FINALLY MET LOOSEPLUCKER

[Dennis La Varenne]

Benalla-20121007-00841.jpg (96.41 KiB) Viewed 3974 times

Here we are at the Rose Garden on the south side of Benalla in North Eastern Victoria on Sunday, 7th October. John is on picture-left and me on picture-right.

John has just brought me a couple of nicley quarter-sawn boards of Osage for me to play around with while Mrs Looseplucker and the children took in the sights of the Rose Garden.

[longbow steve]

My condolences Dennis

[Stickbow Hunter]

My condolences Dennis

I was sent the photo on the day and I questioned how Mrs Looseplucker handled you too talkin' self bows and Bowhunting for who knows how long. I love that yella wood.

John should be in the wilds of Vic chasin' critters by now so I hope he has a good tale to tell when he gets back.

Jeff

[Hamish]

Cool wood, have fun with that Dennis

[Bill]

Who's a lucky happy boy then, great picture........

[RobHunter]

Lol

Maybe you can make me a mollegabet bow out of Osange, so I can see how its done

Rob

[bigbob]

Have fun L/p with that yella wood. My contacts havent come good at all with my promised load, but if there's one thing I have plenty of its time, nothing else mind but heaps of time.

[Dennis La Varenne]

Thankyou, all. I have posted this up before, but this is the kind of bow I would like to attempt from the Ben Pearson catalogue of 1941 -

Ben Pearson 1941 catalogue pp5.jpg (162.47 KiB) Viewed 3912 times

[Stickbow Hunter]

That bow sure has some reflex!

Jeff

[Dennis La Varenne]

Jeff,

The picture and the accompanying advertising indicate that that is the reflex remaining in the bow after unbracing which I find difficult to swallow quite frankly, but I don't doubt for a minute that reflexing a wood bow to that degree would dramatically increase performance and there would almost certainly be some remaining reflex after tillering and shooting in.

The little 64 inch hickory-backed Red Ironbark flatbow which we glued up on your old form (I think it was) had something like 32mm of reflex off the form and it still holds 5mm after breaking to my 26inch draw. I don't see why there should not be proportionately more remaining reflex in a bow with up to 6 inches of built-in reflex. The tillering would need to be spot on, but it is not beyond realistically buildable. Pearson, after all, was effectively using what we now call 'Perry reflexing' way back then. The amount of built-in reflex actually drew the belly wood into a moderate tension state and puts the back into moderate compression.

So . . . when the bow is bent right through to brace height, a lot of energy is being stored without putting much tension and compression load on the limbs. This design would have a very high string tension despite the moderate limb loading, and I suspect, a fairly flattish f-d curve.

I am trying to devise a test to measure comparative amounts of string tension so it can be factored in to an f-d curve to influence its shape. Unfortunately, this is difficult. Presently, ALL f-d curves using any kind of scale or weight dependent from the braced bowstring MUST start at 0 lbs at brace-height. There is no way in which to measure the amount of stored energy in the limbs of the braced bow that I know of, and that amount could be as much as 25% of the bow's stored energy in a bow with straight limbs, more in a reflexed bow and obviously less if it has string follow because the distance the limb-tips must move from rest to brace heigh is different in each case. That distance from rest to brace-height is a good indicator of how much energy a bow stores compared to another.

The soapbox -
It is notable when reading through my old Pearson and Bear catalogues from the 1940s through to the 1950s how this design persisted well into the fibreglass era, particularly with the Bear Cub and Polo bows and even with the early glassed Grizzlys which were just a Polo with static recurved tips. Pearson had their versions as well. Bear Polos and Cubs had the same resting limb profile as the Pearson above but when braced were called 'semi-recurves' by both Bear and Pearson because the fibreglass prevented the heavily reflexed outer limb from straightening out completely, leaving an obvious but gentle reflex in the outer limb exactly the same as the modern day 'deflex-reflex' design has.

For those 'iconoclasts without a cause' among us, this is the first time the term 'semi-reflex was used. The term 'deflex-reflex' was never used to describe such bows in the era of their invention. It was coined in the 1980s when the design was resurrected and commercial bowmakers needed a new marketable name for the design. That term is traditional to no tradition in archery that I know of. The design had already been named 3 decades previously.

But, I am telling you nothing of course.

[longbow steve]

Hi Dennis, interesting project. Would you mind documenting your observations when tillering the highly reflexed stave. I have a stave with 7" of reflex and am dreading the job of tillering it. Thanks Steve

[Dennis La Varenne]

Steve,

Yes, I will . . . on the reciprocal proviso that you do the same with yours of course. I suspect that both will be rather thin somehow with a shallower taper rather than the 8 thou/inch which seems to be common among my straight limbed bows.

