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Author Topic: How do I cast a fibre glass hull?  (Read 17716 times)

boatmadman

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How do I cast a fibre glass hull?
« on: November 13, 2008, 07:56:40 am »
For my next project I am thinking about building a mould to cast the hull in fibre glass. The trouble is, I dont know where to start, so, could one or more of you experts knock up a description of how to do it, materials required, type of epoxy/cloth, gel coats, mould release agents etc... the whole works really.

I have seen the thread on one off mould using newspaper and plaster, but I was thinking of a mould I could get more than one hull off.

Thanks in anticipation.

Ian
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #1 on: November 13, 2008, 09:02:38 am »
I am right in the process of making a production mould for a new lifeboat model at the moment. If you pm me with your email address I'll send you all the photos of the process so far with notes, as I would hope to put it on here as a thread once I have finished. Or if you are anywhere near Fleetwood, pop in and have a look and lend a hand. :embarrassed: {-) %%
No finer way of learning than hands on experience. :-))
 neil.
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boatmadman

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Re: How do I cast a fibre glass hull?
« Reply #2 on: November 13, 2008, 02:55:23 pm »
Nice one Neil,

I am in Barrow. Thanks for the invite, it would be useful to see the process as it happens. Practically, I am not sure when I could get over - will check it out.

Ian

email address removed on request - admin.
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andrewh

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Re: How do I cast a fibre glass hull?
« Reply #3 on: November 13, 2008, 04:28:52 pm »
Its only a 10 mile swim to Fleetwood!  When I last stayed on the front it looked as if I could touch Ulverston!

I will help as much as I am able - but have only ever moulded hulls directly over a plug  - finishing the outside as the hull surface.
I have never used polyester resin - only epoxy and papie mache :}

Using the boaters version of papie mache (newspaper and emulsion you can still make a female mould and make repeat hulls out of it in either glass-fibre or papie mache. 
The female mould needs to be strong, and papie mache takes time to dry out and develop strength and stigffness  - so I would suggest laying 3 or 4 leayers up over your plug, leaving 3 or 4 days to harden slowly, then sitffening and thickening the mould with thick CSM (chopped strand mat) and polyester resin - including moulding in a couple of stands so that the female sits securely when dry and upright.
andrew
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boatmadman

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Re: How do I cast a fibre glass hull?
« Reply #4 on: November 13, 2008, 05:25:31 pm »
10 mile swim, yes, wayy too far for me :}

I have seen somewhere a method that you lay a keel and frames, then fill the gaps with foam and cut/carve/sand to shape, then use this as a plug.

Anyone done this?

Ian
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andyn

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Re: How do I cast a fibre glass hull?
« Reply #5 on: November 13, 2008, 05:42:40 pm »
The bloke in the plans special with the T.S Astrid in it has, track him down, and you've got your answer

To be honest I'm just posting here to remind me of this, as i would love to have a go at it myself...
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #6 on: November 13, 2008, 05:56:02 pm »
I used that method, Ian, for the last boat mould I did, the Interceptor Pilot boats,from Safehaven Marine, but the problem with that was that no matter how well you get a good finish, the plywood cross frames tend to show up on the master mould even though you can't see them on the plug, and you have to then do a lot of cutting back on the mould with wet and dry.
The plug I've just done for the lifeboat is p on f because the boat is quite large, saving weight when you're moving it on the bench.but in the past I've used bread and butter in solid and shaped planks of both Obeche and even mdf. however mdf can only be sanded, and not wet and dried as even with plenty of coats of sealer, it still lets water soak in and then it balloons up and spoils the plug.......I've tried quite a few methods over the years and to be honest, the finest for making a plug has got to be ( in my humble opinion) solid or shaped bread and butter obeche.........it carves beautifully and sands perfectly.
Neil.
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andrewh

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Re: How do I cast a fibre glass hull?
« Reply #7 on: November 13, 2008, 07:20:08 pm »
JayDees schoner website shows exactly this in detail - can't find it now, I'm afraid

