Primitive Archer
Main Discussion Area => Bows => Topic started by: bentstick54 on January 16, 2023, 09:01:14 pm
-
I’ve been using dry heat to make corrections on some Osage bows after floor tillering. Depending on how much correction is needed I get some drying checks on the back of the limbs. I haven’t had a breakage problem because the all have run with the grain, but would like to minimize the checking. For those of you that use oil when using dry heat, is one oil better than another, and how much do you use? Do you just rub a little on the belly, or really saturate it? Does the oil “cook” or evaporate out during the heating process? How long do you wait after cooling do you wait to start tillering?
-
I just use regular cooking oil, just rub on belly, not real heavy. It mostly cooks away, I like to give it a day if I heated it much, some don’t and say cool is cool. Another thought with your checks, if the wood is not seasoned and still a little wet it can do that also. Pappy
-
Thanks Pappy. I roughed out a stave the other day that I had split in 2013 and stored in my basement the entire time. Average year around controlled temperature runs around 66 to 68 degrees, 35% to 50% relative humidity. After working to almost floor tiller stage I let it sit for another month before floor tillering. I put in some slight reflex evening up both limbs, taking some minor twist out of 1 limb at the same time. I kept heat gun about 4 inches away and used a medium/hot temperature, and did about 4 inches at a time clamping as I went.
-
If you seal the back first it will minimize the checking. I keep a can of spray shellac on my work bench just for this purpose. Any time I expose a fresh back, no matter how well seasoned I seal the back with shellac.
-
Thanks Pat. I haven’t sealed the backs once I got to this stage, but never had a problem with any that I did not try to heat correct any imperfections. I will sure give that a try on one that’s waiting for me to get to work on.
-
I just use regular cooking oil, just rub on belly, not real heavy. It mostly cooks away, I like to give it a day if I heated it much, some don’t and say cool is cool. Another thought with your checks, if the wood is not seasoned and still a little wet it can do that also. Pappy
I do the same for minor corrections and such. Canola oil works for me. To get any excess oil left behind afterwards I wipe with a cloth after heating up the area then quickly wiping as the oils surface. Best of luck.
-
I use zero oil and never have even tried it. The only time I get any checks is when the wood isn't dry enough. When its dry enough you can pour the heat to it and have zero side effects, like checks opening due to moisture expansion.
-
I use zero oil and never have even tried it. The only time I get any checks is when the wood isn't dry enough. When its dry enough you can pour the heat to it and have zero side effects, like checks opening due to moisture expansion.
[/quo
This x2 . That’s s scary pearl. You and me thinking alike.🤠🤠
-
Chris and Arvin. Are the backs of your staves sealed before you put any heat to them?
-
Yes, sir. Checks mean stave is not dry. I agree with PD and Arvin.
-
Chris and Arvin. Are the backs of your staves sealed before you put any heat to them?
Nope, never do that either.
-
Not sealed for me either.i will say this I was able to see and afford the need for a stave stash years ago. My wood could have been cut 5 years ago if need be. And it gets dry in central Tx.
-
I think the R/H of your area might have something to do with it. Because I've had a few osage backs check when heat treating I started spraying the back of any newly exposed stave with shellac and haven't had any check since. Some of these staves were 10 years in my basement shop before I used them. It's little enough effort and cost for me to continue the practice.
-
Thanks everyone. The stave was 10 years old when I removed bark and sapwood, chased the back ring, and then floor tillered. Then left at that stage for about 30 days. My humidistat? showed an average 33% and temperature held a steady 66. I guessed according to the charts the wood moisture should have been somewhere between 7% and 8%. I didn’t think that was too much for Osage, or am I missing something?
-
I think 9% to 11% M/C is more acceptable for osage but I've never had one 7% to 8% M/C so it's only what I've read.
-
if the stave is not dry enough,, the oil might help
-
Guess we will just have to agree to disagree , :) I have had problem with checks on the back even with dry wood especially if they needed much correction, but with oil on the bell, seal the back and heat slow I have had none so for me it's not worth the chance. :) once it happens it to late, it don't usually ruin the bow unless they run off the edge but just looks bad. ;)
Pappy
-
This is the 3rd one I’ve had this happen on. Bows are shootable, but i would like to figure out what’s causing this and how to prevent it. These have all been staves that I have kept avoiding due to twists and bends. I finally decided it was time to try and learn how to straighten them. (Ran out of straight staves). I think all of the above advice definitely has merit, and the 1st 2 where only 2 years in storage, taken down to a thin layer of sapwood, sealed with several heavy brushed on coats of shellac. I chased them to a clean back ring but did not seal again before applying heat. These 2, I can agree were probably still had too much moisture in them. The 3rd one I really feel was dry.
