Author Topic: Reflex form with a heat gun?  (Read 2370 times)

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Offline justsomedude

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Reflex form with a heat gun?
« on: February 26, 2017, 09:59:00 am »
I'm getting ready to make a 2x4 form as shown in the Gary Davis DVD.
2x4x6' that is full width in the middle and curving down to 1/2" wide at tips and a second 2x4 attached to the flat side as a stop to clamp to for lateral straightening.

Just using it to fight set and Stringfollow for now.
Flipping tips will be next in the list.

Can this be done with a heat gun? I know you'd have to do it in sections starting in the middle and working towards the tips. Just wondering if it would need a steaming rig

Offline Limbwalker

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Re: Reflex form with a heat gun?
« Reply #1 on: February 26, 2017, 10:29:05 am »
Hey man, you can accomplish a lot with a heat gun and patience. I've used localized steam once on green Osage. I have used dry heat on many types of wood. Get some scraps and get a feel for what is happening. Using the scraps you won't fear breaking them. I broke several testing the limits of different wood. I've noticed a lot of opinions on bending and different people are comfortable with different methods, it seems.

From what I've been able to bend with my heat gun, getting the whole core above the 150 mark is critical as far as minimal spring back. Yesterday I flipped the tips on a green dogwood stave using coconut oil and dry heat. I had cut the dogwood down three days ago. Many people would choose steam for that. The point is, I'm set up for dry heat and I was being lazy. It worked, no cracks or checks at all, but it probably took as much time as steaming n the end. I had to heat it up while giving it as much oil as it wanted. Many times I would turn the heat Gun off for 30-60 seconds and rub in some oil, let it cool slightly and then turn the gun back on and keep going, as to not scorch anything. Once I reached my target it bent like rubber, it just took time and patience getting there. I've done this with several staves now, green or dry. So yes you can bend a lot with a heat gun. You don't have to pick one or the other, you can use both methods.

With steam you have to work quick and calm once tyour ready to bend on the form, because once the core temp drops it won't work. That's the main thing. Whether dry heat or steam, getting that core temp up is the key. With dry heat it's much easier to scorch the wood, so both methods take patience.

Get your heat gun and some practice pieces and try out your new form. It will build your confidence and you will get a much better handle on bending wood. This is only my experience.

Offline Pat B

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Re: Reflex form with a heat gun?
« Reply #2 on: February 26, 2017, 10:49:33 am »
It takes more than a form and heat gun to fight set and string follow. Set is inevitable with natural materials under stress. The heat gun and form can assist you but most of the set is cause by the way the bowyer tillers, with how patient the bowyer is while tillering. Knowledge of the properties of different woods and using well seasoned woods is as important as any other tools you use while building.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Limbwalker

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Re: Reflex form with a heat gun?
« Reply #3 on: February 26, 2017, 11:25:33 am »
I don't know Pat, but have seen many pics of his bows and I know he knows his stuff. I failed to mention that none of the bending I am speaking of is to combat set. Th Dogwood for intstance is now put away to season.  Bending for me is part of design and can add different qualities to the function of the bow. I believe and time will tell, a bow will 'Set' the same amount no matter how much heat bending is done. I believe set has to do with what Pat said

Offline justsomedude

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Re: Reflex form with a heat gun?
« Reply #4 on: February 26, 2017, 11:35:19 am »
The gary Davis form seems like a lot of bend to me, but I know nothing....so I want to see how it works out. I have a pile of twisted Osage to learn on

Offline DC

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Re: Reflex form with a heat gun?
« Reply #5 on: February 26, 2017, 11:39:57 am »
Yes you can use a heat gun and a caul (form) to bend staves. I didn't bother with the second 2x4, I just screw on scraps of wood as needed to align the stave. I found that on wiggly staves the 2x4 seems to direct the heat around the back and cause scorching. Others results may vary. I've never used oil because I'm afraid it may cause problems with the finish later. Hold the gun on high temp about 3-4 inches from the wood. It takes a few minutes to get warm enough to bend. If you are planning to heat treat the bow save minor bends for then and do it all at once. If you get the wood hot enough to start to turn brown all you bends should stay. I have had them not move at all when I unclamp them. Leave them clamped until the wood is cold(couple of hours) and most leave them for a day or so to re acclimatise.

Offline Bob Barnes

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Re: Reflex form with a heat gun?
« Reply #6 on: February 26, 2017, 01:02:10 pm »
I have watched and worked with Gary many times over the years and still use my replica of his reflex for to straighten and reflex staves that I'm working.  Mine is made from a 2x4 screwed to a 2x8, and I would be glad to take measurements if you are interested.  The first osage bow I ever made came off one of Gary's forms and still holds some of the reflex after 17 years.  I just checked and the 2x4 tapers from full width in the middle to nothing on the ends, but it's a full 72" long.  I know the trend now is D/R forms for heat guns, but this still does a great job.
Seems like common sense isn't very common any more...

Offline justsomedude

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Re: Reflex form with a heat gun?
« Reply #7 on: February 26, 2017, 02:06:36 pm »
I going to watch that section of the DVD again. As I recall, it tapers 1/4" each 3" as you go from the center to the ends. He mentioned that he started out doing 1/2" for every 6" and it created high spots so he subdivided it more.

EDIT. Those are the markings used to make his basic reflex form but not exactly how it is executed. Get the DVD...he explains it well. He also shows how fudging the numbers in either direction creates a more drastic reflex or a straighter form.
« Last Edit: February 26, 2017, 03:47:31 pm by justsomedude »

Offline gfugal

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Re: Reflex form with a heat gun?
« Reply #8 on: February 26, 2017, 04:06:30 pm »
Straightening the limbs asfter set may not fix the set. Once the damage is done its there for good. So steaming the set out is practically pointless, but if you heat treat the wood, you actually are changing the properties of the belly wood making it stiffer. So while it doesn't fix set, heat treating will still help a lot. It might even turn out better heat treated after set then no set at all, but i'm not sure about that. Whatd best though is no set then heat treated.
Greg,
No risk, no gain. Expand the mold and try new things.

Offline justsomedude

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Re: Reflex form with a heat gun?
« Reply #9 on: February 26, 2017, 05:02:39 pm »
I just marked Center and 1/2" marks on a 6' 2x4 and clamped some thin trim wood on to make the arc. I have confirmed that it is at least fairly symmetrical by taking measurements at various spots along the curve. CUTTING the arc however... :) I'm not a fine carpentry guy. I'll cut close with a jigsaw and sand it I guess

Offline justsomedude

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Re: Reflex form with a heat gun?
« Reply #10 on: February 26, 2017, 06:54:59 pm »
So yeah...drawing the arc like that works great. I totally failed at the cut though. My Jigsaw blade went crooked....time ti visit my friend that has nice tools and knows how to use them!