Primitive Archer
Main Discussion Area => Bows => Topic started by: rcoen2 on August 01, 2021, 07:28:27 pm
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Hi All,
I'm working away at my second attempt to build myself a bow and I'd like to get some community feedback and support to help move through some of these last phases.
I'm working with Oregon Ash and am doing a design inspired by Paul Comstocks section on white woods in TBB1. So its about 67" long, 1 3/4" starting width, and slightly tapering down towards 1/2" tips.
Slimbob has been helping me get this far, and his approach to tillering is to get off the long string fairly early. So that's what I've attempted to do, but in the process of my beginner level tillering a bit of set has come in towards the end of the limbs. I think mostly just from straining the limbs too fast and too soon.
These pictures shown are with my bow strung at 4"BH and pulling down about 1-2"
(https://live.staticflickr.com/65535/51351730784_576b52819a_z.jpg) (https://flic.kr/p/2meM3uG)side1 (https://flic.kr/p/2meM3uG) by Ryder Coen (https://www.flickr.com/photos/192969628@N04/), on Flickr
(https://live.staticflickr.com/65535/51351733249_dbb2ce4b15_z.jpg) (https://flic.kr/p/2meM4ec)side2 (https://flic.kr/p/2meM4ec) by Ryder Coen (https://www.flickr.com/photos/192969628@N04/), on Flickr
(https://live.staticflickr.com/65535/51350264437_4f9bd2016a_z.jpg) (https://flic.kr/p/2meDwAR)unbraced (https://flic.kr/p/2meDwAR) by Ryder Coen (https://www.flickr.com/photos/192969628@N04/), on Flickr
So I am considering heat treating the belly and inducing a bit of reflex where the set has taken. The only thing I don't want to build proper caul/form for inducing reflex at this stage in my bow making journey. So slimbob has offered the suggestion to place some shims under the handle and at about 10-12 inches from the tips to lift up the limbs so I can clamp the tips down with heat to add some reflex into them.
It seems like this would counteract the amount of string follow and hopefully limit more set from coming in while I finish the tillering.
So my current plan is to use shims and clamps to bend back the areas where set has taken in towards the end of the limbs, heat treat the belly, and then continue tillering. And my current trajectory with tillering is to move the BH up to 5" check and even out the limbs again with a couple inches of bend, then once good increase BH to 6 inches, and continue on.
Thoughts, feedback or guidance appreciated!
(if you are going to offer feedback on the tiller, please make sure to notice how each limb has some prop twist in opposite directions that messes with the eyes a bit.)
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Set up I'm considering
(https://live.staticflickr.com/65535/51352117650_af01cc7f17_z.jpg) (https://flic.kr/p/2meP2uN)heattreat (https://flic.kr/p/2meP2uN) by Ryder Coen (https://www.flickr.com/photos/192969628@N04/), on Flickr
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In my early phases I was causing my set trying to string to early before the limbs were balanced, lack of patience on my part...Your outers and the left fade are slightly stiff here...And I agree with you on tempering that belly with induced reflex...
Don
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Thanks Don, when you say left fade, do you mean from picture 1/side 1 or picture 2/side 2?
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Picture 2 left side
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Here...
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Hey Donald, good to hear from you. So I have recommended he stay off the fades until the mid and outers were bending well. It is stiff and does need to be loosened up, but only a tiny bit at this point. My advice has been to stay off the fades for now, get the limbs bending from a few inches out and beyond. Temper, induce an inch or so reflex, and bring the fades around then.
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My apologies, I went back and reread the post and seen where you were already helping rcoen2...
Don
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No, I asked him to post it and solicit advice, so I am glad you answered. The concern he has at this point is should he temper and reflex. My advice was yes, but asked him to check the opinion of others.
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Definitely agree on a good heat temper with induced reflex...
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It’s taking set where it’s bending the most but it’s surprising that it’s that much set so early. What’s the MC of the wood and what is it pulling right now? Also looks like your handle and fades section is quite long. Definitely stiff in the outer half of the limbs.
