My horn bow build-a-long

[DC]

Have you used a hair drier for heating bows. I just tested one and it has a setting that is very close to 50°c. Can't overheat it but may be drying? Seems like the way to go to me.

[bownarra]

No I haven't so can't really comment. I use an electric hotplate. I got mine for very little money and it has served me very well. Remember it is the core you need to get hot enough to bend so slow and steady is best. It can take 20 mins heating with my set-up to get upto temperature. I also use electric heating pads wrapped around the limb.
Its best to do the corrections and let it sit for at least a few hours with the tillering stick in place and spread apart far enough to take into account any 'spring-back'.

[DC]

 Remember it is the core you need to get hot enough to bend so slow and steady is best.

Really? The core at this spot is only about 3mm thick and heating wood to 50°c(122°f) isn't warm enough to do anything. Am I missing something?

[DC]

Adam says to take very little horn off when scraping. Is that just a general tillering statement or are these bows a lot more sensitive to horn removal than a selfbow is to wood removal?

[bownarra]

The core gives the bow its shape. Simple If you don't get the core hot enough the shape won't change.
Common sense - go slowly

[DC]

OK bring this up to where I am
I spread the limbs to about 24" apart on the pegboard. I heated the kasan eyes(at least I think it's the kasan eye) Used a hair dryer so I wouldn't overheat it. Heated about 3" to 50°c (125ish f) and held it there for 30 minutes. Heat was checked with an infrared thermometer. Did both limbs at the same time. Waited 2 hours for it to cool off. Took it off the pegboard and it went right back to where it was Put it back on the board and spread the limbs to about 30" apart and repeated the whole procedure but used a little more heat, 55°c and same time. This time I left it on the pegboard overnight and when I took it off in the morning it didn't look too bad but not as open as I thought I wanted. There was 15" between the tips. Went and did a few chores for an hour, came back and it had closed down to 12". I just looked at it about 5 hours later when I took these pics and it's closed down to 10". I don't think I made any progress with the heating at all. Is this supposed to happen? The picture showing me heating it was just staged, I actually heated it yesterday. I haven't done any actual tillering yet. Makes me wonder why I didn't keep it from reflexing so much when I was sinewing it. Very frustrating, especially when the damn thing is probably going to break anyhow.

[bownarra]

If the bow has been in 35% rh it will be hard to correct. I have no problems with my electric element. For the sort of corrections you are attempting it would take about 20 - 25 mins per limb.
As I said above if you don't get the core hot enough you won't change a thing.
So your heating cannot have got the areas hot enough.
I wouldn't heat it on the pegboard either- it will lead to uneven heating. You should be heating it with the tillering stick in place. Don't try to re-invent the wheel!

[DC]

If the bow has been in 35% rh it will be hard to correct. I have no problems with my electric element. For the sort of corrections you are attempting it would take about 20 - 25 mins per limb.
As I said above if you don't get the core hot enough you won't change a thing.
So your heating cannot have got the areas hot enough.
I wouldn't heat it on the pegboard either- it will lead to uneven heating. You should be heating it with the tillering stick in place. Don't try to re-invent the wheel!

When you say 20-25 min per limb it sounds like you're doing one limb at a time. Are you?

I'm not trying to reinvent the wheel, I know my limitations and I could see myself overheating this thing if I tried to heat it over a stove. The hair drier seemed like a safer way. I'm going to put it in a plastic bag with a wet rag for a few days.

I'm making a tillering stick. I realised yesterday that the pegboard was less than optimal for showing twist.

[bownarra]

I meant by heating it on the pegboard.  You need to be able to move it.
A normal stove is likely too hot. The hotplate elements I mentioned are very gentle and don't dry the bow out too much either.
Heating with the tillering stick in place must be done on both limbs equally or else things will start going south. I heat each limb for 30 secs then swap, 30 secs, swap.
I like wrapping both limbs in heating pads first to pre-warm them, then go to the hotplate.
This part can be frustrating but patience is key. You need to develop the feel for a lot of things before you can do the corrections quickly. Over heating is easily done and non reversible so much better to work your way upto things slowly.

[DC]

Just to clarify things. If I get this thing open into a "C" shape should it hold that shape forever? I had it out to 19" between the tips, left it overnight and within a few hours of taking the tillering stick off it was down to 15" and the next morning it was 11". Should I be leaving the stick in. I'm heating it on the stove, doing everything I should, I think. I'm heating the horn side until the sinew is about 120°(50c) and holding it at that temp for 20-30 min. That's actually overheating the belly side a bit. Adam says to spread the tips to about 24" and I'm spreading them to 30". I left it in a bag with a wet cloth overnight. I'm about out of ideas.

[Russ]

steaming??? try that?

[DC]

Don't think I'd want to steam something that is 20% hide glue.

[bownarra]

Yes steaming may be a very very bad idea
You aren't getting it hot enough if the core isn't relaxing. Heat takes a good time to 'soak' into the core. The surface temps shouldn't be exceeded but that isn't what matters.
The reason to reduce the reflex is that the bow will be much easier for you to tiller. Less strain and much less chance of twisting around the kasan eye.
However it is possible to continue tillering without altering the shape. Obviously once its strung/drawn it will naturally start losing some reflex (likely to be mostly in the sals tho).

[DC]

I was heating from the belly and the back was 45-50°. The core had to be 50. I want to try the heating pads but the only ones I can find are 12x15". A bit cumbersome for heating a 4" length of bow. I also only have one and another would cost $25.

[Russ]

well maybe just heat it at a lower temp, longer. but i dont have that time so i get to see how you do it.