, how do you know how it will sound?. Are you going to go for a rough copy of an existing flare that you know sounds ok?. I'm just interested to find out how you propose to approach this!.

Yes its a flare model that I have built out of wood and confirmed as the final model, I could very well stretch the lycra over the inner frame of this, fibreglass a few layers on the inside, then hopefully the structure would have enough rigidity that I could remove it from the frame and add more layers to what would be the outside.

Reckon that would work ok?

Stu

If you've got ply sides all round in the shape of the flare,you will have to put a release layer on the surface first. I think the lycra will allow the resin to seep through, and you'd wind up with a ply former covered with a glass fibre coating permanently attached. You will be better off making a mould from your original first. Then take flares off the mould. They would have a much better surface finish, and would be an exact copy of your original, and so sound like the original.

Ok well what would be the best substance to take a mould from?

I really am quite a novice at this fibreglass thing!

My girlfriends brother is at Soton Solent Uni studying boat design so I expect he knows where to go to find the materials for fibreglassing but just trying to get a handle on the best materials to use and the right approach for speakers (rather than boats)

Stu

Hi Stu, sorry I haven't got back to you yet, but I'll post a few thoughts a bit later on. I've got to go and earn some pennies. More later tonight.

Stu, If you make your prototype with wood and filler to give you the required horn, this will be good enough to cast your mould. After sanding every thing to a fine finnish, you should then polish with a special mould release polish and then coat it with mould release agent. In production you don't have to be so fussy, as regular use builds up a protective barrier. On new moulds straight out of the prototype, I always double up on the polishing procedure, just to be safe.