John, like me, takes the moulding directly from the plug and sails it, but you could do this repeatedly - I am about to make a second square-rigger off my Volante plug
andrew

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Ron1

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Re: How do I cast a fibre glass hull?
« Reply #8 on: November 13, 2008, 10:35:10 pm »
This is how I do it.

frame work,  fill with polystyrene and plaster, lay up matting and resin, leave to harden, you then have a base for your hull.

the last picture is what it looks like 1/2 way though. ;) ;)

on the water.
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martno1fan

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Re: How do I cast a fibre glass hull?
« Reply #9 on: March 25, 2009, 01:32:44 pm »
Hi Niel where in Fleetwood are you? i live in Blackpool i build my own plugs and moulds for fast petrol powered hulls ive just pulled the bottom and top mouldings from the moulds this past cpl of days.They still need to be trimmed some wet sanding here and there and then i can buff them up with some compound etc.I made the plug from plywood and balsa,the mouldings are made using polyester gelcoat ,resin and csm and cloth.
Mart
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stevext

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Re: How do I cast a fibre glass hull?
« Reply #10 on: March 25, 2009, 08:24:19 pm »
Hi
You can also use foam to make your plug,then cover it with high build primer (brush or sprayed) and rub it back to a very good finish.Remember the more effort that's put in now will be reflected by a better surface finish.I use divinycell foam  that's widely available in boat building suppliers due to the fact that the polyester resin does'nt affect it in any way and it shapes really well.Neil,what class of lifeboat are you moulding at the moment?

cheers
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Circlip

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Re: How do I cast a fibre glass hull?
« Reply #11 on: March 26, 2009, 12:34:15 pm »
Jelatong is the preferred paternmakers wood if you can get hold of it, similar to Obeche but finer grained.

  Regards   Ian.
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #12 on: March 26, 2009, 07:43:25 pm »
hi martin,
I live in carleton, just outside poulton, close to the Castle Gardens Pub.

Steve, the lifeboat I've just finished moulding is of the 51 ft Stromness (not what Vic Smeed called a stromness. he got the name wrong, that was a 52 ft boat) Barnett class boat.
This is it still with it's mould release agent still colouring it blue before |I washed it off.
1:12 scale and 51 inches long.
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stevext

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Re: How do I cast a fibre glass hull?
« Reply #13 on: March 26, 2009, 08:23:24 pm »
Hi Neil

Nice one mate,i take it that's a generous coating of pva release on the moulding......
A bit far away for me to have a chat over a beer though.

Good luck with the boat mate!

stevext
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #14 on: March 26, 2009, 09:18:00 pm »
not too generous, Steve....a spray coat in fact.
I'm a tight sod. {-) {-) {-)
where you based, steve.
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TCC

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Re: How do I cast a fibre glass hull?
« Reply #15 on: March 26, 2009, 10:29:57 pm »
PVA as a 'relase agent'? That's a new one on me. I've had 2 types, a tin of furniture polish (wax) and one was a liquid that you  applied and you'd got it right when it had a texture 'like a rubber balloon'. I never got round to using either back then as I was too timid.

But now it'd be a piece of pxxx. The hardest thing is getting the release agent right or planning the thing so there's no deep undercuts and the cast actually comes out of the mould. Some guys fix a car inner-tube-type valve on the mould and when the cast has set, apply air to the valve which slowly blows the 2 apart as air is introduced down the join between them... is that an old trick?

To the lad who got the frames showing when he filled between them with 'foam/plaster/etc' Did you give the master a coat of resin/filler over fom and frames and then sand that down to a finish?

My advice to newbies is cast something small first and get your confidence in your workflow before you tackle a hull but do like for like... if you're going to take a cast of a plaster hull mould, make your little piece from plaster as well.

