Primitive Archer
Main Discussion Area => Bows => Topic started by: PEARL DRUMS on November 02, 2014, 08:24:24 am
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Here are some pics of a new project of mine. PLEASE feel free to comment on anything you see that needs changing, or PLEASE feel free to give me suggestions and cautions. This is all new to me and quite different than my usual bow(s). Its just something Ive wanted to attempt. I had the wood around and just needed to order some Unibond 800 and hardware.
Here is where I am so far:
The riser is 14" long tip to tip - the limb beds are 2.5" long
The portion of limb beyond the riser is bout 27" - hope its enough for 50-50 @ 28"
The belly is 10 yr old 1/4 sawn osage, spotless - soon to be backed with flat sawn hickory, spotless. I pre-shaped and tempered the osage.
Im debating adding a short piece of ipe on the belly of each limb where it seats in the bed, just to be sure the bending stops, basically create thicker fades? I also question if the bed needs to be 2.5" long? Seems over kill to me. Are my limbs long enough? I have a good bit of deflex off the handle.
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One showing my limb angle, roughly.
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Boards? (http://rabbittalk.com/images/smilies/icon_surprised.gif)
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The only caution I would have is right at the cut in for the limb pads. I had a very similar hickory riser let go on me at full draw. I was told that is the reason they usually just sit on top of the riser. I would give it a bunch of full draws on the pulley before shooting.
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Pearlie, my only concern would be the one piece riser. An "I" beam through the riser would add just a bit more security and look good too. Looking forward to the end results.
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Steve that was my first concern, I though maybe since the grain was swirly and not flat, it may hold? I should just glue up an I -beam style and not worry about it.
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This has always interested me. Lookin forward to the finished product. What Pat and Steve said makes sense to me. I think i would split the riser section once or more times and put a tuff peice or 2 of hickory or the like in there. Just my 2 cents.... Brian
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Brian I already went through my stash of lumber and found some walnut planking. Ill make an I beam style with 5/8" wide osage in the center to anchor the limb bolts, then walnut on the outsides. That should solve that problem. Seems like osage is always stuck doing the tough jobs? :)
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Just the glue line(s) will add strength.
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I would be a little concerned with the length of the limb beds. You need to be sure that the tension load on the bolts is within allowable loads. Figure it this way, if limb is 27" and distance to bolt center from fulcrum is 1-3/4" then the tension in the bolt is (27/1.75 x 50#) / (0.059) [approximate root area of 5/16" bolt] = 13,500 psi which is a safety factor of about 2 for Stainless Steel (allowable stress is pretty close to 27,000psi). Though geometry of the limb needs to be taken into account, I used 50# just to give an idea of what needs to be accounted for.
I've made 3 attempts at a takedown so far. I use grade 8 1/4" bolts (yield of 120,000 psi) and I try to get a saftey factor of 4. My limb beds are 3-1/2" and the lever arm is 2-3/4"
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Wouldn't the amount of deflex added change the stresses at the fulcrum? By the way I ordered actual T/D hardware from Binghams.
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What really matters is the geometry at full draw. I would recommend looking up "method of sections", this is the technique I would use to evaluate the forces existing just in front (limb side) of the fulcrum point (1" in front to make the math easier). Then evaluate the the anchor load from there.
I'm pretty sure the Bingham hardaware is 5/16" bolts, but regardless, the forces need to be evaluated to make sure they are within spec. I have never used their hardware, so I can't comment on its strength, but I would be surprised if they didn't supply some guidelines about the positioning of it to stay within the safe zone.
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Congrats on launch in new direction!
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I like what you are doing. If its your first attempt I would go a little longer for the limbs say 29". Limb beds are 2.5" long, I would at least go 3 1/2" that will give you a better transition more security.
This is how I do it. 30" limbs 30X2 = 60" Riser 14" Limb pads 3 1/2" X 2 = 7"
total limb length minus pads equals 60-7=53"
Add 53" to total riser length minus the pads you have total length for bow. +7" = a total of 60"
The other thing is the grain on the riser it should be opposing.
