The Experiment...

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hunterguy1991
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The Experiment...

#1 Post by hunterguy1991 » Sun Nov 09, 2014 3:55 pm

Experiment Title : Linen backed English Warbow

Background information:

After a bit of research into some commonly used timbers in English warbows and into material properties of these timbers the choice of Brazilian Teak was made as a test subject. It was cheap ($15 for a board) and seemed suitable with a high crushing strength, MoE and MoR...

The design utilised was a combination of one provided to me by Dennis (see other threads of mine for details) and also some small things I noticed when making my own warbows previously. My 115lb bow has a tip thickness measurement half that of the handle (I'm an engineer and cant help but measure things as I'm making them), as did the other warbows I have made which pulled a nice circular curve, bending through the entire length.

Linen was selected for a backing for 3 reasons. Firslty, I ran out of hickory strips (bugger!!), secondly I wanted to keep the price and availability of materials to a minimum and lastly, I wanted to see if the linen can hold up on the back of a high draw weight bow.

Hypothesis: A linen backing on a warbow has sufficient strength to withstand failure and Brazilian Teak has sufficient material properties to be used in such a bow of over 120lbs draw weight.

Method:

Construct the bow using tools available.

Dimensions on rough shaping: total length 82", 80" nock to nock.
handle width: 38mm
handle thickness: 30mm
tip thickness/width: 16mm (1mm to allow for tillering)

Note: handle thickness was achieved by ripping a 89mm wide x 19mm thick board in 2 and gluing it together to double the thickness and then trimmed to desired measurement (another little test in the bow's design)

Having spoken to some good authorities with regards to making English warbows I have decided to tiller the bow leaving the tips thick and establish a good bend in the handle section first then slowly bring the tips around later to ensure an even bend over the whole limb. (see the EWBS website for photos in a build along)

Progress photos to come.

Colin

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Re: The Experiment...

#2 Post by hunterguy1991 » Mon Nov 10, 2014 4:00 pm

Here we are after the days work so far... Doubt I will do any more today as I'm waiting from some input from a chap over seas that seems to think he's the best bowyer ever and I want to be a smart **** :biggrin: Seems to think the slight whip tiller I usually look for is inferior to his "somewhat" stiff tipped design which he ensures me shoots further. Personally I don't really care since bows with a slight (slight being the key word here!!) whip tiller are more historically accurate ie Ascham and I think they would shoot further due to higher tip velocity and hence string velocity.

Bow is currently holding a 5 inch brace height (lower end of shooting height but would give a wicked power stroke!!) and pulls 115lbs @ 24 inches (pictured)|
Brazilian teak warbow - 5 inch brace 115 at 24 (640x480).jpg
Brazilian teak warbow - 5 inch brace 115 at 24 (640x480).jpg (178.69 KiB) Viewed 3542 times
Target weight is 130lbs at 30 inches (true DL) so I just need to sink it a little and get that last few inches of draw. I feel like it would go to 30 now but I don't want to over stress the limbs past my target weight.

As a side note... To any beginners reading through this thread and anyone else who thinks it worth while, get yourself a Shinto Saw rasp for shaping bows!!! They are unreal!! Incredibly fast and easy to use and much more forgiving than a traditional wood rasp or farriers rasp.

More progress and results of the experiment to come.

Colin

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Re: The Experiment...

#3 Post by The Ranger » Mon Nov 10, 2014 4:47 pm

Looking good Colin. Keep the photos coming please.

Stuart
Don't practise until you get it right. Practise until you don't get it wrong. Ranger Bows.

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Re: The Experiment...

#4 Post by hunterguy1991 » Mon Nov 10, 2014 4:56 pm

Thanks mate!! I have some more but they're just brace shots so not very interesting. Might chuck a couple up later and there will be lots more tomorrow as I progress with tillering it further.

Colin

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Re: The Experiment...

#5 Post by greybeard » Mon Nov 10, 2014 5:47 pm

hunterguy1991 wrote:....After a bit of research into some commonly used timbers in English warbows and into material properties of these timbers.....
Are you referring to the timbers used around the 14th./15th. century or those currently being used to replicate war bows?

Can you let us know what timbers were used for the comparisons?

The bow is looking good, but if you were to mount the tiller stick on the wall and draw a grid pattern on the wall it would make life easier when trying to evaluate the bows tiller.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

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Re: The Experiment...

#6 Post by bigbob » Mon Nov 10, 2014 5:54 pm

130#, I 'll get a hernia just thinking about that! Good work so far, Colin.
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Re: The Experiment...

#7 Post by yeoman » Mon Nov 10, 2014 6:43 pm

I reckon you could do the rest of the tillering on that bow without touching the inner part of the limbs.

Your contact overseas is doing something wrong with his conventionally tillered warbows of his rather stiff tipped ones are faster. If it were the case that this property is in fact better than the historical solution, our ancestors would've adopted it.

It'll be good the see the results of this experiment. Keep it up!
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Re: The Experiment...

#8 Post by hunterguy1991 » Mon Nov 10, 2014 7:27 pm

Cheers guys!

Daryl, I should have clarified better... I meant the timbers being used currently in high end warbows made in England. For a look at belly timbers look at Heritage Longbows "warbows". There is that many timber options I cant remember them all. Messerandubra (spelling is probably wrong) and Ipe are both used and are what lead me to the Brazilian Teak... I wanted something with a high crushing strength to minimise the chance of chrysals in the belly.

