hazel primitive hollow-limb set?

[stuckinthemud]

Hi All,

so I am in work at the moment and can't post a photo till later but I have just about finished tillering a hazel bow, 2" wide limbs, parallel width to half-way then straight taper to the tips which have been left stiff for the last 6".  66" ttt  with a 6" stiff handle and hollow-limb.  The stick was cut and split last September and when I started working it I thought it was fully dried out but it has lost a lot of weight during tillering, so it couldn't have been as dry as I thought. After roughing out, and before tillering, the stave had a little heli twist, which I heated out, and about an inch of deflex, evenly spread along its length.  Currently the bow is 45# at 24" with 2" of deflex evenly spread along its length.  Is this what is known as 'set'?  I am going to heat treat it, so should I straighten the stave at the same time, or leave it alone?

[FilipT]

How do you mean hollow limb? Hazel has really thin and narrow pith, easy to avoid as it goes away during tillering and btw, it doesn't need to be removed at all. Its not elderberry

[loon]

That "hollow limb" thing is just confusing and makes me think of PVC bows, I think concave belly makes much more sense
edit: Not really, but the first thing I thought was that it must've been two laminations hollowed out and then glued such that it'd be like a tube. But no, it makes sense, like hollowing out a canoe or something. I think I like how "hollow limb" sounds more than "concave limb"..

isn't it usually recommended to clamp bows to a form when heat treating, or something else? or otherwise heat treating ends up inducing more deflex..?

[Del the cat]

Yes its set, but a little set is to be expected. IMO it's a rare bow that has none*.
Would you rather have set, chrysals or a broken bow (I'll go for the set!)
Pulling it straight and heat treating will reduce the set and increase the draw weight. I think the stiff tips don't help, ideally if all the limb is working (obviously the last few inches can't do much) it helps spread the stress, reducing the risk of chrysals or set.
Have a good look and see if the set is evenly spread along the limb, if it is mostly in one place, then it's telling you the rest of the limb should flex more to take the load off the area that is over stressed.
Del
* some of the bows that are ram rod straight, started out with a bit of reflex, and those bows with 1" of reflex probably started with 2"

[SLIMBOB]

Yes, that is set based on your description.  Evenly along its length is preferable to localized in one spot.  2 inches is bordering on too much imo.  Too short, too heavy, to wet, so let that information guide you on the next one.  On this one clamp it past dead flat by an inch or so and temper the belly.  that is what I would do.

Cross posted with Del, but it looks as though we agree.

[stuckinthemud]

thanks guys, I like the concave belly in hazel because I think that it might reduce the risk of crysals (just the opinion of this novice), the actual set is about 1" as the stave was deflexed before I started to flex it.

[stuckinthemud]

"One more thing" ( I love Columbo), once I clamped a high-crowned bow down to my bench to apply heat via a hot air gun and the air wash was trapped by the bench against the back of the bow and scorched it (the bow), so any advice on how to avoid this happening would be welcome.

[Del the cat]

"One more thing" ( I love Columbo), once I clamped a high-crowned bow down to my bench to apply heat via a hot air gun and the air wash was trapped by the bench against the back of the bow and scorched it (the bow), so any advice on how to avoid this happening would be welcome.

Clamp thin slats of wood to the sides of the bow.
This does several things.
1. It protects the back.
2. It spreads the heat along the belly avoiding the hot spots you so often see on heat treated bows.
3. It shortens the time to do the job substantially.
http://bowyersdiary.blogspot.co.uk/2015/02/two-steps-forward-one-step-back.html
Very short video here:-
https://www.youtube.com/watch?v=kM1_A2A0_TI
You may need a few layers of masking tape along the edges to help stop hot air leakage between the side cheeks and the limb... but trust me on this one. It really is a big improvement.
In fact if you are not 100% satisfied, I'll give you your money back 
Del

[stuckinthemud]

"if you are not 100% satisfied, I'll give you your money back 
Del

From a man as generous as you, I'd have thought you would have doubled it (my money, that is)

[FilipT]

Excellent advice Del! I will apply that for both hazel bows I am making (currently being dried though).

[stuckinthemud]

OK, some pictures:  the set is not so bad as I remembered at 1.5"


something weird going on with the tips: if you look really hard at the right tip you might see the twist and a kind of hinge at the beginning of the stiff section 3" from the end - think I'm going to narrow the tips, maybe go over to an eiffel tower shape instead of the straight taper?

[FilipT]

I think also its possible hinge there

[Del the cat]

Left limb looks a tad weak out of the fade and stiff over the outer 2/3 to me.
Right limb maybe a tad stiff on the inner 1/3?
It's all very subjective and subtle....If you draw it until it breaks... that will show you where the weak spots are
If you take a tad off the outer 2/3 , strap it down and temper it, it will prob be a lot better.
I think its perfectly good to adjust the tiller, straighten and temper when a bow is still young... gotta teach it some manners
Del
PS I don't see that as much set.
I reckon when you put it down with the tips on the floor, if you can get one finger between floor and grip, that's good. Two fingers is ok, three is a bit much and I'd really call that set.
If the tips are off the floor then it's probably had a load of reflex heated into it.

[stuckinthemud]

Starting to struggle with the tiller on the left limb.  Am also 10# over my preferred weight, and when I heat treat it that may rise to 15# or more. Any thoughts?

[Del the cat]

I'm a tad confused. How far are you drawing it and at what weight. What is your target weight.
The tiller looks better, just taken an even few rasp stokes off the entire belly... that will increase the draw length at target weight.
Del