first laminate bow

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Sabinus
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first laminate bow

#1 Post by Sabinus » Sat Jun 04, 2016 11:56 am

hi everyone - after a few years of trying to produce a functional, shootable selfbow/wood laminate bow, I 've decided to change tack. You can't even procure large diameter bamboo in Adelaide to back grain violated billets of otherwise potentially useful timber. Failures can teach us a lot,granted, but frankly, sustained failure in what should be a fun pastime, um, sucks.

My plan is to get started on my first fibreglass laminate hill-style longbow. Straight laid as that means the very simplest form to make, and will be using the multiple clamp/rubber tube method for clamping the stave for gluing.

We are lucky down here in that John Clark and Ausbow are still supplying simple longbow kits and a good instructional book which I've already secured a copy of. In the future I may nail down a bandsaw, beltsander and a lamninate grinding setup to prep my raw materials, but for right now it's the pre-prepared kit of components for me.

I've noted an earlier post regarding someone else's build of a woomera longbow, and the comments surrounding the fairly steep riser fadeouts. After looking at the riser template in John's book and him stressing about how the fadeouts need to be feathered until transparent at the tips, I'm comfortable it'll be on the money. If not, well I guess I'll be buying a sanding drum for my grinder motor and sorting that myself first.

So now it's down to selecting my riser, laminate and glass colour combo so I can place my order. I'm drawn to transparent glass on at least back or belly if not both. John told me he feels the clear botuff is less forgiving visually of gluing imperfections (I can understand why), but that also it's not as strong as the opaque varieties. I hadn't heard this theory before - what have you experienced glass laminate bowyers found in this respect? I'm building a 55lb@28" and 68"ntn - not the most highly strained of bow designs.

Thanks in advance,
Darren

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Re: first laminate bow

#2 Post by greybeard » Sat Jun 04, 2016 3:35 pm

Sabinus wrote:....... I'm drawn to transparent glass on at least back or belly if not both. John told me he feels the clear botuff is less forgiving visually of gluing imperfections (I can understand why), but that also it's not as strong as the opaque varieties. I hadn't heard this theory before - what have you experienced glass laminate bowyers found in this respect?...........
"From: Greybeard [mailto:greybeard@pcsol.com.au]
Sent: Wednesday, September 15, 2010 5:44 AM
To: 'Bingham Projects Inc.'
Subject: Bo-Tuff clear glass.

Hi Elmont,

I have a question regarding Bo-Tuff clear glass.

For the given thickness of the laminated core of a bow does clear glass i.e. .043 ULS yield a lower performance/draw weight than coloured glass of .040 ULS?

I am led to believe there is less glass fibre in clear glass. If there is a notable difference is there a percentage value that I should build into the core of a bow?

Regards,

Daryl.

Hi Daryl,

Thanks for your e-mail. Thickness for thickness, they are the same. The same limb thickness with black will yield the same weight as the same limb thickness with clear. The black glass is harder, not stiffer.

Sincerely,
Elmont"


Darren,

If the epoxy is not applied evenly to all surfaces and clamping/binding pressure is inconsistent or insufficient, air bubbles can be trapped and are visible through the clear glass.

Generally you will find some small imperfections in the clear glass, however they do not appear to affect durability or performance.

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!....

Sabinus
Posts: 138
Joined: Tue Mar 26, 2013 8:56 pm

Re: first laminate bow

#3 Post by Sabinus » Sat Jun 04, 2016 5:15 pm

Hi Daryl,
Thanks for the reply. If I'm understanding right, you made a similar query to 'Mr Binghams', and he reassured you the performance (stiffness) is the same, but that the clear is not as hard ie. would perhaps scratch and dent a little easier? Interesting distinction, I hadn't thought of it in those terms...
Have you used Bowtuff glass Daryl? Any experiences you could relate?
Thanks,
Darren

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Re: first laminate bow

#4 Post by greybeard » Sun Jun 05, 2016 9:14 am

Sabinus wrote:...... but that the clear is not as hard ie. would perhaps scratch and dent a little easier? Interesting distinction, I hadn't thought of it in those terms...
With normal usage I have not noticed any difference.
Sabinus wrote:......Have you used Bowtuff glass Daryl? Any experiences you could relate?
I have only ever used Bo-tuff glass, about 200 strips and not experienced any major issues. At times there have been variations up to 10% in thickness within the strip.

There is usually sanding dust left on the sanded side of the glass so I always give that side a good wash down with methylated spirits.

