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[NoNuFink]

I've acquired a styrene hull (NO drawings) which I intend to use for experimental drive/construction and learning purposes.  Being just the styrene hull it needs frames and perhaps a keel adding to keep it symmetrical and rigid - probably before glassing, either inside. outside or both. 

Without drawings, making a correctly shaped frame is a bit of a problem.  Presumably a cereal packet former using trial and error is the way to go to produce a template?  I'm sure I've seen it done in a build log somewhere.  Can anyone give me a pointer?  Any other suggestions?

TIA

NoNuFink

[inertia]

One of these is a good start. http://www.ebay.co.uk/itm/High-Precision-250mm-Profile-Contour-Gauge-45mm-Deep-Decorating-Tiling-Template-/381359524030
DM

[Martin (Admin)]

 Soft metal template, e.g. Soldering wire.   

[Brian60]

You mention glassing. I think you will find that normal polyester resin will melt your plastic hull into one big heap of scrap. I'm not sure as I have never used epoxy resin, but you may be ok with that, but the stuff is expensive compared to polyester.

[Subculture]

Why do you need to glass it inside and out? A styrene hull should be strong enough to be self supporting.

Don't forget that until you add a deck it's a three sided box, but with a deck bonded in, it will become much stiffer.

[NoNuFink]

@Inertia - Good thinking - I've think I've already got something similar- somewhere.

@Martin - Another good idea I'll give it a try.

@Brian60 - I have no intention of using polyester.  I should have said that I meant epoxy. I've used it before.

@Subculture - As you say, it should be strong enough with just styrene but it's a bit insubstantial in places and glassing would make it a lot more ding proof - 'though I agree that inside and outside might well be overkill.  Some of the experimentaion will involve having no permanent deck so I need a good framework to hold the shape as there may also be a removeable entire deck. (If I can work out how to make it waterproof).

Thanks for the suggestions guys.

NNF

[MikeK]

Presumably the styrene will take glue in which case the way I ribbed a couple of yacht hulls was to laminate thin strips of 1mm ply around 5/10mm wide. Starting with the first strip glued with the aid of tape to force it to follow the curve and so on for a minimum of three thicknesses laminate, preferably 4 or 5. It ended up with sufficient bracing to the hull with little weight added This was of course in addition to keel plank and inwhales etc

Mike

[NoNuFink]

@MikeK
An interesting approach that hadn't occurred to me.  However I think the hull would have to fairly rigid to start with, as the hull is holding the wood into the correct curve.  In my case the opposite is needed.  i.e. the wood has to hold the styrene into the correct curve(s) so the bulkhead templates have to be quite accurate

I'm now thinking along the lines of adding inwales, keel, and a few bulkheads using cereal packet templates. Then glass the inside to stiffen/strengthen and then reduce the bulkheads to frames and add more wood as needed for construction/aesthetic purposes.

It looks like I may have to eat a lot of cornflakes.      ('though I'll certainly try the other two methods suggested so far.)
 
NNF

[MikeK]

Hi NNF
Yes that is how I did it ie have enough bulkheads to give the  rigidity with correct curvature.
When building a racing yacht I was also after achieving strength with least weight
Hope to see some pics of your progress. With no plans it will be a difficult job to make bulkheads to the right shape ?

[Plastic - RIP]

@MikeK
An interesting approach that hadn't occurred to me.  However I think the hull would have to fairly rigid to start with, as the hull is holding the wood into the correct curve.  In my case the opposite is needed.  i.e. the wood has to hold the styrene into the correct curve(s) so the bulkhead templates have to be quite accurate

I'm now thinking along the lines of adding inwales, keel, and a few bulkheads using cereal packet templates. Then glass the inside to stiffen/strengthen and then reduce the bulkheads to frames and add more wood as needed for construction/aesthetic purposes.

It looks like I may have to eat a lot of cornflakes.      ('though I'll certainly try the other two methods suggested so far.)
 
NNF

Why wood? As the hull is styrene, why not use styrene sheet? It cuts like thin ply or card and ordinary liquid model glue will bond everything.
Then it is all the same material so delaminating or cracking shouldn't occur.
You can make ribs & bulkheads with just a pair of scissors.

[w3bby]

Line with cling film and fill with expanding foam, remove foam when set, slice thin strips in appropriate places, glass for stiffness and fasten to hull.
Being an open hull the foam shouldn't deform it as all expansion will be up. You could also just spray ribs, less foam, less chance of deforming the hull.

[MikeK]

Line with cling film and fill with expanding foam, remove foam when set, slice thin strips in appropriate places, glass for stiffness and fasten to hull.
Being an open hull the foam shouldn't deform it as all expansion will be up. You could also just spray ribs, less foam, less chance of deforming the hull.

There you go ! That's why this forum is priceless ! There is someone just waiting with a logical solution. I've stored that tip away for future use

[NoNuFink]

@Plastic
Why wood?  Basically 'cos I prefer working with wood and don't like plastic. The styrene hull is only going to be used as a prototype for a scratch built wooden hull. However, I'm not going to waste effort drawing/constructing a wooden hull for what will be (propbably) be unusual construction which may not work.  I intend to experiment with the styrene hull to get things right.   The hull is a fair size, 8" beam at the widest part so the initial bulkheads will need to be a bit substantial.  However, the query was not about construction methods it was about getting the templates accurate.  The lack of drawings is a problem.

