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Author Topic: Un-bending plywood  (Read 7643 times)

Hande

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Un-bending plywood
« on: February 01, 2016, 06:28:17 PM »

In my Billing boats kit came the large plywood deck piece.
May be because of a lengthy time in storage, it was bent overtime.


And it has a strong memory with that!


I have tried hot steam.
I have soaked the deck for 18 hours in warm water with vinegar.


But the plywood does not relax back to straight.
Right now - after the soaking operation - it is under tension into the opposite direction. I figure when trying to remember the bent form, it wouldn't have it to return all the way back.


Should I make a new one?
Should I attach some structure beneath to counter the bending tension?
I could make a couple of clamps to hold the piece straight - disguised as some movable equipment on the deck.


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Unsinkable 2

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Re: Un-bending plywood
« Reply #1 on: February 01, 2016, 08:09:50 PM »

I would try exactly what you are doing, soak and then bend in the opposite direction and let it dry under tension.


After that it can only do one of three things, 1, go back how it was. 2, go back to flat. 3, stay bent in the new direction.


If I wasn't satisfied with the result I would just make a new one.


Is it possible that gluing it in position would help it to keep the correct shape? If it's only a little bent it may be ok!


Without knowing all the details the above is my best offer...... Good luck    U2
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Hande

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Re: Un-bending plywood
« Reply #2 on: February 01, 2016, 08:45:09 PM »

Thanks U2!


It's the bottom of the removable superstructure. So glueing won't do.
To make it worse, the bent end is the one with just empty space (it's a tug). Under the boat house the house's rigidity would fix the problen.

I'm thinking it should stay straight by well positioned fasteners, when in place.
Maybe, with time, it may even straighten-up on its own.


It's just that I would hate it being all curved every time I take the superstructure off...




Now waiting for one of three possible outcomes from the unbending exercise.

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ballastanksian

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Re: Un-bending plywood
« Reply #3 on: February 01, 2016, 09:23:09 PM »

I hope you get the result you are after. If bodgers can bend chair legs out of good thickness timber then you should be able to get your ply straightened alright.
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Re: Un-bending plywood
« Reply #4 on: February 02, 2016, 03:56:14 AM »

I am trouble seeing how the ply will fit to the boat. Any chance of a picture?


Assuming, dangerous, the image I have in my head is correct.
If there is no support under one end. You could glue a straight square section timber under the ply to hold it flat, in such a position that it does not foul anything else. Alternatively, if you cannot really see into the superstructure, you could glue similar pieces of timber to the inside walls of the superstructure to provide more rigidity to the walls, and then glue the ply to that.
Solutions might depend on if the ply is curling up or down at the edges.


Without a picture it is hard to advise.
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roycv

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Re: Un-bending plywood
« Reply #5 on: February 02, 2016, 08:32:59 AM »

Hi weak amonia will bend ply like it is tissue paper.
Roy
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Colin Bishop

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Re: Un-bending plywood
« Reply #6 on: February 02, 2016, 08:38:30 AM »

Yes, Roy but it will also reduce its strength. Rather than keep messing about with it I would literally start with a clean sheet! Just use the old part as a pattern.

Colin
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Re: Un-bending plywood
« Reply #7 on: February 02, 2016, 09:31:20 AM »

Hi Colin, I don't disagree but how much strength do you need in a deck on a relatively small boat.  I have just "un-bowed some 6 mm ply 4' x 2' using hot water and heavy weights and that has been satisfactory.  (Model railway baseboard)

Personally I would write off the existing ply and start again. I have done so in the past.  Cost does not come into it as most would make a model they expected to last and using cheap materials is never a good idea.
All my models are still going strong apart from a couple of accidents and one dates back to 1964.  Paint finish from my experience is a major factor in longevity.
regards Roy
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Colin Bishop

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Re: Un-bending plywood
« Reply #8 on: February 02, 2016, 09:39:23 AM »

Roy, yes, you are right, it would probably fit the bill but the quantities of material that go into models are so small in most cases that I personally like to keep the quality level up as much as possible! Just my preference.

Colin
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Re: Un-bending plywood
« Reply #9 on: February 02, 2016, 09:49:08 AM »

Any chance of a photo of the piece and where it fits (or should fit) .......      U2
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Hande

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Re: Un-bending plywood
« Reply #10 on: February 02, 2016, 10:41:50 AM »


I really appreciate your interest and advice!

Here's the photo.
I'm totally with quality as a priority.
On the other hand, the original is laser-cut and no way I can make an accurate copy of it.
I don't have the means to saw straight - and there is the square hole there, too.
Would have to find facilities...



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Colin Bishop

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Re: Un-bending plywood
« Reply #11 on: February 02, 2016, 11:53:28 AM »

Use a Stanley knife or similar surely? Just cut round the original.

