calling all fibreglass experts

kdf

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I need some advice on how easy/difficult it would be to build a removable cockpit locker in fibreglass. My boat is designed for two of these lockers but the manufacturer want's to charge me a small fortune for them. I can borrow two existing lockers from another boat and the idea would be to make moulds out of the existing ones and build two new lockers (port/starboard are mirror images of one another). The lockers have lots of curves plus an opening lid.

Not being an expert in fibreglass I need any advice on how feasible this is.

thanks
 

vyv_cox

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It is possible, of course, but I would seriously question whether it's worth doing, firstly because there is considerable skill involved and secondly beacause of the time and money involved.

You will need to make separate moulds for each locker. From the sound of it these need to be at least three pieces each, two for the complex locker itself and one for the lid. This is a minimum, it could be more. Having made the split moulds they need to be flanged accurately. There is a risk that you will damage the lockers you have borrowed during the mould making process.

Having made the moulds you need to lay up the new lockers, trim them, clean them up and add fittings. Lay-up is not something that you get right first time and there is a very real risk that the finished article will have defects and will not match for colour. I have built over 40 canoes and many other articles in GRP and could certainly not guarantee to produce a perfect article, even from existing moulds.

Finally, the cost of the resins and other components is not insignificant and you need more than twice the article weight to allow for the moulds.

Having given you the negatives, if you have plenty of time and are prepared to accept the challenge, I know that it can be done. If you charge your time at all there is no way it will be economic but maybe you could sell some more to other boat owners to defray mould costs?

The big GRP suppliers can provide useful booklets and probably websites nowadays. Try Strand Glass and Glasplies, no doubt Google can find some more. Good luck.
 

kdf

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Thanks for the extensive reply. I still believe it's worth it although I may end up getting some local grp shop to do the work. The cost of the new lockers from the manufacturer is over 1000 pounds each so this way is still probably cheaper.

So that I understand the process fully - I can take an existing locker, strip off the lid, hinges etc, coat it in some release agen (can I also seal the entire locker in shrink rap to protect it?) then lay on fibreglass mat , allow to set and then separate the two. Lay some additional mat on the inside of the new locaker, trim and make good all the edges etc then apply gel coat to the exterior.

Have I got it right?
 

vyv_cox

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At 1000 GBP each I would think it would pay to have them made, unless they are enormous.

Very basically you are correct about the process. You need firstly to ensure your plugs (the old lockers) are in near perfect surface condition. This rules out any form of shrink wrap. Then polish with wax and usually a release agent also.

The simplified process is to apply gel coat, coloured as required. When set, lay up glass and resin to the desired thickness, wait until it partially sets, trim the rough edges, then wait some more until it cures and release the completed moulding.

Making the moulds is quite complex. For a simple shape, say a canoe, you need to make two half moulds which have to be flanged together accurately. My normal method is to make the hull half first, add the flanges to this half, then lay up the deck and its flange in one. This is a lengthy process. For a more complex shape with re-entrant curves you may need the moulds to be in more than two pieces, the worst I ever say was a rocking horse that had an eight-piece mould! Then you drill the flanges for subsequent bolting together, then separate the two parts from the plug. Now lay up the finished article inside the mould, by a virtually identical process.

It sounds easy if you say it fast. It's a very messy procedure for the beginner, temperature control is important, some safety considerations but not too arduous. It is very rewarding but don't underestimate the effort involved.
 

oldsaltoz

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Hi there KDF.
Have you considered making the lockers from a composite such as foam? It’s a lot simpler than making complicated moulds and I would think cheaper as you don’t have the expense of left over moulds.
Take the measurements and profiles of the lockers, reduce them by the thickness of glass and filler you plan to apply and reproduce them with foam, it’s easy to cut and sand to any shape, apply your fibre glass, sand it, and apply a coat of filler and sand that, then coat it with a polyurethane paint in a colour of your choice.
Avaniceday Old Salt Oz.
 
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