[greybeard]

Dennis,

Your new project is going to be an enjoyable challenge. Photos and a story will make interesting reading.

Have you been able to calculate how much extra reflex needs to be built in to the form to offset the amount that is lost when the glued up stave comes off the form and subsequent losses during the tillering and shooting in process?

Daryl.

[longbow steve]

Steve,

Yes, I will . . . on the reciprocal proviso that you do the same with yours of course. I suspect that both will be rather thin somehow with a shallower taper rather than the 8 thou/inch which seems to be common among my straight limbed bows.

Yes I will however mine is roughed out as a Mollegabet but should be interesting regardless.
Cheers Steve

[wishsong]

Dennis , do you know of Jim Fetrow ? He is known to be somewhat of an 'icon' amongst yew fans on both sides of the "pond" ...
when building his hills style bows , he puts up to 6" of reflex on them ...

[Dennis La Varenne]

Daryl,

I haven't worked out how much extra to build in to allow for the loss. It would only be a guess. If I ended up with anywhere from 4 inches +, I would be happy, but I will build an adjustable form along the lines of yours which can bend up to 7 inches over a 66 inch bow. I have come to the conclusion however that WIDE will be the secret with this kind of bow. The Pearson's and Bears were 1 1/2 inches wide from the specs in their catalogues.

Steve,

A Mølegabet with 7 inches of reflex. Crivvens!!! Your work WILL be cut out for you. I don't know if the process for a conventional flatbow will help that much.

Ben,

I know OF Jim Fetrow but almost nothing about him. I seem to recall reading some of his stuff in the real early Longbow Digests waaaaaay back in the '80s and I think I have published (with permission) his schematic and instructions for making Flemish strings on Ozbow. Does he make all wood or glassed bows? I certainly did not know that he put THAT much reflex into them . . . or anybody else for that matter in the last 40 years . . . where straight-ended bows are concerned.

I have discussed the issue of heavily reflexed glassed bows with Jeff on a few occasions, but he has advised against it from his experience because of increasingly heavy handshock. I couldn't offer an opinion there as it is outside my bowmaking experience.

Anyway, I have spoken to somebody who is capable and willing to adapt my old 600x40mm flatbed belt linisher to a lam-grinder. I will start investigating the making of a master-taper lam of 8 thou/inch so I can form the taper in the belly lam to which I will then glue the backing lam of hickory which will pull the belly wood into the required amount of reflex. The handle block will be glued on first and the master taper will taper only the belly wood outside the handle block to prevent any flexing putting stress on the glue joint between the handle and the belly wood.

With a few bows, it would not be too difficult to be able to begin with a specific tip thickness and a standardised backing lam thickness to bring one with reasonable cooee of intended draw weight so long as everything else remained unchanged. Pearson, Bear, York Archery and Indian Archery built thousands of them using a similar recipe back in the primeval '40s.

I have recently been offered a hickory backed bow made with about 4 Yew laminations in its limbs which was made back in the 1940s. It is about 40lbs at 25 inches, 1 1/2 inches wide and 60 inches n-n, but looks in the pics to have only about 1/2 inch of set.

Multiple lams would be another approach, but I would prefer less gluing quite frankly. One backing lam and one handle block are quite enough for me.

[wishsong]

Dennis, I am certainly looking forward to seeing the results of what you come up with

[GrahameA]

Hi Dennis.

I am trying to devise a test to measure comparative amounts of string tension so it can be factored in to an f-d curve to influence its shape. Unfortunately, this is difficult. Presently, ALL f-d curves using any kind of scale or weight dependent from the braced bowstring MUST start at 0 lbs at brace-height. There is no way in which to measure the amount of stored energy in the limbs of the braced bow that I know of, and that amount could be as much as 25% of the bow's stored energy in a bow with straight limbs, more in a reflexed bow and obviously less if it has string follow because the distance the limb-tips must move from rest to brace heigh is different in each case. That distance from rest to brace-height is a good indicator of how much energy a bow stores compared to another.

I am not quite certain what you are trying to achieve - brain is working in slow mode.

Whilst the conventional D/F curve starts at a load of zero at Brace height it does however show the pre-load in the bow at Brace plus delta with an error of the extra load caused by the draw length of delta.

I would strongly suggest that with a small delta the error may well be lesss than the error in the measuring equipment.

May I suggest that you could measure the load from rest to brace height. If you want the tension in the string then you could resolve the vectors to ascertain the tension in the string..

