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Can anyone point me towards sites with good step by step guides on how to make fibreglass parts or give guidance and suggest suppliers to use?

I've got a rough idea of what I want to make, but I'd like to see what limitations there might be. The plan is to fabricate a cold air feed box to the inlets on my PI, so it has to be quite wide, approx 500mm (19.5") long, clip onto a backplate and probably have two inlets to the bottom, which the pipes from the front of the car would attach to. Hopefully I could make the plug out of a heavy foam (plant arranging stuff?) as it would probably have to be destroyed to release the part.

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I was lucky to find a company whose business is glass fibre constructs in my town.

The owners are very kind and were willing to sell me resin, hardener and other chemicals, lengths of glass fibre cloth and matting off their rolls, at trade price.  Even more valuable, they would advise me when I had a problem.

If you can find a firm like that near you, make friends!

 

John

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That would need to be made in three pieces, the airbox itself, and then the two pipes.

 

I would construct a plug out of wood for the shape of the box, or i believe you can use some kind of foam, then make a mould, problem would be getting the fabric to smooth round those curves, i never mastered that, i also use far too little hardner.

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Smooth fabric... I reckon you are either dealing with really small sections of fibreglass which takes forever or you go for much larger straps going around the surface. To hold to the curve you need it have enough holding strength past the curve. I think longer sections.

 

Forgot how tricky this can be.

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Steve,

 

I think you could simplify the construction of that airbox.   Making it in three peices, main body and two inlets (?) means that they must be joined together after they are made, which is always a weak point.

 

If you positioned the inlets so that the diameters were in the same plane as the diameter of the outer curvature of the box, then a 'fence' all around the plug in that plane would allow you to make it in two parts.  One part would be the outer, rounded part of the main body with the outer part of each inlet, while the other would be the inner, oval part of the main body and the inner aspect of the inlets.    Then, the joints between body and inlets would be as strong as possible, and not where strain will applied in use.

 

I would suggest a further vertical fence at one end of the main body, so that the mould can be sprung open to release the part once it is made, else getting it out will be a problem!

 

Are you familiar with the 'fence' idea?  It's a flat flange, at right angles to the surface of the plug, so that you can make a mould in two (or more) parts.  The mould will have flanges that match the fence and are fixed together when casting a part.    Such multipart moulds allow you to make complex shapes without destroying the mould afterwards top get the part out.  The mould I made for the roof of Silverback was in seven parts!

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make the mold shape out of firm cardboard layer over it then use hot water to dissolve the cardboard or form  polystyrne to your shape layer up then dissolve the styrofoam with solvent.the grp will shrink when dry so will be difficult to remove if layered over a hard object so yo could use the inside of a large diameter tube. when dry it can be removed from the center. several suggestions from a friend of mine who built bodies for lotus and Watsonian sidecars

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The radii on the top of model I drew are probably a lot greater than I would want to use. The basis of the outline size at the moment is the readily available baseplate, JC55 from ITG, though as this is only a flat bit of alloy with fasteners at the top I might end up making this myself also.

 

It would be a lot simpler to modify an existing box, but I have not been able to find anything suitable yet, anybody got any links?

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Sometimes its nice to cut out the middle man.....

Go straight to mold.

If a mold isn't needed to be kept.

Laminated sides/ a 90 degree is required, from base plate?

Often these things are led by fixings, if any.

And those tube sections , fixing,approach with caution?

From memory, didn't Dave fabricate an  air box?

One way would be to approach the task, by setting up a mold that you could strip down, after, article was laid up, if the sides are to be 90 degrees.

If at least a 4/5 degree angle could be accepted, a mold that didn't.

If i class the open side as the top, the opposite, side , that is joined to all others, as bottom, and others as sides.

I would then attempt to join the four sides, thinking how i would allow base plate to sit, very easy possible channel,allowing for thickness of material to be used, as of course this join is facing up.

Fix to the base work board, usually thicker, with outer facing  brackets.

Work board , depending on profile of curve/dome, would need to be laminated, covered, or alike.

So now i would have a shoe box type shape, dimensions decided by base plate sitting on top surface.

If i want to explore the shaping, i could then picture the curves, and make a template to apply filler, being my choice, others use clay, plasticine........

Using filler, i either search for a curved item, that has same profile, which sees me raid kitchen,

work areas and i am deeply ashamed to say, even ....

I've used washers, lids from bottles.....

Applying the filler to the required areas, with sourced, or fabricated , item gives a relatively stable finish.

Although, laminated surfaces and filler........and a mold that strips down.

 

After, deciding the curves, mark , drill, loads of holes, countersink slightly on other side, apply filler so that it has grips, ie, work it in, which invariably requires certain shaped utensils. Best to seek beforehand, and bare in mind with the catalyst to filler ratio.

If i want to be able to detach all four sides, i would also need to cut into the filler, with a sharp pointed knife, when the filler is rubbery, again, thinking of catalyst to filler ratio.

Or, incorapate a non stick "card" in each corner. And ones running full length, middle line of filler. The filler, i use, isn't immensely strong in thinish areas.

After using 80/180 grit, and applying a few more layers, of filler, i would hope to have a reasonable shoe box type shape, with outer lines of required shape, in place, sat into the bottom.

Take these sections apart. Depending on accuracy of cut/cards, wooden rims ,you might have some jagged joins.

Cello tape on edge (Reassemble, or not), filler, sand.

Reassembly. Sand.

Now add further outer sides, slightly taller. On the upper edges, an outer rim of battening.

The filler would need release wax, and just as a matter of course, i more often than not add release wax to laminated surfaces.

The filler I use, seems to absorb a fair amount of release wax.