Colin
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essex2visuvesi

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Re: Un-bending plywood
« Reply #12 on: February 02, 2016, 11:56:13 AM »

Something that's worked for me :)


Take the wood into the sauna with you, have a nice long sauna then place the sheet under some very heavy weight (I used 2 Tractor batteries)
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Hande

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Re: Un-bending plywood
« Reply #13 on: February 02, 2016, 03:41:04 PM »


This is a good one! Only connosseurs know what you are talking about.
My wood was already in the sauna, too. Something a finn would think about as a cure among the first things...





Something that's worked for me :)


Take the wood into the sauna with you, have a nice long sauna then place the sheet under some very heavy weight (I used 2 Tractor batteries)
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Hande

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Re: Un-bending plywood
« Reply #14 on: February 02, 2016, 03:42:49 PM »


...and a steady hand, to be sure.
This [size=78%]may well end up there eventually.[/size]

Use a Stanley knife or similar surely? Just cut round the original.

Colin
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Capt Podge

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Re: Un-bending plywood
« Reply #15 on: February 02, 2016, 04:41:49 PM »

If your model is the Smit Nederland, there should be 4 pieces of wood (pre-shaped) which fit together underneath the part you are trying to straighten. These should hold the ply in the correct position and with the correct deck sheer, like this:-

Regards,

Ray.

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cos918

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Re: Un-bending plywood
« Reply #16 on: February 02, 2016, 04:56:46 PM »

I really appreciate your interest and advice!

Here's the photo.
I'm totally with quality as a priority.
On the other hand, the original is laser-cut and no way I can make an accurate copy of it.
I don't have the means to saw straight - and there is the square hole there, too.
Would have to find facilities...




Hello
Having built 4 Billings kits for old to new ones . They all had one thing in common ,Poor quality wood that warps easily .Try what Ray has said about the 4 pre shaped wood glued to yours first . If that does not fix it the new wood time .
A tip for when building the kit . Photo copy all the parts. If you ever need to remake a part you have a full size template .


john
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Hande

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Re: Un-bending plywood
« Reply #17 on: February 02, 2016, 04:59:41 PM »


Uh-oh.
At the bottom of the last page of the instructions they show, indeed.
I expect them to fix my problem.
Thank you Ray!
I take it the S.N. is your build?


Thanks everybody for yet another learning experience!



If your model is the Smit Nederland, there should be 4 pieces of wood (pre-shaped) which fit together underneath the part you are trying to straighten. These should hold the ply in the correct position and with the correct deck sheer, like this:-

Regards,

Ray.


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Hande

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Re: Un-bending plywood
« Reply #18 on: February 02, 2016, 05:02:26 PM »


I will photo copy everything right away. A good tip!
thanks, John




Hello
Having built 4 Billings kits for old to new ones . They all had one thing in common ,Poor quality wood that warps easily .Try what Ray has said about the 4 pre shaped wood glued to yours first . If that does not fix it the new wood time .
A tip for when building the kit . Photo copy all the parts. If you ever need to remake a part you have a full size template .


john
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Capt Podge

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Re: Un-bending plywood
« Reply #19 on: February 02, 2016, 05:27:15 PM »

Uh-oh.
At the bottom of the last page of the instructions they show, indeed.
I expect them to fix my problem.
Thank you Ray!
I take it the S.N. is your build?


Thanks everybody for yet another learning experience!




Hi Hande, yep, the photo is from my rebuild here:-

http://www.modelboatmayhem.co.uk/forum/index.php/topic,52330.0.html

Hope you get your deck sorted - looking forward to your updates as well :-))

A tip for when building the kit . Photo copy all the parts. If you ever need to remake a part you have a full size template .


john

Excellent idea - I'll remember that one !  O0

Regards,

Ray.

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essex2visuvesi

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Re: Un-bending plywood
« Reply #20 on: February 02, 2016, 06:59:45 PM »

There's a couple of chaps on here with laser cutters.... I'm sure one of them might be able to cut you a replacement for a few beer tokens :)
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Colin Bishop

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Re: Un-bending plywood
« Reply #21 on: February 02, 2016, 08:13:59 PM »

But do they live in Finland?
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Re: Un-bending plywood
« Reply #22 on: February 02, 2016, 08:48:29 PM »

Ha a do they not have 'post' in Surrey Colin {-) ......... I even get bits from England here in France, it's AMAZING! :} ..........
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Colin Bishop

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Re: Un-bending plywood
« Reply #23 on: February 02, 2016, 09:18:53 PM »

But compare cost of sending awkward shaped item from Finland to the UK and back again with simply placing the original over a sheet of ply and cutting round it. Seems the long way round.

Yes, we get bits through the post in the UK too, trouble is they sometimes commence the journey as a single item...... ok2

Colin
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ballastanksian

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Re: Un-bending plywood
« Reply #24 on: February 02, 2016, 11:53:54 PM »

Ha a do they not have 'post' in Surrey Colin {-) ......... I even get bits from England here in France, it's AMAZING! :} ..........

But Finland has so much Birch that they may not like more birch wood being imported!

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