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Author Topic: moulding a fibreglass hull from a abs one  (Read 5982 times)

Ian Robins

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moulding a fibreglass hull from a abs one
« on: June 19, 2011, 10:09:56 AM »

Hi all,
I have a soling 1m yacht that i brought from a uk supplier, the kit is produced in the usa.
My hull has started to split after 5 years of almost constant use, the rest of the yacht is fine.
my options are
1 buy a new kit from the states.. not now availiable in the uk
2 mould from the abs hull in fibreglass
3 try to get the shape of the hull, so i can make a plug in wood and make a fibreglass hull.

i would like to have a fibreglass hull as i believe the hull will be longer lasting

thanks in advance

ro88o0
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Subculture

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Re: moulding a fibreglass hull from a abs one
« Reply #1 on: June 19, 2011, 10:40:01 AM »

Ethically, you ought to seek permission from the supplier of the original hull before making any copies, even if it's for your own use. Some will be cool with it, others won't.

nhp651

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Re: moulding a fibreglass hull from a abs one
« Reply #2 on: June 19, 2011, 10:47:04 AM »

you could almost certainly repare your own hull using a mixture of finely chopped "chopped strand" matting and polyester resin.

you can find this advertised at http://www.glasplies.co.uk/   and can be applied by mixing with resin and painting into the inside of the hull with brushes addapted to paint into the spaces.

neil.
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nhp651

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Re: moulding a fibreglass hull from a abs one
« Reply #3 on: June 19, 2011, 10:48:46 AM »

OOOOps sorry, just notices that your hull is a Styrene /abs hull....please defer the last instructions....abs and grp just don't mix at all.

sorry.
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grasshopper

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Re: moulding a fibreglass hull from a abs one
« Reply #4 on: June 19, 2011, 11:41:16 AM »

I reckon if it's only to prolong the life of the model, spare hulls not being available, moulding a single replacement for your own use only shouldn't be a problem.

With it being ABS / stryene, you'd have to be careful that any heat created whilst any kind of curing takes place doesn't distort the hull.
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tobyker

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Re: moulding a fibreglass hull from a abs one
« Reply #5 on: June 19, 2011, 11:25:56 PM »

Maybe it would be better to use epoxy resin rather than the polywhatnot stuff.
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Roadrunner

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Re: moulding a fibreglass hull from a abs one
« Reply #6 on: June 20, 2011, 12:45:30 AM »

Epoxy is one of the worst for heating up while curing, (good stuff just gets hot!) you will need a slow drying resin to not deform the hull with the heat given off during the curing process, Polyester resins can fill that need but there not really the best not actually being water proof with out a protective gel or wax coat.

If i was honest ( haha normally am) i wouldn't bother not with ABS anyway, not a great material to cast off lot of issues and even the so called experts cant get it right all the time, you have a few other options, one would be to make a full plug of the hull taking measurements off the original and create a  plank on frame or a foam plug coated with p38 to get your mould off of, and then cast a hull with a gel coat using epoxy resin.

Expensive and time consuming, and that's if you have the ability's to copy the hull accurately for the original,

 If it was me i would just be careful with the boat, dents and scrapes can be sorted with p38 and a touch up of paint. and when it finally is time to retire her, just buy a whole new (different) yacht, there are so many hulls out there you can buy of similar shapes, the chances are you may be able to take the sails and running gear of the original and put on a new hull, if its a IOM  size then you will have no issues finding replacement hulls, fairwind (800mm) classes are out there too, there are also a ton of other hulls, A class J class ( at cost) and all the other shapes i have missed.

You must be aware that some boats were not designed to live forever, (you find most abs boats are cheaper, for the main reason to get people to buy cheap = profit for many nowadays) ... and it would be foolish to think an abs hull will live as long as a GRP hull under normal use, (the regularly bangs and bumps) given the cost of many yachts ,kits and blank hulls out there i'm pretty sure you can find a 'similar replacement' or have a fresh start with 'salvaged parts'.

Don't get me wrong abs hulls can live forever if taken care off but really its a poor material to make any boat of sizes over 500mm, anything over i would be expecting wood, laminated or GRP cast.

