possible to make a wood recurve without laminations?

How to make a Bow, a String or a Set of Arrows. Making equipment & tools for use in Traditional Archery and Bowhunting.

Moderator: Moderators

Post Reply
Message
Author
AlexanderArcher
Posts: 22
Joined: Wed Jun 20, 2012 11:53 am
Location: Brisbane, Queensland

possible to make a wood recurve without laminations?

#1 Post by AlexanderArcher » Tue Jul 28, 2015 3:41 am

G'day all,

I've tried a couple of times to make a single piece wooden recurve from a piece of massuranduba board. Now what I've encountered is not that it does not steam bend, but that as soon as you string the bow, the recurve pulls out almost completely, im talking 80-90%. Not only that, but the limbs, due to the tension of the string, try to warp as if there is limb twist and tries to pull out unevenly. The dimensions of the bow are 174cm NtN with them being 3mm thickness at the nocks but 2.3cm wide. I was aiming for 35# hence why its so small. The steam bend went perfectly but I read somewhere that kiln dried wood (which it almost certainly is) will not hold a steam or heat bend due to the lignin being destroyed in the drying process.

So this is the look im trying to achieve:
recurve_gall.jpg
recurve_gall.jpg (12.85 KiB) Viewed 3155 times
And this is what the steambend turned out like, im not sure if you can see it too well:
IMG_3840.jpg
IMG_3840.jpg (107.72 KiB) Viewed 3155 times
IMG_0617.jpg
IMG_0617.jpg (102.67 KiB) Viewed 3155 times
*edit sorry, just to clarify, the photo of it on the floor is prior to any stringing. It's straight off the form
Firstly I must apologise, this was an experimentation bow, the handle section that I'd glued on to give it more depth fell off (need to fix that with something stronger than 5minute araldite :roll: ) and it might not look too well in the picture but the wood held the curve perfectly without any indication of cracking or chrysals or splinters.

I have an utter fascination with making single piece recurves without lamination. I REALLY do not want to laminate, I want to try to preserve the naturalness of the timber without overt gluing.

So my question is, can it be done? I've tried and it felt like the wood just wasnt holding properly, it was warping upon stringing with a sideways twist and pulling unevenly as if one limb was much stronger than the other (even though it was perfectly tillered prior to steam bending) and eventually pulled all the curve out of its lower limb and part of the upper. Does anyone have any idea what went wrong? Are my tips too thin? do I need to leave a thicker section towards the tips of the bow that dont do any functional bending at all? whats the plan?

Thanks all, I very much appreciate the advice. I've looked around for bows like this and not found any. The closest I've found were limbs that had left a thick section on their tips to 'hold' the curve in them.

Cheers,
Alexander
Last edited by AlexanderArcher on Tue Jul 28, 2015 4:27 am, edited 1 time in total.

AlexanderArcher
Posts: 22
Joined: Wed Jun 20, 2012 11:53 am
Location: Brisbane, Queensland

Re: possible to make a wood recurve without laminations?

#2 Post by AlexanderArcher » Tue Jul 28, 2015 3:44 am

I should also mention that this is a continuation of this prior thread http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=15642 and experiment. =)

hunterguy1991
Posts: 859
Joined: Mon Jul 09, 2012 10:18 am
Location: Woodford Queensland

Re: possible to make a wood recurve without laminations?

#3 Post by hunterguy1991 » Tue Jul 28, 2015 7:42 am

Gday Alexander

I think you might be asking a bit much of the timber to get that result you pictured. One of the main reasons that recurve bows hold their shape is because of the laminations being able to slide a fraction when they are glued making the curve have little stress once it is dry and with the glue being strong enough to hold it there.

Ive played around with recurves a little after looking at some of Daryl's steam bent recurves and found that the best way to keep the curve is to make a Kerf cut and glue in an insert to help it hold its shape. Search "kerf" and you should find a thread about it Daryl wrote a little while back.

To make the Kerf more or less invisible you would simply make the insert the same timber as the main limb so that it blends in...

Using a backing like Bamboo would further enhance the bows performance and also how it holds the recurves...