@w3bby
Brilliant! I probably wouldn't use the slices as bulkheads but they would certainly make accurate templates. 

Off to Screwfix now to get some expanding foam - Cheers

NNF

[NoNuFink]

Well that didn't go as well as hoped! 

First off, trying to line the hull with smooth cling film was impossible.  In the end I decided that a few dozen wrinkles & creases weren't that important.

Second off, I opted for the Screwfix rapid set manual foam canister.  The trigger spout mechanism was useless. - there was no mechanism, the trigger was just a solid lump of plastic moulded with the rest of the spout i.e. no moving parts.  Took it back and swapped for the standard manual foam canister which has a totally different spout.

I half filled the hull with foam and left it overnight.  In the morning it looked like the picture below (STOP laughing)

The beam had increased by at least 7mm so it would be no good if scale (it isn't so I don't mind).
16hrs after foaming I prized the foam out only to find that it had not set at the bottom of the hull.  I put it back in quickly and left another 24hrs,  I've just prized it out again only to find that, A) it still hadn't entirely gone off & B) the first prizing out had damaged the cling film and I now had foam stuck to the styrene.
"Oh sugar" was approximately what I said.

Of course, generally stuff that dissolves foam also dissolves styrene.  Luckily the stuck bit of foam had not entirely  set so I managed to remove it using Isopropyl alcohol ('though meths would probably have worked) and I am left with just a slight yellow stain. (In the hull, not in the trousers  )

If the foam ever sets properly I'll see if I can get any useable slices out of it.  Otherwise it's back to the cereal packets etc and all I've wasted is some cling film and a can of foam.

NNF

[MikeK]

While my face is still straight - hopefully, that is a handle you have grown on the side ? 

Mike

[Martin (Admin)]

Not laughing at all..... yeah, I am!   
Been there, done that too!

Great idea in principle, are you you going to have another go with.... much less foam?

 M

[derekwarner]

NFF...in all seriousness  ...the foam does clearly show that it has expanded at a relatively uniform rate of or in dimensional proportions

Could have serious build considerations for an LNG tanker...... ... Derek

[w3bby]

Should maybe have tried the rib version, lot less foam.... I will stand up and accept partial responsibility as I should have advised against spraying it all at once. It is a known problem with the cans that they do not expand and set in deeper recesses.. Apologies 

[NoNuFink]

Well the block of foam is out of the hull with the cling film removed and after at least 56hrs, the patch that was at the bottom of the hull still hasn't set properly.

Will I try it again?  Er...NO.  'though I will slice the foam block to see if it's any use - assuming it ever sets.

NNF

[Danny]

The one-part builders foam relies on moisture in the air to set.  You should always 'layer' it, having each layer no deeper than 1" or 25mm.
Leave it to expand (up to 40 times volume depending on make) and set, then apply the next layer.
Bear in mind that this is an "open cell" foam so will collect and hold water over time, also it does not have a good reputation for evenly setting.
If you can get it, the "closed cell" two-part expanding foam is much better, although you still have to use 'layering' due to the possibility of heat distortion of the container (hull, etc).  You can get it from good GRP material suppliers (or a local canoe builder might sell you a small amount).
You "trials" show why it is not used much for boat bouyancy (risk of bursting the hull), even though the 2-part foam is water resistant.
It still may be a viable method of getting accurate sections if you support the outside of the hull with rough frames, but making them does rather defeat the object of the exercise.
Anyway - cereals are good for you!

[Martin (Admin)]

BTW: I foresee no problems with flotation!   

[NoNuFink]

Just for information - the foam has finally set. 
Where the cling film had been damaged and the foam had leaked out, there is now a bulge in the shape that needs sanding down if the foam insert is going to fit back into the hull properly.  However, it has now all set and it has become obvious that it has shrunk. I estimate about 1.3% in length.  Doesn't sound like much but the lump of foam will now slide backwards & forwards about 1cm so if I do use it to cut slices out of, I'm going to have to be careful about where it's at.

The foam won't get sanded or sawn in a hurry as there is wet paint around.

On the whole I'm inclined to just chuck it in the bin and put it down to experience - I could have made several sets of cereal packet templates while I've been playing silly beggars with the foam.  Still if you don't try, you don't learn.

Cheers

NNF

[Martin (Admin)]

               

[tobyker]

If you do go the wooden rib route, I can recommend UHU plus acrylit for sticking wood - or anything else- to a styrene hull. I think Leadbelly used plastic hulls too - who can forget "goodnight Styrene".

[NoNuFink]

Just for further info; -

I was having trouble getting accurate cardboard templates due to the flexibility of the styrene & the cardboard. - essentially, I ran out of hands.

So, for a trial, I sawed the foam blob and got a couple of useful templates about 1cm thick and was pleasantly surprised.  The foam itself is akin to Gruyere cheese but otherwise better than I was doing with the cardboard.

NNF