Primitive Archer
Main Discussion Area => Bows => Topic started by: Tommy D on April 10, 2020, 07:10:33 am
-
Hi everyone - its been a while since I posted - but have been a regular lurker on Primitive Archer for a number of years. I recently got the bow building bug again after a bit of a hiatus - it is quite an obsession that tends to get in the way of things - but its so addictive. Anyways, I am based in England at the moment - and was lucky enough to pick up a bandsaw and a belt sander the cheap and find a bunch of ipe boards - so I have glued up three now.
I used west system - with the 403 microfibers or two of them - and then bought the G-flex to try. I used to build epoxy-wood boats - so I have my hours up when it comes to epoxy!
Anyways, cut a long story short - my first bow was 68 inches and about 45 pounds and developed a bit of a compression fracture right at the fade. It did have a "power lam" - between the bamboo and the handle. With hindsight there was a slight hinge there that I think was the result of me trying to "blend" the glued on handle fades to the belly.
I decided to cut the bow in half and shorten it by 7 inches and re-glue it with a "scarf" joint so that the compression fracture was in the non-bending handle. I figured I could have it a little lighter and shorter and the wife would enjoy it!
Well... I have now completed finishing my second handle - right up to the point where there are nicely blended "fades" - and I have noticed that the handle and belly are coming apart. I added some acetone to clean some ink off where I had been tillering and it followed a capillary action up under the handle highlighting this quite nicely. The first handle I managed to catch before catastrophe when I heard it pop.
I have attached a few pictures. Bow is now 35 pounds at 26 inches.
I am wondering whether ...
1) GFlex not as good as everyone says it is.
2) When I thin and blend the fades, I create too much movement and that is when the problem starts. I guess I could glue on an ugly "square ended" handle with a more abrupt fade that won't flex?
Any thoughts on how to fix this...
Debating wrapping some fiberglass and epoxy (A) around the fades and then hiding it under some colored serving thread... I know I know its not "pure" but would rather save the bow and have an archery companion to "self-isolate" with...
I fear if I re-glue a handle it will happen again ... OR... is this a problem specific to me trying to blend the fades and not having a power lam? I used to be ambivalent about "power lams" - but this has me thinking they are worth it...
(https://7600230-646359173733290791.preview.editmysite.com/uploads/7/6/0/0/7600230/kimmy-bow-bbi_orig.jpg)
(https://7600230-646359173733290791.preview.editmysite.com/uploads/7/6/0/0/7600230/kimmy-bow-crack-handle_orig.jpg)
(https://7600230-646359173733290791.preview.editmysite.com/uploads/7/6/0/0/7600230/kimmy-bow-handle_orig.jpg)
-
Move the bend out from the fades on the next effort.
-
How thick are your ipe boards? I save the blending into the fades for the very last. That is the most vulnerable portion of a bow, wood or glass because that is where the leverage of the limbs is the strongest.
Please post pics of your tries. A side view of the handle area would be a good start.
-
You have no fades to speak of.
-
Hi Pat - thank you - I have modified my post - I submitted it before I was done.
I rip the Ipe to about 1/2" to start - so I can get more use out of them - hence the "power lam". But this one which I shortened for the wife (to rescue from the compression fracture) I couldn't add a Power Lam - so its obviously flexing right into the handle... or I need to stop fading it ... or ... chuck it and start again... or fiberglass?!
Here are a few more images...
(https://7600230-646359173733290791.preview.editmysite.com/uploads/7/6/0/0/7600230/kimmy-bow-2_orig.jpg)
(https://7600230-646359173733290791.preview.editmysite.com/uploads/7/6/0/0/7600230/img-5115-3_orig.jpg)
-
Pat - are you saying my fades should taper more? Was thinking I could try a “power lam” between the handle and belly?
-
When doing a backed bow with lumber either leave it the full 3/4" thick an start the limb taper past the fades or add a power lam between the belly and the backing. Otherwise the center of the bow bends because of the leverage and that causes the the glue line at the handle pop.
-
You have no fades to speak of.
Glad it wasn't just me that was thinking this.
Pat - are you saying my fades should taper more? Was thinking I could try a “power lam” between the handle and belly?
You don't want a straight taper, it should be a smooth radius that blends in tangent to the belly surface. Like this:
(https://i.imgur.com/lPPbfNJ.jpg)
Yours is a straight taper into an almost sharp corner onto the belly wood. The transition from the limb thickness to the handle thickness is very abrupt and is causing your handle to pop loose.
