building fibre glass hulls

[Alasdair AllanParticipant @alasdairallan37423]

Hi – I have a thought at the back of my mind about building another Clyde paddle steamer at some future point… i was wondering if anyone had views on moulding a fibre glass hull as a method of construction? I like the water-tightness of the hull I was able to purchase for my present project, but suspect trying to build a hull like this from a home made mould might be a masive task. Views welcome!

[Stephen GarradParticipant @stephengarrad28964]

Have a look at the start of Neil Howard-Pritchards last build of Barnett Lifeboats, he started by building the plug, to make the mould, to build the hull, and ended up doing two at once.

Perhaps someone could do a link, its beyond me I’m afraid.

Stephen

 

[Richard SimpsonParticipant @richardsimpson88330]

I’ve never done it but I’ve followed someone else doing it on forum threads.  Have a look at Neil’s lifeboat thread he did last year when he built two lifeboats.

You do end up with a strong, well sealed and sound hull but there is a lot of work to get you there.  If you think about it you basically have to build a wooden hull first to make your plug, then make the mould from the plug, then use the mould to lay the glass fibre.  It is a lengthy process and a lot of work.  The advantage though is that you can then use the mould to make other fibre glass hulls to sell on, thereby recouperating some funds to offset the extra work.

[Alasdair AllanParticipant @alasdairallan37423]

thanks – will consider, but as you say it sounds a lot of work! I suppose I probably just need to reassure myself that I can make a traditional scratch-built wooden hull waterproof instead!

 

[Colin BishopModerator @colinbishop34627]

Link to Neil’s topic here:

61′ Barnett class lifeboat

The hull construction starts quite a way in.

As Richard says, it is a heck of a lot of work, much easier to build plank on frame and sheath the hull in glass cloth.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Go along with that. A nice smooth hull only needs one layer of very fine glass cloth and resin to do the job.

Neil is a bit of an expert and makes it look easy.

I have made a fibreglass hull by shaping a solid hull from foam, painting it with a release agent, covering it with fibreglass and then scooping out the foam. The foam should come out fairly easily. There’s always loads of that silver backed yellow stuff in skips, in large blocks. It is useless for most things as its too soft….however for this purpose it great. Free and very easy to sand.

Ashley

[Alasdair AllanParticipant @alasdairallan37423]

Very interesting article in this month’s MB byColin Laugherne about his Atlantic Salvage Tug model. Particularly his method of constructing a fibre glass hull. I see he used polystyrene to create a former, covered that in builder’s plaster and then covered that in fibre glass, before digging out the polystyrene.  I wonder if Colin might be willing to explain a bit more about that process? I have a notion in future to build an enormous paddle steamer, and if I could master this process I would be interested one day in maybe giving it a go!

[Tony HadleyParticipant @tonyhadley]

Found this in a 1966 Model Maker and Model Boats magazine. I think the materials will have been updated since then, but the procedure would be similar.

[ashley needhamParticipant @ashleyneedham69188]

Alasdair. Didn’t I post the very same thing before you saw the mb article??

Making a Hull from yellow builders foam, toughening it up with paint and getting a smooth surface, then painting it with a release agent then covering it in fibreglass/epoxy resin. Smear with filler, sand smooth, dig out foam. For a big hull, leave some foam in place.

“Easy Composites” sells everything. Look them up. Other suppliers available.

Ashley

[Alasdair AllanParticipant @alasdairallan37423]

I was just thinking that just now Ashley- I do you a disservice there!

[Alasdair AllanParticipant @alasdairallan37423]

Sorry I am dipping into this site quite infrequently so am not recalling all the helpful advice that comes my way! Anyway, on the subject of fibreglass… like most people who have bought a caldercraft puffer, the keel is arching a little off the ground. Am keen to flatten bottom of ship and have heard that applying a little heat and putting weights in will achieve that end, but keen to hear if people have a view, before I attempt that one. Thanks.

[ashley needhamParticipant @ashleyneedham69188]

No probs Alasdair!

Dipping in now and again I can understand, and my mention of the ‘lost foam’ method of hull building was sort of just a one liner. It does work really well though and is relatively straight forward.

For my Sutcliffe Valiant battleship, I left the centre blocks of foam separate, wrapped in clingfilm, so that when the hull had been built I simply teased out the blocks, leaving a nice ready made compartment for fitting the gear.

Foam can be left in the hull to support, say, the bow or stern, so not all of it has to be cut out.

