Crack from steam bending, help needed

[WingS]

Hi all,

Long time lurker, first time poster. I would love some advice on what to do with a crack which has resulted from unsuccessful steam bending!
I am a novice working on my first "real" bow - a tawa sapling stave. Tawa is a native wood here in New Zealand, it's a straight grained, medium density white wood, and I have heard it is similar to oak. The stave is a 60 inches long and I was hoping to turn into a 45+ pound bow for hunting   
It is bending a few inches in each limb and is getting to the end of the floor tillering stage.
I gave steam bending a go in order to make the originally straight tip match the other naturally recurved tip. It was semi successful but over time it straightened back to about half the initial recurve it had immediately post steaming.
I went back for a second go with a more aggressive bend in the form, but a 5cm/2 inch diagonal/longitudinal crack split down the tip!
I filled it with PVA wood glue and have filed it back as far as I will dare (the tip is about 1cm (3/8 inch) at the thinnest) but the crack just keeps going!

As it stands the straighter tip has about 5cm/2 inches of recurve (from tip to belly of the handle), while the naturally recurved tip has about 8cm/3 inches or recurve.

The way I see it I have 4 options going forward:

1. Cut the stave shorter now and make a short bow/kids bow
2. Continue on floor tillering and hopefully finish the bow, even with the mismatched tips
3. Risk steam bending more recurve into the straighter tip again, perhaps after some filing (I have aluminum flashing now, and will make sure to sand the belly down and put it on a rolling not simmering boil for an hour this time)
4. Steam bend and straighten the naturally recurved tip to make it match the straighter tip and continue on with floor tillering.

Any advice on this would be invaluable. I hope you all had a merry Christmas and I wish you all a happy new year!

Cheers,

Wing

[WingS]

Here are some more photos

[eastcreekarchery]

I wouldn't try bending the cracked tip anymore. If you want the recurves to match, I would try bending the naturally recurved tip back to match the reflexes. Use can use a heat gun for that. I would put some cooking oil on the surface you're bending to even out the heat distribution. Try filling the crack with a superglue that will wick (travel) into the crack. Gorilla superglue should work well. Don't use the gel version of the superglue, just the standard type. I'm a novice bowyer but I think those suggestions should help. I'm sure other, more experienced people will chime in. Good luck and let us know how it turns out!

[Morgan]

I would mirror what eastcreek said. I wouldn’t give up on that stave or cut it down. I believe that it will hold up if you don’t try to stress it there any more. There isn’t much if any bending happening two inches from the string nocks. I don’t think the flashing will help what you have going on there. That looks to me more like a heat check split rather than a belly splinter raising. Recurves are nice and elegant and they have their attributes, but you can make a fine shooting plenty fast for hunting bow with straight limbs. Good luck and please keep us posted.

[Pat B]

Those "cracks" look like checks (drying cracks)to me. Even steaming can cause drying checks in a stave. I think of cracks running across the grain. These look like they are running with the grain. I like to keep the back of a stave I'm working on sealed with shellac to help prevent these checks.
You need thin super glue so it goes down into the checks, sometimes you may have to add more if the checks are deep. PVA glue is too thick to get down into the checks.
You can tiller an uneven stave. It might be a bit more difficult but it can be done.
 I'm not familiar with the wood you are using so I don't know if my advice is appropriate for it. If you want to match both limbs together a caul(form) will help to keep the bending even. For this I would try dry heat, maybe with a little oil on the wood. I find the oil helps hold the heat better and help hold the heat longer and that oil can be removed later with alcohol or acetone, even dish soap and boiling water.
If you are trying to match one limb to the other you are dealing with reflex and not recurves, big difference.

[scp]

Not clear how deep the crack is. If it has any depth, the tip is doomed even without any recurving. I would suggest a rather long and high tip overlay that covers the whole crack and more. You can get it even an inch or so high. You might also need an underlay as well if the crack shows up in the belly. You might need to wrap the whole thing with sinew after soaking it in thin hide glue or crazy glue. Good luck.

BTW we need to get over the fiberglass/manufactured bow aesthetics. What matters in self-bow is not how symmetrical it looks unstrung but how it evenly bends when strung and pulled.

[Allyn T]

The crack is in the belly

[scp]

The crack is in the belly

Thanks. I missed that in the photo, probably because I was mainly looking at the words.

I don't know how steaming can cause that kind of crack in the belly. It must have been there before steaming. And I am seeing a thin crack that is several inches long. Not sure why it is said to be just two inches. Am I even looking at the correct crack line?

Anyhow I would cut it off or wrap it in sinew. I often simply cut it off and add a siyah with fishtail joint if the tip is thick enough.

[Pat B]

Those checks are not the end of that stave. If you feel uncomfortable then give them a wrap.
 Steam can cause checking in wood. I've seen it happen many times.

[Morgan]

The crack is in the belly

Thanks. I missed that in the photo, probably because I was mainly looking at the words.

I don't know how steaming can cause that kind of crack in the belly. It must have been there before steaming. And I am seeing a thin crack that is several inches long. Not sure why it is said to be just two inches. Am I even looking at the correct crack line?

Anyhow I would cut it off or wrap it in sinew. I often simply cut it off and add a siyah with fishtail joint if the tip is thick enough.

He has a ruler next to the crack measuring it at just over 50mm. Is that not 2”

[scp]

He has a ruler next to the crack measuring it at just over 50mm. Is that not 2”

Thanks. I was also looking at the crack at the tip above the string nock. I must have confused the ruler with an American one with both metric and imperial scale. My brain is a mush this morning, no, this afternoon. I should not be posting here while I am designing a test bamboo slat bow with a lot of reflex and tight recurve. Sorry.

Anyhow, it appears that the wood was already cracked before or was not pliable enough when the recurve was forced on the brittle tip. Steaming too little before bending or even too much and too long might do that.

[WingS]

Thank you everyone for your advice!
From what you guys have said it seems that the check may have already been there from drying, tawa wood does tend to check easily while drying in my experience. The check lifted up when the stave was bent on the form in a "V shape" with the right hand line being the check you see now. I believe it formed, at least in part, from there being a bit of a lifted flap of wood where the fibres had been sheared by the farriers rasp.

I will track down some thin super glue and perhaps sinew wrap too! Any recommendations for what glue to use in the sinew wrap? I don't have hide glue.

I think I will continure floor tillering with the uneven reflex and see how it goes, witht the possibility of straightening the more recurved tip later on with steam if it isn't going well.

Cheers all!

Wing