Be careful handling the glass strips as fibreglass splinters can be quite nasty.

Daryl.

Check out the taper rates of the core laminations, some of his designs appear to be a bit whip ended.
"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!....

Sabinus
Posts: 138
Joined: Tue Mar 26, 2013 8:56 pm

Re: first laminate bow

#5 Post by Sabinus » Sun Jun 05, 2016 10:30 am

Thanks for the reply Daryl,

Were you referring to the binghams or woomera design as potentially whip ended?
The issue with being a beginner is that I'm in a position of having to trust that the experts know what they are giving me........

Could I ask you Daryl, if planning a 68" hill style 55@28", what would your approach be regarding number of laminations, mix of flat/tapered, and the overall amount of limb taper? Width taper is 1 1/8"down to 1/2".

Please understand I'm not asking you to do the work for me, but it sounds like I could do with some independently sourced information, so I don't need to be lead through this experience blindfolded!

Thanks for your help,
Darren

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Re: first laminate bow

#6 Post by greybeard » Mon Jun 06, 2016 4:12 pm

Sabinus wrote:Were you referring to the binghams or woomera design as potentially whip ended?
Both.

Darren,

I run a .001” taper per linear inch. By choice I prefer slightly stiffer tips and an elliptical tiller.

You will have to make the decision as to what type of limb action you want and adjust taper rates accordingly.

For bow weights under 50# and using .040” glass three core laminations appear to be suitable. As I run a belly lamination up the fade outs I tend to keep it around .070” at the butt end so it is easier for the lamination to lay in the curve.

With regards to the number of laminations and lamination thickness using a .001” taper note the following for a 36” limb;

A lamination thickness of .200” will be .164” at the tip.

A lamination thickness of .150” will be .114” at the tip.

A lamination thickness of .100” will be .064” at the tip.

As you can see 2 x .100” laminations will total .128” at the tip whereas 1 x .200” lamination is .164” at the tip.

If for some reason I want to reduce the overall taper in the limb I will use a parallel lamination on the belly.

There are numerous ways of designing / building laminated bows so I played around until I found a formula that worked for me.

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!....

Sabinus
Posts: 138
Joined: Tue Mar 26, 2013 8:56 pm

Re: first laminate bow

#7 Post by Sabinus » Mon Jun 06, 2016 6:21 pm

Hi Daryl,
Thanks very much for this valuable input. It seems to me too, that an eliptical tiller with stiffer tips is an appropriate profile for the hill-style limb.
I've read as much as I can find about this topic on the forums, and 3-4 tapered laminations @ .001/lineal inch per lamination has come up more often perhaps than other combination. Apparently John Clark includes a 4 stack lamination with a 55lb@ 28" kit.
Thanks very much for your patience Daryl- does 4 laminations each tapering @.001 for a 68" 55pounder sound within the ballpark? The exact stack thickness of course I'll be leaving in John's capable hands this time, and I'll begin to generate my own tables and graphs as time goes on.

All the best and many thanks,
Darren

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Re: first laminate bow

#8 Post by greybeard » Mon Jun 06, 2016 9:04 pm

Sabinus wrote:........does 4 laminations each tapering @.001 for a 68" 55pounder sound within the ballpark?......
Hi Darren,

Sounds ok but you are at the stage where you will have to trust Johns judgement.
Sabinus wrote:...... I'm drawn to transparent glass on at least back or belly if not both.....
Unless you are using fancy back and belly laminations clear glass may be a waste of funds. Coloured glass is almost half the price.

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!....

Sabinus
Posts: 138
Joined: Tue Mar 26, 2013 8:56 pm

Re: first laminate bow

#9 Post by Sabinus » Fri Jun 10, 2016 8:55 pm

Hi All,

Well I received my longbow kit in the mail from John Clark the other day, the contents were really interesting and raised a few points worthy of mention.

Firstly, the riser block, or more to the point - the fades. Well they are primo - fade is very smooth and gradual, with 5-10mm of transparency at each end. I thought it was pretty rough a while back when a certain other member used this forum to slag off John's knowledge of and ability to produce good fades. Any chance the beginning bowyer in that thread didn't understand the function of said tapers and filed those pesky fragile feathery bits off each end? No idea, but my riser was bang-on. Although, as warned by others, it's narrower than all the other lams and glass. A bit of a pain really, but I've got a couple of ideas to get around this come glue up time.

