Bent Lamination Resaw Technique?

[Robin Cruz]

I'm resawing 4" wide 1" thk oak to make about 1/8" thick laminations to glue and bend to a curve for a rocking chair back and for the rockers. I'm using a 1/2" 3 tooth/inch on a 14' Rockwell bandsaw.

Can I glue the lams together right from the resaw with the rough sides.......or.......do I have to plane the surfaces first with a planner?

Thanks for any tips

[Chris Padilla]

I've watched David Marks do this a thousand times and he always run the strips through the drum sander to clean up the bandsaw marks before gluing them together in a bent lamination.

Think about it...as you bend the strips, they will no longer line up with each other so that if you made a poor bandsaw cut...that cut won't line up once you start bending the strips. Hence, you must sand them nice 'n clean to ensure tight/invisible glue lines. You may wish to go slightly thinner than 1/8" but maybe you don't need to bend them so much for a chair back.

[mreza Salav]

Yes, you'll have to smooth those surfaces and a drum sander is the best tool for this. But if you don't have one (just like me) you may use planer which isn't so easy. Typically, you cannot feed those thin (under 1/8") strips into a planer or it will chew it up. I use double-sided tape to attach them to a thicker board and feed them through the planer. Works Ok but isn't hassle free.

[Robin Cruz]

ahhh. I remember seeing that now. I have a planer (no drum sander) so I would plan on using it. I would think to keep things square, one would resaw, run both 1/8" piece and remaining thick piece rough side through the planer.....resaw and repeat. Its just time consuming and the planer sometimes takes a bite out of the end of the thin pieces.

I suppose it could be worth the drum sander investment. Any suggestions on a model for a 1 car garage size workshop?


I've watched David Marks do this a thousand times and he always run the strips through the drum sander to clean up the bandsaw marks before gluing them together in a bent lamination.

Think about it...as you bend the strips, they will no longer line up with each other so that if you made a poor bandsaw cut...that cut won't line up once you start bending the strips. Hence, you must sand them nice 'n clean to ensure tight/invisible glue lines. You may wish to go slightly thinner than 1/8" but maybe you don't need to bend them so much for a chair back.

[Howard Acheson]

You want to have real smooth, flat surfaces when you are making up laminations for bent lamination applications. To get the best adhesive surface and to minimize the glueline, flat surfaces are required.

On another point. Avoid PVA yellow adhesive when making up bent laminations. PVA adhesive has a characteristic called "creep". This means it wants to slip past it's adjacent surface when in shear pressure. In addition, laminations that are subjected to the forces in rockers can cause it to delaminate. The adhesive to use is a urea formaldehyde. A good one is DAP/Weldwood Plastic Resin. This is the one David Marks uses for his projects. It is a better adhesive for bent laminations.

[Robin Cruz]

the DAP plastic resin was hard to find locally but I finally found some. I noticed on the bucket instructions that the open time is only 15 minutes. I thought it was a slow setting glue that gave one a lot of time to set up before clamping?

I did experience once in a while the planer chew off a piece of the 3/16" lamination. Thanks for the double tape tip.

Used drum sanders I see for sale in my area are in the $500 ballpark. Maybe 1/2 to 1/3 of new cost.

[Doug Shepard]

There's also a method for doing it with an OSS if you've got one. At 4" you're right around the limit but it should work fine.

[Paul Zonneveld]

Robin have you thought about steam bending that piece rather than using a bent laminate method. I have avoided projects with bent laminations until recently when I purchased a drum sander. The sander allows you to get smooth flat pieces to bend and glue together. I have not steam bent before, but it may be an option for you.

Paul

[Robin Cruz]

Seems like steam would be a lot less work and I experimented with it this weekend. Thats why I'm going the lam approach. I have made the molds already (same for either approach) and set up a steamer using a 4" ABS sewer pipe about 3' long capped on each end, canted and with a drain hole drilled. 1000w burner into a metal kettle with 1.5 in opening that that piped to the ABS pipe. I vigorously steamed a single piece of 3/4 x 4" x 19" red oak for 45 minutes. It basically didn't budge when I tried to bend it.