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It’s taking set where it’s bending the most but it’s surprising that it’s that much set so early. What’s the MC of the wood and what is it pulling right now? Also looks like your handle and fades section is quite long. Definitely stiff in the outer half of the limbs.
I just haven't worked on the handle and fades yet. its designed to be 4" handle and 2" fades but its extra bulked out and so it looks off. I don't know the MC but its been seasoning for about 6 months so I don't think that's the issue. I also don't have a scale yet so I'm not sure about weight that its pulling. I have to go get a cheap scale sometime soon
it's also confusing to me that the set seems to be coming in towards the end of the limbs because that's where it also appears to be stiffer....
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Depending on your relative humidity it could still be quite wet. 6mo very well couldn’t be long enough. From the unbraced picture it doesn’t look like the set is near the tips at all. Even though your handle and fades might be marked out that way the center 12-14” is totally rigid. You need to get the inner limbs working at least a little bit because they take the most stress and takes stress off the rest of the limb.
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I just finished tillering of my 2nd ash bow. The first one is 70" tip to tip, pyramid style with 1" wide, 4" long handle, 1 1/2" at the fades tapering down to 5/8" at the tips. The 2nd one is 68" tip to tip, 1 3/4" wide at the fades, and also tapering to 5/8" at the tips. Both have about 4" of set, developed during tillering before the bows were even shot. The staves were purchased from a lumber mill which said they were cut about 9 months ago. The wood was quite oxidize and appeared well cured. I am thinking the bow set is just a characteristic of the wood. I think mine is white ash since that is common in my area of Western NC. The bows pulled at just under 30 pounds at 26" draw before being backed with 2 layers of fiberglass cloth and surfboard quality epoxy. They both shoot VERY WELL. Unless the set gets far worse, I am not going to worry about it. I suspect trying to induce reset is not going to do a lot of good, but if you are firm in wanting to try that, I would suggest steaming the area that will be bent for 45 to 60 mins, then clamping it down to a form. Leave it clamped over night. Good luck. Ash is very nice to work with compared to my usual choice of black locust, which is often riddled with worm holes and imperfections that you don't find until late in the tillering phase. Also, the ash bows seem to have low hand shock compared to black locust bows.
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Backing white ash with the devil material seems to be just asking for frets.
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You need to get the inner limbs working for sure. I also suspect the m.c. is a bit high, the ash we have here fraxinus excelcior likes to be dry dry. Time isn't really the be all and end all factor - r.h., temperature and airflow are the main things that matter and of course the woods thickness whilst drying.
Another 'problem' with ash is its strength in tension and only so so compression resistance. Trapping the limb eg. making the limbs cross section a trapezoid (narrower back) will take some laod off the belly.
Heat treating is another way to achieve a more optimal balance between compression resistance and stretch resistance. You can safely do both with ash.
Your set is happening where the limb is over strained/bending too much. Watching the set carefully is important. Set is the wood speaking to you!
GreenWood - adding glass to the back of a wood bow will give you the 4" set you mentioned. Glass is about 40 times stiffer than wood. The glass resistance to stretching forces the belly to semi collapse. It has to give somewhere. This is why glass bows are always made with glass on the belly too. Glass back and belly gives you an optimal balance. The core is really there just to space the glass lams the correct distance apart for the draw weight you want.
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Thanks everyone that's offering thoughts. I ended up going for some induced reflex + heat treating with a heat gun. I did that this morning so I'm going to give it ample time (like a week or so) before unclamping it and seeing how the reflex took. Then I suppose I'll move forward with the tillering again, starting with getting some more bend in the inner limbs as suggested.
Actually, Is it unnecessary to leave it clamped that long, while the moisture comes back in to the bow? I know its important to wait before bending the wood again, but I do I need to wait with the clamps too?