I think I got that right.......have not finished my 1st. cup of coffee yet. >:D
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Marc has made this style with toilet bowl hardware. It's the anchoring of the threaded part that is more of an issue than the strength of the actual bolts.
BTW I'm disappointed in you Pearlie.
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How thick are those osage boards that make the limbs?
I think you have enough length as is, but not any to play with, and the added little lam of ipe might be a good idea. But if the osage is thick and the hickory backing is added, and you work down fadeouts from the limb pockets out, then the limbs might not really start bending until an inch or two beyond the limb pockets. That would be correct, in order to relieve the stress at the fulcrum point of the limb pocket, of course, but then, do you really have enough limb lebngth?
It does help that it is deflexed. In R/D backed bow glue ups I do this very thing, and the deflexed portion of the limb off the handle only bends a little bit. If you can pull that off, you'll be fine, esp with perfect osage.
Consider putting the ipe UNDER the hickory, like a power wedge version of a power lam?
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I was just going to add that a wedge between the backing and belly would work better as SB suggests.
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Chris I just saw this, 2 1/2' bed is fine that's what I was using when I was building mine, my limbs just set on the riser without a shoulder, I didn't use a wedge in the attached limb area but it wont hurt, I took a solid walnut riser and cut a arch the length of the riser and put a pc of hickory in but I wasn't worried about it splitting, it look's like you have it worked out to me just some tinkering here and there
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Disappointed? How so Pat?
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Spring buck the osage and hickory together will be almost 3/4" thick, should make for some fades. Although I think Ill still add the underlays. The limbs are over 1 5/8" wide now. So maybe though they are a tad short, the width will make up for it. I do need to study up on proper ways of installing the threaded insert into the riser. I agree that's probably more important than anything else.
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http://i623.photobucket.com/albums/tt320/bubncheryl/100_2795.jpg
here's how I did mine Chris
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Chris the insert thing came up on tradgand a bit ago, 1/2 13 , 27/64 drill is what they said
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I like the riser look Chris
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Disappointed? How so Pat?
Boards, bolts and I beams.. :P
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Just one more style to check off Pat! I like to have experience with a lot of styles so when topics come up I have some background and maybe even some insight.
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Just one more style to check off Pat! I like to have experience with a lot of styles so when topics come up I have some background and maybe even some insight.
that's why I did it, built several in fact, sometimes the norm gets a little boring ::)
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Chris I just saw this, 2 1/2' bed is fine that's what I was using when I was building mine, my limbs just set on the riser without a shoulder, I didn't use a wedge in the attached limb area but it wont hurt, I took a solid walnut riser and cut a arch the length of the riser and put a pc of hickory in but I wasn't worried about it splitting, it look's like you have it worked out to me just some tinkering here and there
Forgot yours was 2 1/2" I guess the 2 bolts helps with a short limb pad. Your tiller on that bow is amazing.
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Chris you are doing fine quit fretting and get it done !
a riser is a riser no need for extra gimmics
I have been doing some dreaming about a way to do a three peice with out the bolts and think I have it worked out in my mind just not the energy for the go at it maybe you can give that a try next!
Have fun!
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Just one more style to check off Pat! I like to have experience with a lot of styles so when topics come up I have some background and maybe even some insight.
He dont like being kept in a box! And neither do I >:D
Pearly, if I were you, I would either start another riser and laminate it or slice the one you have in half of more and add some 1/8" slats of some dense wood vertically. If you start another riser leave it a square block with only the angles cut . That way it will be strong as heck during the tillering and you can also flip it around to get the string tracking.
as for the angle, if making a D/R, I would plot it so that at brace height the limbs will be straight if you know what I mean. You should also consider getting your limbs a bit more uniformly reflexed throughout. Also, consider getting some smooth on(go all in) ;) Thats what I use now because it is stronger than tb3 and there is no joint creep. This is all my own opinion and I know that you have a lot more knowledge than I do.
