First bow build form question

[K30bowfisher]

Hello all, first post for me. I've been reading the board for a while and am very impressed by the work that I see other people doing. It is very inspiring to see that kind of talent.

I have decided to build a bow. I bought plans from Bingham's for their 64" r/d longbow. I have my forms built but I have a concern about the straightness of my form. I made it out of 15/32" plywood with one layer of 1/8" masonite to make a full 1.5". I suppose I wasn't careful enough when I glued up the form blank because it has a little crown to it, maybe 1/16" or so at the center looking along the top edge of the form. Is this something to be concerned about?

Has anyone ever had to fix this issue before?

Thanks in advance.

[Mike Most]

Any chance for a picture  of it??

[K30bowfisher]

I'll get one taken and posted up tomorrow morning. Thanks.

[Mike Most]

The primary concern for  "the form" is the bottom half, which is where the laminations are laid after applying epoxy.

It must follow your pattern as closely as you can get it and be square and true without dips and or waves.

Whatever your form is "your bow will be" and any little wave or twist if in the form will be in your bow. (a mold so to speak)

If I get your question correctly, the 1/16 along the top edge would not be much of a problem if the pattern you make is square.

The biggest issue is guys using "some types of MDF" which when placed under pressure of the fire hose method Binghams uses and placed in the oven they suggest. The MDF cracks or comes apart at the bolt holes for the metal brackets which hold the top to the bottom. (why they recommend plywood)(I think they recommend 60 pounds of pressure in the hose)

This may or may not ruin your bow (for me too many hard earned  american $$.ouch)

KennyM on this site has an excellent way to form build which minimizes said dips and waves,

You will get a shootable bow, probably the first time but if attention to detail is used on the form building you will get an excellent shootable bow....

my 2 cents sorry to be a bit verbose

Good luck

I am just as excited as you are as I am ready to build another myself.... yahoo.

Mike

[K30bowfisher]

I used Kenny M's method of cutting the form shape with a pattern cutting router bit. It is very smooth and symmetrical, but there is a curve in the form lengthwise. If not for the warp I would be very pleased with this form.

I do appreciate the advise. I'll get a photo up tomorrow.

[Trux Turning]

As stated above- the side of the form that the bow gets glued up on must be square and level. If you have some crowning end to end you need to straighten the form. This is how I have done it to this form- I added (glued and screwed) a piece of 3/4" plywood to the bottom of the form and then took a piece of angle iron and bolted it on- the form hasn't moved any since.
 

[K30bowfisher]

Here are a couple of photos.

 

 

I think I'll try what you did Trux.

Thanks for the help.

[GREG IN MALAD]

If there isn't any twist in the bottom form, I wouldn't be too concerned about a little bow, if the form is twisted it will be easier to build another one. I have a form that warped in the oven, but it didn't twist, and it still works fine.

What part of Idaho are you in?

[K30bowfisher]

I laminated a couple of strips of 1/2" plywood onto the bottom form after clamping it straight on a piece of steel. It now looks straight to my eye. Hopefully it won't move in the oven. Thanks for the suggestions.

Greg: I am in Preston

[rich w]

Hey K30bowfisherman I got my frist bow about done. I too bought it from bingtom bow the only problem I had with the form was getting every thing in it. I cut it exacely to the tin plate drill the holes perfit.But when i put every thing in it i could not close it enough to put thr bolts in . so make a dry run with every thng

[K30bowfisher]

Hey Rich, thanks for the tip. I'll be sure to check that. Which bow of theirs are you building?

[bamboo]

make sure the angle iron is straight too
-------------------mike
form and box look great

[rbbhunt]

I also used Bingham's plans for a recurve and couldn't get the bolts in so I used bar clamps to clamp the top down just enough to put the bolts in.  By the way, I had problems bending the 1/2" bolts in the top half, so I got some grade 8 bolts and that seemed to have fixed the problem.

[GREG IN MALAD]

Originally posted by K30bowfisher:


Greg: I am in Preston

It's good to know there is another bow builder close to home, and good luck with your project.

[K30bowfisher]

Thanks for all the help. I am now just an airhose away from gluing up my first bow!

Anyone know if airhose is available locally, like at Home Depot or Lowe's?

If not I'll put in an order to Bingham's I guess.

[GREG IN MALAD]

I have never found fire hose locally, and the heart of the system is the plugs.If you want to get a bow glued up this weekend you can borrow one of mine.

[K30bowfisher]

Greg, that would be super, and also super generous of you. I'll send you a private message to discuss further.