Robin bamboo build along

[Sam Harper]

It's later already!  I'm still getting the bow ready to tiller.  I had to file in some nock grooves.  I used to hold the bow down with one hand and file with the other.  Here's a video showing how I used to do it.

 

That was especially hard to do with a recurve, but now I use a vice, and it's a lot easier.

 

I glued leather padding onto the vice for just such occasions.

I cut an arrow shelf about 1.25" above center.  It curves in at the top of the fade because I don't want to cut into the fade too much and weaken it.

 

People always ask me how far in they can cut and whether they can cut to center.  There are too many variables to give a tidy answer to such questions.  It depends on how thick your handle area is, how wide your handle is, what kind of wood/materials you're using, and how strong your bow is going to be.  Even if I knew all that, I couldn't necessary say.  I used to cut my shelfs really shallow because I didn't know what I could get away with.  I guess over time, I just developed a feel for it.  I have noticed on some of the bows I've made where I waited until the end to cut the arrow shelf that although the bow didn't break, it did cause an alignment problem.  Whereas the string might originally have tracked straight through the center of the handle, after cutting in the arrow shelf, it drifts in the direction of the shelf, which means the cut weakened it a little.  I've used that as a gauge for how far in to cut on subsequent bows.  For this one, it's pretty narrow already, so I didn't want to cut anywhere close to center.

 

I'll remove wood from inside there when I shape it later anyway, and it'll be closer to center but still not there.

I use my disk sander to radius the shelf.

 

I've been doing it that way for a long time because it's quick and easy.

 

I saw somebody somewhere use a template and a router to cut the arrow shelf.  I may try that some day.  I would think it would reduce the amount of work later on when you have to sand and use files to get everything smoothed out.

The last thing I do before tillering is round all the corners on the limbs on all four sides.  First, I run each corner down the elbow of the belt sander.

 

Then, I go over each corner with a piece of sanding belt and a block of wood.  My block of wood is rounded on one side so I can do the inside of the curve on the back of the bow.

 

That's all I do to the belly side, but I want that backing to be nice and smooth, so I use the scraper to smooth out the corners on the bamboo.

 

The belly side will get smoothed out more as I tiller.

No more stalling.  There's nothing left to do but tiller.

[bigbob2]

Thanks for posting Sam I'm enjoying your build along.

[Sam Harper]

Thanks bigbob2.

I'm going to stall just a little bit more.  I was looking it over while ago, and I saw this crack.

 

That could cause a failure, and it looked like it might be too deep to just rasp off, so I put some superglue on it.

 

Superglue is really thin and can wick down into the crack.  I don't know how far it'll go in, though.  I can only hope that it'll work.

[robin]

Sam your mid section of the osage in 3/8 thick and the riser fade out seems kind of steep...wont it cause the riser piece to pop off?

Rob

[Sam Harper]

No, Robin.  The shorter a bow is, the thinner the wood will end up being for a given draw weight.  This bow is pretty short, and 3/8" is plenty of thickness.  Plus, I have that power lam.  The fade will continue past the end of the glued on handle, and the limb probably won't be bending at all near the glued on handle.

[Sam Harper]

Of course that depends on how strong you want to make the bow.  I'm going to be shooting for somewhere between 45 and 50 lbs.

[robin]

Sam your mid section of the osage in 3/8 thick and the riser fade out seems kind of steep...wont it cause the riser piece to pop off?

Rob

[Sam Harper]

No, Robin. The shorter a bow is, the thinner the wood will end up being for a given draw weight. This bow is pretty short, and 3/8" is plenty of thickness. Plus, I have that power lam. The fade will continue past the end of the glued on handle, and the limb probably won't be bending at all near the glued on handle.

Of course that depends on how strong you want to make the bow. I'm going to be shooting for somewhere between 45 and 50 lbs.

[takefive]

That is a neat trick using your disc sander to radius the shelf, Sam.  I have yet to cut a shelf in, but if I ever do I'll give that a try.

Are splinters pretty common with bamboo backing?  I've only made two bows with the stuff.  One raised a small splinter that I could super glue down, no problems with the other one.  I scrape the top layer off like you have shown and try to sand carefully on the nodes.

Very cool build along    

[Sam Harper]

Splinters haven't been that common for me, but I've had a few raised.  I just sanded the bamboo down until the splinter was gone.

[Sam Harper]

This is my old tillering stick.

 

It's been with me now for 10 years and two or three months when I first started making bows.  Every time I show anybody a picture of this thing in use, it's always followed by gasps of horror and condemnation, so last night I thought I'd spare myself that, and I made myself a tillering tree in the garage.  That required me to do a lot of moving (which in turn lead to cleaning), and I was up until 2 am last night cleaning and rearranging the garage.

Here's a first look at the bow on the tillering tree.

 

And here is the very first pull on this tillering tree.  I pulled it to 40#, and the limbs moved about 3-1/2".

 

Although I used a level when I made that platform the bow is sitting on so I could get it perfectly level, it looks like the bow is leaning to the left a little.  Notice how before I pull it, the left limb is already lower than the right, then when I pull it, the left limb looks weaker than the right.  If I were to even those limbs out before bracing it, I suspect it would result in the right limb (i.e. the upper limb) being too weak, which I wouldn't noticed until I braced it.