Here are some pics of a couple I have been working on.
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Thanks 101
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Like Steve I'm a bit concerned about the riser as well.
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Just one more style to check off Pat! I like to have experience with a lot of styles so when topics come up I have some background and maybe even some insight.
He dont like being kept in a box! And neither do I >:D
Pearly, if I were you, I would either start another riser and laminate it or slice the one you have in half of more and add some 1/8" slats of some dense wood vertically. If you start another riser leave it a square block with only the angles cut . That way it will be strong as heck during the tillering and you can also flip it around to get the string tracking.
as for the angle, if making a D/R, I would plot it so that at brace height the limbs will be straight if you know what I mean. You should also consider getting your limbs a bit more uniformly reflexed throughout. Also, consider getting some smooth on(go all in) ;) Thats what I use now because it is stronger than tb3 and there is no joint creep. This is all my own opinion and I know that you have a lot more knowledge than I do.
Here are some pics of a couple I have been working on.
That highly reflexed bow is likely to give you fits. I've tried 2 or 3 like that and have sworn off them.
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Just one more style to check off Pat! I like to have experience with a lot of styles so when topics come up I have some background and maybe even some insight.
He dont like being kept in a box! And neither do I >:D
Pearly, if I were you, I would either start another riser and laminate it or slice the one you have in half of more and add some 1/8" slats of some dense wood vertically. If you start another riser leave it a square block with only the angles cut . That way it will be strong as heck during the tillering and you can also flip it around to get the string tracking.
as for the angle, if making a D/R, I would plot it so that at brace height the limbs will be straight if you know what I mean. You should also consider getting your limbs a bit more uniformly reflexed throughout. Also, consider getting some smooth on(go all in) ;) Thats what I use now because it is stronger than tb3 and there is no joint creep. This is all my own opinion and I know that you have a lot more knowledge than I do.
Here are some pics of a couple I have been working on.
That highly reflexed bow is likely to give you fits. I've tried 2 or 3 like that and have sworn off them.
actually Marc it doesn't look it from the pics but it only has about 3.5" of reflex. I'm taking it sloooooowly!
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+1 on the riser. Look at the internal angle of the pad and look at the grain configuration there. Personally i'd cut it into thirds and glue in something tough.
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The riser issues is history. I laminated 3 pieces of hickory heartwood together. Ill turn it on edge and cut a new riser out. My limb beds will stay at 2.5", they have to for me to feel good about my limb length. My new riser is shorter, about 12.5" now. So the over all length wont be over 66".
Cody Im using Unibond 800, not Smooth on. I should have, but I don't have a hot box. I just use my dual shop lamp and stand a 2 x 12 on edge to reflect heat back. Works like a charm in just a few hours.
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For those of you that have made successful bows like this, what glue did you use to hold the inserts in the riser?
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For those of you that have made successful bows like this, what glue did you use to hold the inserts in the riser?
JB weld Epoxy
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You can find a number of specialty epoxies that are great for bonding dissimilar materials. Some of the best are used for bonding hardware in either airplanes or boats.
3M DP 460 is a very good one.
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Thanks Pat. Ill spend whatever I have to to make sure they "stick" for good. To be honest, its my biggest concern.
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For those of you that have made successful bows like this, what glue did you use to hold the inserts in the
I used a different set up chris, that might be a question best asked on tradgang
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Pearly
cant you still get inserts that screw in ?
Been a long time since I did them
Never used glue ins that I remember
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You can get the "Keen" type inserts at any hardware store, their not expensive and have internal and external threads. They come in many different common sizes... Brian
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Spring buck the osage and hickory together will be almost 3/4" thick, should make for some fades.
I agree that is plenty. What I was worried about was that it might be SO thick that by the time you have the fades worked in, you've lost another inch plus of working limb each side, so that effectively shortens them further. But the deflex should help that.
