Bamboo and Maple Kerfed recurve

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hunterguy1991
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Bamboo and Maple Kerfed recurve

#1 Post by hunterguy1991 » Sat Apr 11, 2015 9:01 pm

Evening all,

Daryl has once again inspired me to learn a new skill that can be utilised in bow making. Decided to give kerfing a crack on a recurve.

I attempted to make a recurve using a maple board I purchased a while back but on cutting it and some shaping it seems that that board did not want to be a bow in that orientation, however at 28mm thick I decided it was wide enough to cut an 8mm lamination off and try as a recurve that way.

The bow is going to be 70" nock to nock, bit longer than my last attempt as I don't want to fret the belly. I set the kerf length to 9.5 inches as the form I have is 9 inches long around the curve and that allows a good hold on the inserted piece at the base of the kerf cut with a clamp.

Got the Kerfs cut using a hand saw ( band saw is playing up at the moment) and I also thought that the rip saw would give a good width of cut, about 2mm. I used some Silver ash as the filling piece for the kerfs, thought it would be a nice colour choice.
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There seems to be a tiny bit of twist in the recurves (must be the form I think, need to make a better one) but it should be ok.

Next step will be to get a handle built up early tomorrow morning after I shape the tip profiles. Leaving it to dry in the sun should have it dry by mid afternoon and ready to get the bamboo backing glued on. Will prep the bamboo back while the handle is drying.

Need to get some more clamps before backing glue up tho, strapping will work fine for the limbs and handle area but the tips need clamps as I discovered on my last attempt.

I will most likely glue in about 3/4 or so of reflex into the stave, I don't want to push the maple too far since the recurves are so long and the bending limb length has been reduced quite a bit.

More photos to come as I go

Colin

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Re: Bamboo and Maple Kerfed recurve

#2 Post by mikaluger » Sat Apr 11, 2015 9:21 pm

Nice one Big fella, cant wait to see this..

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Re: Bamboo and Maple Kerfed recurve

#3 Post by hunterguy1991 » Sun Apr 12, 2015 10:07 am

Progress update!!

Got up early this morning and got stuck into it.

First up I marked out the centreline and the limb tip profile and shaped them. The tips will be 12mm wide at the nocks, very fine and light so hopefully very fast. The taper then goes out to full width 15" in from the tips. No real reason for this other than I thought it looked nice. The tips have a tiny bit of twist but because they are so thin its barely noticeable and shouldn't be a problem.
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Glue lines did not come up as nice as I'd hoped ( they were cut with a handsaw after all) so a little gap filling was required. The Silver Ash filling piece I used do look quite nice tho so Im happy. Function over fashion on this first one tho.

I then cut the old maple handle section off the other bow and prepped it to be glued onto this one. I made the total riser and fades 16" long so I can really feather them out into the limbs. It was then glued on and set in the sun to dry.
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Onto prepping the bamboo next using draw knife and my medieval bowyers stand. Works a treat and I can have a bamboo back flattened in about 15 mins with a little work.
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I need to replace the straps with some leather ones to make a better hold on the work piece but for now I just use a clamp at the base. The spring underneath is a piece of spotted gum decking and I sometimes regret using it for this as it bends really well!!

Next step after the handle is dry will be to mark out the profile onto the bamboo, shape and then thin it once again so it will bend into the recurves.

More later today when I can do more work.

Colin

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Re: Bamboo and Maple Kerfed recurve

#4 Post by rodlonq » Sun Apr 12, 2015 3:49 pm

Looking forward to the next episode Colin, it is coming along nicely.

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Re: Bamboo and Maple Kerfed recurve

#5 Post by mikaluger » Sun Apr 12, 2015 5:03 pm

As you have cut the tapers already Col, be careful when you glue it up and clamp it that it doesnt distort....this can cause the limbs to come out of alignment. I learnt this the hard way. I glue mine all up THEN mark the centre line and tapers...........
I'm sure you will be right tho...
Mick.

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Re: Bamboo and Maple Kerfed recurve

#6 Post by hunterguy1991 » Sun Apr 12, 2015 5:21 pm

Cheers Rod,

Next lot will be up a little later as Ive got the bamboo back glued on now ready to tiller tomorrow.

Cheers Mick. I had the recurves left at full width when I glued them, then after they were dry I marked and I tapered them down to the width I wanted at the tips so I could mark the profile onto the bamboo and thin it accurately as Daryl does with his. Once the kerfs are dry they're rock solid and near impossible to twist where they're glued.

I did notice on glue up of the backing that the limbs can twist below the kerf base but I made this the point I put the stave on the reflex block to try and minimise any twist.

Will know more tomorrow when it comes out of the form...