Daryl, I did bug you a little over lamination/taper details over the last few days so as to try and educate myself on this. Well at least I knew enough to see that the four sets of laminations each tapering at .002/inch I was supplied with will not a longbow make - now that's what you would call 'whip ended'!!!! Obviously a mistake with the order - I'll be ordering two sets of parallel lams to combine with two sets of the .002s, thereby achieving the same taper rate as 4x .001s. Daryl, is there an established sequence in which you feel it's best to stack two tapered and two parallel lams?
You also poo-poohed my use of clear glass over my plain maple and myrtle limbs- and you were quite right! The price differential is minor however, but I reckon I'll get another piece of brown glass to match the other piece I have for this bow. So belatedly - thanks for the advice!

This long weekend I'm going to start on prepping my cauls and form, and sourcing as many g clamps as I can get! Also thinking of how to attack the bow oven. I see the very impressive rigs a lot of you guys have up and running in this respect, but I sense my initial version will be a little more rudimentary. Unfortunately it being winter I have to rule out the 'hot car' option, but we'll work something out!

I'm keen as mustard to get stuck in you guys - having been stiffed and robbed by a former 'bowyer' recently has prompted me to take the power into my own hands. Yes this is the first, but I'm already thinking about the next! Will keep you all posted on progress and anything interesting that pops up. And yes, I'm sure I'll need a bit of a pointer here and there too!

Thanks,
Darren

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Re: first laminate bow

#10 Post by greybeard » Sat Jun 11, 2016 9:01 am

Sabinus wrote:........... in that John Clark and Ausbow are still supplying............and a good instructional book which I've already secured a copy of........
Darren, is mention made in the book or has John made mention of reversing the tapers.

The following is from Bingham's' catalogue.

“Tapers are most commonly used in a .002 per inch taper 36” long. Some bowyers use several tapers with a .001” taper per running inch. I prefer a combination of a taper used with parallels. With this combination, you achieve excellent limb action and a fast, smooth limb…………
……………..For our 1 piece longbows and our shallow t.d. longbow, the limb thickness is composed of 2 pieces of Bo-tuff, 3 parallels, and 1 taper (.002”). The total limb thickness is the sum of all six layers, the taper being measured at the butt end. For our pronounced t.d. longbow, the limb thickness is composed of 2 pieces of Bo-tuff, 1 regular taper (.002”), 1 parallel, and 1 reverse taper (.002”). The reverse taper is simply a taper that is reversed so that the thin end of the taper is at the butt end of the limb. The total limb thickness is the sum of all five layers, the regular taper being measured at the butt end and the reverse taper being measured at the thin end.”

Perhaps you could play around with some of the tapers to see if a suitable limb profile can be obtained.
Sabinus wrote:............Daryl, is there an established sequence in which you feel it's best to stack two tapered and two parallel lams?.........
When using parallel laminations in conjunction with tapered laminations I would place a thicker [parallel] one under the back glass and a thinner [parallel] one under the belly glass.

This configuration is a personal preference, I do not believe it has a bearing on bow performance.

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!....

Sabinus
Posts: 138
Joined: Tue Mar 26, 2013 8:56 pm

Re: first laminate bow

#11 Post by Sabinus » Sat Jun 11, 2016 9:51 am

G'day Daryl,

Thanks so much for your reply. I indeed have played around with reversing tapers to get enough thickness in the tips, and lessen the rate of taper, but there just ain't enough wood here for the limb weight and limb action that I want. For days I was just looking at the laminations thinking there was just something really obvious I was missing.....
Luckily I already own a beautiful example of a custom Hill style bow in the same limb width, limb length, material, profile, and glass thickness, so it's been a very valuable visual reference for me, and helped confirm my suspicions that I had not all the right materials. Someone with less experience and without a similar bow may have launched into glueing, shaping, and ended up very disappointed with a terrible bow.

Thanks also for your opinion on how you'd lay the lams up. If I can obtain one thinner and one thicker parallel I'll follow your lead on using the thinner to conform more easily to the belly taper.
Thanks also for referencing the Binghams catalogue info - with John's book and the Binghams info combined, there's not much unsaid as far as I can tell. John features lots of graphs and equations that I'm sure will make more sense with time (although nothing re. reversing tapers) Whereas perhaps Binghams has better mastered anticipating the queries and confusions of the amatuer.....how blessed are we nowdays in the amount of data we can access- 20 years ago a bloke with no experience or teachers would still be breaking off tree limbs and tying on some fishing line at each end!
Darren

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