I've taken the repaired MkI crossbow prod to full draw and got a Force/Draw curve for it. I've shot it again with the string catchers and a temporary string buffer (see pic) the shot was clean and fast but the string still went over the prod some how, but without damaging the prod! Close inspection of the tips show how the string has ridden up. Presumably the slightly heavier bolt (14" long with 100gn point), the string catchers and buffer all absorbed a good deal of the energy and saved the prod from breakage.I can now experiment with string catchers nearer the nocks and moving the string buffer slightly closer to the brace position.
Not much string groove in the belly on that left tip, so maybe that would help.
Meanwhile I've got the Mk II prod glued up and sanded to an even thickness taper ready for nocks.
All in all a very productive time. I'll also be able to try a shot through the chrono'.
Note the MkI has lost a llittle weight due to reshaping the lower edge of the tips and rounding corners. The Mk II is over 1 mm thicker and I'm aiming for about 90-100#
Update:-Just shot it through the chrono' 202.6fps, not bad from a 76# bow !
I'd moved the string buffer forward a tad but the string still jumped over the left tip. More development needed, before I get the MkII going.
Do you think changing the angle the prod is mounted at might help?
ReplyDeleteIt may, but I'm currently working to raise it about 5mm and add small string catchers near the nocks.
ReplyDeleteIt's good having the MkI prod to experiment with, it means I should get it right on the MkII :-)