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How to straighten a Bowed cedar for a model ship display case ?

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Forum topic by fernandoindia posted 05-16-2014 04:27 AM 3116 views 0 times favorited 15 replies Add to Favorites Watch
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fernandoindia

1081 posts in 2408 days


05-16-2014 04:27 AM

Topic tags/keywords: question milling bowed board straighten bow board

Hi fellows,

I am about to build a display case for a model ship which should look like so

However it will measure 7´long X 6´tall X 2´deph. That is 210 cm X 190 cm X 60 cm.

It is a huge, heavy display case, as is the model.

I bought some 2 X 6 cedar 8 feet long. No idea about how was dried, nor the humidity content. Was adequately stored in a dry building.

Brought it to the shop. After Squared, I ripped 3 2×2 long boards, to be the side stiles of the case.

Final boards are wildly bowed. Widly means a 3/4 ” sagitta of cord

like so:

I waited 3 days to see how the wood still behaves, but no change at all.

Couldn´t leave the boards at the sun, simply because has been raining all the time, and is foreseen to continue until next week.

Planning the 8 feet piece is out of the question. If it were possible the outcome would be a 2 X 1

So I am seeking an opinion on this procedure to bring a straight stile, while I keep awaiting for the sun to appear:

Thinking of ripping each board once again, and after getting two 2 X 1 boards, flip sideways one of them and glue them together opposing the bowed side, (like “()”) into almost 2×2 (less the kerf)

This seems to be an awful job, since there are a total of eight 8 feet long boards to get straight. And frankly I don´t want to start that process while not being sure that it is a sound practice.

I´ll appreciate any input on this matter, or any other suggestion that may crop out.

Thank you

-- Back home. Fernando


15 replies so far

View runswithscissors's profile

runswithscissors

2189 posts in 1490 days


#1 posted 05-16-2014 06:56 AM

You might be able to straighten these boards out with heat (no moisture necessary or desired). Clamp one end, then apply heat on the convex side. A heat gun works well, but you need to be careful about scorching the wood. It will take a while for the heat to penetrate a 2×2, but you don’t need to impart a lot of bend. Try to apply the heat over most of the bend, but concentrate it where the bend is worst. When it’s good and hot, pull the end toward you. Over bend, as there will be some spring back. Remove the heat, and hold it in position for a few minutes. With that large cross section, it will take a while to cool. I straightened out an oak crown molding that way one time that looked like a ski. Worked like a charm.

But having said all that, I’m wondering if cedar is the most suitable wood for your project. Have you considered others?

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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shipwright

7173 posts in 2263 days


#2 posted 05-16-2014 02:39 PM

How much force does it take to spring them back and how thick (stiff) is the glass? If the glass is going to be fitted into a slot in the wood, it may solve the problem.
If not you could try band sawing a straight line through the length and glueing the convex edge to the concave edge. I’ve used that trick many times to make curved pieces out of straight pieces with no scrap. I see no reason it wouldn’t work the other way around.

BTW, I really like the model.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

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fernandoindia

1081 posts in 2408 days


#3 posted 05-16-2014 02:39 PM

Thank you RunsWS.
Secondly and most important, I did not considered other species. Should I? I choose cedar since is not so heavy, easy enough to mill, and quite friendly for the blades. I can still use the cedar for other projects. Now that you´re asking, I also wonder. Do you suggest a better wood for this task?
Thank you again. (BTW, even we have a sunny day right now, I will go for the heat trick)

FIrst off, I´ll try replacing the sun with the heat on the convex side.

-- Back home. Fernando

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fernandoindia

1081 posts in 2408 days


#4 posted 05-16-2014 04:41 PM

Hi Paul. The bandsawing trick is the one I am trying to confirm. Appreciate your opinion. If it worked for your boats, it will work here indeed.

However I´ll check the spring back forces as you suggest. The glass is two 1/8” (3mm) laminated, totaling 1/4” (6 mm). But the glass will be fitted in a rabbet and then kept with a 1/2” (12mm) brad nailed molding, which will bw making the retaining force. I´ll check that too.

