Press form straightening

[TrenchFoot]

Got a form bottom made. ply wood, titebond and screws, just have to sand it flat, but there’s a small bit of twist and bow in it. What’s the best way to straighten it permanently?

[TrenchFoot]

45 lb plates and a concrete floor? Dry heat and then 45 lb plates and a concrete floor? Bracing?

[Noah70]

I would recommend you throw that one out and start with a new form.  When assembling, reverse the two sheets of plywood, so if there is any twist or bow, they oppose each other. I glue up the sheets, then clamp them flat onto my table saw table, 100% flat. The screws are irrelevant at that point, but can be added for additional stability. Give it 24 hours for total cure and if its a long form for a one piece, mount a length of angle iron along the bottom edge.
Good luck!

[dbeaver]

I wouldnt turn anyone away from getting into this, but i see youre diving head on after the first post you made.  You should make a flatbow out of a backed 1x2 board and successfully tiller a bow out. Its important to see the full process and understand it before moving straight to building forms.  Are you making your own design?

[Kirkll]

Nothing worse than starting out with twisted limbs right out of the form on a glass bow.

Ive had a few twist up on me back when I was laminating plywood for forms and used angle iron on the bottom and edge banding on the top after getting it straightened out. Sealing them good with shellac helps a lot too.

Getting them straight is pretty easy. But getting a twist out of a form is damn near impossible and have it hold up in a hot box. Adding all that steel makes them heavy and hard to handle too.  I had one that I used angle iron to hold it straight , and a brace in a vise to hold a slight twist straight while using heat strips.  But I finally built a new form using 1.75” LVL material. 

Btw… building forms from LVL material works excellent. But keep the full thickness and do not sand down the factory surface or it will move on you.  Just a heads up on that fact.

[Buemaker]

Make a new one or if you have access to a large jointer/planer remove screws joint it flat and run through the planer. Then add a sheet of plywood with same thickness as what you removed.

[TrenchFoot]

I wouldnt turn anyone away from getting into this, but i see youre diving head on after the first post you made.  You should make a flatbow out of a backed 1x2 board and successfully tiller a bow out. Its important to see the full process and understand it before moving straight to building forms.  Are you making your own design?

I appreciate that but that’s just not the way I’ve ever done anything. If I mess up I’ll learn from it and try again, and on the last, yes and no, I found a pretty standard r/d blueprint and imported it into CAD and tweaked the reflex a bit for what I want to make. Exported the new plans got the printed out made a template, routed out a form and got the form surface dead fly square, sanded and sealed. About to do the same for the top half.

For the record I didn’t use any of the ai generated stuff as a guide.

[TrenchFoot]

Make a new one or if you have access to a large jointer/planer remove screws joint it flat and run through the planer. Then add a sheet of plywood with same thickness as what you removed.

That’s a great idea, I’ve got a 6 inch planer, I could cut some material off the bottom of the form to make it fit that… but I doubt that’s a good idea. there’s a wood shop around here somewhere though

[TrenchFoot]

Nothing worse than starting out with twisted limbs right out of the form on a glass bow.

Ive had a few twist up on me back when I was laminating plywood for forms and used angle iron on the bottom and edge banding on the top after getting it straightened out. Sealing them good with shellac helps a lot too.

Getting them straight is pretty easy. But getting a twist out of a form is damn near impossible and have it hold up in a hot box. Adding all that steel makes them heavy and hard to handle too.  I had one that I used angle iron to hold it straight , and a brace in a vise to hold a slight twist straight while using heat strips.  But I finally built a new form using 1.75” LVL material. 

Btw… building forms from LVL material works excellent. But keep the full thickness and do not sand down the factory surface or it will move on you.  Just a heads up on that fact.

So is it that your bows are 1.75” or the press is wider that your materials?

[Kirkll]

Nothing worse than starting out with twisted limbs right out of the form on a glass bow.

Ive had a few twist up on me back when I was laminating plywood for forms and used angle iron on the bottom and edge banding on the top after getting it straightened out. Sealing them good with shellac helps a lot too.

Getting them straight is pretty easy. But getting a twist out of a form is damn near impossible and have it hold up in a hot box. Adding all that steel makes them heavy and hard to handle too.  I had one that I used angle iron to hold it straight , and a brace in a vise to hold a slight twist straight while using heat strips.  But I finally built a new form using 1.75” LVL material. 

Btw… building forms from LVL material works excellent. But keep the full thickness and do not sand down the factory surface or it will move on you.  Just a heads up on that fact.

So is it that your bows are 1.75” or the press is wider that your materials?

I pretty much use 1.75" materials on all my bows except my 1 pc Flatliner longbow.  I built a new form for that one not long using 1.75" LVL  and center up the 1.5" glass and lams and heat strips. i used a router on each side of the form in spots 1/8" deep across from each other leaving 1.5" centered, and use zip ties to hold them in place in the center of the form when airing up the hose..... Trust me... i tried milling an LVL to 1.5" when i first started using the stuff for forms. There is no keeping it straight or from twisting either.

