Ozbow

Not quite finished yet but at the draw stage - Hickory backed Celery Top Pine with kerfed & recurved tips, currently 45#@26".

Took a lead from Hunterguy & Greybeard on a 'safe'/going-to-work design.

Apologies for the poor pictures, I'll get a few better ones when finished.
It's still a bit rough around the edges and needs a lot of prettying up before being finished. I've used calipers to check thickness & limb comparison as part of tillering before but this time I used the calipers from the start for the entire length of each limb. The tiller was achieved with only a little bit of hand sanding on one spot, otherwise it was like that when the string went on.
I also wedged the kerfed section, a la Yeoman, to increase the stiffness on the recurved section. The tips themselves have ended up probably a little chunky, so I may round them out a little to reduce mass.

I'm liking what I see! Perhaps to this jaundiced eye the right limb looks a smidgen more rounded first third past fades? Should make a nice bow!

I like it too. But I agree with Bob: it might need some sanding on the inner half to 2/3 of the left limb. Just a bit, then the right could perhaps the the lower limb?

I'm very keen to see how the celery top pine looks with a nice varnish or wax on it.

Which limb is bottom? Looking at it I would suggest using left as bottom and it should time nicely with a shelf cut half inch to 1 inch above centre. Might need a few scrapes at most where the guys have already suggested.

Nice to see you banging them out tho mate! I'll have to up my game soon

Colin

Yeah, still a bit of tidying up to do and tiller adjustment, but for straight off the calipers I was really surprised. A bit of time & a few pairs of eyes on it can do wonders for a bit of tillering. I'm going to round out the tips a lot more, too, they've got a bit of weight to them.

Was thinking of using the left for the lower limb, should come up alright, I hope!

Will get some more pictures up when done.

Neil,

It is rewarding to see bowers using kerfing as an additional tool in their ‘skills kit’. Knowing when and how to use kerfing can be a little more challenging.

Your bow design is ‘different’, was it based on a particular design or more of an experimental project?

I do not know if it is the angle the photo was taken at or if one limb was made longer by design. With bows that have different length limbs I sometimes find it is better to tiller by feel rather than using measurements. If the limb timing is out this often reveals itself as ‘jarring’ in the hand upon loosing an arrow.

High speed photography or slow motion video if available is a reliable method to check limb timing. Most digital cameras and some mobile phones have a video function.

The following photo compilation shows that the bows tips are virtually static which reduce the working limb length. The bow has a little under fifty percent of thicker non working limb which is adding unnecessary mass at the outer parts of the limb. I believe that reworking your existing design could produce a more efficient bow.

Embarking on projects as yours is about the only way we can develop our bowyer/design skills.

Hopefully more bowers will respond to your post.

Daryl.

Daryl,

I had a little bit of a panic when you raised the issue with the limbs. I took the unbraced picture and placed lines much like your own as a check method.
I've measured the working limbs several times - as a necessity for limb thickness comparison - and they measured equal. The picture above shows that, unbraced, they're the same. The two lines are equal length (differing width & colour though). I can only assume it was the bow angle - holding the tillering rope, a phone AND pressing the 'take picture' button can be a challenge at times, especially with a dodgy left leg. I'll be going back to the proverbial drawing board and building a new tillering set up soon. Perhaps with a bolt at 28" to hold the draw there when taking pictures. Certainly with a backboard this time, and perhaps a better seat for the bow handles.

Incidently, I'm in the finishing stages of a light poundage shortbow where I've left one limb 3/4" longer than the other to account for hand placement. It's a prototype of a new design and made from ground laminates, so it will be interesting to see how it turns out.

greybeard wrote:Your bow design is ‘different’, was it based on a particular design or more of an experimental project?

It is a little 'different', for sure. The concept grew from my initial shot at the kerf method (http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15852) which stemmed from your own, Colin & Dave's efforts (your own post - http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15516 - Colin's - http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15843 - and Dave's - http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15876). I took Colin's advice in reducing the angle of recurve and lengthening the overall design to 68" ntn. I also included Dave's 'wedged' limb insert and reduced the number of kerfs cut to one from two.

