I need to sorta replicate this part

[TassieBloke]

Hi All,

It has been a long long time since I posted here, and much has happened in the meantime.

Anyway, to matter at hand.

I need to sorta replicate this part in fibreglass with some alterations to the size.

Since I know nothing about fibreglassing (yet) I seek advice on how to go about it.

I thought it might be best to build the exact sized part from plywood (or similar) and then make a plug (if that's the right word) from that. What concerns me the most is how to replicate the flange in the plug since this really must be exactly the same width etc to match on the topside area its being attached to.

Any comments are welcome

Cheers,

Tassiebloke

[JPA Cate]

What's wrong with it that it needs replacing? Why not clean it up, paint if necessary, and re-install?

[TassieBloke]

Hi Ann,

It no longer fits. It needs to be about 30mm higher and about 300mm longer.

Tim

[jimbunyard]

Originally Posted by TassieBloke

Hi All,

It has been a long long time since I posted here, and much has happened in the meantime.

Anyway, to matter at hand.

I need to sorta replicate this part in fibreglass with some alterations to the size.

Since I know nothing about fibreglassing (yet) I seek advice on how to go about it.

I thought it might be best to build the exact sized part from plywood (or similar) and then make a plug (if that's the right word) from that. What concerns me the most is how to replicate the flange in the plug since this really must be exactly the same width etc to match on the topside area its being attached to.

Any comments are welcome

Cheers,

Tassiebloke

More information would be helpful, but from your description, we can make some preliminary assumptions...

Since the flange needs to match the original to fit, the 'alterations to the size' must refer to either the convexity or concavity of the 'protrusion' in the center.

If this is the case, then using the old one to make a mold, (probably the easiest for conventional construction, [female plug mold, gelcoat, followed by layup]) is out of the question.

Much depends on your resources, the function of the cover, and your desired level of cosmetic appearance for it.

If you have room on the inside, and you don't need the mirror finish of a sprayed-gelcoat-followed-by-layup-female mold construction (difficult and time consuming), probably the easiest method would be to mask off on the deck where the mounting flange seats, make a mold out of (if I estimate the size correctly), ideally, 1/4" coosa board or similar, and glass over that in situ, leaving the 'mold' in as reinforcement, even glassing over the interior after removal to make it superstrong if desired. That would also cut down on the outer layup schedule and resin requirements.

Less ideally, one could use 1/4" or so plywood as the mold/core for the almost the same (slightly heavier, less rot resistant) result...

That of course leaves finishing, and this is where the most time will be spent using a 'backward' method of construction; if you want a mirror finish, time spent here is directly proportional to the 'mirroricity' of the finish...

The 'raw' glass surface will have to be filled by troweling on a mixture of the appropriate resin and glass beads, probably 2 or three times, sanding between each to achieve a smooth, paintable or (gelcoatable) surface. Then priming and painting (or gelcoating, though if you use epoxy many people [me included] would say gelcoating over epoxy is a no-no).

There are many ways to skin a cat though...

[El Pinguino]

I'd be thinking of a 'jumboise' job...... thats when they lengthen and often widen a ship.... works on big ships... should work on your bit....

Cut thwartships and longitudinally into four bits.... insert new bits to make length you require and depth you want.. use this as the plug for your mould ...

Sounds complicated and probably is....

Have I ever done it... nope

Good luck.

[Scaramanga F25]

Follow El Pinguino or: make one out of smooth stiff cardboard wooden sticks and duct tape
to fit. Use underside as a mold. Use thick wax to round off the inside corners and paste wax to the cardboard.
You have a female mold.
Gelcoat, mat and cloth to thickness desired. Let cure.
Soak in water until cardboard is removable.

[coastalexplorer]

AS a retired Engineers Pattern maker producing a part like this would be very simple...However I see that you are down under in Australia. So that changes things?

How successful I could be at directing you from Western Canada becomes a rhetorical question. While another two questions would be how adept are you at wood work? and do you have the same materials in Australia?

Within the British Commonwealth there are many versions of the English language and terms are different. In Britain counter top laminate is called Formica. In Canada & the USA the similar product is called Aborite. It is available in basically three thicknesses. Post forming is 1/16" thick General is about 2 MM and institutional is over 1/8" you can buy it with a high gloss finish that is protected by a peel able cellophane protective film. You only really need the post forming grade. often builders stores will sell slightly damaged sheets at a discount. and you should not care about the colour or pattern. should choice be available white, red, or Black would be the preferred colours.

Do you have a mill-board product there called MDF? Here is is cheap and available in thicknesses from !/8" to over one inch. 1/4" or 5/16" thick would be most suitable.

Start by building a frame the dimensions of the flange in Hardwood. Cut a rebate in the face of the stock the depth of the desired flange thickness. into the frame build the geometric 'Box' of the desired fibre glass cover. glue it all together. making all the dimensions of the female shape to the out side sizes of the finished cover plus the thickness of the plastic laminate that you acquired. Then cut corresponding panels of the laminate and glue them in with contact adhesive. Water based is easiest to use it lakes a bit longer to dry but worth the wait. Shape up a rounded end of a cheap putty knife and screed in light weight body filler into the corners to make fillets. striking off the excess just before it cures. these can be sealed with a coat of epoxy resin or urethane paint. the mould thus made needs several coats of mould release wax.

