New Flatliner form

[Kirkll]

I finally had to retire my old one piece Flatliner long bow form. The original one lasted 15 years, but was taking a bit of a twist on me after all these years. So i decided to use this 1.75" X 12"  LVL material on this one.

It has a unique system i use on some of my forms making it real easy to use. I've taken a little video with my phone here to show you what i've got.... Thought i'd share this with you.  BTW.... The blocks on the form between the hinges are where i screw a couple pieces of flat metal before airing up the form.   Kirk

 https://photos.app.goo.gl/B5FSD38dryUNqyG38

[Stagmitis]

Hey Kirk I wish I had more confidence in the LVL material but every form I made from it warped after just a few bows-

I ran the stock 1.75" material through my sander until I got to 1.5" which is what I use.Maybe invading the laminate had something to do with warping? Any ideas?

[Buemaker]

Them hinges should work fine.

[mmattockx]

It has a unique system i use on some of my forms making it real easy to use.

That's very slick, much better than handling a loose top piece and fitting it down onto the bottom with flat bars on the side.

Hey Kirk I wish I had more confidence in the LVL material but every form I made from it warped after just a few bows-

I ran the stock 1.75" material through my sander until I got to 1.5" which is what I use.Maybe invading the laminate had something to do with warping? Any ideas?

Which way does it warp? Removing some material might be releasing internal stresses, but those are laid up with bits of wood and glue on a big press so I wouldn't think that is your problem. With no grain or fibres running full length there should be no tendency to warp. Did you remove material from both sides evenly so the finished skin is gone completely?

Maybe try one where you use a router to narrow just the edge where the glue up occurs and leave the rest of the form full thickness?


Mark

[Buggs]

That hinge is a great idea    

Do you guys seal your forms and keep them sealed?
Any uneven moisture absorption, plus the inevitable  hot and cold sides of a form, will make a prime environment for warpage. Especially when using materials comprised of many layers of dissimilar fibers and species of wood, which will all move at slightly different rates. 

[Stagmitis]

As evenly a i could mark. I thought about reducing the width with a router but i was worried I wouldnt get it dead nuts

[Longcruise]

As dry as it is here I haven't had a form warp.  Except that one that I built the warp into!! 

[kennym]

Likin the hinges , looks like it will work well.

[onetone]

Slick form Kirk! Is the reason for the single bolt in the hinges so that they can pivot to align with each other when the top of the form is closed? I’m wondering if that approach would work on a recurve form.

[Kirkll]

In Oregon here…. EVERYTHING warps if not handled properly. I’ve had excellent results with the LVL material…. But I do not sand it or mill it down, and I seal the hell out of my forms as soon as they are made. I also do NOT cook my forms in a hot box over and over again. The use of heat strips save your forms BIG time…

This one was for 1 1/2” glass, and I thought briefly of milling it down, but decided to keep it full width and just center up my lower pressure strip and epoxy it right into the form. I did seal it first, and let the lacquer cure over night. But I thought this would help keep it straight….. but you still need to check these things for twisting a bit….. That’s what happened to my old one piece form.  Nothing worse that starting out with twisted limbs coming right out of the form.

That hinge idea works really slick for the shorter limb forms as well. I have 3 or 4 sets of those that are over 10 years old. I worked as a finish carpenter on a lot of motels, schools, and commercial projects, and collected a lot of hinges over the years.


Kirk

[Kirkll]

Slick form Kirk! Is the reason for the single bolt in the hinges so that they can pivot to align with each other when the top of the form is closed? I’m wondering if that approach would work on a recurve form.

Basically the heavy screws hold the hinges in place, and the bolts are there for extra strength when you air up the forms….. Just screws alone do not hold very long, and they move around.

I’ve got some for my hybrid long bow limbs and they work fine, but just use bolts on my serious RC forms.

[Nicholi]

Kirk, Do you have any videos on how you install/wire your heat strips? Is it just heat trace?

[Kirkll]

Nichol,  I use 305 stainless steel in 22 gage for the strips, and a battery charger with a voltage regulator. On my shorter limb forms I have enough length on the heat strips to clamp one end together , and just clamp the battery charger jaws to the other ends.   My longer forms, like this one, I have to attach wires to one end to hook up the charger. The form is cut to 70” and the heat strips are 72”.

I have a pretty good PDF explanation with photos on how to build this system if you are interested. Let me know and I’ll post it once I get back to my shop pc.

Kirk

[Nicholi]

Please do. So you are basically just connecting negative and positive to the same piece of metal and the resistance is enough to make it a heater. Did it take a lot of fine tuning to find the voltage sweet spot for the right temperature?

[Kirkll]

Yes Sir.... That is EXACTLY how i came up with the right voltage....  Here is my PDF on this system.

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 72” 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

……..

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
…………
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

[Nicholi]

Thank you! I'm going to reread this tonight a lot slower... It makes a lot of sense though.

[BO-R]

I also have been using that setup for last 5 years,
and is a great alternative to hot boxes.

Great stuff!

[Kirkll]

The only down side is that the battery chargers with manual settings are getting harder to find on line….. but I usually get a couple hundred bows out of one before she burns up….

I’m quite sure in this day and age, there is a better system using Nichrome and low voltage…. But ……this stainless steel is tough material that takes a beating, and you can easily sand any glue off without deforming the surface.

The thing I really like about this system is that you put your form in a vice, and that’s where it stays until you change things up and use a different form.   Kirk