Bob, I'm pulling 115 now so I figured 15lbs jump wouldn't be too bad... Will be a challenge tho but I want to be up near the records and need a high draw bow to get there.

Yeoman, by my calcs if I leave it as is it would go 145 @ 30... so I need to sink the whole thing but I think just the tips need to be brought around a bit more and it will be spot on as far as bending goes. More scraping tomorrow and I should get it there. Just need to get it to 30 inches true draw length and its done.

I don't understand their fascination with "compass"... most of the time what looks compass to the eye is actually stiff in the tips when you look at limb in segments or measure them, but they don't get that.

Colin

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Re: The Experiment...

#9 Post by hunterguy1991 » Tue Nov 11, 2014 10:51 am

Well... that's the experiment finished.

While working on the bow this morning a big splinter lifted under the linen at the handle... I think it occurred when I pushed the bow out to 26 inches as I heard some little noises but wasn't sure if it was the bow or the tiller stand and pulleys.

At the 26 inch mark the bow was holding just under 130lbs on my scales so I think it would have been 150+ at 30 inches... bit of a beast!!


Conclusion:

1. The Brazilian Teak holds up excellently as a belly timber as I have had no issues with fretting in the belly even up at 130lbs @26" so I will be re marking this bow with slightly smaller thickness dimensions so its not as far over target weight as this one was.

2. The process of gluing up 2 19mm thick boards to make the required thickness was a success as they didn't look the slightest like separating...

3. Linen is a life saver!! pretty sure if this thing was not linen backed it would have blown up quite spectacularly on me when the splinter lifted. I will be using it again on the next one to see if it is possible to get a working warbow with a linen backing.

4. My dimension change to Dennis's template worked marvellously and my thoughts on proportions were spot on. Very little work was needed on this bow to get the bend in it that it had, so I think having tips half as thick as the handle is a good starting point for a design. For comparisons sake the thickness taper ends up at 1 and 1/13th mm per 3 inches so, around 0.34mm per inch...

5. I think to get bows up around the 130+ mark you need to have an 84 inch stave to minimise the deflection in the limbs to reach full draw since its a combination of stress and deflection that pulls splinters.

6. 150lbs @ 30 is too much for me to pull!! haha I had a little play with the bow in the yard before I noticed the splinter and got 2 shots at around 26 maybe 27 inches draw, that was all I could manage... But HOLY CRAP did this thing throw an arrow!!!

I will post some brace photos and a shot of the splinter later today.

Will continue the tillering on this one and see if I can get it to 30 inches even with the splinter under the linen and see what weight it goes without failing catastrophically.

Then onto the next one!

Colin.

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Re: The Experiment...

#10 Post by greybeard » Tue Nov 11, 2014 3:45 pm

hunterguy1991 wrote:... I meant the timbers being used currently in high end warbows made in England. For a look at belly timbers look at Heritage Longbows "warbows"...
I checked out their web site and they have some good looking laminated longbows.

Personally I believe they are misusing the term 'war bow' as they are producing heavy draw weight laminated longbows.
hunterguy1991 wrote:I don't understand their fascination with "compass"...
From memory the wording "coming round compass" referred to selfbows [not laminated bows] on the tiller stick when the bow tips were at the equivalent position of full draw and and the stave was bending through the handle.

If the splinter won't lay down I have found that by binding the area with serving material and coating the serving with superglue fixes the problem.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

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Re: The Experiment...

#11 Post by hunterguy1991 » Tue Nov 11, 2014 7:22 pm

I did some more reducing to the belly of the bow this morning and thing put it back on the tiller... lifted some more splinters further along the limb so its pretty much fire wood now.

It needs a better backing material, either hickory or bamboo would be the best options. Not too fussed that it broke because I was testing it as a belly wood anyway and it worked superbly as that.

Definitely needs to be 84 inches ntn to reduce the required deflection to reach full draw with the high weights. My experience is that high stress + large deflection = splinters... same high stress + low deflection = no splinters.

Daryl, they are warbows, because a warbow bends through the handle with the same or very similar curvature to the limbs... a longbow does not carry this curvature through the handle. At least that is my understanding of the difference between the two.

Typically though a true warbow would be a self bow made of Yew, Wytch Elm or another suitable European timber, but still carrying the distinguishing curve through its full length.

Unfortunately not everyone has access to/the funds to get true self warbows so these laminated replicas are a good representation and just as much fun to shoot.

Colin

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Re: The Experiment...

#12 Post by greybeard » Tue Nov 11, 2014 8:34 pm

For what it is worth;

Wiki;

"Organizations which run archery competitions have set out formal definitions for the various classes; many definitions of the longbow would exclude some medieval examples, materials, and techniques of use.[1][2] According to the British Longbow Society, the English longbow is made so that its thickness is at least ⅝ (62.5%) of its width, as in Victorian longbows, and is widest at the handle. This differs from the Medieval longbow, which had a thickness between 33% and 75% of the width. Also, the Victorian longbow does not bend throughout the entire length, as does the medieval longbow. Longbows have been used for hunting and warfare, by many cultures around the world, a famous example being the English longbow, during the Middle Ages."

It would appear that rigid handles were a late modification in longbow design.
Periods And Eras In English History.jpg
Periods And Eras In English History.jpg (67.29 KiB) Viewed 3454 times
Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

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