Can I be applying the heat too fast, too hot, or too long?
I’m starting another one, another 10 year old stave, that I’ve chased the back on. I think I will seal this 1, then get it to floor tiller, and try oil. I’ve got nothing to lose. I no different techniques work in different areas, I just have to find one that works for me.
-
I've always used oil when bending wood with dry heat. I believe it helps to prevent scorching, it helps hold the heat a bit longer and by doing so it helps the heat penetrate better. I have no proof of any of this but it has always worked for me. As far as adding shellac to the back when heat correcting, since I started doing this I don't get checks in the back with heat treating and like I said I've had staves that were in the dry for 10 years that checked when heat was applied for tempering or correcting. That is why any time I chase a clean ring on a stave or or a bow I seal the back, no matter how well seasoned it is.
The only time I don't use oil is if I'm tempering the belly. Then I want the dry heat to scorch the belly to help improve the compression values of the wood. I do however seal the back with shellac beforehand.
-
I like to use oil on major corrections. I've done it plenty of times without oil also but once in a while I get a crack and like to blame it on no oil
-
Guess we will just have to agree to disagree , :) I have had problem with checks on the back even with dry wood especially if they needed much correction, but with oil on the bell, seal the back and heat slow I have had none so for me it's not worth the chance. :) once it happens it to late, it don't usually ruin the bow unless they run off the edge but just looks bad. ;)
Pappy
Looks like we will have to arm wrestle next time we meet up :)
Hope you are well old friend.
-
Ok bent stick if I under stood you your on twisted staves. I know you are a good bowyer. Working with twisted grain I’ve encountered this before. Only so much you can unwind the rope 🤠that why I don’t buy or cut them anymore. Sell that to the snake lovers and go buy you some straight ones. 🤠 just funning guys. Pat may be right about where we live affects it. That’s kinda what makes us different. 🤠
-
No Arvin that ant what makes you different (lol) Pappy
-
Sorry. I got confused. I use olive oil on the back when bending too. When heat tempering I just put oil on the belly.
-
Thanks for the compliment Arvin, but you must have me confused with someone else. I’m just a hobbyist bowyer. Probably 18 to 20 attempts, with 7or 8 that I would not hesitate to give to friends, 5 or 6 that needed a little superglue and a wrap on a lifting grain on an edge, and well 4 or 5 that I just cut up. I cut and split my own wood, just part of the journey for me. I have no desire to go into building and selling bows, or chasing flight records. I just like the gratification of building my own, shooting 3d, and hunting with them. I do admire you and the others that have pushed bow building and performance to the level you have, and the willingness to share your knowledge with us backyard bowyers.
I got the profile close today, cleaned up the back of scraper marks, and sealed the back with shellac. I’ll let it sit awhile before working it to floor tiller. Once I get started back on it, and start heat corrections I’ll update progress.
Thanks for everyone’s input so far.
-
if you dont have a moisture meter,, you are just guessing... if you having a problem,, there is a reason,,
-
I never get any checking on heat corrections, I don't use oil, I only heat a limb enough to get it moving. I use the "can I still hold my finger on the wood briefly" method of determining the temperature I want.
I heat my limb in the channel of a piece of aluminum angle, this distributes heat really well, the aluminum soaks up heat, gets really hot and stays that way.
I do use wood forms as well and wrap the correction with tee shirts but still go light on the heat.
After I gently make the correction and while the wood is still clamped, I wrap the limb and the piece of aluminum in several tee shirts to let the retained heat in the aluminum soak slowly into the wood. I leave everything clamped and covered until the aluminum and wood return to room temperature.
My method is seldom a one-shot deal, it is bend, cool and check, bend, cool and check until I am satisfied with correction.
-
I agree Brad, I’m just guessing, but trying to make educated guesses lol. I need to pick up a moisture meter rather than winging it, but just haven’t been trying any serious heat corrections until recently, so has not been a problem in the past.
When searching the internet for pin moisture meters I see them starting around $13 and going up from there. How expensive of one would everyone recommend for just an occasional user?
-
Thanks for your input Eric.
-
Totally agree with Pearl on the to much moisture yet.
I do alway seal my back on any wood as soon as I first expose it. No matter how long it’s been cut. I’ve had staves that were aged when I got them and left with the bark on for a couple years before I got to them.
Chased a ring on them and the next day they already had drying checks. I had a quite a few that checked on me before I sealed the back. Never really hurt the bow, but some people don’t like the look of it.
