ELB build along & piller tiller discussion

[Shaun]

First, thanks for the positive comments on the couple of recent ELB bows posted. There were some questions and a build along seemed like a good idea. Plus, I have been making these for others and wanted one to play with myself.

The other half of the stave from Timo was about 1 1/8" square by 72 1/2 long. I drew a grain follow center line - this piece is clear but wavy. Then I marked 5" increments from the ends and laid out profile with each segment 1/8" less in width. This makes the center about 1 1/16" tapering to 1/2". The first pic shows this profile cut and the same taper laid out on the side profile.  I cut the top lay out square to the back (chased ring) surface.



Make the same tapering layout on both sides and cut with approximately 10 degree lean of the back surface. This prevents cutting too deep on the opposite side where the wood is twisted. After making cuts from both sides you will have a ridge in the middle of the belly.




Application of power rasp (edge sander) removes this ridge and general shaping towards the arched belly shape and general view towards leaving a tapering in both width and thickness from center to ends.




With the bow flipped back side up you can see that this stave is not straight. Since we are headed for a rounded shape (ELB rule is that the bow can be no more than 8 to 5 ratio of width to thickness) it is MUCH easier to tiller a straight stick. A flat bow resists bending sideways - much less so in a rounder shape.



So, onto the cull with heat gun and clamps.

[Shaun]

I like to use a piller tiller system before brace height. This allows me to get back and sit looking at the arc, then mark with pencil and take off wood where there is less bend, flat spots. Here is the stick off the cull with induced backset and nearly straight.



My belief is that you can do little harm to the stave before reaching brace. The bar clamp allows continuously variable draw and is more solid than using a long string on the tree or a tiller stick. Here is the first bending. As always, stop as soon as you can see a flaw in tiller and correct.



I see flat spot in the center and about 1/2 way out the right limb.

[Shaun]

Correct and repeat process until the arc is pleasing.



Still a little flat in the center, just to the left of center, and last third of left limb, but getting real close. At this time I return to the heat gun as some of the original waviness has reappeared  during tillering - this is common with heat adjusted wood. These smaller and area specific adjustments are made one at a time on the bench.

[Shaun]

After re straightening, continue adjusting tiller on the posts. I switch from 40 grit to 100 grit on the edge sander and start to work on smoothing and tapering in both width and thickness as the tiller progresses.



When it gets this close I cut string nocks and try first brace. I use the pillers to brace as the bow is still to heavy for push pull hand stringing. Love the moment of first brace!



With this method 90% of the build is completed before the bow is ever drawn past first brace. Now is the time to put it on a tiller tree and/or start shooting it in. As the wood is worked it will change and need re adjusting of tiller. This is also the time to check draw weight and start reducing towards desired finish weight and refining aesthetic lines. Also, minor adjustments of limb alignment will be needed by either heat or tillering (cutting material from off center of the width will make the limb bend towards that side). Here is the bow nearly complete - needing finish smoothing and more shooting in with minor adjustments as they appear.

[JackCrafty]

My belief is that you can do little harm to the stave before reaching brace. The bar clamp allows continuously variable draw and is more solid than using a long string on the tree or a tiller stick.

 

[Shaun]

This bow is still slightly heavier than the mid to low 50's I want, but final tiller adjustments and sanding will bring it in. Time to shoot it a bunch and get the wood to finish settling in to its working shape.



Another note; I mentioned the ELB ratio of 8/5. The center of the limb is under more twisting stress than the hand held center or the tips, so this area is often shaded more towards the 8/5 flatter profile and the handle and tips left round. This makes the limb cross section progress from round center to flatter mid limb and back to round at the tips in most ELB bows.

[Shaun]

Jack, is that JR pup asking for clarification?

Before bending past fistmile brace height little set or fiber damage is likely because so little deflection has been made. It is yanking a bow back to 20" while it shows tiller flaws that induces set and hinging. By correcting tiller flaws in the very early stages of bend this is avoided. It does leave the wood untested and further bending will create new flaws as the fibers stretch. These need to be corrected as soon as they show during the working in by shooting (short draw) or working on the tiller tree. In the first brace picture on the posts, the arc looks nearly perfect. This will change as the wood works - that is the last 10% of tillering required until full draw is reached.

[JackCrafty]

Yep, thanks for the clarification.

[PEARL DRUMS]

I remember you mentioning your tiller system before Shaun. Im glad you posted pics. I have to have one now. That has to speed up the process allot without stringing and unstringing so many times before you can leave it braced and tiller. Thanks for the pics and post.

[Gordon]

That's an interesting tillering setup - I never thought of that...pretty cool

[coaster500]

I like it!!

 "piller tiller system"...  Why wouldn't it work with a non bending handle?

Looks like a real time saver?

Thank you

[Shaun]

Thanks Gordon, any praise from you (my tiller inspiration to do better) warms my heart.

I wish I could claim credit for thinking this system up. One of my favorite sayings is, "All wisdom is plagiarized, only ignorance is original." So, credit to Brad Merkel - who passed it on to me. It works equally well with elliptical tiller on flat bows and making the posts clamp-on style allows adjusting for shorter bows. I also move them in a little to brace the bow as then I can have the string on the bow with the bottom loop on and the top loop ready to slide up. The top loop must be outside the post to slide. This puts less stress on the bow than bending far enough to get the top loop over the end. It also makes adjusting brace height easy - just reverse the stringing process.

[Elktracker]

I like your setup there! Thanks for doing the build allong!

Josh

[blackhawk]

Do you put leather in between the tips and your posts on softer woods like yew so it doesn't accidentily dent or ding the back of the wood? Interesting set up for sure. Looks like it works well for ya.

[BowJunkie]

Shaun:
I agree with Gordon, this is a very interesting concept.
I was wondering if you use any kind of tiller gizmo or do you just eye it?
I have to try this method out on my next bow.
I already planned on making an elb style  bow, out of some 3'' diameter pecan trees I cut a month ago.
Could you please post the dimensions of this bow?