Thank you for passing by

-- Back home. Fernando

View DocSavage45's profile

DocSavage45

7705 posts in 2307 days


#5 posted 05-16-2014 04:53 PM

My thoughts are relating to the forces in the wood as it grew? Is it quarter-sawn? You let moisture out when you cut the board. Charles Neil suggests that we wrap the boards un plastic wrap and let them sit for awhile if we run into warpage or cupping. clamping them with culls should re stabilize the wood. Seems like a reasonable response.

Best of luck!

-- Cau Haus Designs, Thomas J. Tieffenbacher

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fernandoindia

1081 posts in 2408 days


#6 posted 05-16-2014 06:29 PM

Hi Doc.
It is flatsawn, that when ripped cut through qsawn on 2 sides. But is bowed to the flatsawn part.
Tried the Neil trick only for three days unclamped. I have just clamped two pairs with plastic wrap. We´ll see next week.

Now I am cutting a groove in a piece as Paul suggested, and check whether the glass can survive the spring-back

Thank you

-- Back home. Fernando

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DocSavage45

7705 posts in 2307 days


#7 posted 05-16-2014 06:55 PM

BE VERY CAREFUL! :)

-- Cau Haus Designs, Thomas J. Tieffenbacher

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DocSavage45

7705 posts in 2307 days


#8 posted 05-16-2014 06:55 PM

PLEASE. LOL!

-- Cau Haus Designs, Thomas J. Tieffenbacher

View LiveEdge's profile

LiveEdge

486 posts in 1085 days


#9 posted 05-16-2014 09:06 PM

Here’s an honest question. If we can find a trick that straightens them out, why wouldn’t we assume they are going to bow again once they are returned to normal conditions and used in the display?

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fernandoindia

1081 posts in 2408 days


#10 posted 05-16-2014 09:58 PM

Agree with you LiveEdge. As marriage: you can´t assume anything. The truth happens to be the opposite. :)

-- Back home. Fernando

View runswithscissors's profile

runswithscissors

2189 posts in 1490 days


#11 posted 05-18-2014 07:45 AM

In answer to your question, LiveEdge: the trick is the same as when you cram more stuff into a closet than will fit. You give a shove, shut the door, and hold your breath. In this case, straighten the wood, make the case with the glass panes, then tiptoe away as you whistle a casual tune. It should be alright as long as you don’t make eye contact with it.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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fernandoindia

1081 posts in 2408 days


#12 posted 05-20-2014 04:18 PM

Not so fortunate so far with neither acclimatization nor heating.

So I´ll try Paul´s band-sawing trick.

BTW, uploaded an unlisted 2 minute unedited video of the ship model

https://www.youtube.com/watch?v=CZ8nIbC27Z4

-- Back home. Fernando

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DocSavage45

7705 posts in 2307 days


#13 posted 05-20-2014 04:33 PM

Good luck,

Hope it’s for a friend, cause it’s more than you initialy thought? LOL! Always is?

If possible I’d try to get more ceder?

-- Cau Haus Designs, Thomas J. Tieffenbacher

View shipwright's profile

shipwright

7173 posts in 2263 days


#14 posted 05-21-2014 12:34 AM

Beautiful model!
She looks so much more real than the average spit and polish pristine ship model. She looks like she’s been sailed and fought hard and lived to tell the tale. The detail is excellent too, from the fidded topmast and deadeyes to the anchorstock joints in the aft railcap. This is my kind of ship model.
Did you build her Fernando?

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

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fernandoindia

1081 posts in 2408 days


#15 posted 06-05-2014 06:33 AM

Hi, have just arrived home from a business trip. Hope to enter the shop shortly

I did not build her Paul. A friend of mine bought it in an auction. As a kind of therapy he is restoring it at a very slow pace. Kind of 1 hour daily. So I hope to have enough time to finish the display. ;)

-- Back home. Fernando

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