Main Discussion Area > Bows

Chrysalling diagnosis

(1/4) > >>

Marin:
Hey,
I have not posted in a while but have been experiementing a lot. I recently had an issue and was curious if anyone else had any ideas. I was making a beautiful little short bow I had sinew backed with two layers of sinew. It was a replica of a central Californian Miwok bow, which were already narrower compared to the more northern "Paddle" bows. I used a spare piece of ERC I had that I thought I wouldn't be able to use for anything else, as it was rather narrow and had a bad hairpin grain. While shaping, I accidentally made one of the limbs slightly narrower than the other. It was not a major difference and still within the threshold that is known for these bows, so I thought it would be fine, so long as I watch it when I tiller.
The bow itself was short at around 43" with working recurves, with the idea of getting about a 19" draw length.
I began tillering the thing and was getting a nice even bend throughout, with both limbs bending about the same amount. Once it was bending at about 6 inches or so with a long string, I thought it would be ready for low or medium brace. I was working with a friend who has made more bows than I and we both thought the tiller looked fine and that it was ready. Once we strung it, the tiller still looked perfect, but a large chrysal developed in the middle portion of the narrower limb. We were both confused as the tiller did not seem to indicate that this region was bending anymore than the other limb, nor did this limb portion have a hinge in any way. The only thing I can think is that the narrow design, which has a rounder cross section, was just too crowned for the bow at this width. But this also is a little confusing, as these bows were made rather narrow in the first place and the bellies were always rounded in that manner.
I'm thinking one of two things:

1: the narrower limb, despite bending the same amount as the wider limb, was taking more strain in the bow overall for the amount of width it had. The recurves, which were bending quite a lot during the long string, took less strain once I strung it, thus focusing more strain at the center of the limb where the chrysal formed

2: the bowwood, ERC, while being mostly identical to juniper was perhaps not as well made for compression as Utah Juniper or Incense Cedar, the material the originals were made of, and is thus not as well equipped for the narrower design of these Central Californian bows.

I have pics of the bow's tiller shortly before the "disaster" which I can post if ya'll want to see. And like I said, I had a second pair of eyes on the tiller when it happened. We are both confused as to how this happened, and while I can't fix it, it has been a puzzle for me in the last couple of weeks, and I would like to actually learn something from this. Maybe someone else has an idea?

Hamish:

Hairpin grain(worst culprit), with a narrow limb. Combine that with a short, highly stressed design = problems.

Without the dodgy grain it probably would have been okay, and free from chrysals.

Grab a clear stave and get at it.

George Tsoukalas:
Yes, Marin, please do post the pictures. Jawge

Marin:
Here are some of the photos of the bow, including my most recent tillering photo before I strung it. Unfortunately don’t have the strung profile, but all I can say was the inner limbs were bending evenly and the recurves were not stressed. It matches what I see in historical photographs of strung Miwok bows

Marin:
More photos

Navigation

[0] Message Index

[#] Next page