Primitive Archer
Main Discussion Area => Bows => Topic started by: shofu on March 31, 2017, 11:37:11 am
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Hi everyone. My name is George and this is my first post. I am an an aspiring bowyer and have learned much from this great community already (long way to go).
To get me started, I was given some seasoned staves from DC and TreeNinja from PA (thank you!). I bought 2 humidistats and after taking the wood from 70degrees 50% RH at DC's, I got home and my house registered at 70% RH everywhere I tried and one stave developed a crack (Ocean Spray).
Not sure how to proceed - is wood stable? Any advice greatly appreciated.
Thanks,
George
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really depends on where the crack is,, need more info and pic if possible,,if that is on the back,, or end put more sealer on, glue paint varnish,, something,,
put the stave in a cool room for now,, till we have more info to go on,,
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Hey George. My first suggestion would be to calibrate your hygrometers(not humidistat). I found them to be rather inaccurate. Just do a Google search on "calibrating hygrometers". It's quite a simple process. Cigar guys are paranoid about RH. :D Table salt will give 75% and calcium chloride gives 25% I think. That said OS can be fickle. Was it one that wasn't already cracked? Where did the crack form, in the handle? I've seen some crack from a quick change in RH.
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Thanks Brad. I can't figure out how to load pics yet. I guess I am wondering is when is wood dry and can I start building a bow in higher humidity? My shop the humidistat redlines to 100%
Cheers,
George
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Yeah, like Brad said, if in doubt....more sealant.
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Is your shop heated?
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Thanks DC. I saved and bought hygrometers and a scale to check weight. Also traded for a small bandsaw. Just want to start building but don't want to wreck anything! The roughed out OS stave was not cracked before and did crack on the belly at the fadeouts and through the centre of the belly of the handle. Back is not cracked. Thanks for tip on calibration - will do.
Thanks Springbuck and Brad. Hopefully I can figure out pics and try to contribute something soon.
Cheers,
George
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Shop is not heated but dry and closed so keeping staves in stablest part of heated house. Want to build a bow but wife doesn't like me carving in the kitchen. Is it safe to work in shop?
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At 100% I would suspect the calibration. If your shop is unheated the RH should be the same as outside, maybe a bit drier. Weather Network says your RH is 90% at the moment. That's pretty high. You can go ahead on the bow but expect a little set. Keep the stave in the house when you are not working on it. Living on the coast can be a PITA. You may have to build a hot box. Look on "Poor folks Bows" for instructions.If you can find a spot that's a few degrees warmer it will help.
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Thank you! Coast can be a PITA true but lots of great wood!
G
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You said you bought two hygrometers. Do they agree with each other? They look like a lot better quality than mine. They may be accurate. Apparently even the good ones disagree by 5-10%. The calibration test involves closing up the meter in a bag with wet salt. That might not be very good for an electronic device :-\ :-\ :-\
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george
I have a hygrometer ($20?) that was sold for a humidor. It is a bit better than the general use variety, but still is really only useful for helping to gain an understanding of how to store wood, longer term, in a particular environment. the scale is your day to day friend.
my hot box uses about half the foam as the po folks because I substituted a couple of old fluorescent shop fixtures for the incandescent.
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Does the heat come from the ballast? I didn't think the tubes warmed up. I used waterbed heaters in mine.
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This is the other one - they do not agree which is why I bought 2. They were both $11 ea at Home Hardware so not sure of quality difference. I will try salt trick with manual one and try to borrow a third to see if any 2 agree!
g
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The RH went from 50-70% RH and your stave cracked?
Staves do not usually crack from absorbing moisture. It's the other way around.
Jawge
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Thanks Willie I will go to my friend's cigar store - good idea! Hi Jawge - yes that is what happened - seems weird but it seems Ocean Spray is fickle in drying?
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here is pic
g
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heat from the ballast? I dunno, they are the older style hanging shop type with 1.5 in dia 40w tubes The box is only about 12" on a side, and I am only running a single tube per 4' fixture for a 60 degree Fahrenheit temp rise. had to add a 24 hour timer to keep things from getting too dry.
fancy digital readouts are not good indicators of quality sensors, with those kind of meters
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you have to put alot of sealent at the handle and fades, that will always crack if the wood is a bit green,, or not cured enough,, after you work on it .... seal it there just in case,,
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This is the other one - they do not agree which is why I bought 2. They were both $11 ea at Home Hardware so not sure of quality difference. I will try salt trick with manual one and try to borrow a third to see if any 2 agree!
g
That's the same as what I have. I have two of those. I had to calibrate them. They were quite a bit off. It's a frustrating thing to do, you never know what to trust. In general, I'm with Willie, Trust your scale, But your scale will only tell you when wood has reached equilibrium. You still have to know the RH. I know I get kind of anal about this but everything I've read preaches that the MC has to be around 10% or you're not getting the best out of your bow. Maybe I should settle for good enough but I'm not built like that.
George, if you do decide to calibrate give me a call and I'll talk you though the adjustment part. No sense both of us having to break one to see where the adjustment is >:( >:(
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Thanks for the advice Brad - will be more liberal with sealant.
Thanks DC! Will do and will contact you when ready to calibrate. I am with you - I don't want to waste good staves by not maximizing them but it is frustrating not working on a bow when that is all I want to do!
BTW, scale from 1+ seasoned wood shows 18 gram gain with change in location and RH. Other staves consistent with this average gain of mass.
g
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Even going to a higher RH means little, the wood is still drying. As it dries it shrinks. It is the wood on the outside of the stave drying quicker than the center wood which caused it to check.
You can take your staves to a good floor tiller without worrying about the moisture content and this will reduce the likelihood of more checks.
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George- Maybe you should complete the bow you're working on and see how it goes. "Damp" wood will increase the amount of set. I know of people that don't concern themselves with it that much. They dry it until it stops losing weight and that's it. This chart will give you some idea of your moisture content. http://www.csgnetwork.com/emctablecalc.html We live in a crummy area as far as bow making is concerned. Even in the summer it's too humid to dry wood properly. Somehow the native peoples dealt with it though, so just fly at the first bow and see what happens. There's lots of staves out there.
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Oh, I just thought George. Put a trouble light in that ski box you had in the back of your truck and you have a hot box. Monitor it carefully for the first couple of hours though.
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In my experience, ocean spray will check like that easily. I'd say its just a hard wood to avoid checks. Rh meters are a good way to monitor wood moisture content, but it takes a while for wood to stabilize. I have had OS check like that after a year sealed.