Mark
-
Thanks - in answer to Pat - I would have put a “power lam” between the backing and belly - but because I shortened the bow I couldn’t do that.
Mark .... thanks .... do you think a better taper on a glued on handle stops this sort of hinging effect? I can see with your bow that you started with a thicker belly and tillered the fade into it. I understand that. Trouble is I don’t have that luxury now that I have shortened the bow in the middle (You can see the splice if you look carefully (or not even that carefully!!))
So my only option really is a more tapered glued on handle/ fade.
-
Mark .... thanks .... do you think a better taper on a glued on handle stops this sort of hinging effect?
If you can get a longer, radiused fade that blends smoothly onto the belly wood it will help compared to what you have now but I can't say if it will be enough or not. You will want your fades to taper to almost nothing similar to this riser for a fibreglass lam bow:
(https://images.squarespace-cdn.com/content/v1/58c59dad2e69cfc360a768d3/1514859215969-GVIVPICHR8TS4BEMFLN3/ke17ZwdGBToddI8pDm48kDHPSfPanjkWqhH6pl6g5ph7gQa3H78H3Y0txjaiv_0fDoOvxcdMmMKkDsyUqMSsMWxHk725yiiHCCLfrh8O1z4YTzHvnKhyp6Da-NYroOW3ZGjoBKy3azqku80C789l0mwONMR1ELp49Lyc52iWr5dNb1QJw9casjKdtTg1_-y4jz4ptJBmI9gQmbjSQnNGng/SANY0102.JPG?format=750w)
Mark
-
Remove the handle and add a stack of thinner lams going farther out the limb. Eric Krewson has posted a pic showing this solution many times.
You basically want to mimic growth rings on a stave bow.
-
Unfortunately this bow is toast. Nothing can be done to fix it other than blending the fades thickness as shown above and then wrapping the heck out of the fades with some strong thread and soaking in epoxy....not pretty but if you must try and get something to shoot.
The other problem is your shelf.
Where in England are you? I'm from near Durham.
A powerlam would allow you to use your 1/2" thick ipe belly lams with no fear at all of handle sections 'popping off'. However a good powerlam isn't the easiest thing to make or indeed get right for the bow design. I have been making lam bows for a good few years now and have made a jig for my drum sander to make powerlams. If you want I could send you one then you have something to copy. Just send me a PM if you want one.
-
Nott the best photos but on the upper one note how thin the belly lam is. About 1/4" from memory. This is achieved with the use of a powerlam and a tapered core - 0.003" per running inch. Thus giving a compound taper to the fade area.
-
Hi Bownarra - thanks for the advice. I may try the Eric Krewson method - I am curious - I guess its how you learn. But I was definitely going to bind the fades as a last resort just to keep the thing shooting till I make another one.
I am based in Hertfordshire - though originally from Kenya, in East Africa. We tend to bodge stuff a fair bit! I know that an arrow shelf cut out like that gives an Englishman heart palpitations! I will get round to building a "proper" longbow one of these days...
I would definitely love to see one of your tapered power lams - never one to look a Gift horse in the mouth! Good to know there are a few bow builders about in the UK - I joined the NFAS recently - so that has opened up a few new connections; looking forwards to doing more once this "situation" is over...
Thanks very much for the kind offer and the advise... I will PM you...
-
Thin belly lam is the main problem as the other guys have pointed out.
I would also look at the type of glue. Those West Systems and many other epoxies might be very good glues for most purposes, but for such a highly stressed joint, you need a proven bowmakers epoxy, like Smooth On, or Techni-glue(Australian) to have any reasonable chance of success. They dry so much harder.
As you are in England, powdered resin urea formaldehyde, Cascamite would be my glue of choice. It has 70 odd years of success with bows and is used by many excellent English bowyers to this day. Dries glass hard, strong, virtually waterproof and heat resistant.
Many of the bows from the 1940's and 1950's were glued up with this stuff, and had quite thin bellies(around 5/8" for combined back and belly), with the glue line starting pretty much directly at the fade/dip transition, rather than above it. They seemed to hold together just fine.
-
in the second pic down at the top of the page, it looks like the handle you have doesn't extend out to the widest part of the limb. maybe stops short by 1/4"? or so?
