Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: arachnid on August 20, 2017, 09:20:00 AM
-
Hi Guys.
I finished a KennyM 60" longbow, came out 46#@28".
I had a 18" long riser, 20" long powerlam and 8" ling tip wedges.
Took it out today for some test shots it shot very well. Until I draw it and as I reached full draw- BOOM.... the top limb broke. No warning.
No the thing is, it seems like the back glass peeled of and remained intact. I don`t have a clue as to what went wrong and I`d like to know so I won`t make the same mistakes again. Here are some pics... Please tell me what you think.
Thanks.
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20953348_10209778790377434_5317589828793555769_n.jpg?oh=d101fcc4584990dafcbe488036f466a8&oe=5A2EDB73)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/21034471_10209778790337433_7477849762838225046_n.jpg?oh=094721712974970c3b001ab0f47a7594&oe=5A307B92)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20953770_10209778790897447_605463414486263853_n.jpg?oh=a6aab8132e0871a624f121b99328b799&oe=5A353FE3)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20914240_10209778790417435_3121814485506785450_n.jpg?oh=52c5a51c3f3c292e6a0d3f5d86ef36c9&oe=5A18FA31)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20994220_10209778790937448_3181871528166673614_n.jpg?oh=8f634d470f55624a49e9c4690ec0694c&oe=5A16E2BA)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20882883_10209778790977449_9126269887704919996_n.jpg?oh=df8247511d3eb5cb4d99b7bb765b6db8&oe=5A16B4C0)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20914206_10209778791697467_1264732980876224021_n.jpg?oh=4c2e03e9eca1e0c7c7db91c423affb33&oe=59EB243E)
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20953773_10209778791617465_898126073299452934_n.jpg?oh=639e1195d30ad9ef4dfa67dd704e4568&oe=5A39A328)
-
If more pics are needed, let me know
-
Looks like a De-lam failure to me. I hate it when they BREAK..! As long as ya dont get hurt.
:scared:
-
Originally posted by Wolftrail:
Looks like a De-lam failure to me. I hate it when they BREAK..! As long as ya dont get hurt.
:scared:
What can be the cause of it? And do I avoid it?
-
Is it salvageable?
Can I make a new limb?
-
Looks to me like the core wood gave loose for some reason. Curly woods are violated when sawn but I would have thought the glass and glue would have held it together. You can see how the wood separated along the grain. Whether it was material failure or manufacturer failure I can't say.
-
The glue around the fade had bonded. Everywhere else, it just let go. It's like the wood was contaminated with oil or wax. Was the epoxy from a fresh can? Is it possible that the glass had mold release on it?
Those are some possibilities that come to mind.
Sorry to see that. It was a nice bow.
Dave.
-
Originally posted by wood carver 2:
The glue around the fade had bonded. Everywhere else, it just let go. It's like the wood was contaminated with oil or wax. Was the epoxy from a fresh can? Is it possible that the glass had mold release on it?
Those are some possibilities that come to mind.
Sorry to see that. It was a nice bow.
Dave.
The glass was all good. The glue wasn't a new can, it was actually the end of a can... I didn't measure the amounts, I just eyeballed it, can that be the reason?
About the oilly wood- I didn't wipe it with aceton (I've read the it releses more oils) , I sanded it and then made grooves with a hacksaw blade to give it more gluing surface.
Don't know why it gave....
Well, is there a way to make a new limb and salvage this bow?
-
Hey Dor, hate that for you.
It is really hard to say what caused it, once the delam starts, there are a lot of things that happen that might have held forever til the stresses get changed by the thing that started the prob showed up. Hope that made sense!
To me it looks like the glass started coming loose at the tip and then tore the wood lams toward the riser.
Can't really say tho.
As far as making another limb and putting it on this bow, there were some guys at one time doing a half form and doing one limb at a time on one pieces, but I never tried it.
How many lams in there between the glass?
-
Kenny, I had 2 lams- one parallel and one tapered. Does the number of lams really matter?
I took another look at the fades, and I noticed something on the lower fade (the one that didn`t break). Eventhough I had a pretty good glue line, once I bend the limb, it the lams rise. So something wasn`t going well...
That`s the lower fade when the limb is not bent
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20992979_1431642480258805_892650880360576595_n.jpg?oh=c8bfcfe63177db4848be844bb28abf33&oe=5A2DCB5D)
That`s the fade when the the limb is bent. | gap appears between the powerlam and the core lam
(https://scontent.fsdv1-1.fna.fbcdn.net/v/t1.0-9/20953368_1431642476925472_1165900514968421352_n.jpg?oh=8d180285b1617962d58472875620e268&oe=5A1AD6CE)
Don`t know if that caused the bow to fail or if it`s a result of the bow faliure...
