Bamboo Backed Rock Maple Bow

Where to source materials etc. Also the place to show off your new bow or quiver etc.... Making things belongs in Traditional Crafts.

Moderator: Moderators

Post Reply
Message
Author
indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Bamboo Backed Rock Maple Bow

#1 Post by indie » Mon Mar 09, 2020 4:37 pm

Hi All, been a while. I'm wanting to make up a few bows for myself and my kids. I've had a go at using red oak backed with linen and made a few bits of kindling instead. :biggrin: I'm still keen so will keep going.

Style of bow I'm looking at is a bamboo backed board bow glued into a reflex deflex profile with only the two layers plus a power lam plus glued on handle.I'll make up a simple form for this. I've got the bamboo and have a few boards of red oak/rock maple/spotted gum to play with yet so happy to just do it and see what happens. The bamboo has a reasonable crown on it so probably limited to around 1.5" width maximum. Got a few questions though for the wise.

Projected bow layout; 66" tip to tip, likely taper from just beyond fades so as pyramid as I can get with 1.5" width, about 45lb at 28".

1. To make the most efficient use of the bamboo, can I splice it in the handle area? This would allow me to reverse the nodes so they space evenly along each limb. I'm thinking the use of the power lam and non-bending handle would mean it's reasonably safe to do so. I'll be using EA40 for glue. I could also cover the splice with a leather handle wrap.

2. For the belly timber I'd like to get it down to thinner strips before gluing. For a 45lb bow at 64" ntn and 28" draw what thickness would the belly lam' be? I'm thinking 12mm through the handle and fades then down to say 9mm at the tips. This would mean I would thin the timber into 12mm strips (approx 40mm wide each) to begin with. Of course draw weight etc would determine this but looking for a starting point. Considering the bow would be wider towards the handle and therefore the bamboo thicker due to crowning, would I get away with having the belly lam' the same thickness all the way? So maybe 9mm? This would make life easier to set things up.

So if I'm looking at the reflex-deflex style then it would certainly be easier if I can get everything thinned down close to where it would end up before I glue it all. And I'm looking to glue the handle on in the initial gluing and not after. Not totally sure as yet but think it will be a fairly basic handle but will include an arrow rest.

I've probably missed some important parameters there so let me know. Thanks in advance.
Last edited by indie on Mon Apr 20, 2020 2:48 pm, edited 1 time in total.

User avatar
Stickbow Hunter
Supporter
Supporter
Posts: 11637
Joined: Sat Jul 26, 2003 8:33 pm
Location: Maryborough Queensland

Re: Bamboo Backed R-D Bow Questions.

#2 Post by Stickbow Hunter » Tue Mar 10, 2020 1:00 pm

Sorry I can't help you with making your bow as I have no experience with making one of that type. Hopefully someone who has made a similar bow will reply. First up you need to clear up if you in fact want to make a bow with a reflex/deflex limb design or are you really meaning you wish to make a deflex/reflex limb design? People regularly mix this terminology up these days. If you want the limbs to deflex from the riser and then reflex in the outer part of the limb then this type of limb design is known as deflex/reflex.

Anyway all the best with making the new bow.

Jeff

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed R-D Bow Questions.

#3 Post by indie » Tue Mar 10, 2020 1:14 pm

Thanks Jeff. I know technically it is indeed a deflex reflex design but so few people call it that as saying it in reverse rolls off the tongue better. But yes deflex through the handle and reflex towards the tips.

User avatar
greybeard
Supporter
Supporter
Posts: 2992
Joined: Tue Feb 07, 2006 9:11 am
Location: Logan City QLD

Re: Bamboo Backed R-D Bow Questions.

#4 Post by greybeard » Tue Mar 10, 2020 2:26 pm

Hi Indie,

I would recommend using a ‘Z’ splice with the bamboo backing rather than a ‘butt’ join.
Diagram For Z Splice.JPG
Diagram For Z Splice.JPG (23.27 KiB) Viewed 7056 times
To my way of thinking incorporating deflex in a bamboo/wood bow is akin to building in string follow. A lot of reflex would probably be needed to be built in to compensate for the anticipated loss of stored energy caused by deflex in the limbs.

Apart from the taper obtained when shaping the bamboo backing I have found it advantageous to taper the core as well.

Do not have the core too thick otherwise you stand the chance of running out of belly wood during the tillering process.

If your belly timber is thick enough you could incorporate the handle and fadeouts and do away with the power lam.

The following link is for a tri laminate bamboo backed bow that I made a few months back.

viewtopic.php?f=34&t=17112

Dimensions of the above bow are N to N 68” and the limbs are as follows.

Widest; 1.23” or 31.30mm and .530” or 13.47mm thick.

Mid limb; 1.039” or 26.39mm and .453” or 11.5mm thick.

Tip; .690” or 17.58mm and .357” or 9.07mm thick.

The above yielded a bow of 40# @ 28” but had I not messed up during the tillering process it could have easily been a 50# plus bow.

Hopefully the above information is helpful?

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!....

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed R-D Bow Questions.