It’s not just dry heat either. I’ve had it happen with steam to.
Bjrogg
-
I never use oil to prevent checking, it won't. That's what the shellac on the back is for and it has for me.
-
I never use oil to prevent checking, it won't. That's what the shellac on the back is for and it has for me.
I haven’t either Pat. I always thought it was to keep the scorch marks from happening.
I don’t know for positive if it does anything to cure checking on back seeing I’ve never tried it before, but I don’t understand how it would applied to belly if it does. I have used oil on back when I didn’t have anything else to seal a freshly chased ring.
Bjrogg
-
I need to retract my statement that I never get checking on dry heat corrections and change it to very seldom get checking.
I went out to the shop yesterday to work on a bow that I had trouble with belly cracking when I tried to bend in the recurves and there it was; a little 1" check on the back where I made the most extreme bend. I tried the bend twice and got belly splintering both times. I went out to the shop to file off the splintered wood and glue an underlay on to build the wood back up.
It was then that I thought back and remembered a few staves over the years that did indeed get a small check or two, I remembered that I kept a tube of superglue close at hand on these staves and instantly put a puddle of superglue over any crack that started to form no matter how small.
Sorry for mis-information, at 75 these senior moments come around more and more often for me.
-
I’m only 68 but starting to understand about those senior moments Eric. That’s how I have treated the checks also, by saturating them with thin super glue before finishing.
-
I hit them up with superglue while the wood is still hot from correcting, the glue seems to penetrate better hot and stops small checks in their tracks so they never get bigger.
-
I had some very old osage gifted to me from fence post,, 50 years old had been laying on the ground,,
I tried working to a ring, and a check came up,, I would go to next ring and the check would open again,, till I was running out of wood,, so put the super glue and just made the bow,,, but sometimes I think it may be the quality of the wood more than how we treat it, some wood maybe more prone to checking,, but just guessing,, so not so much the heating process causing it,, but the wood is just a bit different,,than another stave that might not check at all,, but who would think a 50 year old stave would start to check when you worked down to a ring,, I was surprised,,
-
Hi,
Just a quick reply without reading all comments: I used muskrat fat with good results. If I want to put a layer of sinew, I use wood ash in water solution for degreasing.
I even experimnented with brake cleaner (quick and dirty (lazy), I know), but it works as well.
Cheers Uwe
-
You may be on to something Brad. I did two staves within days of each other with close to the same corrections needed to both. The one that checked which led to this thread, was cut 10 years ago, split, ends sealed and stored in my basement with bark on. The 2nd stave was 3 years old and treated the same way. I had no drying checks in the back of the newer stave.
For information purposes our house has central AC/ gas heat. Basement maintains 66 to 68 degrees year around with humidity running around 33% to 37% in winter and around 50% in the summer.
-
If my meter (8-10 %) shows the osage stave is not dry, after chasing a heartwood ring, I automatically give it a coat of poly. Jawge
-
coat of poly is a great idea just in case
-
You may be on to something Brad. I did two staves within days of each other with close to the same corrections needed to both. The one that checked which led to this thread, was cut 10 years ago, split, ends sealed and stored in my basement with bark on. The 2nd stave was 3 years old and treated the same way. I had no drying checks in the back of the newer stave.
For information purposes our house has central AC/ gas heat. Basement maintains 66 to 68 degrees year around with humidity running around 33% to 37% in winter and around 50% in the summer.
My staves are in the top of my bow shop getting to 120 or so in the summer. With a higher average humidity. Maybe it’s the heat more than the humidity.
-
Maybe Arvin. Like Brad said, without a moisture meter I’m just guessing. Going to see if I can pick one up later today so I can take some guess work out of it.
-
Ok, so yesterday I picked up a moisture meter yesterday, and could not get a reading on a roughed out bow that I had done after the last one that I had the drying checks develop on the back while making heat corrections. The moisture meter won’t register below 7%.
This stave was way worse than the last, so I took Pats advice and sealed the back with a coat of shellac, then I went ahead and used a little canola oil on the belly and grabbed the heat gun. I did the worst limb this morning and just took the clamps off. Pulled it over almost 2” sideways, and took the twist out at the same time.
Don’t no if it was the shellac, or the canola oil, or combination of the two, or none of the above. But it did not check, and I believe the oil may have helped pull the heat into the wood deeper quicker so it didn’t scorch the belly. The wood seemed to reach the bending point faster and easier.
I hope to do the other limb tomorrow, and will see how it goes.
