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Main Boards => The Bowyer's Bench => Topic started by: TrenchFoot on February 23, 2025, 05:27:36 PM
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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?
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45 lb plates and a concrete floor? Dry heat and then 45 lb plates and a concrete floor? Bracing?
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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!
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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?
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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.
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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.
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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.
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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
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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?
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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
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Best bet is just build TD bows with shorter limb forms... LOL
I enjoy a challenge :shaka:
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Best bet is just build TD bows with shorter limb forms... LOL
I enjoy a challenge :shaka:
You will have plenty of that getting into this trade. The learning curve is endless.... Good luck, and have fun! :thumbsup:
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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.
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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?
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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.
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Kirk mentioned how this would be relevant to your glass width just a few comments back..
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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
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Kirk may be nice enough that he'll probably link you a Google photos album with an example if your inclined to ask.
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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”.
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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
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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
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I can take a few photos of my form if you like…
but going back to your tests… after applying the angle iron brace. Did you cook it for 3 hours in a hot box and check it when it’s hot? Steel expands and moves when it gets hot. If not… I would do that test…..
When I used angle iron on my bent form, It was setting in my form vise and I was using heat strips and the angle iron never saw any heat. I haven’t used a hot box for cooking bows since 2008, and I don’t miss man handling the forms in and out, and cooking them to death. I like my heat strips. Kirk
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Here are a few pictures of my 1.75" thick form using 1.5" heat strips and glass. you can see how i used a router to bring ti down an 1/8" and the holes are for heavy duty zip ties. The heavy ones hold really well.
https://photos.app.goo.gl/eXA2TqNLg2kvPHan8
https://www.amazon.com/XINGO-Strong-Plastic-Outdoor-Resistant/dp/B09WY1GVB6/ref=sr_1_1_sspa?crid=3IDTAR8D30GCP&dib=eyJ2IjoiMSJ9.PmrNJT-Q4naNYSvuFUe-1v0vhrhOCvpr_pvDHvNwGB984MDiepn8_T1SGHjSTD9ORa5_7giXG1l8wo8IyqDAFuzVPS5S6o65dMEGjwubxXPuRGbC-ZHA0grfW7UvvfRqrN8_JBXgQRAlLS8-0ehTKaWI8AZG3MBHutMMZKRZosB4RfPb950DP8JmrFJDr6fWjG7T-q587IQy7cuUJraW1PzmVJtxT6f1DZj40Jtobkk.XhqgdF2okhpCfbPIn9lgE4VQl2XpLsyR0KIb360u_m8&dib_tag=se&keywords=heavy%2Bduty%2Bzip%2Bties&qid=1740709187&sprefix=heavy%2Bduty%2Bzip%2Bties%2Caps%2C179&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
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I can take a few photos of my form if you like…
but going back to your tests… after applying the angle iron brace. Did you cook it for 3 hours in a hot box and check it when it’s hot? Steel expands and moves when it gets hot. If not… I would do that test…..
When I used angle iron on my bent form, It was setting in my form vise and I was using heat strips and the angle iron never saw any heat. I haven’t used a hot box for cooking bows since 2008, and I don’t miss man handling the forms in and out, and cooking them to death. I like my heat strips. Kirk
Havnt tested anything yet, not gonna be ready to even dry run for at least 2 weeks
You got a link to these heat strips you use by chance?
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here ya go...
Bow Press Heat Strips
This system for building laminated fiberglass bows is the best I’ve come up with in 15 years. But…. There are a few details in getting set up and operation that needs to be documented here.
First of all you will need 22 gage 304 stainless steel strips that are used both top and bottom in your form. I had mine cut to 1.5” and 1.75” widths and 75” lengths prior to shipping. You want these “Cut” not sheared too. You want enough length on these strips to have about 3” sticking out of each end of your form. I purchased enough strip material to have a pair for each bow form I use. I put the bottom strip in the form and attach it permanently and leave it there. Here is the link to my supplier:
https://www.stainlesssupply.com/order-metal-online/docs/g1c1045s1ss0p0/304-stainless-steel-sheet-4-finish.htm
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Next you will need a fairly large battery charger that has manual settings. These are difficult to find now with all the electronic safety over ride models they have available now. The automatic ones with circuit boards will not work for what we are using this for. Look at the photo of the charger I use.
https://photos.app.goo.gl/SxemPLaXwT66Ad6B6
This one below will NOT work
https://www.amazon.com/Schumacher-SC1353-Wheeled-Battery-Charger/dp/B07BVFGVQ1/ref=sr_1_21?crid=2O3KDCXISAPSA&keywords=battery+charger+automotive&qid=1642610980&sprefix=battery+charger%2Caps%2C399&sr=8-21
This manual wheel type below is what you want.
https://www.amazon.com/Schumacher-Manual-Wheel-Charger-Engine/dp/B08PQ28NPB/ref=sr_1_27?crid=3G7TN835WBGWC&keywords=large+battery+charger&qid=1642611374&sprefix=large+battery+chargers%2Caps%2C195&sr=8-27
OK….. once you have your brand new battery charger, you need to tear it apart and rewire the cooling fan. There is a small fan that runs on 110 volts that needs its own power source. Why? Because the battery charger is going to run off of the voltage regulator at a reduced voltage….. That reduces the voltage to the cooling fan too, and slows it way down if it doesn’t have its own power source, and….. it WILL over heat the fan and the charger, and eventually burn up…. Trust me on this one….. The only other option is to attach another fan to the battery charger body that blows cool air into it while its running. This is real important.
