My 2015 bow

[Badger]

   Allen, what length bow do you think would be optimum for flight arrows. This was intended as a broadhead bow. The slow takeoff on the limb makes me think it may have  help with clean arrow flight on light flite arrows.

[avcase]

Steve,
Okay, I'll give it a shot and see what you think.

If the Broadhead bow in this post can be drawn to 28", then I'd make the flight bow for the minimum 23" long arrow, which may be a equivalent of a 24-25" draw depending on the depth of the handle.

I'll assume the flight bow has a 24" draw for the maximum draw with a 23" flight arrow.

I'd make the flight bow identical in thickness and width, to the broadhead bow, except scale all the length dimensions (overall length, handle length, etc.) by the ratio of the draw lengths. Flight bow length = (24"/28") * 62" = approx. 53-3/16".

If it ends up a 23" arrow can be draw the equivalent of a 25" draw length, then the overall length would scale down to (25"/28")*62" = approx 57-3/8" long.

The nice advantage of the shorter flight bow is that the lateral stibility will go up significantly. If you think about it, this is one of the key reasons great flight bows end up being so short.

Alan

[Aaron H]

Lots and lots of valuable information here guys. Thanks

[joachimM]

Hi Badger,
there seemed some discussion on whether or not you should have a crowned back or not to maximize performance on your bow.
I'm inclined to think a crowned back is favourable because it shifts the neutral plane towards the belly, thereby allowing set at a later stage of bending than with a flat back. I'll start a new thread with the detailed explanation I'm giving to it, since this is going a bit astray from your initial post.
Joachim

[Badger]

   I have never found a crowned back that I could get as much bend out of as a flat back. I have never really studied trapping and things like that but just from personnal experience I prefer no crown.

[joachimM]

here's a link to my thinking on crowned backs http://www.primitivearcher.com/smf/index.php/topic,50344.0.html

[Badger]

  Think of it this way, the belly is much more elastic in compression thatn a back is in tension. Backs don't stretch much. You really don't want to attempt to put the nuetral plane in the center of the bow. If the back starts to stretch it is ready to blow.

[Marc St Louis]

Wood may be more elastic in compression but it is much stronger in tension than it is in compression especially tension strong wood like Elm or Hickory.  Finding the right balance is key.  I have found that a flat back on Elm does not work well even when the belly is heavily heat-treated.  The bow will take more set than one with a crown.  Too much crown and there's a risk of pulling a splinter but it will keep more reflex up until it pulls that splinter.  Same thing with HHB.  It's all about balance

[Badger]

 Mark, I have also found that high crowns will tend to hold reflex better. And one more time I am not absolutely certain about this but I suspect that the high crown will pull the stave back into shape masking some set. Flat backs will show set readily but when you start measuring the effects of set in draw weight the higher crowned bow will have slightly higher losses in weight for lower losses in set. This would be a good thing to actually test and take notes on. I will sometimes draw a conclusion on something I think I see happening when something else is actually having the larger effect.
I am open to learn here.

[Badger]

   I dropped Dan Perry a line, hopefuly he will weigh in. I believe he was around at the very begaining of primitive flight shooting.

[Marc St Louis]

I can't say I believe that a high crown can pull a bow back into shape.  It's more likely that a flat back would do that since there would be more wood on the back working to do so.  No I think that a high crown takes some stress off the belly by making the back work harder thereby allowing the belly wood to take less set.  I'm convinced that a balance between tension forces and compression forces will give optimum performance.  Elm for instance is much stronger in tension than it is in compression and that's why it does so well when heat-treated.  The increased compression strength it gets when heat-treated makes the bow work harder in tension giving the wood a better balance.

[sleek]

^ What he said. I would add to that but id only be parroting the TBB without any original thoughts, though I do agree.

[Matthias Wiltschko]

Steve

You wrote that the bow did not reach the intended 50#. Do you think it would be a wise idea to heat treat the working section of the bow into a little bit of reflex, only 1/4", to reduce the set and increase the draw weight? Of course it would not reach the 50# but give you some fps more. Or would then the bow be to unstable for save stringing and shooting?

I was also wondering if you heat treated the recurves to a high degree to increase stiffness.

Matthias

[Badger]

  The bow underwent extensive heat treating several times durring the building and tillering process. I cut the bow down to 57" NN to gain weight but after retillering wound right back up at 35# but with a better tiller. Performance is still very good but it lost quite a bit of stored energy at the shorter length.

[Badger]

  I was fortunate that the gentleman who supplied me the first stave sent me the sister stve which was almost identical so in effect I was able to get a rematch.
I went a little less aggressive on this one. Slightly shorter riser, a little more working limb and less reflex. I charted the draw curve when the bow was fresh and immediately after charted it agin so I could see the difference due to set. The bow came in at 51.8#@27"  so hopefully will settle in at 50# after sanding and break in. Very happy with it so far, a little handshock but tips have not been reduced yet. Will try and test when finished.

8"            12.4#       7.8#
9"            17.4         12.2
10"          20.2         15.2
11"          23.2          18.0
12"          25.6         20.6
13"          27.8         22.8
14"         29.2          24.4
15"         31.0          26.2
16"         33.0          28.0
17"         34.4          30.2
18"         36.4          32.6
19"         38.0          34.0
20"         39.6          35.8
21"         41.0          38.0
22"         42.5          40.2
23"         44.8          41.2
24"         46.2          43.8
25"         47.6          46.0
26"         49.8          48.2
27"                          50.2
28"                          51.8

  The reading on th right is freshly drawn bow, excersised at each point, the left is the second reading. You can see where the breakdown first starts to take place at 17". This is where the spread between the two sides starts to narrow. Just based on the stored energy and typical efficiency the bow should hit about 190 fps which is faster than any self bow I have ever built. I believe Mark St louis has crossed that bridge allready.