Author Topic: Extending recurves  (Read 579 times)

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Offline DC

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Extending recurves
« on: May 31, 2020, 04:59:15 pm »
My brain is mush today. I'm working on this Molle. It used to be an R/D but I glued on a belly lam and made levers. If I extend the recurves like in the second picture what is going to happen? Lets say I extend them an inch and lengthen string so the brace height stays the same. I've put in two boxes to represent the extensions. Correct me if I'm wrong. They both make the bow longer so the draw weight will drop for the same draw length. But with the same DL does the increase in reflex do anything? The string will lift off at about 20" same as now with the red box, it will be delayed some with the black box. What does delaying string lift off do to performance? Anything else that might happen?
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Online willie

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Re: Extending recurves
« Reply #1 on: May 31, 2020, 06:29:32 pm »
Good experiment Don,

I suppose when the lift off starts and stops is one consideration. I would also want to know if more lift off at the beginning of the draw is more desirable than having the most part of the liftoff happen later in the draw. Do you think your red and black options might change that? 

Offline DC

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Re: Extending recurves
« Reply #2 on: May 31, 2020, 07:16:30 pm »
How would you control the rate of lift-off? The shape of the curve? Probably. Too much fiddling for to little gain I think. If you look at the FDC(if you can see it) string lift off is at 20-23". It's not much but I think I can see it. I don't think the rate would affect it that much. It could just be stack. Anyhow if it had carried on with the same curve from 20" right to 28" it may have taken the top off the curve. I think that would be a good thing. I've glued on new tips and made them wide enough to delay my decision until tomorrow.

PS I should have gone over the numbers with a Sharpie. 40# on the left in 5's and 30" on the bottom in 5's
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Online willie

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Re: Extending recurves
« Reply #3 on: May 31, 2020, 07:26:54 pm »
See it fine. When I posted last, I was guessing the liftoff might have started sooner. Did'nt read your first post close enough, sorry.
With it the way it is, my last question is probably a moot point.

Offline Corvus

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Re: Extending recurves
« Reply #4 on: May 31, 2020, 07:28:38 pm »
Maybe if stacking was an issue? Delaying lift off would mean less stack later in the draw? Only thing popping into my head right now. Like how string bridges on certain asiatic designs help you out later into the draw. My brain is on vacation today as well, so I may just be rambling.

EDIT: I see now that you have mentioned stack. Posted before reading the newer comments lol. Got distracted by the crazy af news after I finished typing
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Offline Del the cat

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Re: Extending recurves
« Reply #5 on: June 01, 2020, 04:28:34 am »
Good thread.
As far as I can see it will keep the early draw weight but ease off the weight once the string lifts, making it more comfortable at full draw.
Mind you could add some cams for even for let off  >:D ::) >:( ;D ;)
Del
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Offline DC

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Re: Extending recurves
« Reply #6 on: June 01, 2020, 10:05:48 am »
Here's the tip glue up.
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Online bradsmith2010

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Re: Extending recurves
« Reply #7 on: June 01, 2020, 10:19:18 am »
very cool, DC,,, the best way to find out is what you doing, thanks for posting )P(

Offline DC

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Re: Extending recurves
« Reply #8 on: June 01, 2020, 10:22:05 am »
Good thread.
As far as I can see it will keep the early draw weight but ease off the weight once the string lifts, making it more comfortable at full draw.
Mind you could add some cams for even for let off  >:D ::) >:( ;D ;)
Del

OK now what do I do.
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Offline Corvus

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Re: Extending recurves
« Reply #9 on: June 01, 2020, 10:33:47 am »
Good thread.
As far as I can see it will keep the early draw weight but ease off the weight once the string lifts, making it more comfortable at full draw.
Mind you could add some cams for even for let off  >:D ::) >:( ;D ;)
Del
That is what I was trying to get at yesterday lol. Does not so much directly influence performance, but the easier it is to manage at end of draw the better you will shoot. Similar to how stacking amplifies errors in form and also makes it harder to retain good form. So even if it does not stack it will make full draw more comfortable
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Offline DC

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Re: Extending recurves
« Reply #10 on: June 01, 2020, 11:06:32 am »
I'm thinking that it will improve performance. How to explain? If the FDC curve stays the same but there is let off at FD that means that the DW is lower. Knowing that before you start the bow if you now tiller for the original DW the whole curve will be higher. That's if you're starting a new bow. If you retrofitting like I am and the DW drops that means that(using 10gpp)I can use a lighter arrow and the speed will go up. If that makes any sense at all ;D ;D
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Online willie

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Re: Extending recurves
« Reply #11 on: June 01, 2020, 11:24:37 am »
are you hoping the you can get some let off from the straight line FD?
I guess if you can reduce stacking, you might be able to make the curve go the other way.
 Are there any examples of non wheelbows that let off?
 

Offline DC

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Re: Extending recurves
« Reply #12 on: June 01, 2020, 01:14:04 pm »
Here it is. Well, the new tip anyway. I added an inch on each tip. I used OS for strength. I made a new string and put it on the tree. 38#, loss of two so a little lighter arrow and on the chrono. 193fps, it was 191 when I started all this. Second shot was 191. Took a little excess wood of the tips, still 191. So a net gain of nadda. One inch on each tip and after a couple of pulls on the tree and 3 shots through the chrono I only gained 1/2" of reflex. Set must have taken the other 1/2". That and the extra weight of the new OS tips must have negated any gain there may have been. And now the bow is harder to brace. So I started with an R/D with a little wonky tiller(one weak limb) that shot 191fps and I ended up with a Molle that's scary to brace. The levers are as narrow and thin as I dared and I keep thinking I'm going to break one bracing it. But the tips stayed in with a 1 1/2" V groove and it doesn't throw the string(so far). With this and every other thing I have tried in order to gain a little speed after the bows first testing what have I learned. Well I don't think I have ever gained more than 3 fps with bigger hooks, shaving weight off the tips, heat treating or whatever I've tried after the fact. I'm starting to wonder if the mid 190's is all there is in a Boo Yew. I still have some Yew and Boo so I'll keep fiddling. Maybe a BooYew R/D Molle made with new materials. Yeah, that's the ticket ;) ;)
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Online bradsmith2010

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Re: Extending recurves
« Reply #13 on: June 01, 2020, 01:50:09 pm »
very nice,, (-S

Online willie

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Re: Extending recurves
« Reply #14 on: June 01, 2020, 03:08:06 pm »
Quote
I'm starting to wonder if the mid 190's is all there is in a Boo Yew
I wouldn't write it off too soon.

making it longer dropped weight because you could not make it thicker.
 
adding reflex means it needs to be thinner. I suspect the extra set.

If the set was not too permanent, you might try taking some off the belly and finding a new arrow.