See the extra lamp cord I have plugged in to 110 and notice the battery charger plugs into the voltage regulator.
https://photos.app.goo.gl/T5qa6trSMqEaEx7J8
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Next you need a voltage regulator. This will adjust the temperature of your heat strips. Get the “10 amp” version…. The 5 amp model will be popping fuses all the time. This is what you want.
https://www.amazon.com/LVYUAN-Variable-Transformer-Regulator-110V-120V/dp/B082KYKP9P/ref=sr_1_6?crid=3PF7ACKQJN850&keywords=voltage%2Bregulator%2B120v&qid=1642611136&sprefix=voltage%2Bregulator%2Caps%2C141&sr=8-6&th=1
https://photos.app.goo.gl/sKNmmsB6kfPizvtP9
The last item needed is an accurate thermometer. There are many different types of probe thermometers out there, but I like this one the best because it has a high temp alert built into it…. I can set the alarm for 180 degrees and if the strips get too hot it alerts me and I can turn down the voltage a bit.
Here is what I use. https://photos.app.goo.gl/ZyzWkz1hz3vHBVfs5
OK….. so now you have all your parts and pieces and equipment, and have a set of heat strips ready to go….You install one in the bottom of your form, wrap your bow laminations in a thin painters plastic , and put them directly on the heat strip. Then put the other heat strip directly on top of the limb and use zip ties to hold everything tight to the form. Take care to align the heat strips so they are the same length coming out of the form, and use a small clamp, or needle nose vise grips to clamp the two heat strips together on one end, and the battery charger clamps red on one strip, and black on the other. Be sure these two do not touch each other. I separate them with a scrap piece of wood lam.
Next is your air hose and button up your form. Then slip your temp probe in between the air hose and the top of the heat strip and give that hose about 20-25# of pressure. Check your lamination alignment and let it set 60 seconds before going up to 50-60#s of pressure…. No more than that is needed. I’ve laid up limbs completely using 25# before and they came out fine…. That was an ooops though… Recurve limbs need that extra pressure.
Now turn on the voltage regulator and adjust the voltage to about 40-45 volts. That is a good place to start for 2 -36” heat strips…. One piece bows with long heat strips will need more voltage, and going from 1.5” width to 1.75” width needs adjustment too. You will have to do some dry trials to establish the right settings. But what you want is the temp to slowly rise to 160 degrees in about 30 minutes and stay between 160-180 for another 20-30 minutes. I set my timer on the battery charger for one hour and its perfect every time once I have my voltage setting established. Btw…. Hot or cold temp in the shop can effect the setting a bit too.
The only other thing of note is to wait until the temp cools to 90 degrees before removing them from the form. You could easily lay up 3 sets of limbs per day with this set up.
Here are some of my bow forms I have set up.
https://photos.app.goo.gl/1ihdPa5SExkyBCma7
Kirk
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That’s awesome, thanks for that definitely wasn’t expecting the full Monty. ever seen someone use a bench top tester instead of a battery charger though? Might not have enough voltage on mine, 60v 10a for a one piece form
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I've talked with a few guys that recommended using a buzz box welder rather than the battery charger. But i'm not sure how i would set that up.
My system has worked well for many years and i have got between 200-300 bows out of a battery charger and i'm on my 3rd one now. So for a buck a bow investment, i can live with it.
I played with a few home made heat strips using low voltage @ nichrome wire that worked for awhile but that was years ago. and.... they didn't hold up well.
The stainless steel strips are bullet proof. You can easily sand epoxy off them without deforming the steel when you get a leak in your plastic wrap. I've got to the point where i prefer a 3 mill painters plastic over that thin stuff. But i'm using the thin stuff right now because that's what i got. I quit using masking tape on my limbs 15 years ago. Just wipe the glass down with lacquer thinner before wrapping them in plastic, and it works excellent without cooking masking tape to your glass. The plastic comes right off easily.
Kirk
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well I think I'll give a shout out to just about everyone in this thread and say, everyone was right about something. I went and got some lvl over the weekend and took the lessons learned off of my first attempt and have a full form ready but for mounting the hardware. the old form came in handy for patterns and the whole thing that took me a couple weekends of sanding and tweaking to get to a place i was happy with condensed down to 4 hours start to finish. thanks everyone
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