#5 Post by indie » Tue Mar 10, 2020 8:31 pm

Hi Daryl,

Thanks for your input. I'll indeed use the Z style splice for joining. What you say regarding incorporating deflex makes sense so why is the deflex reflex so popular? I thought it gave the bow better manners - not sure how though. Mind you there's a lot of recurves out there sporting a lot of deflex so not sure what the go is.

I do like your tri lam' bow, simple but looks great and I gather performs well. I was going to make this a bi lam' bow for simplicity. Note I have no way of sanding tapers but could rough out something close before gluing the two laminates together. Thanks for the dimensions, from those I think I'm close to the mark. There's really only one way to find out. :D

User avatar
Stickbow Hunter
Supporter
Supporter
Posts: 11637
Joined: Sat Jul 26, 2003 8:33 pm
Location: Maryborough Queensland

Re: Bamboo Backed R-D Bow Questions.

#6 Post by Stickbow Hunter » Wed Mar 11, 2020 1:13 pm

indie wrote: Tue Mar 10, 2020 1:14 pm Thanks Jeff. I know technically it is indeed a deflex reflex design but so few people call it that as saying it in reverse rolls off the tongue better. But yes deflex through the handle and reflex towards the tips.
Few people use the term now days but it doesn't make it right and it just leads to confusion. It is akin to saying you are going to deflate a tyre when in fact you are going to inflate it; just makes no sense to do so.

I agree with Daryl regarding the deflex; I don't see any real advantage, performance wise, with the deflex/reflex design. Having the tip recurving a little helps with string angle, especially in shorter bows. Deflex/reflex also gives you a bow with a lighter early draw but the draw weight increases quickly in the latter part of the draw. With a reflex only bow you have a higher early draw but the draw weight increases evenly to full draw. I much prefer the reflex design (within reason) as it will result in a better performing bow IMO, especially so in wood bows.

Have fun building your bow and please share your results with us.

Jeff

User avatar
greybeard
Supporter
Supporter
Posts: 2992
Joined: Tue Feb 07, 2006 9:11 am
Location: Logan City QLD

Re: Bamboo Backed R-D Bow Questions.

#7 Post by greybeard » Wed Mar 11, 2020 2:40 pm

Hi Indie,

For some reason I misread your post, I thought you were building a tri laminated bow.

We must be mindful that wood / bamboo bows are different to glass composite bows and must be treated as such.

A deflex reflex design incorporating today’s modern materials may have some advantages but there is not a lot of statistical data out there to back up the claims.

The following is from a leading archery company in the USA.

“Longbows are the icon of traditional bows. Longbows are considered easier to shoot as the longer length disperses the bow weight over a larger area making it draw smooth back to most draw lengths.
Today's longbows use a reflex/deflex design for performance that is a match or better than today's recurve bows. Expect blazing speed, hard hitting performance, and accuracy from one of today's modern longbows.”

Unfortunately they did not include any data to substantiate their claims.

The following is a rather lengthy read but overall has some interesting information.

https://www.dryadbows.com/Defining%20Bo ... 0Dryad.pdf
indie wrote: Mon Mar 09, 2020 4:37 pm
and have a few boards of red oak/rock maple/spotted gum to play
The rock maple may be the better choice for the belly.

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!....

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed R-D Bow Questions.

#8 Post by indie » Fri Mar 13, 2020 8:57 pm

Thanks for that link Daryl, indeed interesting. Hope I'll get a bit of a run at it soon. This Carona Virus has just cancelled the bulk of my weekend sporting commitments which certainly helps. :D

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed Rock Maple Bow

#9 Post by indie » Mon Apr 20, 2020 3:36 pm

So I've moved past analysis paralysis and have now cut the rock maple into 12mm thick pieces. There are a few little pin knots in it which weren't visible earlier. One of the boards could only be maxxed out to 1580mm long so will yield a bow of about 60" NTN. The other will get about 62" NTN. To begin with I'm working on the 60" board. Design is essentially a pyramid with a 4" handle and 2.5" fades. 4" handle is located centre of bow. Width at fades is 1 5/8th (43mm) and width at tips is 5/8" (15mm). I'll add some reflex to the ends on the glue up. Desired draw weight is 45# at 28. My draw length is about 27.5 so it won't go past 28.

I've cut out the profile and sanded the edges to shape and used that to mark out and cut the bamboo keeping the nodes equally distant from the tips. So far I've sanded one end of the boo down to 2mm at the edges as it has a fair bit of crown. At this point I have not done anything about the handle/riser area and will have to source some wood for that. All seems to be going well so far but I'm a bit nervous about one of the pin knots which is a couple of inches outside the fades. See the attached images.