-
Can the reason be a too short fade-out?
-
Sorry to see that! Gaps between lams are not good. What kind of epoxy? Did you use a hose on your form?
-
As a general rule I think the the fade should be about 1/16" at 1" from the end...
How many pounds did you air the hose up to?? I am not a big fan of going over 40 lbs... Did you have enough resin on there and get plenty of squeeze out??
The time you waste fixing that one, you could build a new one... Maybe give it to a guy with one arm... :)
I know it did not fail there, But IMHO I would stay away from glue joints in the fades... I like a solid piece of wood there... It is a very high stress area...
-
It looks like you may have issues with your form and clamping pressures. I see another gap up the Belly ramp... Did you make the Lams yourself, if so what grit paper..Did you use compressed air or a brass brush to clean the lams well after using a hacksaw blade? Check for moisture in the wood? Did you use smooth-on?
-
Originally posted by Stagmitis:
It looks like you may have issues with your form and clamping pressures. I see another gap up the Belly ramp... Did you make the Lams yourself, if so what grit paper..Did you use compressed air or a brass brush to clean the lams well after using a hacksaw blade? Check for moisture in the wood? Did you use smooth-on?
I don`t have a air hose, I use clamps. I make dry runs and check the glue lines (especially the fades) before I glue it up.
I make the lams myself with an attachment to my oscillating spindle sander, using an 80 grit sanding sleeve (I can`t find a lower grit). After I use the hacksaw blade I sand and clean the lams so theres no chips and dust.
I use smooth on.
A german guy on facebook (bowyer`s corner group) said the problem was my fade outs being too short. Possible?
-
Shredd may have hit on something with the accents into the fades, look at how the black bends right at the joint on belly.
But it may be the fades are a bit blunt too. 1/16" at 1", and 1/8" plus a little at 2 (.140" and yes I measure with dial calipers when grinding them) is what I always try to get.
-
Originally posted by kennym:
Shredd may have hit on something with the accents into the fades, look at how the black bends right at the joint on belly.
But it may be the fades are a bit blunt too. 1/16" at 1", and 1/8" plus a little at 2 (.140" and yes I measure with dial calipers when grinding them) is what I always try to get.
Well, at least I learned something so this failure wasn't for nothing. Guess it's just the learning curve... Too bad it cost so much time and money...
While were at it.. Is there any other important things I need to know? Mistakes usually made? Things I should avoid? Important measurements I need to know (like the fade length and thickness)?
-
What kind of core wood? It looks curly to me. If you use curly grain for much more than veneers you are asking for trouble.
-
Originally posted by Crooked Stic:
What kind of core wood? It looks curly to me. If you use curly grain for much more than veneers you are asking for trouble.
It's Maple. I use 2 lams, one parallel and one tapered.. No veneers.
I thought that only all wood needs straight grain.. Thought glass lam bows can get away with any grain
-
I don't think your core wood is the cause of the failure. However, it may have contributed to the failure once the glue began to let go. We are all just speculating here as to the cause or the 'why did this happen". During the shot, there are a lot of forces acting on the bow stressing wood, glass, and bonds. Based on the pictures I have seen, I am betting on the bonds between the lams and glass being the cause.
-
Originally posted by Crooked Stic:
What kind of core wood? It looks curly to me. If you use curly grain for much more than veneers you are asking for trouble.
yep
-
Hey arachnid... I found that in life it is usually 3 steps forward 2 steps backward, and that is if you are living a progressive and positive existence... Chit is gonna happen, especially in this craft... Learn from it, Cover all your bases and Move on... I can't tell you how many experiments I have done and failed to hit my mark...
Put that bow up as a reminder of lessons learned
and start making a new bow...
I would keep the accents out of the fades...
Make them fades lean...
Put ample glue on...
Don't clamp too tight... (under 40 psi)
The more lams the better... Anything over 35#
should be more than 2 core lams...
Watch the woods you use...
Keep your fingers crossed... ;) :)
These are my opinions that might lessen the chances of this happening again...
Best of Luck, Bro...
-
Originally posted by Shredd:
Make them fades lean...
...
Please explain
-
Originally posted by arachnid:
Originally posted by Shredd:
Make them fades lean...