These thing are built perfectly straight under pressure when laminating them. When you remove material from one side, it takes tension off one side and moves.   

Its really much like milling any material....  Take a beautiful perfectly straight piece of S4S  lumber say 6-8' wide and run it through the table saw.... Now look down the edge. 9 times out of 10 your two 3-4" pieces will no longer be perfectly straight.... Why? because you have relieved the tension in the grain that was holding it straight.... Same thing with a thickness planner on 4/4 , 6/4 , or 8/4 stock. You start out with a perfectly flat board, plane it on one side an 1/8", and now your board has a cup in it end to end.... You can either plane the other side equally to flatten it back out by equalizing the tension, or use moisture and weights to straighten it out again. then seal it after its dry.

I suppose if you planed an LVL both sides and brought it down slowly watching for straightness. it's possible it could be done. i've never tried it. All i know is that the factory LVL material is pretty darn stable if ya don't mess with it on the thickness.

The only way i've had decent luck with laminating plywood forms is using thick hardwood edge banding on the bottom and laminated edge banding on the top. But.... it's still wood. and wood moves with variable moisture content.  Best bet is just build TD bows with shorter limb forms... LOL

[TrenchFoot]

  Best bet is just build TD bows with shorter limb forms... LOL

I enjoy a challenge 

[Kirkll]

  Best bet is just build TD bows with shorter limb forms... LOL

I enjoy a challenge 

You will have plenty of that getting into this trade. The learning curve is endless.... Good luck, and have fun!

[Birdbow76]

A warped/twisted form will move even more in the heat box. It's not worth messing with it to try and straighten. Throw it away and start over. I've made several forms this year with the LVL 1.75 boards and they work pretty good. Take a straight edge with you to the lumber store and check for straightness and any cupping issues. They can warp but not as bad as the garbage plywood being sold these days. My local Ace has them in lengths up to 40' long. I buy the 10 footers for about $100.

[TrenchFoot]

A warped/twisted form will move even more in the heat box. It's not worth messing with it to try and straighten. Throw it away and start over. I've made several forms this year with the LVL 1.75 boards and they work pretty good. Take a straight edge with you to the lumber store and check for straightness and any cupping issues. They can warp but not as bad as the garbage plywood being sold these days. My local Ace has them in lengths up to 40' long. I buy the 10 footers for about $100.

Ok sure but the materials I have are 1.5” so if I was to redo the form with 1.75” lvl how’s that gonna work with what was said about not altering the width of lvl?

[dbeaver]

[/quote]

I pretty much use 1.75" materials on all my bows except my 1 pc Flatliner longbow.  I built a new form for that one not long using 1.75" LVL  and center up the 1.5" glass and lams and heat strips. i used a router on each side of the form in spots 1/8" deep across from each other leaving 1.5" centered, and use zip ties to hold them in place in the center of the form when airing up the hose..... Trust me... i tried milling an LVL to 1.5" when i first started using the stuff for forms. There is no keeping it straight or from twisting either.

[/quote]

Kirk mentioned how this would be relevant to your glass width just a few comments back..

[TrenchFoot]

Kirk mentioned how this would be relevant to your glass width just a few comments back..

You know what, I misread that as saying that didn’t work.good call out

[dbeaver]

Kirk may be nice enough that he'll probably link you a Google photos album with an example if your inclined to ask.   

[Birdbow76]

On Kenny’s archery supply website he shows how to build a form and router the edges to reduce width. It’s as simple as laying the form on its side and running the bearing of a rabbit joint bit along the surface. You’re reducing the contact surface down to 1.5”.

[Richard Korte]

Don’t throw the twisted form away just yet. You can still make some mini- forms in the shape of your risers to glue riser trim to the riser...like the Purpleheart trim on the Bear ‘59 Kodiaks. You can also use the small forms to glue on the grip overlays. I have several I use on every bow I make. Mine are 18-24” in length and use a fire hose a few inches longer. Use your imagination! Richard

[TrenchFoot]

i mean, the thing only bows 1/8 inch and sits dead flat after settling a couple days so if theres twist anymore, i can't tell,  im gonna heat it up and clamp it and put a angle iron brace on it and run it for this first bow and we'll see what happens, if it does like a few said here no big deal, first bow problems. but im hardheaded and im gonna use it. Then ill go get some lvl from lowes and make a new form with that for the future. i would def like to see Kirk's set up though if you dont mind Kirk

Edit- actually I said that but I had already heated and clamped it over night 2 nights ago and got most of the bend out and was gonna do the angle iron. However I left it sitting on my table saw deck since then in clamped. Just put a straight edge on it for the heck of it and it’s actually perfect. I guess sitting did the trick. Still gonna put angle iron on it for the hot box though