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I have found that when you are cutting a machine thread into wood if you run the tap through, then soak the area with CA, let dry and then run the tap through again you get a real nice strong thread. May be useful here.
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There is a threaded metal insert. I don't think anyone would trust just threaded wood no matter what it's shored up with.
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Ill need glue with my set up. Its all walnut and walnut isn't especially hard at all.
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I changed gears and ordered some purple heart and goncola alves to make an I beam style riser. I got one limb glued up last night and will do the other tonite. I didn't add any more reflex, simply glued the hickory to the shape the osage took. Takes 2 hours to cure the Unibond 800 under the lamps. I check it every 30 minutes to be sure nothing over heats on me. Slow and steady on this one. I have all my hardware in hand as well as all the epoxy for the inserts.
Ive tried explaining alternating clamps before, finally have a good pic to describe it for me. It keeps the weight distributed evenly and keeps limb twist at a minimum.
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Well at least it will be made out of pretty wood ! ;)
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I'm watching. ;)
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Gonna be sweet Chris, all wwod three pc t/ds are a learning experience
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Drums and I must be sharing brainwaves. :-\ ;) I was glueing up a limb at the same time he was! Here's my setup. I just parked it in front of a baseboard heater with some tin foil over top. Has no trouble taking it to 180 degrees!
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I like Cody's set up better :P :laugh:
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So do I. For whatever reason, I had gaps all over town. I tossed both out and started another set from ipe, because its all I have.
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Pearly what do you want ?
I can look to see if I can fing ya some
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I want to use osage Guy, but I refuse to cut up a good billet or stave to make slats.....isn't that a sin? If not, it should be!
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Geez Chris... I thought you knew that. You can't just clamp directly on to your backing strip... it's too thin. What you ended up with is what happened... gaps and waves. You can use clamps like you did, but you need to put a strip of wood over top of your backing strip, so it's sandwiched between them. That way, it evens out the pressure. You could ditch those expensive clamps and get some inner tubes. Also, don't waste that osage. Sand off that backing strip and start over!
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Heck no Adam, I know stave bows. Ill try again with another set up and a backing strip as you mentioned. Bub also mentioned shrink wrap.
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Here's my setup.
Like the use of pegs in your caul design!
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Heck no Adam, I know stave bows.
You're livin' & learnin'. And we have privilege of learning a bit during your experiencing. Best of luck with next iteration!
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Im not a happy failure Mr. Mike! I tend to get grumpy when I do.
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Here is why I like the inner tube method! 8)
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That's not glued! That grew like that-right? >:D
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Air hose is the way to go really..... >:D
Pearl - One clamp every two inches max spacing. Make up a pressure strip with good thick chunks of wood, I make mine 2 x 2 x 3/4, then lay these blocks side by side butting up against each other on a piece of strong material. Glue them in place. You now have a flexible pressure strip.
If you are going to use inner tube with a thin backing then you must use another waste strip/lam as a pressure strip. I make these about 1/4 thick. Still thin enough to follow whatever curve but thick enough to give even pressure across the whole backing.
If you use innertubes and thin backings lams with no pressure strip you run the risk of an inadvertantly crowned backing....don't ask how I know this!
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Well looks like you learned a lesson there
I use a form on both sides of my limb glue ups but others don't so it may not be necessary but I dont have those issues even in a cold shop with thick glue I can get a even press
Never done learning
Have fun
As for Osage I wish we could get to Illinois , there is have a fellow there that has a barn full of Osage flooring boards that are about 100 years old I would love to sort thru !
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If you are going to use inner tube with a thin backing then you must use another waste strip/lam as a pressure strip. I make these about 1/4 thick. Still thin enough to follow whatever curve but thick enough to give even pressure across the whole backing.
If you use innertubes and thin backings lams with no pressure strip you run the risk of an inadvertantly crowned backing....don't ask how I know this!