If so, I would cut/sand off the handle and remake longer in addition to feathering in more
-
Ok ... so here we go. I’ve made two thin tapered lams. A shorter one and a longer one. I am planning to glue these up today ... then fit the handle.
Any thoughts before I go ahead.
Am in two minds about this G-Flex epoxy. Does anyone use it? Has anyone added a thickener - microfibres to it?
Otherwise I might use the West 105/205. It’s a “stronger” epoxy. Just not as flexible. There seem to be two conflicting schools of thought as to whether flex is good here or not...
I have a hot box.
Here are some pics...
-
I thought the gflex already had some thickener? Is the gflex you removed brittle hard or slightly rubbery?
-
It’s hard - but not brittle - a little rubbery. I have used Ampreg epoxy in the past on boats - so when I called the Gurit technician to ask if they sold something like EA-45 for bows - a little rubbery - he laughed and told me “just don’t mix your epoxy right!” But in serious, Gurit’s attitude as a company to these “flexible epoxies” is that they are basically taking a premium glue (epoxy) and making it weaker. So they don’t have an equivalent to the West G-Flex system is what they said!!
So I am in two minds - I know Urac or Cascamite is meant to dry hard hard - but needs a really good glue surface - which I am reluctant to work on too much cos it will mean thinning the parts I don’t want any thinner on the bow limbs
-
I use system 3 so I can't speak directly to the use of gflex, but I agree that the products with additives are usually weaker. I have had problems when mixing in small quantities. and mix by weight now. I do use a thinner product mostly. I believe with the new handle and doing the job over, you will most likely get the glueing right as I think your previous handle design was the primary cause of problems. I dont think you can have a "too hard" glue in the handle area of the bow
-
What do you reckon? Two of these “skinny lams” and a handle over the top should achieve the “Eric Krewson” method?!
-
Side view... the shorter one will be under the longer one I think!
-
I use G- flex all the time. It's not "rubbery" at all.
You can also use 105 mixture and add a small amount of pre-mixed G flex to it to add toughness and thicken the mix a bit.
-
You don't want the glue line to flex at all, that's how you get a lift. Glass hard is the glue line you need. Worth the trouble to get the cascamite. Scuff sand the surfaces with 40 grit.
-
He DOES want this glueline to flex. The added on bits have to be helping the working limb.
-
The wood is going to flex, and needs glue line needs to be rigid, rather than flex. The glue line has been failing, due to it being rubbery and peeling away from the wood.
Its a bit counterintuitive so I can see how it might be hard to accept. I've had this same argument with die hard lovers of TB3(which is an excellent glue by the way, it just won't hold up to this kind of joint on such a shallow belly lam) . Admittedly I've never used G-Flex(so I'm happy to be proved wrong), but I have had total success with bowmakers epoxy, urac/cascamite, and resorcinol. These glues give an absolutely rigid glue line. Every other glue I tried with a shallow belly lam has lifted at the riser. I have had some success with non rigid glue lines, when the belly lam was substantially thick and the join was higher up the dip/ fade area. I also had failures sometimes despite having a thicker belly, so that's why I now always glue up the riser with a rigid glue, even if the lams have been glued up with TB3.
The only way I've seen for this type of joint to work(without a power lam) is with a really hard glue line. Most glues just aren't up to it. It doesn't even work all the time with the best bowmakers glue.
I hope the G Flex will work, it just might. The addition of a power lam is definitely stacking it for success,. If it is successful it could be due to the power lam, not the integrity of the glue.
I'd personally go with something that has had 70 years of proven success on tricky joins, like cascamite, rather than risk it, and have to take it apart again and try again.
-
"Bowmakers" Epoxy/glue doesn't actually exist. It's just re-purposed epoxy or glue.
His handle is failing because of its construction and execution, not the glue choice. The longer lams need to bend and carry some load.
If his epoxy is rubbery the mix ratio might be off.
-
Bowmakers epoxy, is just a term for an epoxy that has been proven to work in all aspects of bowmaking, eg Smooth On, or Techni Glue(industrial formulated recipe for strength). They were used by early fibreglass bowyers, because epoxy has a better bonding ability than Urea based glues in the wood/glass bond.
Not all epoxies are equal, regardless of mix ratios of resin to hardener, some wont dry rock hard. 5min or even 24hr hardware store epoxy falls into this category. Even quality boatbuilders epoxy don't usually meet the requirements.