Ther is no reason why your D/F curve cannot start at rest and you can measure from there to wherever.

[greybeard]

Dennis,

Have you worked out the ratio of the hickory back to the osage belly?

Looking at the values shown in the following chart too much osage may over power the hickory and pull out most of the reflex. Perhaps steaming heavy reflex into the osage before gluing up will alter its memory so that when laminated to the hickory most of the reflex may be retained.

Wood Comparison.JPG (120.18 KiB) Viewed 3800 times

With regards to stored energy at brace height I obtained some figures from the bow below. My methodology may not have been exacting but it did provide some numbers as a guide.

Glued Up Bow.JPG (32.57 KiB) Viewed 3800 times

The bow is 68” n to n, limb tip travel from unbraced to braced height was twelve inches and the scales registered 38#. The draw was extended by three inches which represented ten inch draw and the scales registered 59#.

It was obvious that this bow was massively overbuilt so I did not take the test any further.

Daryl.

[yeoman]

That is a supremely reflexed bow indeed.

I'm just armchair-engineering here, but I am going to hazard a guess that in perry reflexed bows, the brace height must be greater than the rested-reflex measurement. Perry reflex bows that I make a notorious for twisting and unstringing themselves, or reverse twisting themselves, when I give them a low brace height. The bow naturally wants to be in its unstrung position, and will do literally anything it can to be so. Ergo, if you give the Perry reflexed bow an inch (or even a quarter inch) it will take a mile.

Now, this may be the cynic in me, but I wonder if that reflexed bow pic was sneakily strung with a black string and photographed. The UFO skeptic will potentially see a black line between the tips.

Those that engage in flightshooting report a remarkable phenomena when tillering very highly perry-reflexed bows. They report that the reflex can actually increase as tillering progresses, as belly wood is removed the back lamination is free to pull more toward a reflexed shape. Bizarre, but true.

If I were to make a such a supremely reflexed bow, I would make a straight bow of the same width and thickness to begin with, and measure it's thickness carefully. I'd then make two laminations each half the thickness of the straight bow, and glue that into reflex. Actually, maybe a back/belly ratio of 1/3:2/3. Then glue it into reflex, then tiller.

Dennis, I understand what you're after with regard to finding the stored energy in the braced limb. But it's not quite the figure you're after. The only energy available to the arrow is that which can be supplied to it as allowed by the maximum length of the bowstring. What is magic about Perry reflexing is that wood close to the neutral plane is put under stress, which does not happen to anywhere near as much in a selfbow. It allows more wood mass to store energy when bent. What you would want to calculate is the amount of stress experienced by the wood on either side of the glue joint.

This isn't any easier to do, mind.

However, I think you can measure how much energy is stored in the limb in taking the tip from reflexed to braced. You will need to clamp the bow with industrial-strength tightness. Use a bow scale to pull on one limb at 90 degrees to the plane of the handle. Do this in increments measuring the force each time. This will give you data to plot a sort of force draw curve, the area under which line will be related to the amount of energy stored. But as I said, this energy will not be available to the arrow. Rather, the more even distribution of stress allows for a higher density of energy storage and mass-utilisation.

Hopefully I'm not telling you how to suck eggs here.

Oh, and LoosePlucker is a top bloke. Always good for a chat and a few tales about huntin', bowyerin' and fly-tyin'.

[greybeard]

Dennis,

Is this the information you require? This bow was massively overbuilt and having high stored energy at brace gives high string tension at the start of the draw cycle.

I believe that this high early string tension will help the bow store more energy however as Dave pointed out that the stored energy before brace height will remain in the bow.

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Graph To Six Inch Draw.jpg (116.52 KiB) Viewed 3771 times

Daryl.

[looseplucker]

Struth

Who would have thought it would have gone that far!!! Anyhow, Dennis traded me some nice lams of hickory from rudderbows and I have secretly recorded him promising to make me a bow out of the yaller stuff I shot his way

Jeff - did post a story about the wilds of Victoria..... but that was out with Piggy - you wait until you hear my tales of shopping down at Fountain Gate!!

And as for this:

Oh, and LoosePlucker is a top bloke. Always good for a chat and a few tales about huntin', bowyerin' and fly-tyin'.

[greybeard]

Struth

Who would have thought it would have gone that far!!!

John,

The power of pole bamboo is amazing. I am reworking the bow to reduce the poundage.

Daryl.

[looseplucker]

Dead right there. It is why I like doing the boo back and belly bows and will one day do one with a single core. Not laminated. With the right timber and proper dimensions I reckon a very good bow can be done.