If you have done all this correctly you should be able to lay up the part and have the minimum of clean up afterward. or you could source a company that makes fibre-glass mouldings and contract them to do it. in a similar way you could contract a pattern shop and have them make the mould for you, however DIY can save you a lot of money IF you can do it your self.

[Cadence]

I would use the existing one as a mold not a plug after adding the what ever size changes you need by cutting plating and filling the gaps with thickened resin. Parting wax the hell out of the inside and flange. Lay up your new one from the inside.

[Cheechako]

Bees wax is available in sheets and various thickness. You can lay it on that part and glass up a female mold.
If you need to change the size, you can do that crudely on your old part before the bees wax to make it different. (Bondo, foam or etc) Then lay up the new fiberglass part in the thin mold you made. By using the female mold, the surface will then be nice and smooth like the old one.
Use some plywood pieces on the mold to keep it rigid etc. You can laminate them on or use bondo etc.

[Wulf]

El Pinguino is on the right track. Relatively easy to cut, taper edges, then set up and support in the desired configuration. Next connect across (on the backside) the resultant gaps with backing that’s stiff enough to work on and that won’t melt from contact with resin being used. Finally fibreglass to join it all together and then grind/sand/paint etc to final finish. Sounds worse than it actually is. Just take your time and think the steps through beforehand.

[hellosailor]

Since it is mainly "bent plates" it might be worth getting a couple of cheap sheets of foamcore or PVC plastic sheet, sold in hobby shops or art supply stores, or even using some corrugated cardboard or artists mounting board, all of which can be easily scored and bent.

When they are sized to fit, tape of brace them to hold the correct bends (slit the surface and the bend will take cleanly) and use epoxy resin to coat the bend. When it sets, you've got the bent plate. Recheck for fit, and if it is correct, apply a thin layer of fiberglass cloth and resin to wrap the core material. If this is non-structural, it is quite possible to use corrugated cardboard and simply saturate it in resin, then paint it white with a good opaque paint afterwards, no FRP cloth needed.

Obviously some consideration has to be made in advance to match up thicknesses, but that's just math, and finding materials of the right thicknesses.

You might also be able to get a metal shop to simply bend up two pieces of aluminum or steel plate, tack weld or rivet them together, and do it that way. "Give me a copy of this in metal plate" and then just paint it.

[Dymaxion]

Great advice here, thanks for when it's my turn. If you could sketch "on top" of your photo where the 30 and 300mm enlargements need to occur I think it may help get better answers. Styrofoam used below grade (on basements) is fine grained and carves well. Usually pale blue or pink around here.

[guyrj33]

Clean up the part and pull a mold off of it.
That will give you the flange area, then modify the mold to your new dimensions.
Pulling the mold will be easy if you vacuum bag it.
All the usual caveats apply.

[El Pinguino]

Originally Posted by guyrj33

Clean up the part and pull a mold off of it.
That will give you the flange area, then modify the mold to your new dimensions.
Pulling the mold will be easy if you vacuum bag it.
All the usual caveats apply.

Pull two moulds off it....

Cut first mould as I suggested above ^^^^ and pull apart to make correct outside dimensions...

Cut bits out of second mould to fill the gaps in first mould

Stick all bits together to make mould of the correct dimensions.....

[billgewater]

See hellosailor's comments above.
If, and only if, it is acceptable for the purpose, you may consider having it made in aluminium (alumina to foreigners). Having all flat surfaces, and utilizing folds, you may get what you need with minimal effort and cost. One edge seems to have a gentle radius which can also be done readily with thin sheet metal.
Some welding or even riveting may be acceptable. Maybe even stainless steel. Every suburb has quality sheet metal workers available. They could probably make it from off cuts! Just take the item to the workshop with your new dimensions and discuss it with them. You will at least get a finished product quote and tradesmen quality.
Yes, painting is an issue, but car body repair guys may do a super spray job that saves purchasing resins etc. and hand sanding. It's a fraction of the price. (Although using a suitable aluminium grade you may never need paint at all - just for cosmetics?) They make masts from aluminium don't they?
The original item in FG presumably came from an well engineered mould and was presumably produced in large numbers keeping costs down. To create a mould for a one off item seems a bit of a waste of effort if not money. However, if FG is definitely needed, then there is lots of advice above. Remember that if you increase any of the dimensions then you may require an additional increase in material thickness ..... depending on what loads the item takes in use.
If the item has a walk on surface i.e. it is used as a step, then gluing a non skid synthetic surface such as grooved rubber etc. can allow you to avoid much surface painting and effort and make the item an improvement on the original. If a flat surface is expected to take body loads, then underneath the load surface you can simply rivet some alloy angle bar to stiffen the surface. Easy peasy.
I also noticed that your item appears to be held in place using through bolts or screws through existing holes. This would imply that aesthetics were not paramount so by using a thicker alloy on these edge bits you could use recessed holes for the screws or machine bolts or whatever you use. You could thus improve the aesthetics!