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Backing with epoxy resin saturated fiberglass cloth is the most common form of backing in use today and is far easier to do than backing with another wood such as bamboo. I doubt that my builds needed backing, but if you have ever had a bow explode in your hand or even on the tillering rack, you give great thought to backing that holds the pieces together should you have such a massive failure.
With fiberglass cloth and epoxy resin, it won't prevent a poor build from failing, but epoxy is very strong and flexible and will work like the membrain of safety glass in your windshield or sliding glass windows to help prevent you from getting seriously injured. I have had two red oak bows made with big box harware store wood littlery explode due to what I think was over cooking in a kiln to dry the wood fast. One of the breaks embedded a large chunk of wood into my arm. I thus don't use kiln dried lumber any more and I continually err on the side of caution and back all my bows with cloth/epoxy. Don't use polyester resin because it is brittle. High quality epoxy is very hard to break. It just bends and bends some more.
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All true, but we are building bows from natural materials. Yes, some will break, but the magic is in finishing one out of natural materials that holds together, and rivals the glass bows. There is a beauty in both, but FG is just not in the mix here.
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No harm in leaving it clamped. Since you are going to let it dry for a bit, might as well leave it clamped. I think you will see a marked change in the compression strength, worth the trouble.
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Hey Greenwood, thanks for sharing your thoughts and experience. I'm not personally interested in doing FB backing. I'm much more drawn to self bows and if backing using rawhide or sinew. So I'd prefer if we kept the FB discussion off of this thread.
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I am thinking the bow set is just a characteristic of the wood.
Don’t start blaming the wood. Next thing you know you’ll be saying “Osage is king!” >:D
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No need. We ALL know that.
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(https://live.staticflickr.com/65535/51356465747_0415c4c5b7_c.jpg) (https://flic.kr/p/2mfcj2Z)IMG_3342 (https://flic.kr/p/2mfcj2Z) by Ryder Coen (https://www.flickr.com/photos/192969628@N04/), on Flickr
I'm guessing you can't tell if a dry heat treatment was thorough enough for the suggested reflex to hold by color alone.. but I'm wondering if at a glance it seems like I under did it. Some of the pictures I have seen of other's heat treatments are quite dark. I'm not sure how much different types of wood express the color differently too. I think I was a little cautious on not wanting to push it too far, so this is what I got. Thoughts?
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No way of knowing just on the color as that’s just on the surface. Some guys heat with minimal color and some get it quite dark with similar results. What was your process in terms of heat gun setting, distance from the belly and how long it took?
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Backing with epoxy resin saturated fiberglass cloth is the most common form of backing in use today and is far easier to do than backing with another wood such as bamboo. I doubt that my builds needed backing, but if you have ever had a bow explode in your hand or even on the tillering rack, you give great thought to backing that holds the pieces together should you have such a massive failure.
With fiberglass cloth and epoxy resin, it won't prevent a poor build from failing, but epoxy is very strong and flexible and will work like the membrain of safety glass in your windshield or sliding glass windows to help prevent you from getting seriously injured. I have had two red oak bows made with big box harware store wood littlery explode due to what I think was over cooking in a kiln to dry the wood fast. One of the breaks embedded a large chunk of wood into my arm. I thus don't use kiln dried lumber any more and I continually err on the side of caution and back all my bows with cloth/epoxy. Don't use polyester resin because it is brittle. High quality epoxy is very hard to break. It just bends and bends some more.
The bow won't break if you select your board well.......as I said and explained above backing a wood bow with glass cloth is a very bad idea.....Compounding poor wood choice with a poor backing choice isn't going to make you a good bow.
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Sinew and glue, or decent rawhide, is also 'indestructible' and won't overpower wood.
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Thought experiment. Attach a steel band onto the back of the bow. When the limb bends, either the back stretches, the belly compresses, or both. With the steel band on the back, the back will not stretch, so the belly does all the work. That is a recipe for disaster. FG will overpower the wood belly with about the same results.