Form Question

[Shore08]

  Please

Hey folks,

I am planning out my first fiberglass bow. I've decided to go with a takedown recurve for a few reasons. I know that is supposed to be tougher for a first go round, but I figure if I botch a limb or the riser, I can replace that part rather than having to scrap the whole bow      

Will that 1/8" cause a huge problem? I figure that is only 1/16" to either side if I get it dead center, but I also know that twist is twist, so what do ya'll recommend?

If it matters, I will be using the firehose method.

Thanks!

 

[carver]

my friend, you are thinking too much.  you cannot get 1 7/8 by using 1/2 inch ply.  sandwich a strip of half inch ply between two layers of 5/8 and you are good to go.

Why not break your cherry on a single piece, man?  Ya gotta walk before you can run.

[Shore08]

I'll try to get some pictures to show what I am talking about. I got the plywood from a friend who told me it was 1/4", but after I got it cut and started looking at it, there is no way that it is. Now I am starting to wonder what I have here haha.

I'll be at the firehouse tomorrow, so it'll probably be Tuesday when I get some pictures up.

As for why I am doing the take down first, well...

Ya gotta be tough if you're gonna be dumb    

Plus like I said, I figure if I blow it on one part, I didn't wreck the whole bow, I can just re-make the part I messed up on.

[Shore08]

Ok, couldn't stand it. Here are some poor quality cell phone pics. I measured the wood, it's 1/2". It's like 2X4's or anything else, it isn't exactly the measurement it is supposed to be.






Close enough or start over? Bear in mind I haven't glued it or anything yet, which is why you get my ugly ole finger in there haha.

[carver]

right, the stuff is 3/8".  You can always just make the bow fit the form, no?  make it slightly oversized, and then sand to the line?

[Shore08]

There ya go, that'll work.

I just needed to think it through. Or, errr, have you think it through for me    :D

Thanks man.

[bjansen]

It will work.  I've made 1.75" bows from a form like that before....its not ideal, but it will work for you. I recomend gluing on a strip on the top 1.75" not only to smooth out the top but also help you stay alligned during the glue up.

[carver]

[Shore08]

Ya know, the more I think about this, the more I realize I may be setting myself up for failure...

Looks like some new plywood is in my future  :D

Thanks for the sounding board!

[mater]

your doing fine. 1/2 ply measures 15/32 its stamped right on it. I would prefer my forms a fuzz wide. Tape the lams together when gluing and they will stay put.

[ChristopherO]

Multi layers are actually better to keep warp out of the form, the beauty of plywood, so what you have should work.  If you want to exact width, then use your router to shave off 1/16" from both sides about an inch or so down from the bed of the form (watch out for screws) and then you have the 1 3/4" you are looking for.
Hope this project works well for you.

[Shore08]

More excellent suggestions. Thanks folks! I need to stop second guessing myself and coming up with excuses not to do it, and just get my order placed so I can start.

:D

[Trux Turning]

On my forms--if I use plywood,I build them over sized and then use my router to trim off the overage down to size on the form- I don't worry about the top part of the form being a little big or you can get a product called versa lam to the width you need. Here is a picture of the last form I built- you can see the bottom side of the form was reduced this way.

[JGray]

Plywood is generally 1/32" less than what we see marked as 3/8, 1/2, 5/8, 3/4 etc.  Four pieces of 1/2" ply will get you 1-7/8", as you've found (4 x 1/2 = 2", then subtract 4 x 1/32").  If you want to hit 1-3/4" dead on, try three pieces of 1/2", plus a piece of 3/8" and you will be right there.  I've spent way too much time pondering the same dilema and this is what I did on my last form - it is exactly 1-3/4" as close as can be measured.  You will have the added expense of one sheet of 3/8 (with a lot of 3/8 left over for another project).

Two other combinations that will get you real close are three pieces of 5/8" ply (if you can find it), or two pieces of 3/4" and one piece of 3/8".  I just glued one up in that combination and it is 1/32" over 1-3/4", so is just a little fat.  Overall, I think I prefer using four pieces with (3)@1/2" + (1)@3/8".

Jerry

[Shore08]

Originally posted by mater:
Tape the lams together when gluing and they will stay put.

This keeps bouncing around in my head. By this you mean a few strips to help hold it together, right? As opposed to a total wrapping of the bow.

By the by, I got the form glued up but I am not happy with the outcome. I got caught in a rainstorm bringing the plywood home and it developed a little set. I thought it would still be usable (like I said, I got the sheet free so figured I'd give it a go) but after gluing and screwing there is some separation that I am not thrilled with. Looks like I get to try again haha.

Oh well.

[Shore08]

Meant to add, thanks for all the additional tips gang. I really appreciate the help.

Jerry, if I wind up rebuilding (which I think I am going to) I think I'll take your advice and go for the exact fit so I can use the washer method to help hold it.

Thanks again everyone!