-
Looking good - you really moved it a lot! I have a few of those sideways staves, and whenever I see them my inclination is usually to keep looking for a straighter one...
-
Looks really good Bentstick. I have done exactly what Pat recommends with very good results on straightening Osage. Good luck with your other limb. Hope you get a nice bow out that stave.
-
I've heat bent with shellac on the back, and still got little ruptures. Osage from a 1" thick board, not kiln dried, but seasoned in my shop for many years, so it didn't have a high moisture content.
I've also got mixed results from shellac on staves, even when they have been roughed out, floor tillered, not from a supposedly seasoned large split with potential moisture.
I switched to canola oil and haven't had any splits since.
I think shellac is good for protection when the stave is green and you are going to use wet heat to bend.
Once a stave is dry, I suspect the shellac(which is quite tough) stops the air in the woods cells from escaping, until the pressure builds up and the air is forced violently out of the cells, causing fissures.
It doesn't always happen with shellac, and dry heat. Many guys never seem to have issues. Like I said once changing to oil I've never had any problems, ever.
-
So I repeated the process on the 2nd limb today with the same success. This limb needed about 1/2 the correction as the 1st limb.
I wiped a thin coat of canola oil on the belly, and hit it with the heat gun. It didn’t take very long before the wood started becoming pliable enough to move. I waited a couple of hours for it to cool and took the clamps off, and it held the correction, with no drying checks showing up on the shellaced back.
From never using oil before, my first impression is that it seems to help carry the heat deeper into the wood at a faster rate. I felt like it took a shorter period of time for the wood to become pliable with the same amount of heat when I didn’t use oil. I’m wondering if a combination of shellac retarding moisture being forced out the back, and the oil transferring the heat quicker into the wood causing less time for any moisture to be forced out, is a possibility?
I don’t have any other staves ready to rough in yet, but I do have a corner full of future candidates to test on. I will definitely try the same combination of shellac and oil in the future and see if the results repeat themselves.
Definitely worth the little effort to experiment with again.
-
I haven’t used shellack yet but I do and have used oil based and water based poly coat on the back of my stave for drying. I find the water based stuff little better. I also use canola oil with good results as mentioned and no splits. I will occasionally get splits with boiled or steamed tips if I rush the drying out and heat tempering of the recurve. As long as I wait couple days then I’m usually fine.
-
Well I finally got this bow finished up. Not the best looking bow I’ve made, but it shoots pretty well, especially for as much correction as the stave took. I wanted something a little less weight than my normal 50# goal, so I brought this one in at 46# @ 28”, 66” ntn.
-
So I had another piece of Osage with a serious dogleg in it so I thought I would try the dry heat with the back shellaced and some canola oil on the belly again. I did not mark the harvest date on this stave from some reason, but it is at least 2 years old and probably older and has been stored in my basement all along.
I used the high heat setting on my heat gun, held 4” to 5” above the belly, heated about 4” at a time, pulled the limb over, clamped, moved to the next 4” and repeated, plus going slowly back over to the previous area to hold heat in longer. Then after the whole limb was done and clamped, I slowly went back over the whole limb and then let cool. I tried to do a slow heat for deeper penetration without scorching the belly.
After cooling and unclamping, I hit the last 4” of the limb again to align the tips a bit better. After finishing and letting cool, I was very pleased with the results. I see no drying checks on the back or belly, and it’s holding the corrections.
For reference I left limb thickness at approximately 5/8” thick and 1-3/4” wide at the fades tapering to 3/4” at the tips. I wanted to leave it wide enough and thick enough to have room to narrow and thin.
-
Osage is just so cool for heat correction. Well actually it’s hot but it sure can be transformed into the shape you want.
Bjrogg
-
Well done!
-
Kansas has a ton of Osage, but it’s still hard to find a straight one. So I’m just trying to figure out how far I can go with it. Learning every time. But so far seems like shellac on the back, and vegetable oil on the belly seems to be working on keeping the drying checks down.
-
Bentstick. What is you mix for shallack? Did you mix your own shellack flakes with a thinner or store bought stuff.
-
nice work,,, :)
-
Dave, I just used the store bought stuff. I bought a quart of Zinsser brand. I’ve sealed about 24 staves, and maybe 6 roughed out bows after I chased rings, and maybe used 1/2 of the quart. And it is easy, lol.
-
Ok that’s good bentstick. I think I have some of that stuff. Good to know it works.
-
Like everything, there’s no guarantees, but that’s 2 for 2. I will definitely go this route again as I have plenty of staves that will need corrections when their turn comes around.