...
Please explain [/b]
Think Rich meant thin them out nicely...
-
When using more then 2 core lams, say 1 tapered and 2 thin paralles, does is matter in which oeder you place them and where you place them (on the back/belly side of the riser)?
-
Not in my opinion, once glued up it is a composite structure, all bends the same....
-
Did you butter up all glue surfaces?
-
Originally posted by kennym:
Shredd may have hit on something with the accents into the fades, look at how the black bends right at the joint on belly.
But it may be the fades are a bit blunt too. 1/16" at 1", and 1/8" plus a little at 2 (.140" and yes I measure with dial calipers when grinding them) is what I always try to get.
Leannnn... What Kenny said... That's how I do mine also... 1/16" thick at the 1" mark and just over 1/8" at the 2" mark... You want a nice smooth transition that distributes the load...
-
Originally posted by Holm-Made:
Did you butter up all glue surfaces?
Which means?? :confused:
Shredd, does these measurements (of the fade transition) apply also when using a powerlam?
-
Did you put smooth on epoxy on all of the surfaces to be mated?
If you are epoxying two laminations together, you need to spread the epoxy on both laminations completely before putting them together.
-
Originally posted by Holm-Made:
Did you put smooth on epoxy on all of the surfaces to be mated?
If you are epoxying two laminations together, you need to spread the epoxy on both laminations completely before putting them together.
I actually did not... I spread glue only on one side.
Why spread both? It'll just cause a big squeeze out, no?
-
It's best to apply epoxy to both surfaces because..some of it soaks into and fills the air spaces in the wood grain. This makes for a better bond between the 2 surfaces. I use a auto body plastic squeegee and it pushes smooth on into the glue surfaces. I make a couple of passes, wait a minute then apply more epoxy to the surfaces.
-
How thick of a glue layer should I apply on each surface?
-
A starved glue joint was the reason the bow failed. You MUST apply epoxy to all surfaces to be mated or a high percentage of your bows will fail. This is standard procedure for building bows.
Good luck. Chad
-
Originally posted by Holm-Made:
A starved glue joint was the reason the bow failed. You MUST apply epoxy to all surfaces to be mated or a high percentage of your bows will fail. This is standard procedure for building bows.
Good luck. Chad
X2
-
The reason I know curly is not a good core wood it failed on me twice before I figured it out. You may get a few shots out of it and boom. It may have grain running length wise but the curly part of the grain goes from front to back of the lam and will take no pressure. When in veneer form between glass and a good straight grain wood you are fine. Be sure to do a dry run and check everything out on your next one. Keep those fades thin for a couple of inches on each end. They bend a little bit to.
-
Originally posted by arachnid:
How thick of a glue layer should I apply on each surface?
This is hard to explain......I also use the plastic squeegee. I use just enough pressure on the squeegee to leave a nice thin coating on the lams. A good light will help you check to make sure that the lams have a nice slick wet look to the ENTIRE surface. Look closely for any dry spots.
And yes, you will have squeeze out. Better to waste a little glue then waste an entire bow(and a bunch of time).
-
Arachnid, what I do is use my plastic squeege to push "smooth on" into the lamination, add smooth on onto the squeegee and go over the lams again, wait a minute or two and repeat.. The last pass I use no pressure and build a thin layer of epoxy over the lams. I am a hobby builder and I don't care if I use a couple more ounces of epoxy doing this. **Edit* And use a good light so you can see any dry spots..
-
Originally posted by Holm-Made:
A starved glue joint was the reason the bow failed. You MUST apply epoxy to all surfaces to be mated or a high percentage of your bows will fail. This is standard procedure for building bows.
Good luck. Chad
That makes a lot of sense. After it broke, the inner side of the glass and wood feeled smooth, as if there was no glue remains in them.
-
Originally posted by Holm-Made:
A starved glue joint was the reason the bow failed. You MUST apply epoxy to all surfaces to be mated or a high percentage of your bows will fail. This is standard procedure for building bows.
Good luck. Chad
That makes a lot of sense. After it broke, the inner side of the glass and wood feeled smooth, as if there was no glue remains in them.
-
Originally posted by Robertfishes:
Arachnid, what I do is use my plastic squeege to push "smooth on" into the lamination, add smooth on onto the squeegee and go over the lams again, wait a minute or two and repeat.. The last pass I use no pressure and build a thin layer of epoxy over the lams. I am a hobby builder and I don't care if I use a couple more ounces of epoxy doing this. **Edit* And use a good light so you can see any dry spots..