Well that was long winded (and probably didn't make any sence)... you can ignore it, i'm babbling tonight!
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CF-FZG

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Re: moulding a fibreglass hull from a abs one
« Reply #7 on: June 20, 2011, 07:51:12 AM »

Epoxy is one of the worst for heating up while curing, (good stuff just gets hot!) you will need a slow drying resin to not deform the hull with the heat given off during the curing process, Polyester resins can fill that need but there not really the best not actually being water proof with out a protective gel or wax coat.

That doesn't sound right - in my experience of using resins over the last 30 years, (mainly professionally), epoxy never gets hot - polyester on the other hand can get hot enough to set on fire! 

The only advantage for using polyester resin is cost, it's a lot cheaper than using epoxy.


Mark
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Roadrunner

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Re: moulding a fibreglass hull from a abs one
« Reply #8 on: June 20, 2011, 08:30:53 AM »

Epoxy will get real hot when curing especially the quick drying one's, polyester gets hot too and has that fire risk if not used correctly but using slow cured resins tend to reduce the heat build up, i suggested polyester for the cost reduction on making a one off mould, no point using epoxy for 1 hull mould.

For someone who's worked with GRP for 30 years should know that epoxy resins or polyester cures by Endothermic reaction 'heat' being the bi product of that, slow curing is reduced but do get quite warm, and in this case enough to warp or damage an ABS hull.

Pretty much ALL boat hulls are polyester built (full size ones) for the shear cost reduction, and using a combination of a gel coat, a waxed '' internal'' skin (water proofing a porus resin :o)  and 2 part epoxy based paint, standard paint, anti fouling paint's etc to the outside can protect a some what inferior cheap resin to do the job that epoxy can do without the extra.
Epoxy can be laid on top of polyester but not the other way round, since it can de laminated at the surface, they do not bond well together.  

Either way its pointless to argue (since im right  {-) :P ;D)... ABS being used as a plug to cast with epoxy or polyester not a good idea risks to high of failure and damaging the original , as i said best to just retire the boat and start with a new hull of similar shape or style. 100 on avg for a reasonable hull from a good stockiest, none of that imported rubbish from china.

RR but in a mad mood this morning  %%
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triumphjon

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Re: moulding a fibreglass hull from a abs one
« Reply #9 on: June 20, 2011, 08:36:59 AM »

im in a similar situation with a seawind & been thinking of making a grp hull from it , having used polyester ive tried a small section of my now removed deck which didnt melt or distort during  cure ! currently the hull has been braced with some quarter inch square pine until i decide the best route .
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Subculture

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Re: moulding a fibreglass hull from a abs one
« Reply #10 on: June 20, 2011, 04:19:44 PM »

slow curing is reduced but do get quite warm, and in this case enough to warp or damage an ABS hull.

No way a GRP laminate epoxy or otherwise is going to get hot enough in model form to do owt to an ABS hull unless you go pouring the resin on with ladle. If you want to make a very cheap and dirty mould, just use plaster, unlikely there are any undercuts in a yacht hull so the mould can be one piece.

Epoxy resins also have a much gentler exotherm than epoxy- they usually take longer to cure, although once cured the laminate is much more stable.

CF-FZG

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Re: moulding a fibreglass hull from a abs one
« Reply #11 on: June 20, 2011, 08:27:28 PM »

Epoxy will get real hot when curing especially the quick drying one's,

If you're getting epoxy hot then you're doing something seriously wrong!!

that epoxy resins or polyester cures by Endothermic reaction 'heat' being the bi product of that, slow curing is reduced but do get quite warm, and in this case enough to warp or damage an ABS hull.

Both resins cure by chemical reaction  In addition, epoxy is an endothermic cure, and polyester is an exothermic cure.


Endothermic which means it needs heat to cure, and therefore cannot give out heat.

Exothermic which means it releases heat as it cures.
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grasshopper

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Re: moulding a fibreglass hull from a abs one
« Reply #12 on: June 21, 2011, 12:11:45 AM »

I reckon if it's ABS / stryene and you'd want to make a mould from it to create a fibreglass hull, strip it back to a bare hull, float it in a container of cold water, fill it with cheap plaster and leave to set. when it's all set and solid the plaster will make sure it doesn't flex whilst you make a female mould for fibreglassing.
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