Colin

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

Re: possible to make a wood recurve without laminations?

#4 Post by greybeard » Tue Jul 28, 2015 3:40 pm

Alex,

The limb design would appear to be unstable; it may pay to use a less radical curve.
AA Recurve With Text.jpg
AA Recurve With Text.jpg (88.24 KiB) Viewed 3107 times
Once you have developed a stable platform you can fine tune the design.

Notice the gentle curves in the Lake Ledro bow.
Lake Ledro Yew Recurve.jpg
Lake Ledro Yew Recurve.jpg (58.61 KiB) Viewed 3107 times
In most instances split staves will produce superior results than those obtained from milled boards.

Recurve bows were a progression from flat bows so the limb plan needs to be considered.

Personally I think Massaranduba is not the best choice when selecting bow woods.
AlexanderArcher wrote:........ what I've encountered is not that it does not steam bend, but that as soon as you string the bow, the recurve pulls out almost completely, im talking 80-90%.......

Although a timber may have good steaming properties this does not mean it is suitable for all applications. In construction projects the steam bent timber is usually fixed to a solid frame.
AlexanderArcher wrote:........So my question is, can it be done?.......
Yes it can but there will be trade offs'.

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!....

AlexanderArcher
Posts: 22
Joined: Wed Jun 20, 2012 11:53 am
Location: Brisbane, Queensland

Re: possible to make a wood recurve without laminations?

#5 Post by AlexanderArcher » Wed Jul 29, 2015 3:22 am

Colin,

Thanks yeah I'd read all the posts I could reasonably find on the actual recurving of bows via kerfing/steaming prior to trying this out. I will probably give kerfing a go at some stage, but right now Im trying to focus on steam bending alone to see if I can achieve the result.


Daryl,

Hmm, I do agree with you that the severity of the curve was probably what caused the unstable limbs. However, the reason the curve was so severe was due to believing 50% of it will pull out, so instead of a 90 degree bend, I should end up with a 45. About the curve pulling out, according to the Veritas steam bending booklet it says:
"Kiln-dried wood must not be used; the lignin in the
wood has been permanently set during the hot, dry
kilning process. No amount of steaming or soaking
will weaken the lignin bond sufficiently for successful
bending. The same applies to air-dried wood that has
been allowed to dry and stabilize below 10% moisture
content; the lignin will only partially plasticize with
steam, not enough for successful bending of anything
beyond a shallow curve."

So I assume this is why the limb pulled straight after only fairly light pressure was applied. However, you're right in saying that maybe massuranduba is not the best bow wood. Im tempted to try to bend in some deflex around the handle area to bring the tips closer to the body of the bow and hopefully this will dispel some of the 'wobbliness' of the limbs.

Also, to adress what you had said in the pictures about the overall percentage of the bow in reflex, I'm thinking that maybe I just need to build a smaller form with a tighter curve, so instead of (just for example) 20ish cm for the bend, make it 12cm or so while maintaining the same angle?

Cheers,
Alex

User avatar
yeoman
Posts: 1563
Joined: Mon Mar 08, 2004 1:32 pm
Location: Canberra

Re: possible to make a wood recurve without laminations?

#6 Post by yeoman » Wed Jul 29, 2015 7:21 pm

I think Veritas might be exaggerating things a bit. I've steam bent limbs from kiln dried wood after a couple of days of soaking. So have literally hundreds of other bowyers.

A couple of points already made that I will echo:
- The amount of recurve is too extreme
- Massarabundah makes nice bows, but these are reflexed or straight bows.

One possible reason that so very much of your recurve pulled out was limb thickness. I suspect you cut your limbs to final limb thickness before steam bending. This is far too thin, I think. You'd be better off leaving the limbs a little thicker (just a little) then when it comes time to tiller, you remove ood where you want it to bend and leave it on where you don't want it to bend. This will leave sufficient thickness to hold the recurve steady. By having the limb when recurved the same thickness as for a flatbow, the limb will only have as much resistance to bending as a flatbow. For the recurve to stay in, it has to be stiffer, which means thicker.

