Bow Form "HELP"

D.J. Smith · November 28, 2009, 05:42:00 PM

I would like to build a 1.5" wide bow form, What's the best materials to use & How do you come up with 1.5" wide exactly??? I have tried 2 pcs. of 3/4" plywood & came up 1/16" to narrow.

bjansen · November 28, 2009, 05:59:00 PM

If you can find a LVL beam that sure does make a nice form, but I usually go to the lumberyard and find a sheet that gets me very close to my desired thickness when stacked 3 sheets thick. If I error. I error on the side of slightly less than the desired thickness.
I have built a form just as you said using 3/4 plywood, but usually I get a bit of caul when I only glue up 2 thick.

Regardless, what I always do is glue a flat strip on the top of the form that matches my desired thickness (e.g. scrap lams, a strip of formica/glass). Thhis strip will make the top of your form smooth and also match your desired width. If it hangs 1/32 over on each side...no big deal.

D.J. Smith · November 28, 2009, 06:19:00 PM

What is lvl???, Can I find them @ Lowe's, Home Depot?? What about 2 pcs. of formica sandwhich between 2 pcs. of 3/4" plywood???? Thanks for the info.

kennym · November 28, 2009, 08:37:00 PM

Laminated Veneer Lumber I think...

ChristopherO · November 28, 2009, 08:46:00 PM

My form was 1/16" too narrow but a friend had some formica leftovers and it was a perfect filler to put me where I wanted to be.

Crooked Stic · November 29, 2009, 05:33:00 PM

To get 1 1/2 wide you have to use 3/4 1/2 and 3/8s glued together =1 1/2 in todays plywood.The LVL is better if you can get it.

bjansen · November 29, 2009, 09:03:00 PM

Yes indeed LVL- laminated veneer lumber...used in home construction over unsupported spans (e.g. over a garage door). Lowes and HD will likely have this in stock as well.

Thats a good tip on the 3/4+ 1/2+ 3/8

TNstickn · November 29, 2009, 10:06:00 PM

I laminate up all different scraps I have, glue it together, remove the screws, lay the bow out, rough cut the two pcs in half 1/8" from the finshed bottom. Then run the two pcs through a 12" table top planer to get down to the 1.5". Sometimes its alot of passes with the planer. I cant really complain though , I get the scraps from building cabinets on the job. After I get it the 1.5" I finish up the glue surface and bore the hardware holes.

Russell S. · November 29, 2009, 11:06:00 PM

on my plywood form I contact cemented a reverse tapper on the form flush with one side, then filled the overhang side with bondo for strength. then sanded the 3" of the bondo side square and painted to prevent mold lock. 2 of my forms i covered with Formica. 2 of my forms are MDF, if your clamping stress is purely compressive like bands and clamps I think the MDF will hold up fine, just reinforce it where your riser clamp goes. MDF has very good compression strength, put some tensile (sp?) stress on in any direction (the fire hose trying to straiten out) and it will break. 2 3/4 inch MDF or 3 1/2 inch MDF come out to the proper width. if you go that way i can post a pic of the way i reinforced mine. both of my mdf forms have made 3 bows.

razorsharptokill · December 05, 2009, 09:06:00 PM

My MDF failed. Back to plywood.

Teagus · December 28, 2009, 01:27:00 PM

Today I tracked down a type of plywood I had seen used by another bowyer. He called it sign board. It's technical name is "MDO". In town we have company "A" who is a specialty plywood wholesaler. "A" sells it to company "B" who is a sign shop supply house. Both won't sell to the public. I have a tax ID so I'm ok. I am heading out to check the dimensions with my calipers.If this is what Bob used, I may give it a try. Comes in 1/2 and 3/4 +/-.032.
www.olypanel.com

Teagus · December 28, 2009, 01:32:00 PM

oops, the salesman said +/-.032, the datasheet says +/-.016 which is even better.

jess stuart · December 28, 2009, 02:51:00 PM

I have used the MDF with the firehose. I left plenty of material between the edges of the form and the holes for the straps. So far so good but have only made a couple of bows on it. This was before I read of some failures by others, think I will stick with plywood in the future.

Teagus · December 28, 2009, 02:58:00 PM

Jess, this is high grade plywood used by the sign industry. Not a chip board or partical board.

Greg Owen · December 28, 2009, 03:17:00 PM

It looks to me like this is a plywood with a Medium Density fiber veneer as the outside layer. This is the smooth face. Is that this is?

Teagus · December 28, 2009, 05:12:00 PM

The factory just called and said the side intended for the sign to be painted has a phenolic resin impregnated paper bonded to a high quality plywood. They run it through a big surface sander. Thickness tol tends to be on the minus side. I think I have a set of recurve limb forms up at the locker. I will snag one and take some pics.

Teagus · December 30, 2009, 01:36:00 PM

Here is some pics of a takedown recurve limb form I got with the machinery when I bought out Bob.

The edge of the sheets show almost no voids.

The calipers read 2.026. The form consists of four 1/2" MDO.

This is primo stuff. Next step is to visit distributor to nail down price. I expect it to be pricey. I would use this on a production form.

D.J. Smith · December 30, 2009, 06:51:00 PM

I used 2 pcs. of 3/4" birch plywood, with 2 pcs. of formica in the middle. The form came out real close to 1.5". Works great, I have made one 62" long bow so far, With Kennym's r/d design and lams. Thanks for all the info.

kennym · December 30, 2009, 07:55:00 PM

Hey DJ ! Pics of new bows are mandatory!! LOL

kennym · December 30, 2009, 07:58:00 PM

OOPS,doubled up!