Colin

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Re: Bamboo and Maple Kerfed recurve

#7 Post by hunterguy1991 » Sun Apr 12, 2015 7:41 pm

Just one photo for this update gents. Got the boo glued on this arvo and will leave it to dry over night...
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Now, before you all start blowing up about the strap all the way along the bow and no clamps... the bamboo is VERY thin and clamps did not seem necessary when I could easily push it into place and have the wet glue hold it there.

I've also found that the strap automatically centres the bamboo onto the blank because of it squeezing in all directions. As for limb twist in the recurves because of the strap, i think its highly unlikely because of how stiff the kerf sections become once they're dry. Im sure Daryl can relate to this after his experiment with the technique.

On initial inspection after putting the bow into the reflex form i thought that the limbs were twisted but after a closer look both are on the same angle in the same direction so i think its the handle that's not square on the contact point with the form so when it comes off the form i will have to make sure its square with the limb axis before i do any tillering.

There is an inch of reflex in the form which I'm hoping will leave 3/4 of an inch when I take it out once its dry.

Will leave it to dry overnight then get the edges cleaned up and start tillering it in the morning.

Colin

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Re: Bamboo and Maple Kerfed recurve

#8 Post by mikaluger » Sun Apr 12, 2015 7:51 pm

Looks good Col,...........

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Re: Bamboo and Maple Kerfed recurve

#9 Post by hunterguy1991 » Sun Apr 12, 2015 7:55 pm

Thanks mate, getting there slowly...

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Re: Bamboo and Maple Kerfed recurve

#10 Post by hunterguy1991 » Mon Apr 13, 2015 8:21 am

Into it early this morning...

Starting to see some signs of life in this one now.
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This it the bend straight off the form with no work done at all... For some reason the right hand fade area is bending more than the left which may become a problem down the track. Should it be, I will cut a very thin piece of silver ash and overlay that onto the fade area to stiffen them up a bit. Of course I will have to work the left hand one down to match the right again but if they look symmetric I'll be happy.

I have the bow bending enough now to make a brace height of around 6 inches so next step will be making up a string to go on it. Not quite sure how long to make the string tho so it will be fun.

More later today.

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Re: Bamboo and Maple Kerfed recurve

#11 Post by hunterguy1991 » Mon Apr 13, 2015 9:18 am

Well I got it up to brace (about 5 inches) and it goes down to 28 without much trouble... disappointed with the draw weight of 30lbs tho
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When drawn all of the bend is in the inner part of the limbs, which I take as the fade area is too weak to support any draw weight, so my plan to up the weight a bit will be to add a 2mm thick maple lamination over the fade area to about half way along the limb. This should hopefully stiffen the fade area and get the outer limb to bend a bit more, in turn upping the draw weight.

I have run a couple of shots through it and it seems to be fairly quick, ( b50 string doesn't help there tho) so hopefully after my little alteration I have a good shooting 45lb or so bow.

Colin

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Re: Bamboo and Maple Kerfed recurve

#12 Post by greybeard » Mon Apr 13, 2015 11:50 am

Colin, this has been an interesting exercise.

At this stage how would compare the results achieved between steam bending and kerfing? I will be using the kerf method on my next recurve.
hunterguy1991 wrote:.....which I take as the fade area is too weak to support any draw weight, so my plan to up the weight a bit will be to add a 2mm thick maple lamination over the fade area to about half way along the limb. This should hopefully stiffen the fade area and get the outer limb to bend a bit more, in turn upping the draw weight.....
If you have not shaped the belly too much is it an option to remove the handle, re sand the belly and glue a lamination between the mid limb points or there abouts, fade the lamination into the limb, do some basic tillering and add a new handle.

This method may give you more opportunity to re tiller the bow as well as increasing the 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!....

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Re: Bamboo and Maple Kerfed recurve

#13 Post by hunterguy1991 » Mon Apr 13, 2015 12:03 pm

Daryl, both methods take a day to accomplish on a blank so time is no issue, however, as you know the Kerfs do not pull out at all when loaded so I think that this will be the option I go with from now on with most of my recurves. I like the heavily recurved look and the kerfs do it nicely.

I feel as though on this one adding a thin lamination over the fade out area as is will accomplish what I want to do, it should up the weight but I will have to tiller it somewhat to get the bends right.

for the next one I do I know now that I need about 2mm of taper in the parallel width section of the limb from fade to tip taper to get a good bend profile, something I probably should have taken into account earlier. This will mean I will cut a 10 or 11mm lamination and then plane the taper into it before doing the kerfs etc.

I look forward to seeing your next recurve Daryl, no doubt it will be a thing of beauty. What timbers have you selected for it?

Colin

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Re: Bamboo and Maple Kerfed recurve

#14 Post by greybeard » Mon Apr 13, 2015 12:21 pm

hunterguy1991 wrote:....for the next one I do I know now that I need about 2mm of taper in the parallel width section of the limb from fade to tip taper to get a good bend profile, something I probably should have taken into account earlier. This will mean I will cut a 10 or 11mm lamination and then plane the taper into it before doing the kerfs etc....
Colin,

This is part of the text of a reply to a post last year.