Fibre-glassing isn't hard but you do need to do things fairly right... and the hardest is releasing the cast from the mould. To that end, my first hull would be a 2 piece mould with the join down the keel and with each held together during lay-up with bolts tightened with wing-nuts.
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martno1fan

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Re: How do I cast a fibre glass hull?
« Reply #16 on: March 26, 2009, 11:12:43 pm »
 hehe dont confuse pva release agent with pva glue lol,i use wax first then two coats of pva release on my moulds when laying the parts,the pva been water soluble comes in handy for any awkward parts that dont want to release ,put a wedge in then pour a bit of water in and it usually helps the parts release.Hi Neil i know where you mean so i take it you boat at fleetwood? you may have seen me with my hydro or heard it lol,shes doing around mid 60s mph at the min .
Mart
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TCC

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Re: How do I cast a fibre glass hull?
« Reply #17 on: March 26, 2009, 11:32:31 pm »
Quote from: martno1fan on March 26, 2009, 11:12:43 pm
hehe dont confuse pva release agent with pva glue lol

I Did! [as TCC sticks his hand up!]  ;)

But it's not as daft as it seems as watered down PVA (glue) is used over plaster/concrete as a sealer!

Talking of wax, I remember someone who reproduced the swipes he made when he applied the wax but on the casted piece... you could see them if you looked at the thing at certain angles.
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martno1fan

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Re: How do I cast a fibre glass hull?
« Reply #18 on: March 27, 2009, 09:56:15 am »
Ive built a plug from pva glue and brown paper when wanting to copy a part,it worked pretty well.The  orriginal one on right was covered with packing tape to stop the pva sticking lol.Only reason i did it was so i had a plug there if i ever needed a new cowl built if the orriginal got damaged etc.
Mart
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #19 on: March 27, 2009, 02:27:12 pm »
Yes that's the lake I use, Mart.
Only when it's flat calm and the sun on my face though ( about 2 days a year,lol).
I'm sadly a fair weather sailor these days, as I get fed up of knackered electrics that the salt water turns into frothing gibberish.
But next time I see a hydro down there I'll make a point of stopping. neil. :-))
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martno1fan

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Re: How do I cast a fibre glass hull?
« Reply #20 on: March 27, 2009, 03:26:49 pm »
Haha yea i know what you mean its not the warmest of places for boating when that winds blowing.Bye all means stop by mate,im normally terrifying the sailing brigade with the hydro  ok2,only kidding i tend to go when theyre not arround this things too fast to be dodging sail boats lol.Like the looks of your lifeboats they look pretty dam big  :o.Stick a strimmer motor in one it would go well with one of those and no charging batterys ,theres a guy local sells em cheap i had one in a vee when i first started with these things.
Mart
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stevext

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Re: How do I cast a fibre glass hull?
« Reply #21 on: April 05, 2009, 10:27:42 am »
HI Neil

I'm in plymouth,busy building some blue/orange boats that seem to be favoured by a few on here as subjects!
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #22 on: April 05, 2009, 12:59:20 pm »
ohhh! you lucky and wonderful man. :-))
I envy you being able to work on the full size rascals.
The nearest I will ever get is building models of them, being "one of those on here" that has a penchant' for likeing those red white and blue as well as orance and blue ones.
Is is asking too much for you to post some pics of your work on here or is that not allowed by your company....now that would be of interest to us lifeboat nuts. %% %% %%
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stevext

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Re: How do I cast a fibre glass hull?
« Reply #23 on: April 05, 2009, 07:22:41 pm »
Hi Neil

I could post some of my model moulding pics or send some to you if you like but alas i would'nt divulge any work pictures or information on the full size boats as client confidentiality is a part of the job and would certainly cause the loss of mine if i did!.I'd love to help any fellow modeller but my hands are tied (another hobby -oops!) ha h.a

cheers
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nhp651

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Re: How do I cast a fibre glass hull?
« Reply #24 on: April 05, 2009, 07:55:55 pm »
no probs, steve.
thought that might be the case.
neil. :-))
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