Oiling before steam bending?

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AlexanderArcher
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Oiling before steam bending?

#1 Post by AlexanderArcher » Tue May 26, 2015 9:54 pm

G'day guys, it's been a while since I've made a post but I've been gradually experimenting away.

I recently made a steambox out of some old wooden timbers I had by adapting the kit I have for a bee hot knife (for uncapping wax on frames) and running a hose from the boiler to the box. I've also set up a form by carving away at a solid piece of timber until I got the curve I wanted.

I have been experimenting with the curvature of the form and the results I get on some old bows I've made and I have been getting cracks appearing on the belly of the bow during the bending over the form and clamping. I'm trying to go for a traditional recurve look on a single-piece pyramid style bow made from massuranduba (which seems to have good steam-bending properties). I was wondering whether these cracks are due to the bow not heating up enough? or is it due to the form being too steep? I leave the bows in the steambox for about an hour and a half to try to make sure it heats up evenly and enough. My form setup is such that I can litterally take the bow out of the box and have it bent within 10-15 seconds, or is this too fast? I've found that the faster I can take it out of the box and bend it, the less cracks that appear.

Should I oil my bow (with organoil) prior to steaming? And is there a way to optimally maintain the 'set' of the curve after cooling down?
Keep in mind that I'm aiming for the look of a traditional recurve with a flat, built up handle but slightly more curve throughout the limbs.

Thanks all,
Alex

hunterguy1991
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Re: Oiling before steam bending?

#2 Post by hunterguy1991 » Wed May 27, 2015 6:49 am

Photos of your form and the cracks might help some of the guys tell you whats going on.

I have a little experience with steam bending and some success with it. I have heard that that particular timber is good to steam bend however if you are leaving it in the box for an hour and a half and still getting cracks maybe its not so good...

The way to get a specific amount of curve is to wrap it over something slightly tighter as it will relax a little after it cools, however, steam bent recurves tend to pull a bit out over time with shooting. One way to avoid this is to Kerf recurve the tips, check out Daryl's post about kerfing to see how its done. These do NOT pull out at all.

Hopefully one of the guys will be able to help you out.

Colin

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greybeard
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Re: Oiling before steam bending?

#3 Post by greybeard » Wed May 27, 2015 10:19 am

Alex, as Colin pointed out photographs are necessary otherwise we are only guessing as to what may be causing the problem.

Have a read of the previous post by Yeoman and take note of the rough sawn timber comment.

http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15118

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

AlexanderArcher
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Re: Oiling before steam bending?

#4 Post by AlexanderArcher » Wed May 27, 2015 12:10 pm

Colin,

Thanks, Yeah I've already seen the thread on kerfing and think its an excellent idea but I like the look of the single-piece bows naturally recurved without gluing. Yeah, I have made the curve tighter than I want due to that relaxing you speak of.
IMG_1289.JPG
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With this photo, it is to show what bend I got out of the bow after recurving, but for that curve I only used HALF of the form. As in, I only bent the bow to halfway over the curve

The bow in the above picture is one of the ones I've done most of my experimenting on, it is an older bow I made a couple of years back and sits at only 26# draw weight after recurving. I found that the only time during the multiple attempts at recurving that didnt crack the belly of the bow was when I completely drenched the limb of the bow in water prior to placing in the steambox.
This was why I was wondering whether it would be worth oiling the bow prior?

Thanks.


Daryl,

I've had a look at this post prior to doing any steam bending and I can assure you that the wood I'm recurving are old bows that have straight grain and have been sanded to a fine finish (although the bow in the pictures is quite old and the oil has run dry :oops: silly me).

thanks again.


Okay, hopefully these pictures will help you guys figure out whats going on.
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IMG_1288.JPG (255.96 KiB) Viewed 3474 times
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steambox.jpg
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Thanks again

*Those cracks in the wood have not inhibited the bow as far as I can tell, I can string and shoot just fine with them, but I am still worried.
Alexander Tuffley

~All that we are, is the result of what we have thought. If a man speaks or acts with an evil thought, pain follows him. If a man speaks or acts with a pure thought, happiness follows him, like a shadow that never leaves him.~

~Permaneo Mucro Vir~

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Re: Oiling before steam bending?

#5 Post by greybeard » Wed May 27, 2015 8:32 pm

Alex, although the stated properties of Massaranduba may include steam bending I believe it could be a bit of a generalisation.

The bending properties may be suitable for use in construction and boat building but small tight curves may be a different ball game.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

AlexanderArcher
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Location: Brisbane, Queensland

Re: Oiling before steam bending?

#6 Post by AlexanderArcher » Wed May 27, 2015 8:50 pm

Daryl,

Thanks, so do you think its a good idea to oil my bow with a naturally penetrating oil prior to steaming? My boiler setup isnt huge so I was thinking it might assist in the thorough heating of the wood.

Also, is it okay that I bend the bow over the form fairly quickly but not abruptly, say, within 10 seconds of it leaving the steam-box, applying even pressure?

Cheers,
Alex

*I forgot to mention that the reason why I ask is because I have a gift bow set up thats ready to go in at 30# draw weight, and Im hoping to end up around 35#. I was just hoping to try to get some pointers from the more experienced on the forum before I attempt to steam bend my first 'good' bow.

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Re: Oiling before steam bending?

#7 Post by hunterguy1991 » Thu May 28, 2015 8:30 am

I agree with Daryl's comment about the possible generalisation on steam bending that particular timber... I have a length of it here and when I purchased it, it was with the intent on using it in an ELB so no bending necessary but the guy mentioned it was good for steam bending, however I was sceptical due to the look and feel of the wood.

I think your efforts are an indication that its not the best for this application. Try with some Red Oak, you will have much more success.

Your process for bending is fine and if the timber could be bent it would work with what you are doing. As far as oiling the wood before hand, try it and see if you have better results with a scrap piece of wood first, just make it the same dimensions (roughly) as a limb tip.

Colin

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Re: Oiling before steam bending?

#8 Post by greybeard » Thu May 28, 2015 11:08 am

Alex, some options could be;

Try a less severe curve,

Laminate a thin strip of matching timber to the back of the bow,

Kerf the tips and use matching timber for the slats,

Shorten the n to n length of the bow if the design permits,

Try dry heat and oil.

If the bow has been oiled it probably will not accept glues.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

AlexanderArcher
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Joined: Wed Jun 20, 2012 11:53 am
Location: Brisbane, Queensland

Re: Oiling before steam bending?

#9 Post by AlexanderArcher » Thu May 28, 2015 12:41 pm

Colin,

Thanks again, Ill have to pick up some red oak when I can and have a go haha. After all, my passion for bow building stems from recurves so it would be well worth it.
I tend to agree with both your's and Daryl's assumption that the prescribed properties of the wood for steam bending may have been a generalisation but I have had success
in bending it before without it cracking so I'm still hopeful I can find the right technique.

Daryl,

the thickness of the tip Im using is quite thin due to trying to maintain a flatter profile, so kerfing the tips isnt an option here :confused:
I've also tried dry heat on massuranduba and found that it mostly just cracked/splintered the wood such that it was rendered unusable.

I'll do an experiment with oiling the bow prior and I'll get back to you guys, thanks.

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Re: Oiling before steam bending?

#10 Post by hunterguy1991 » Thu May 28, 2015 4:02 pm

Its possible to Kerf cut something 5mm thick with some care, how thick are your tips?

I did it in 7mm thick tips on one of my experimental bows... Also, it is possible to make the kerf cut in a thicker piece off centre then carefully thin the belly side to desired total thickness.

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