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Laminating - harder than it looks !


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I have just learnt some new things!!

 

I was about to fit my wale on my Pickle build.

 

Using 1.5mm x 4mm pear I wanted a bit more of a "step" between the wale and the 1mm planking.

 

So  - no problem -  I have  lots of.5mm  x 4mm strip spare probably tanganika

 

Soak and preshape both lengths together on the hull.

After dried - shape fine - so CA the two strips together - great.

 

Fit to hull  -

Just a leeetle bit of an extra bend need on  forrad quarter so a leeeetle tweak  - and the join parted !

 

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Tried all sorts of experiments - all cam apart if the bend was even slightly changed.

I am not saying its impossible with maybe steam etc.

But generally I think one can only laminate like this if the curves are spot on before gluing. 

 

Any comments. Was it just using different woods or , as I think my Uni science said,  a teeny change in the bend gives a HUGE shear along the join

 

(Not a big construction issue - I can just attach each lamination as a separate layer on the hull)

Edited by SpyGlass
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Different woods will expand and contract differently and every part of a laminated item laminated in a curve will have a different radius. Change the curve and every radius length thru the curved item is changed, the changing causes shear forces that will remain until the fibers have slid by each other enough to relax those forces, your glue joint is a weak point. Weak because it is a fastener and not a part of the laminated pieces and not free to move with it, the glue won't  flex, stretch or change shape, as the wood fibers can be made to do. You can use a water soluble glue and soak it and the wood until it is soft before attempting to change the shape of your lamination or you might try a rubberized type of glue that holds well but remains flexible, I would expect a heavy application would be needed to use the flexibility features of that type of glue satisfactorily to change curved shapes. Would expect that treating this like a two layer planking project would work well, first layer dry and in place attached to the ribs or frames and the second layer, a separate project that when done you sand, scrape or trim.

jud  :pirate41:   sorry for needing so many words to get this out

Edited by jud
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Yes thanks chaps all sounds as I expected - this is not a way to go if there is an alternative.

in my case either buy some thicker strip or "plank" it on the hull in two layers.

 

Used lots of clamps and tried PVA - same result.

The curves have got to be exactly matched and precisely the right shape.

 

But nice to try something and learn from it !

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When I did it for my USS Enterprise build (I was making the shaped white-wood pieces that decorate the bows each side of the bowsprit) here's what I discovered:

You can't just clamp the laminations together.  You need a mould that won't deform when pressure is applied.
[ii] A mould is easy to make if your laminated product is going to be 2.5mm thick or less. Just draw the line onto a piece of offcut timber and cut along it with (eg) a bandsaw or scrollsaw.  If you use a thin-bladed fretsaw you may need to sand your mould down, so as to leave more room for the laminations.
[iii] Use ordinary woodworking adhesive, diluted with about 25% water, and use plenty of it.
[iv] Put 2 thicknesses of silicone-coated paper each side of the wood you're laminating, to stop it adhering to the mould.
[v] Leave to dry for at least 24 hours.
[vi] If you want several matching - narrow - strips, make one single, wide lamination and cut it into narrower strips when it's thoroughly dry.

 

Hope this helps.

 

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Years ago I made a Greek Galleass.  The front section was awkward to build so I laminated thepart while gueing it to the structure at the same time. I used 1 MM thick strips and built it up.  then I proceeded to sand and sooth it out and with pant prople thought I had carved the front area to fit.  Lamintate on the hull and do not use CA.

David B

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In my experience, PVA is messy to use for laminating due to the very short opening time. Superglue I would not think it would work very well. Epoxy works brilliantly, thickened with something (I have even used ground coffee!) but it will give you an absolutely rigid piece and there will be some cleaning of hardened epoxy needed afterwards. Pre-bent the wood to avoid spring back, beech is a lovely wood, takes huge bent just by soaking in water without heat.

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