ripping gone crazy

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bobinpowayca
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Joined: Thu Jun 16, 2011 1:40 pm
Location: Poway, CA

ripping gone crazy

Postby bobinpowayca » Mon Jun 12, 2017 8:41 pm

Howdy, just wondering if any of you have had this issue. I'm nearing the end of my Geronimo build and this problem came up while ripping my floor battens today. I've ripped white oak, sappele for the longitudinals in my boat with no problem. What I do is go to my hardwood lumber store and select boards that are smooth both faces and have one side perfectly straight. Then I rip them on my portable table saw starting with the straight side against the fence. No problem.
So today I went and got a 4/4 african mahogany board, 11 feet long and approx 6 inches wide - nice board, not bowed, with one really straight edge. I put the straight edge on the fence and ripped a 2 1/2 inch wide strip, planning to make two floor battens. Well, half way thru the rip I noticed the saw kerf was closing up again, like the sides coming back together. I was able to finish the cut but the board is warped real bad, both pieces are now "bow-legged", no straight edge on either.
Any ideas on what happened? The grain had a little curve to it. The cutting was a little tight in the middle of the cut. Of course a portable table saw isn't ideal to rip 11 foot boards but I've never had a problem before, maybe I better go back to white oak or sappele.
I used african mahogany for the dash and coamings and it's pretty nice. Bob
Bob
_______________
Built the Glen-L 17 (1988), Geronimo under construction (2013)
PBR support (1968)

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billy c
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Re: ripping gone crazy

Postby billy c » Tue Jun 13, 2017 4:04 am

Bob
Wood will move when cut. Kiln drying and the way it was sawn has lots to do with the amount of movement. Quartersawn is the most stable cut and less waste is planned when processing to final dimensions. I would have allowed about 1/4 " oversize, jointed the edge and cut to final dimension. Another approach is to fasten your warped board to your frames, pulling it straight as needed.
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ToddM
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Joined: Mon May 08, 2017 5:51 pm

Re: ripping gone crazy

Postby ToddM » Tue Jun 13, 2017 7:21 am

billy c wrote:Wood will move when cut.


Yeah, what Billy C says. Rarely do I use the "straight edge" from the lumber yard. I cut to approximate size, surface two sides, cut to close to final dimension, and plane to final dimension.

Brad Tucker
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Location: Washington, GA

Re: ripping gone crazy

Postby Brad Tucker » Tue Jun 13, 2017 9:06 am

Generally, it's known as case hardening. Kiln dried lumber will do that, and I noticed that the African mahogany from my suppler had several boards that did it. The wood has stresses in it which are relieved when it is sawn. Kiln drying too rapidly is the main cause. It actually helped on some of my battens because some of them came out already bent! Some came out like airplane props though.
Brad Tucker
Freeing a Tahoe23 from its lumber prison..

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JimmY
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Location: Brighton, MI

Re: ripping gone crazy

Postby JimmY » Tue Jun 13, 2017 9:14 am

I've had the same problem with African Mahogany. It has a lot of internal stress and you never know what it is going to do when you cut it.
-Jim
Nothing says poor craftsmanship like wrinkles in your duct tape!

bobinpowayca
Posts: 317
Joined: Thu Jun 16, 2011 1:40 pm
Location: Poway, CA

Re: ripping gone crazy

Postby bobinpowayca » Tue Jun 13, 2017 12:51 pm

Thanks a lot guys for the education. I was hoping it wasn't just me! Unfortunately I don't have a jointer or planer. When I started this build I had access to an old Navy hobby shop that had very old very big equipment - I think the planer must have weighed well over a ton. But they shut it down part of budget cuts. I don't want to invest is my own at this point. Got a new sappele board today and the store milled it for me (for a fee, of course!) Bob
Bob
_______________
Built the Glen-L 17 (1988), Geronimo under construction (2013)
PBR support (1968)

ToddM
Posts: 52
Joined: Mon May 08, 2017 5:51 pm

Re: ripping gone crazy

Postby ToddM » Tue Jun 13, 2017 9:23 pm

bobinpowayca wrote: Unfortunately I don't have a jointer or planer. I don't want to invest is my own at this point. Bob


Unless I am doing more than one or two surfaces, I don't bother getting out and setting up my jointer or planer, and instead joint and plane surfaces with a hand plane. They aren't expensive, and I accidentally have a couple extra that I can give you. They need some cleaning and sharpening, but heck, they're free. Do you ever get up to Orange County?

Moeregaard
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Re: ripping gone crazy

Postby Moeregaard » Mon Jun 19, 2017 9:37 pm

I had the same problem with some beautiful 5/4 African mahogany I bought for a coffee table. It's beautiful wood, but it has a ton of internal stresses. I was able to save the project only after I resawed and planed the wood into 1/4"-thick planks, and laminated them to a 3/4" MDF core. Honduran mahogany has the same nice color, but seems to be much more stable.

-Mark Shipley
A boat is just a wooden box with no right angles.


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