I add to plastacine surfaces as well, but only very carefully, seems to help blend in.

If card is used for splitting areas on mold, cover in cello tape.

 

After article has been laid up,Carbon Fiber hopefully:) cured, trim/grind, remove battening, release from base? Detach sides?

 

 

A lot of the materials can be sourced for pennies.

After i have laid up main article, i would then add tube sections.

Laying up tube sections, would be in the region of, using CF, braiding, maybe. There appear relatively short, so, knocking up a releasable method should be comparatively easy.

I did see a carbon fiber pipe section, although molded in two halves. If suitably sized braiding was available, maybe a suitable surface for braiding over top, although I would like, all in one.

To, join, cut 5mm or above holes all over tube section, lay up on sanded surfaces, inside and outside, on tube section, to main housing.

The outside join would require attention if you wanted it to look really nice.

The outer join, would it be possible to fabricate an alloy plate, for one side, of sandwich join, and allow on battening stage, in building mold?

Could take up the middle thickness, and allow on battening, or, on alloy plate.

And, a consideration would be temperatures.

Certain resins are suited for heat ranges. Sometimes pre cured, heated.

A multi piece fibreglass mold would make it easier to attain a visually, quality finish on article.

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Meant to say.

 

Polystyrene foam is easy to model, if you want to make a plug.

No idea about flowere arranging foam, but it's very brittle and corners etc would rub off.

Problem with polystyrene is that resin melts it, so you can't lay the gel coat on, or get it off.

Nor can you get a smooth surface by filling it.

Same with cellulose paint.

 

But there is easily avaliable 'polystyrene primer' that acts as a seal coat, so you can overpaint with cellulose or other paints.

Then  skim with filler for a smooth surface.

 

John

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Thanks again for the information and links, it is appreciated. I'm trying to get this 'right first time' so I need to consider other parts of the air box now, e.g.

backplate - buy or make

how to seal and fasten air box to backplate

where to get grommets for the backplate to ram pipes for less than £8 each

where and how to route the air inlets from (stars)

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http://www.vaglinks.com/Docs/Misc/CarbonFiberHowTo1.pdf

http://www.vaglinks.com/Docs/Misc/CarbonFiberHowTo2.pdf

 

^ Deals with Molds as well.

 

http://en.wikipedia.org/wiki/Glass_transition_temperature

 

http://www.mcmc-uk.com/prod-data-sheet/sr-7900-abc-uk.pdf

 

Apolgies for not posting these earlier. Took me ages to find the  "How to's", not online at Home, and used the time to find on Data, then trace here.

Hope they are of some interest/use.

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My Nearest & Dearest gets West System Epoxy from CFS (for injecting into woodworm compromised antique furniture) and we buy IPA in bulk. Cheapest we have found for these two products. Dunno about their more general fibreglass stuff.

 

Richard

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Maybe its covered later on, but just to hopefully add....

each mold has thermal characteristics.

Resins can be cured with fast/ slow hardener.

The amount of laying up, that is possible, includes,  weight of reinforcement, the ratio of reinforcement to resin, the speed and reactivity of the resin, the temperature / humidity of the workshop, the thermal characteristics of the mold or  etc.

Hence why people generally use the two layer rule.

Even though these maybe factors more akin to Industry, its sometimes of benefit to be aware.

 

Edit.

may I ask, the design, is there any info on shape effect etc please?

My initial thought on fabricating my own, was using two sections of plastic tubing for mold, with base plate. Bow caravan, sort of thing.

 

 

 

 

 

(mmmbeer)

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Hmm, I could do with some guidance here. So far I have made a rough mould on which the two alloy air inlet pipes can fit.

 

foam3.jpg

 

 

My question is how best to lay it up? My latest thought was to lay a couple of layers of chopped strand matting all over the main body and leave it to cure and then cut out the holes for the air pipes, pop rivet them in place, put another layer of matting over both the inside and outside to add strength and help seal the pipes in place before a top/gelcoat layer.

 

Does this sound right or is there a better way? As far as I am concerned the mould is single use.

 

airbox2.jpg

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Steve,

If you read my article on GRP use, you wouldn't be so flummoxed.

 

Construct a 'fence' around the plug, that passes through the diameter of the ports.   Lay up the top half, the outer dome of the box and the the upper half of the ports.   Remove the fence, prepare the fence-face of the upper part and lay up the lower part on that.  You should make a half-fence on the lower part, so that the mould can be split in two and taken off the flange you have made.

 

I can't draw this in 'Paint', and my scanner is playing up.

Please aks if I'm not clear.

 

John

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That's it, Steve!

 

below, I've added to your picture the vertical fences I referred to, because if you incorporate that oval flange into the piece, then the bottom part will never come out.  Put the vertical, red ones ones on after you haveremoved the black ones!

 

You will end up with a mould that has three parts - top in one and bottom in two.

Before you disassemble the mould from the plug, drill the flanges.

Then take it apart and re-assemble with small bolts all around, and the mould will then be in perfect alignment.

 

I would suggest that if you want that oval metal flange in the final part, DON'T put it in the mould.

Add it to the final casting.

The table top it's sitting on will form a 'fence' and make a flange all around the mould, IF, and only if , you make it non-stick to resin first!

If that is a a melamine faced piece of blockboard, then all you need is some non-silicone polish - Maguars is best.

 

John

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Got the wrong idea in that first link. Thought the guy had actually made a fuel intake not air intake. Interesting though, what are the actual necessities of a fuel intake and the limits of carbon fibre. Basically it needs to withstand the pressure and be resistant to fire. Complete digression into stupidity.

 

Ahh Steve. Good luck on this project it looks like its getting complicated.

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