Ive read that once wood is kiln dried its not a good candidate for steam bending......or I didnt get it hot enough...or left long enough. I have fairly easily dry bent 3/16 thk for 3/4 x 4 x 19 lams of the same oak in the same mold so I know that will work for me If I can get a process down to efficiently cut the lams.

Id love to get a drum sander but its a pricey luxury when I have a nice Hitachi F1000A planer.



Robin have you thought about steam bending that piece rather than using a bent laminate method. I have avoided projects with bent laminations until recently when I purchased a drum sander. The sander allows you to get smooth flat pieces to bend and glue together. I have not steam bent before, but it may be an option for you.

Paul

[Brian Penning]

Fastest and easiest is simply cutting the strips on the tablesaw. Literally just takes a few minutes and then you're all set to glue.
No need to sand or plane afterwards if you have a decent blade.
I make rockers all the time with this method.
Below is a backslat and a rocker.

http://i47.photobucket.com/albums/f193/Bri68/Building%20a%20rocker/IMG_2843.jpg?t=1210633063


Completed rocker

http://www.brianpenning.com/index_files/image6741.jpg

[Robin Cruz]

that will work for the rockers but the 4" stretchers I dont think cut all the way through on the table saw. Also to get 3/4 in with 1/8 wide would take a very thick plank to get lams that grain match. But will work on the rockers and maybe the narrower stretchers.
thanks for the tip.

[Rob Diz]

Depending on the extent of the bend you are trying to get, you will find that 3/32 rather than 1/8 gives you a lot more flexibility.

I recently made some aprons using bent lam. at first I tried to get my cherry down to 1/8 in the planer, but had a lot of chip out and tearing. others have had success wetting the wood and using a sled.

I went over to a buddy's house with a drum sander.

the other thing to think about is how well your BS is tuned up. You may find that if you are not dead on for drift, that you will have a bit of cupping on the center of your boards. Not a bit deal if you are using the Drum sander, but something to think about.

I used the Dap Weldwood, and really liked it. use gloves when you pick up the dried piece - the rough edges can cut you. Ace sells the stuff on line, or they will ship to a local Ace Hardware without a ship charge.

[Dave Tinley]

Robin-
If you are not ready to invest in a drum sander at this time, you can actually use a hand held belt sander. I had to do this prior to getting my drum sander.
I had the Dewalt belt sander with a frame and it worked pretty darn good.
Just double stick your laminates to the bench and sand away.
Yes it is time consuming, compared to a drum sander but it will get the job done.
If you dont have a frame for your belt sander, you can put 1/8" plywood on each side of your laminations to use as a guide.

Good luck on your rocker and show us some pics.

Dave

[Mike Spanbauer]

You can use a card scaper too which will work just as well as a drum sander.... just take a lot more effort :)

You will need to affix the lamination to a surface for the scraping, but that's actually pretty easy to do if you pull scrape and simply clamp it to a bench. You don't need to attach the lamination such that you can scrape the entire piece at once. It works, just more labor.

mike

[Robin Cruz]

Robin-
If you are not ready to invest in a drum sander at this time, you can actually use a hand held belt sander. I had to do this prior to getting my drum sander.
I had the Dewalt belt sander with a frame and it worked pretty darn good.
Just double stick your laminates to the bench and sand away.
Yes it is time consuming, compared to a drum sander but it will get the job done.
If you dont have a frame for your belt sander, you can put 1/8" plywood on each side of your laminations to use as a guide.

Good luck on your rocker and show us some pics.

Dave

Ive already bent 3/4" worth of 1/8 or a little thicker lams in my mold as a dry experiment and it was no problem. I think I have a very mild curve compared to what most do. Its a chair back. Id like to keep the lam thicker if I can to reduce the work and the waste. I did find some DAP Plastic Resin locally so Im set up there. Does it really have a slow set? The bucket instructions say 15 minutes open time.

I guess Im going to get a drum sander. A small one bench size. Its around $500 new. I talked it over with wife and she bought in to it. You cant take the money with you...right? Maybe the Jet 10" seems to be it.

thanks again for the tips.