End view showing thinned boo
End view showing thinned boo
image3.jpeg (17.72 KiB) Viewed 6821 times
View of proposed back side of rock maple.
View of proposed back side of rock maple.
IMG_7219.JPG (17.69 KiB) Viewed 6821 times
Pin knot on back side
Pin knot on back side
image2.jpeg (17.44 KiB) Viewed 6821 times
Side view of pin knot
Side view of pin knot
image0.jpeg (16.37 KiB) Viewed 6821 times
Proposed belly side rock maple
Proposed belly side rock maple
image1.jpeg (17.93 KiB) Viewed 6821 times

The side shown in the second image I was proposing to put on the back of the bow so laminated under the bamboo. That way it isn't doing all the compressive work and would be assisted by the boo which will be doing the tensile work. The violation shown in the last photo isn't that bad and doesn't go all the way through but don't know how deep it goes. From photos of other similar bows that are bamboo backed, the belly wood is commonly far from ideal with skewy grain and knots but they still seem to perform fine I suspect due to the bamboo doing a lot of the work. I have thought I could insert a thin power lam into the bow but to reduce bending in that area but it would have to be pretty long. The other option I thought of is to put that knot on the lower limb and drop the handle by 3/4 of an inch which would bring the knot closer to the fade. Or is it not worth worrying about? :roll:

Interested to hear what others think about it. Thanks.

User avatar
Stickbow Hunter
Supporter
Supporter
Posts: 11637
Joined: Sat Jul 26, 2003 8:33 pm
Location: Maryborough Queensland

Re: Bamboo Backed Rock Maple Bow

#10 Post by Stickbow Hunter » Tue Apr 21, 2020 7:56 pm

I don't think that little knot will cause any dramas. I look forward to seeing the bow progress.

User avatar
greybeard
Supporter
Supporter
Posts: 2992
Joined: Tue Feb 07, 2006 9:11 am
Location: Logan City QLD

Re: Bamboo Backed Rock Maple Bow

#11 Post by greybeard » Wed Apr 22, 2020 9:36 am

Hi indie,

The faulty grain shown in the photo was at the start of the recurve and the other at the end of the fade out in a bamboo backed hickory bow.

Additionally the grain was fairly wavy along the limbs.
Grain Near Tip And Fadeout.jpg
Grain Near Tip And Fadeout.jpg (109.99 KiB) Viewed 6766 times
The bow was bought by an Ozbow member some time back and to date there hasn’t been any negative feed back.

Pole bamboo is a fantastic product if used correctly.

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!....

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed Rock Maple Bow

#12 Post by indie » Thu Apr 23, 2020 7:22 am

Gents, thank you for your feedback. I had a follow up "consult" with Greybeard and on his advice will reduce the width of the bow and bamboo so that the crown on the bamboo and its resulting effect on the maple is reduced. I've also looked again at Daryl's build here; viewtopic.php?f=34&t=14522 which has recurved tips. I'll probably not go that far but will likely thin the tips a little before gluing in some reflex. I'll probably glue in a little reflex closer to the handle and increase that slightly towards the tip. First up I've got to resolve how I am doing the handle.

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed Rock Maple Bow

#13 Post by indie » Wed Apr 29, 2020 7:56 pm

Time for an update.

I glued the handle timbers together first and then glued those to the main board. I did this before gluing on the bamboo as with the introduction of the reflex I'd be trying to pull the ends of the handle sections onto the board for gluing rather than pushing it all together. I thinned the tips slightly and today I glued the bamboo on. The handle was left flat so that the centre would remain true to the form which in this case was a 50 x 50 RHS tube. You'll see in the attached image the bike tube was wrapped around the form as well as the bow to keep it flat and locked onto the form. The entire bow was wrapped and the tips raised on blocks of timber. I then used compression straps about 6" from the tips and pulled this spot down slightly to introduce greater reflex towards the tips. All measured up and once nice and even the form and bow were moved into the sun to "bake" for the day.
Bow wrapped and on steel tube form.
Bow wrapped and on steel tube form.
IMG_7256.jpg (31.57 KiB) Viewed 6631 times
I've unwrapped it tonight and very happy with the amount of reflex retained. And by the feel of it there will be plenty of wood removed to make this something I can manage.

Next I'll sort out some tip overlays and may just go with some more rock maple. Looking forward to one day shooting this thing.

indie
Posts: 101
Joined: Mon Aug 05, 2013 2:44 pm

Re: Bamboo Backed Rock Maple Bow

#14 Post by indie » Sat May 02, 2020 3:54 pm

So this is where it sits.

First image is on the tree at rest. The tips are covered with leather pockets as no sting grooves are filed in yet. You can see it retained a fair amount of reflex.
Out of the form
Out of the form
IMG_7270.jpg (56.65 KiB) Viewed 6579 times
Next pic shows it at 40# on the long string. Note intended draw weight about 45# but not too concerned about it as this one is a learning exercise. Not much movement as yet. I'm using a set of cabinet scrapers to remove wood so it is taking quite a while and I'm nervous about taking off too much. I'm scraping towards the tips starting with a shorter scrape then increasing the length of the scrape each time so as to remove more wood towards the outer limb and less towards the handle. I've got a table which is slatted so gives me some good reference marks to know where to scrape from. I'm leaving a little thickness for the last four inches of the tips for a little extra stiffness there.
On the long string at 40#
On the long string at 40#
IMG_7272.jpg (53.55 KiB) Viewed 6579 times
Hoping to get it to brace height over the weekend. Happy to get some input from the wise. Thanks gents.

Post Reply