Urac and resorcinol are stronger than most epoxies in a wood to wood bond, water and boilproof/heat proof more than any other glue. You can't say that about epoxies when it comes to heat resistance. Epoxies are popular in this day and age because they are a little easier to use, have a longer pot time, and a much, much longer shelf life. Urea based glues are not as popular these days due to their reputation as being carcinogenic( I bet epoxies are no less toxic though).
His handle is definitely failing due to construction and execution, but not all glues have equal strength regardless of their type whether PVA, epoxy or animal based. So choice of glue can play a big role in the success or failure of a joint.
My friend is primarily a glass bowyer. His first foray into board bows was a success, no lifting at the riser whatsoever.
I kept getting frustrated with some of my risers lifting at the fades, with TB3. Hell I was more experienced than my friend with all wood bows. I had thicker belly slats but was still getting problems. I then used 24hr epoxy, then West Systems and still getting issues. I asked him what his secret was. He said he didn't do any thing special he just used techni glue. I bought some, gave it a try on the same bows that had lifted at the fades, and hey presto no lifts. That was enough to prove to me all epoxies weren't equal.
-
Pat - when I said rubbery I would say to me it definitely felt a little softer than the West 105 ... which it is if you look at the Technical Data Sheet. When I get a chance I will have a look at the specs for Hamish’s techiglue. I find this all very interesting. As I said I’ve built quite a few epoxy/ wood boats over the years. I know that temp and post curing make a big difference. As does mixing enough and perfectly. I use a grain scale to mix these small batches.
One thing with Ipe I am curious is how much pre-glue wiping with acetone go
to do. I try and keep going till I get paper towels with till that yellowish look all gone. But I’ve noticed the glue itself takes on a reddish tinge from being in contact with the Ipe.
Anyways .... here is how it looks with the inner table off. Gonna fit the handle to this and see how she holds up.
Went with the 105 for the glue up - so I have something to blame if she comes apart again!!
-
Ok well I debated adding another thin taper - between the handle but I have two now already - one is quite long - you can see in the picture how far it extends and the other is under it - like a power lam. Went for this way round because it filled the handle section better which had developed a sort of hollow from cleaning up the several handles that had not worked!! Anyways when I floor tiller it you can definitely see that I have moved all the bend away from the handle - so fingers crossed we can get this to work. It’s been interesting - gonna make one of those Eric Krewson tillering gizmos which has been a pleasant side discovery from figuring out what to do with this handle ...
-
I would change your handle to a bulbous shape and make the fades slope through the entire glued area. Also wrap the handle itself in linen cord set in epoxy to support the scarf joint. That's not a great splice technique no matter what your glue choice is.
-
Thanks - I think I will do that and also glue something on the back of the handle.
-
Ok ... here we go... so I now have a total of 6 thin laminations on this instead of the old handle. This includes the bamboo I have added to the back to try and help protect my scarf joint! All the lambs were ground to a thin end when I glued them up with West 105 plus fillers. Last layer I did with GFlex - which is much easier to mix up.
I braced the bow at 5.5 inches and had a look. Doesn’t seem too bad. The lams have increased the draw weight a little I feel and pushed this tiller further to the tips which I think is good. I can’t see any flex in the handle when I draw it a little ... but don’t want to push my luck at this stage.
I also plugged my arrow cut out at Bownarra’s suggestion. If you look carefully in the pics I have put some green lines where the handle lams fade into the bow.
Couple of questions ...
1) should I build up the handle further? Might go with a bulbous handle at Pat’s suggestion.
2) I want to blend the bamboo on the back - but I know that this is a danger area. When people talk about taking off the rind from bamboo where can I get a better idea of what this involves and where/ when to stop?
-
You have a better transition now
-
You don't need to do a true bulbous handle but having the side profile match a typical bulbous handle/fade transition will work well for the shape you have now. A long gradual slope from the center, which you have now. Just smooth it out.
-
Ok ... cleaned her up a bit ... took the tiller further out to the tips and corrected a bit of twist. It’s now 59inch nock to nock unbraced. And 35lbs at 26 inches. Think the lower limb might still be a little stiff ... but it’s an inch and a half shorter than the upper limb.
Put a few arrows through and seems good. Hoping the new handle and fades will hold together. Here are some pics...
-
Here’s one of the Mama giving it a go. And a close up of the temporary handle wrap! Please don’t call me out on the temporary use of non- primitive electrical tape to hold the leather binding temporarily.