Firstly I taper the main stave by marking out weigh points at six inch intervals from the centre. Vernier callipers are used to check the limb thickness. From previous experience I have a pretty good idea as to how much taper is required. When the limbs are even I put the stave on the tiller board to see if they are bending evenly, if not minor adjustments can be made. At this stage I do not take the stave past brace height.

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: Bamboo and Maple Kerfed recurve

#15 Post by hunterguy1991 » Mon Apr 13, 2015 12:53 pm

Yes I remember that now... I should have gone through and read all of the posts before I started on this one. Lesson learned.

I have just glued in my remedy to the bow so if I leave it for a few hours in the sun (pretty mild here today as its a bit cloudy) I should be able to shape the new laminations this arvo and bend it again tomorrow.

Having the laminations go up over the fades makes for a very modern look.

Colin

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Re: Bamboo and Maple Kerfed recurve

#16 Post by Dennis La Varenne » Mon Apr 13, 2015 1:51 pm

Colin,

I would have put a full length lamination along the belly side of the bow up and over the handle if it is still flat enough and could be bent by that much.

A 3mm lam would have done the job and pushed the bow weight up somewhere into your easy draw range.

It would also have provided more than enough material to retiller the bow as well as taking care of that incipient hinge.
Dennis La Varénne

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Re: Bamboo and Maple Kerfed recurve

#17 Post by hunterguy1991 » Mon Apr 13, 2015 1:58 pm

Dennis that's exactly what I did, I just didn't carry it up over the handle, I just ran it up the fades similar to what you see in glass recurves.

Tomorrow once the glue is well and truly dry I will sand/plane/rasp the 3mm lams down from 3mm at the fades to nothing at the base of the curf to make a taper that should get the limbs bending more further out and less in near the fades.

I will get some photos later on of the new lams in place.

Colin

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Re: Bamboo and Maple Kerfed recurve

#18 Post by hunterguy1991 » Tue Apr 14, 2015 8:32 am

Update on the bow.

I have it somewhat tillered to a 28"draw, some slight things I could improve but as the bow came in well under weight I wanted even with the additions I made yesterday, I'm not too concerned.

This is the bow at about a 5 and a half inch brace.
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And this is the bow pulling 40lbs at 28 inches...
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Some things I would do differently on the next one...

- A thicker initial blank to give me more room to move with tillering, maybe 15mm thick and then taper the limbs down to what I want before the handle goes on and the Kerfs are cut.

- Glue the handle block on at the same time the Kerfs are being glued so that I can partially tiller the bow (as Daryl suggests) before the backing goes on.

- Glue in about 3-4 inches of reflex rather than 1 to minimise set.

- Slightly shorted handle section to improve the aesthetics of the bow... the long flat handle section is a tad ugly to me.

Other than that, I cant really complain as I ended up with a shooting bow that I learned a new skill while making.

Just need to add some tip overlays and permanent string grooves,shape the handle then fine sand and seal now.

With a fast flight string and some arrows matched to its weight I think this thing will shoot pretty nicely so it will go into my collection :biggrin:

Colin
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Re: Bamboo and Maple Kerfed recurve

#19 Post by greybeard » Thu Apr 16, 2015 10:53 am

Colin,

Your post has been interesting, particularly seeing a project come together through someone elses intrepretation of a theme.
hunterguy1991 wrote:.....Other than that, I cant really complain as I ended up with a shooting bow that I learned a new skill while making......
One of the pluses is that you have added to your knowledge / skill base.

Did the kerf pull out much after shooting and how would you judge the result compared to steaming?
hunterguy1991 wrote:....Glue the handle block on at the same time the Kerfs are being glued so that I can partially tiller the bow (as Daryl suggests) before the backing goes on......
I prefer to do the pre tiller of the blank before recurving or applying the handle block but ultimately it is about what works best for you.

Perhaps I could have explained this a little better in my earlier posts.

Have fun shooting the new bow.

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: Bamboo and Maple Kerfed recurve

#20 Post by hunterguy1991 » Thu Apr 16, 2015 8:18 pm

Daryl,

Its been a fun bow to build and I will definitely be making more of them to improve the design.

From what I can tell the Kerf has not pulled out even a little bit, but I will have to set the recurves back over the form to check them. It definitely holds more recurve than when steam bent.

Because the blank for this was only 8mm thick I would need to glue the riser block and shape the fades to get an accurate representation of the tiller before the backing went on.

If you are using a thicker board and can shape the fades into it it would be better to do that as you suggest.

I was out all day today and didn't get to work on the bow at all but I will have some photos of it sanded and sealed tomorrow. I think it came out quite a pretty bow...

As it was 10lbs lighter than what I wanted dad has already claimed it for his own, which I don't mind at all if it gets him shooting more.

Colin

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