Another heat treating question

[DC]

In the quest for a nice even brown has anyone tried slanting the heat gun so it aims along the limb some? Any joy from this?

[huisme]

It heats the spot right in front of the bottom of the nozzle faster than the rest of the limb but preheats farther down, so on low I have decent control this way but it isn't really better than straight-on heating in my experience. Going slow is the best way to get an even treatment.

[Springbuck]

  Yup.  I do all kinds of things when using a heat gun, but I have had more luck starting right in the fades and moving the heat more often that any other trick I have tried.  What I mean is start in the fade and give it the full 4 minutes (or whatever), but instead of moving it 3" down the belly, move it 1-1/2" and leave it half as long, so every spot gets the full 4 minutes, but the positions overlap.

  I did try making some walls that closed in on the sides (like a stream running in a culvert) to trap the heat longer and make it run along the limbs for more length. That worked pretty well, EXCEPT I ruined a couple staves where the wall couldn't sit flush to the side (snakes or bumps) and left a gap.  The hot air would get down in there, bounce back and toast the edges of the BACK of the bow black.  Both times the bows cracked at the black spot halfway through tiller.

[willie]

has anyone tried to preheat the bow with a heat trace?  If you get the whole bow a lot closer to the toasting temp, I would imagine that the process would go quickly and easier.

I have used preheating techniques when bending metal with a torch and it makes a big difference in speed and control


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[steve b.]

I've thought about the heat tape thing or slow heating the whole limb, etc. etc.

I always use the heat gun and not only heat at least half the limb prior to settling back to the fade area and working toward the tip, slowly browning it, but I also keep the whole limb warmed well while I move to the tip.   So the whole limb is very warm when I'm done.
 
Today I tried something different with oceanspray.  I slow heated the half limb that I was tempering, but instead of doing the browning thing, I just kept the increasing the slow heating until that half limb was super hot (found out the hard way), and stopped.  So there was no browning at all (maybe just on the edges).  And it worked fine as far as I can tell.  Point is, I don't like the idea of browning the wood.  I think it damages it.

[jeffp51]

I also heat treated a bow today.  Took 2 hours or more (lost track of time) to do 6 feet of bow.  I am not noticing any concavity as described in TBB4.  Did I go too fast?  Or do not all woods do that?

[E. Jensen]

I like to angle the heat gun down the limb but I'm not using a jig I'm holding the gun myself and moving it constantly.   To prevent burning,  to heat evenly,  and also a little slower to brown so the effect is deeper.

[DC]

I did an OS longbow today. Since mine was more or less tillered I was getting concerned that the back was getting too hot. I moved the gun a bit closer and went a little faster.I've noticed that OS doesn't seem to brown, it goes straight to grey. I'm thinking that the thinner the limb, the closer the gun and the faster you should move. This will heat treat the belly and leave the back natural. I don't think heating the whole bow evenly will accomplish what we want. I think it would make the back brittle or hard or something

[steve b.]

DC, I've notice that about OS too.  It so resists browning that I actually coat the belly with beeswax/oil just so it has something that will brown.  But the wood itself does not.  The edges sometimes will start turning black but the flat belly will be white still.
I heat treated a very thin bow last week that had sinew on it.  I would occasionally check dig my fingernail into the sinew to check for heat on the back and it was not an issue.  I actually did it twice that week and no issues with the back overheating.
My form/caul thing for high crowned staves like OS has a channel in it for the crown to lay in.  Not sure if that is why I don't have back-heating problems but I never have back heating issues.
I still think browned wood is damaged wood.  Not saying that the wood underneath is not perfectly tempered and that the brown wood can simply be sanded off.  But I'm just thinking why not try to get the same amount of heat in without burning the surface.??

[DC]

I thought that the colour was an indication that the correct temp had been reached. But I suppose the colour is only skin deep and may only be the wood reacting with the air(oxegen). You may be right.

[Springbuck]

I thought that the colour was an indication that the correct temp had been reached. But I suppose the colour is only skin deep and may only be the wood reacting with the air(oxegen). You may be right.

In Marc's section in the TBB IV, he mentions the color being darkest at the suirface, but that the wood is visibly changed halfway through the limb, when he narrows it with a plane.

[missilemaster]

  There really isn't any substitute for going slowly and taking your time. I hold the heat gun around 4" away from the limb and just work my way down the limb till I get a uniform dark brown color. It usually takes me an hour per limb. Also, use a form that is thinner that your limb so the heat does not bounce off  of it and scorch the back of your bow.

[Badger]

 It has a lot to do with what type of heat gun you have. I like to run my gun from one end of the limb to the other continuously heating the entire limb at one time. It will gradually start to darken at the nds and when it does I just shortern my stroke and gradually work toward the center. I figure about 20 min per limb.