If you didn’t see the article I can mail you pictures of the process if you pm me your email.

Ashley

[Richard SimpsonParticipant @richardsimpson88330]

The process is not without numerous risks.  I would heat with hot water as it tends to be more controllable.  Be careful of any form of point loading as you can end up with ‘dents’ if you’re not careful.

I would sit the hull on a nice flat surface, support the hull either side to keep it upright with a couple of pillows, put some hot water in the bottom and a couple of weights such as a couple of bricks.  Don’t fill too much or the sides might sag outwards.

If the rise is very little I would be tempted to simply tape some abrasive paper to a flat surface and rub the hull backwards and forwards on it.  There is a danger with heat that you can distort the hull more than it is so gently and carefully does it.

[Colin BishopModerator @colinbishop34627]

I have written about the problem of GRP hull distortion on a number of occasions over the years both in the magazine and on the forums as I have experienced it with many of the kit reviews I gave done going back to the Caldercraft Talacre in 1985. It is a common issue and usually easily remedied with the careful application of heat as Richard suggests. In fact it was mentioned in the original Talacre instructions so Frank Hinchliffe must have been aware of it. It is not just Caldercraft kits that are affected.

When a GRP  hull is removed from the mould, it frequently continues to cure slightly for a while. This tends to bow up the bottom and for the sides to curl in at the top.

The first step is to correct the bottom by putting it on a flat surface, preferably wood which is an insulator. Then put another length of rigid wood inside the bottom of the hull and add weight to help flatten it. Then use a hairdryer set to high (NOT a heat gun!) and warm up the whole area along the bottom. You can warm it up safely to just about touchable. Leave it to cool, remove the weights and see if it is now flat. Occasionally more than one attempt will be needed but gently does it.

The top of the hull sides at deck level need to conform to the deck components in the kit, if you try and make the deck conform to the hull you are inviting all sorts of grief unless the deck is obviously wrong in which case you have already got the grief! The various sections of deck need to be forced into the hull at deck level which should usually be possible although it might be a tight fit. Check along the length of the hull that it is s fair run with no bulges. (I did find on one occasion that it was necessary to clamp a piece of stripwood along the side of the hull to help things along).

Tape round the hull and across the deck can help in getting everything in position and trued up. Then reach for the hair dryer again and run it along the outside of the hull. You might need to do this several times but the deck should end up as a slight spring fit inside the hull which will help when you come to fix it in position on the internal wood stringers that are usually fitted.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Hmm…perhaps hulls should be left in the mould for a day or two before getting de-moulded if its a common problem?

Ashley

[Colin BishopModerator @colinbishop34627]

Yes, if you are making it yourself but a manufacturer may have commissioned a short production run to maintain stocks. Many kit makers actually outsource their GRP hulls as they don’t have on site facilities to make them.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Playing Devils advocate for a moment…but you are paying good money for a Hull and should expect it to be reasonably faultless and not have to do any straightening work on it? You could easily ruin it by heating it up.

Ashley

 

[Colin BishopModerator @colinbishop34627]

Ashley,

If you had seen some of the stuff that goes into kits like I have, ironing out a couple of kinks on a GRP hull comes nowhere! Most hulls are OK but some do need tweaking and 10 minutes with a hairdryer beats the hassle of sending the thing back or asking for a refund. You won’t ruin it with a hairdryer. A flamethrower is something else of course.

ABS hulls are vac formed and if the process goes a bit awry then your hull could be paper thin in sections. Not obvious until you realise you can see daylight through it.

Some kits can be a good introduction into scratch building depending on the manufacturer’s attitude to quality control and we are not just talking small UK manufacturers. The quality of some big Continental manufacturers can be abysmal especially when it comes to wood which is frequently of poor quality. There are of course exceptions but many kits have been on sale for literally decades without fixing bits that don’t fit or renewing worn out white metal moulds.

There is one manufacturer who will promptly replace damaged or sub standard fittings but the replacements are just as bad as the originals – a new take on after sales service.

Often the principle is ‘send it out and see if the customer complains’.

An exception was the late lamented Model Slipway. I visited their premises when doing a report for the magazine and their quality control was excellent. You can see my report here:

The Model Slipway

Colin

[Tim CooperParticipant @timcooper90034]

Have to agree with you Colin. I have built Model Slipway Aziz and Tamar Lifeboat . No problems with the hulls or the rest of the kit.

A Graupner kit I built needed major surgery to get the superstructure moulding to fit.

Timv

 

[Author]

Posts