Aghhhh - bamboo backed ipe keeps lifting at the fades... Help!

[Tommy D]

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 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...

[PatM]

Move the bend out from the fades on the next effort.

[Pat B]

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.

[PatM]

You have no fades to speak of.

[Tommy D]

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...

[Tommy D]

Pat - are you saying my fades should taper more? Was thinking I could try a “power lam” between the handle and belly?

[Pat B]

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.

[mmattockx]

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:



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

[Tommy D]

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.

[mmattockx]

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:




Mark

[PatM]

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.

[bownarra]

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.

[bownarra]

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.

[Tommy D]

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...

[Hamish]

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.