An easy way to combat that is to just leave the belly lam full width,n make your backing strip near final dimension front profile wise...this will avoid the backing strip wanting to cup...if your backing strip is the same width or wider than the belly lam you'll run into that issue almost every time..once cured cut out to near the backing strip on the saw...easy peasy. No pressure strips needed for inner tubes.
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That's some good pudding to put your proof in. Great job on the glue lines. Tis a thing of beauty.
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Thanks for all the tips guys. Ill do some fixture work this weekend and take another stab. Ive made a good share of glue bows this same way, this one got me and it was only one limb in length!
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I'm learning from this and might have to try another stab at a glue up. Good luck Chris.
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If you are going to use inner tube with a thin backing then you must use another waste strip/lam as a pressure strip. I make these about 1/4 thick. Still thin enough to follow whatever curve but thick enough to give even pressure across the whole backing.
If you use innertubes and thin backings lams with no pressure strip you run the risk of an inadvertantly crowned backing....don't ask how I know this!
An easy way to combat that is to just leave the belly lam full width,n make your backing strip near final dimension front profile wise...this will avoid the backing strip wanting to cup...if your backing strip is the same width or wider than the belly lam you'll run into that issue almost every time..once cured cut out to near the backing strip on the saw...easy peasy. No pressure strips needed for inner tubes.
What if you want to use a thin belly lam? ;)
I use 3mm steel from a steel fabricators. They cut me a slice on their big guillotine whatever width I want for about £2. Thin belly lams allow you to make any shape you want without having to mess about with steam or heat. Once you get good at doing these sort of things you can work out the required taper and have a basically tillered bow once you've cut the width profile. :) If i'm making a bow like this I try to make full use of the advantages of the technique.
Once the backing gets to 1/4 inch thick you don't need anything.
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BH is talking about width of that lam, not the thickness specifically.
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If you are going to use inner tube with a thin backing then you must use another waste strip/lam as a pressure strip. I make these about 1/4 thick. Still thin enough to follow whatever curve but thick enough to give even pressure across the whole backing.
If you use innertubes and thin backings lams with no pressure strip you run the risk of an inadvertantly crowned backing....don't ask how I know this!
An easy way to combat that is to just leave the belly lam full width,n make your backing strip near final dimension front profile wise...this will avoid the backing strip wanting to cup...if your backing strip is the same width or wider than the belly lam you'll run into that issue almost every time..once cured cut out to near the backing strip on the saw...easy peasy. No pressure strips needed for inner tubes.
What if you want to use a thin belly lam? ;)
I use 3mm steel from a steel fabricators. They cut me a slice on their big guillotine whatever width I want for about £2. Thin belly lams allow you to make any shape you want without having to mess about with steam or heat. Once you get good at doing these sort of things you can work out the required taper and have a basically tillered bow once you've cut the width profile. :) If i'm making a bow like this I try to make full use of the advantages of the technique.
Once the backing gets to 1/4 inch thick you don't need anything.
Mike, How many lams are you talking with a thin belly? 4,5? I can definately see the merits of using thiner stock but at what point does the bow become more glue than wood? ???
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Cool thread. Pearl Drums, I'm sure you will master this just like everything else you've done. I like seeing all the comments. Thanks for sharing. For what it's worth I've used plastic wrap and inner tubes with good success. I usually try to make sure the backing has very minimal overlap before glue up as others have said. Seems to help. I've also used a combination of tubes and clamps to keep the middle down. Wrap with tubes then add clamps...maybe overkill but I hate having to redo stuff. Anyway. Can't wait to see the results.
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Missilemaster - You can use a thin bellylam with 3 lams total. Whatever you want. Gluelines can be made to work too! Althought it is heavy stuff it's awfully thin in a finished bow ;)
PatM - I understand what BH is saying and I agree. There are many ways to skin a cat.....I'm just sharing my way of doing things. You have less chance of lams sliding sideways if they are all the same width as you can clamp them straight, add tape to hold then apply pressure however you see fit. This will also give you more wiggle room when it comes to layout or allows you to use less wood once you are confident in your widths..