On the amount of limb devoted to the recurve: you could do worse than devoting 20-25% of limb length to the recurve. Start with something modest, then work your way up to something more radical. You'll progress more quickly if you develop along a slightly less steep trajectory.
https://www.instagram.com/armworks_australia/

Bow making courses, knife making courses, armour making courses and more:
http://www.tharwavalleyforge.com/

Articles to start making bows:
http://www.tharwavalleyforge.com/index. ... /tutorials

AlexanderArcher
Posts: 22
Joined: Wed Jun 20, 2012 11:53 am
Location: Brisbane, Queensland

Re: possible to make a wood recurve without laminations?

#7 Post by AlexanderArcher » Thu Jul 30, 2015 1:08 am

Yeoman,

haha, you are very right, I did kind of jump into the deep end head first with this one. Although I DID try to do some research prior to experimentation.

Ohhh, I understand exactly what you are saying, and yes you are right in assuming I tillered to approximate final draw weight factoring in the extra that would be added upon steam bending.

I agree with both your own and Daryl's statements that the amount of recurve forward of the handle is too much and probably caused the unsteady/wobbly nature of the limbs. I will attempt a more gradual recurve next time within a smaller radius and progress from there; potentially adding in a small amount of deflex around the handle.

Thank you all, this has helped me understand a lot more,
Alex

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

Re: possible to make a wood recurve without laminations?

#8 Post by greybeard » Thu Jul 30, 2015 9:41 pm

yeoman wrote:......On the amount of limb devoted to the recurve......... Start with something modest, then work your way up to something more radical..
The following bending form [L. M. Stemler, circa 1940] would be a good starting point. A stirrup/bracket mounted at the end of the curve to hold the tip of the stave would be helpful.
Template For Recurve Tips L.M. Stemler.jpg
Template For Recurve Tips L.M. Stemler.jpg (49.85 KiB) Viewed 3015 times
Plate 6 Reflexed Osage Flatbow.jpg
Plate 6 Reflexed Osage Flatbow.jpg (58.87 KiB) Viewed 3015 times
AlexanderArcher wrote:........according to the Veritas steam bending booklet it says: "Kiln-dried wood must not be used; the lignin in the wood has been permanently set during the hot, dry kilning process.........
IOWA STATE UNIVERSITY

"Conventional dry kilns operate with dry-bulb temperatures between 100° and 180°F; wet-bulb temperatures may be from a few degrees to as much as 50° lower. The temperature levels and wet-bulb depression depend upon several factors and vary during the drying period. Generally, the higher the temperature, the faster lumber will dry; low humidity levels also accelerate drying rate. In conventional kilns, vents and fresh air intakes are used to remove excess humidity, making it an open system."


General Technical Report FPL–GTR–190


Rebecca E. Ibach, Research Chemist; Principles of Plasticizing and Bending.

"In simple terms, the wood cell wall is a composite made of a rigid cellulose polymer in a matrix of lignin and the hemi¬celluloses. The lignin polymer in the middle lamella and S2 layer is thermoplastic; that is, it softens upon heating. The glass transition temperature Tg of the lignin in the matrix is approximately 170 °C (338 °F). Above the matrix Tg, it is possible to cause the lignin to undergo thermoplastic flow and, upon cooling, reset in the same or modified configuration. This is the principle behind bending of wood."

International Conference on Bioenergy Utilization and Environment Protection
6th LAMNET Workshop — Dalian, China 2003


2.1 Mechanism

"Lignin and cellulose are the two major compounds of biomass. Lignin distributed among cellulose determines the structure strength of biomass. Lignin is a non-crystallized aromatic polymer with no fixed melting point.
If heated to 200—300°C, lignin starts to be soft, melted and liquefied. If pressure is applied in this case, lignin will glue cellulose together, which is solidified and briquetted after cooling down."


If you read the last paragraph above you will notice the temperatures shown are well above normal kiln drying temperatures.
AlexanderArcher wrote:.........smaller radius and progress from there; potentially adding in a small amount of deflex around the handle.....
Natural string follow will provide the deflex which will probably rob the bow of some draw weight. Reflexing the limbs from the riser would be a better option if you want to retain draw weight.

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!....

Post Reply