I reckon the reason for that lean is that my handle is thicker on the right side than the left side, so I took a file to it to get it level.

 

And here is the result.

 

 

Better, eh?

By the way, I'm giving my tillering stick away if anybody wants it, but you have to come to northwest Austin, Texas to pick it up.

[bubby]

Sam I use locktight professional in the blue bottle, not the gel

[bubby]

the nice thing is you can start shaping the tips in ten minutes

[Sam Harper]

Meanwhile in the bat cave. . .

Tillering wasn't all that eventful.  There were no hinges or problem spots or anything like that.  I just removed wood evenly on both limbs until I got to 45# at 10" of limb travel.

 

It still looked to me like that top limb (the one on the right) was too strong, but I wasn't sure, and it was close enough, so I went ahead and strung it.

 

Sure enough, the top limb was too stiff.  I wanted to straighten that out before going any further, so I sanded on the top limb while it was still strung until I got it even.

 

Then I exercised the limbs some and pulled on it until it reached 45#.  It came to 25".  

 

I was shooting for somewhere between 45 and 50# at 28", so I'm almost there.  But I didn't want to go any further until I got your input.  Why go it alone when I could take advantage of your collective expertise?  So tell me what you think and if you have any suggestions.

My next move is to narrow the tips.  I keep them wide until after stringing it so if I need to make any adjustments for alignment, I can.  In this case, the alignment looks good.

 

On recurves, I don't just rely on looking down the string that way because friction can cause the string to be off.  Also, if you pull it back, then relax it, your bow hand can torque the handle a little bit, causing the string to be off, and misleading you about whether the alignment is good.  So what I like to do with recurves is shoot them a little.  I figure when the string is released naturally, that gives you a true indication of whether the alignment is good or not.  If that string isn't dead center on that recurve after shooting it, then I make small adjustments until it is.  Then I cut grooves in those curves for the string to sit in.

I'll wait a while for your input, and if nobody says anything, then I'll keep going.  But please let me know what you think so far about the tiller.

Oh, I almost forgot to tell you something.  That crack I put superglue in earlier seems to have disappeared.  I rounded those corners pretty good.  Maybe it wasn't as deeps as I thought it was, and it's gone.  I hope so.  I'm starting to like this bow.

[Sam Harper]

Originally posted by bubby:
Sam I use locktight professional in the blue bottle, not the gel

Why not the gel?  I would think that would fill gaps better in case your joint isn't perfect.

[Sam Harper]

Originally posted by bubby:
the nice thing is you can start shaping the tips in ten minutes

Yeah, I used to use 5 or 30 minute epoxy for that reason until I started reading about how some people had failures with it.  Luckily, I've never had a tip overlay come loose.

[wood carver 2]

I've been having good success using gel superglue for tip overlays. I just hold them in place for a few minutes with small spring clamps. The gel takes a bit longer to cure than the thin stuff.
Nice looking bow. Thanks to you and Robin for this build along. Too bad bamboo like that isn't available in North America.
Dave.

[bigbob2]

I really like this bow and your efforts so far.Keep us informed!

[takefive]

Your tiller looks great to me, Sam.  
As far as the Loctite super glue goes, I thought there was just the thick and the thin type.  Evidently they make others?  All I know is that the gel is the thick type and it works great on overlays.
The other day I was at the drug store to get Ibuprofen.  Their rack of pain relievers is 6 feet high by about 8 feet long.  Sometimes I think we are just given too many choices    :rolleyes:

[Sam Harper]

Thanks for the input on the tiller, takefive.

This morning, I narrowed the tips.  If you take more off one side than the other, the tips will be misaligned, so to keep them aligned, I made 3 marks--one in the center, and two where I wanted to grind to.

 

I ended up not grinding all the way to those marks, but I got close.  Then I re-cut the nocks.

Then I continued to tiller.  Each time I removed wood, I exercised the limbs, checked the draw weight, and checked the distance between the string and the limb on both fades.

 

I kept it about even, but as I neared the end, I gave it a 1/16" positive tiller.  Most people seem to prefer a 1/8" positive tiller for shooting split fingered and even for shooting 3-under.  I figured with a 1/16" positive tiller, it could be shot either way.  Honestly, I've shot both ways with the same bow, and I can't tell a difference in noise or vibration or anything.  I prefer a slightly positive tiller because the first bow I made had a weak bottom limb that seemed to get weaker with time, and that left a permanent scar on my psyche.  Now, I subconsciously think that if the top limb is slightly weaker, then it's okay if the bottom limb is under more stress because it'll all even out in the end.  I cannot shake that feeling no matter how many bows I make, even if they are fiberglass bows.  Sometimes I give a bow as much as 1/4" positive tiller because of it.  I wonder if that means I have OCD.

Anyway, as I got closer to my target weight, I started using finer grit sand paper.  I used to tiller my bows to my target weight at 27" figuring that once I sanded it and everything, it would reach my target weight at 28".  But with this one, I figured I'd just finish my sanding simultaneously with finishing the tillering.  I had a broad range in mind, though, so it was going to be hard to miss my target weight no matter what I did.

When I got to 47# @ 28", I called it, and it had a 1/16" positive tiller.

 

And here's what the limb profile looked like immediately after unstringing it.

 

The next step will be to shape the tips and handle, which I will probably do later today.