I don't use a plastic squeegee, I just use a thin piece of wood (usually a lamination cut off).
Hiw do you "push epoxy into the lamination"? Can you explain?
-
As I am first applying the epoxy I am pushing down on the flexible plastic squeegee. The squeegee is not at a 90 degree angle to the lamination it's at a 45 to 60 degree angle.. So the squeegee is loaded like a spring, pushing down against the lamination and hopfully "forcing" the epoxy into any small natural voids in the laminations.
-
Lots of good and important lessons learnd. I consider it a positive experience.
Thanks a lot guys. You're the best.
If there's anything else I need to know- please share with me.
-
yep the glue lines is where it failed and make a sister to original form and use a air hose. that is where the issues went and to much stress and I would like to see a more favorable taper on top side of handle. seems as though to much stress at that point
-
Originally posted by Robertfishes:
It's best to apply epoxy to both surfaces because..some of it soaks into and fills the air spaces in the wood grain. This makes for a better bond between the 2 surfaces. I use a auto body plastic squeegee and it pushes smooth on into the glue surfaces. I make a couple of passes, wait a minute then apply more epoxy to the surfaces.
Excellent point, had a few failures because I did not apply glue to both surfaces.
-
How about my lam grinding setup?
I only have 80 grit sleeves, is that ok? Do need to rough the surface before glue up?
If so, how?
-
Hi Arachnid, btw this is my first post on Tradgang - nice to stop lurking and start getting amongst it!!
I'm still in the process of getting my D/R form made, so you are many steps ahead of me!!
I've made a few laminated hill-style longbows though and felt compelled to add my input to the great and constructive comments you have already received.
The bow in the very first photo looks fantastic! Very disappointed for you with it's sudden (and surely shocking!) demise.
The comments you have already received regarding the steepish taper of the fades and the fact there are one or two glue lines at said fades pinpoint a couple of refinements you'll be able to implement in your next bow, but I kind of breathed a sigh of relief on your behalf when you revealed that you only applied your epoxy to one of every two surfaces. I think that's probably about 90% of your problem mate - if the only thing you do differently next time is glue wet surface to wet surface (with lots of squeezout), you'll be firmly on the path to success!
There is one closeup photo you supplied of the riser area, and it looked to me that a few of your glue lines were just lacking glue.....
Fwiw I would have thought an 80 grit finish will supply ample tooth for good joins, provided that they are clean, tight fitting, and all of each surface wet with epoxy.
get back on the horse mate, show us how u go and best of luck:) :)
-
Originally posted by Dazzad:
Hi Arachnid, btw this is my first post on Tradgang - nice to stop lurking and start getting amongst it!!
I'm still in the process of getting my D/R form made, so you are many steps ahead of me!!
I've made a few laminated hill-style longbows though and felt compelled to add my input to the great and constructive comments you have already received.
The bow in the very first photo looks fantastic! Very disappointed for you with it's sudden (and surely shocking!) demise.
The comments you have already received regarding the steepish taper of the fades and the fact there are one or two glue lines at said fades pinpoint a couple of refinements you'll be able to implement in your next bow, but I kind of breathed a sigh of relief on your behalf when you revealed that you only applied your epoxy to one of every two surfaces. I think that's probably about 90% of your problem mate - if the only thing you do differently next time is glue wet surface to wet surface (with lots of squeezout), you'll be firmly on the path to success!
There is one closeup photo you supplied of the riser area, and it looked to me that a few of your glue lines were just lacking glue.....
Fwiw I would have thought an 80 grit finish will supply ample tooth for good joins, provided that they are clean, tight fitting, and all of each surface wet with epoxy.
get back on the horse mate, show us how u go and best of luck:) :)
Thanks for the kind works dude. I already started grinding the lams for my next one.
I`ve been making wooden bows for 5-6 years now so I know what it`s like to brake a bow. But, lessons were learned and off we go again...
-
I buy my tapers from Tradgang Sponsors. I think they use 40 grit on most tapers. I have seen some that might have been sanded with 50 grit? When I shape riser fades I use a 50 grit zirconia belt. I believe the Smooth On web page says 120 grit. I think 120 is fine for 0.025 veneers where the Smooth on penetrates into the wood maybe completely? but I want my thicker parts like tapers and risers to have a glue surface sanded with something rougher like 50 grit.. You asked if 80 grit is OK, I think it is but 50 grit would be a better choice for me.