The dimensions on this bow are as follows;

- 68" ntn, 70" total length
- 12" stiff riser section (inc. 4" flat handle and two 4" semi-working fades)
- 12" static tips on both limbs with additional limb depth + wedged kerf inserts for 3" of recurve over this section
- 1.5" width at the fades to 23" from centre (start of kerf) then tapering to 1/2" at tips

Aside from horsebows, I've only shot one static recurve, so my hands-on familiarity with them is rather limited. I seem to often err toward a shorter working limb than strictly necessary, probably due to an affection for horsebows, which you've rightly picked up on. However, to my mind, this is not entirely dissimilar to neolithic bows either - long(ish), narrow (ish) static tips with wide (or wider) working inner-limbs. This bow, once I've ironed out the tiller, will have the entire kerfed section rounded out to reduce mass. This, in effect, won't be dissimilar to neolithic bows - not precisely the same, but conceptually similar. As the limb thickens, it will become rounder, if you get my meaning.

greybeard wrote:I believe that reworking your existing design could produce a more efficient bow

Whether it ends up a 'performance' bow, I'm not overly fussed. It's a chance to try out a technique and prove that CTP (with a Hickory backing) is good for a shorter working limb at mid-range poundages. The previous attempt at this showed that a Red Oak backed Cypress (very) short limb didn't fail in compression - it was the lateral twist that caused longitudinal cracking, although I won't chalk that up as 'proof' until a working bow is finished with that combination. With these timber combinations there is never going to be a 'high performance' bow built, but people don't race Austin Mini's because they're the fastest car about - sometimes it's just about the challenge of getting the best out of a less-than-perfect situation.

With that in mind, I'm still interested in your how you would improve the efficiency of this bow - reduce limb mass + something else? Perhaps changing the width profile on the tips? In future I will undoubtedly be reducing the kerfed, static section but I am hoping that rounding these out on this bow should yield a little better performance, at least.

greybeard wrote:Embarking on projects as yours is about the only way we can develop our bowyer/design skills.

And I'm getting there! Slowly but surely, each build is a new lesson and I've come lightyears from the early builds a year or two ago. It's one thing building a bow from a stave alongside a master, it's a whole other thing to do so from boards and on your own.

Neil

For comparison, I placed these bows alongside one another. On Colin's thread it was suggested that hand placement would fix any tiller issues with that bow. Granted I need to get a picture up with a decent angle of the bow, but the left limbs on both would appear to have not dissimilar profiles, which might suggest hand placement would also be a fix for this bow.

Either way, I was happy to have got the result I did after calipers and only one minor scrub with some hand sand paper!

Neil,

I had a longer reply to your post but the internet connection dropped out before I could hit the submit button. I did have the original document saved but did a lot of editing 'live' to include quotes.

This is the short version.

Nezwin wrote:.....Aside from horsebows, I've only shot one static recurve, so my hands-on familiarity with them is rather limited. I seem to often err toward a shorter working limb than strictly necessary, probably due to an affection for horsebows, which you've rightly picked up on. However, to my mind, this is not entirely dissimilar to neolithic bows either - long(ish), narrow (ish) static tips with wide (or wider) working inner-limbs........

Not wanting to derail your post but I thought you may enjoy the following.
Daryl.

Double Post, apologies.

Thanks for the pictures, Daryl. They're something a little bit different, so they do appeal to me!

I've played a little with the tiller, perhaps took a little bit too much off?
I'm almost happy to call it done and get on with the prettying up - this being my favourite part. I also heavily rounded out the tips, which has given the bow a real unique look.

Neil

Nezwin wrote:....I've played a little with the tiller, perhaps took a little bit too much off?......I'm almost happy to call it done and get on with the prettying up.......

Neil, if you have a bow that shoots you are already in front.

I think at times some people get carried away with the limb profile on the tiller rather than how does the bow feel in the hand when loosing an arrow.

Daryl.

I think it looks really good now. A real purdy full draw shape. I'm liking forward to seeing it finished, especially in person!