Redesign forward Riser (Ideas Please)

[wcdurand]

So I build this forward riser 58" bow some time ago and got the itch to redesign the bow somewhat.
Why would you ask... Well I suppose that's what keep us ticking.

 

 

I want to try and get a little more speed out of the bow and it's of course a learning curve.
At the moment 52#@ 27" 490grain arrow gives me 177fps finger release.
I thought about it and on what to change. So my ideas is as follow.
The optimum brace height for the bow at the moment to have the minimum noise is 8".

1. Redesign the angle at handle with 1/4 " less decurve to try and get a braceheight of 7 1/4 to 7 1/2" (should get a little bit more speed? and allow lower brace height without string slap to limbs)

2. Its got a tip wedge of 7" at the moment which makes it quite static with little bend to the tips, so maybe lessen the lenght of the tip wedge to 5 1/2"? (it would also bring the weight down of the tips)

3. The width of the tip at the moment 1/2", so maybe lighten the tip somewhat by narrowing the tip by 1/8" and shorten the tip overlays as much as possible.

Could the members please tell me if I am thinking in the correct direction and what other ideas can I try.

I must say that this bow sends a heavy arrow with authority. I shot a Blue wildebees this year with a 580grain arrow and got a total pass through.

Or should I just be happy and leave it as it is?

[wcdurand]

Or maybe shorten the riser from 16" to 14"

[LittleBen]

I would personally narrow the tips as much as you can stand. I've seen canopyboy go very narrow on tips with no overlay and be ok.
I'd minimize the length of the tip overlay, and I would also minimize the thickness. 2 layers of 1/16" phenolic would be my choice. I cut my string grooves with a 5/32" chainsaw file to half the depth of the file across the overlay on the back of the bow, so 5/64 or just over 1/16". This is a relatively shallow groove, but more than enough and will let you keep very minimal overlays.
Also minimize the amount of tip and overlay beyond the string groove. I make all mine almost like a pin nock in that the tip beyond the groove is as narrow as the groove, it doesn't widen back out to be even with the limb. That extra material doesn't give any strength at all. Just weight.
I would keep the tip wedge, but just narrow narrow narrow the tip.
I might also add more reflex through the relatively flat midlimb section. The bow doesn't have much if any net reflex, the tips look about even with the back of the riser, might want to add an inch or two of reflex.
If you're not using some type of dyneema (FF type) string then you should. Use as few strands as you can. For a bow of that weight 8 strands or 10 strands of 8125 is more than enough. I also have stopped padding the loops on bows with overlays (especially phenolic overlays) because I don't think it matters at all. If you do pad the loops, pad with the same material as the string, don't pad with B-50, it is crap and has low durability. It will wear faster than the actual boys of the string. I also don't pad the servi area, I just use a think serving material. I think I'm using like .030 halo which I believe is also dyneema and is very durable. 10 strands of 8125 and .030 serving gives a good nock fit for carbons. For 11/32 wood you probably need thicker, but even a little piece of masking tape wrapped around the nocking area will do it.

Just one mans thoughts.

[fujimo]

there is a man who knows willem!!

[wcdurand]

LittleBen, thank you, I am going to work on those tips and add a little bit of reflex. Would you think that half an inch brace height difference would also make a difference in speed or not really? i do have some dyneema and will build a string. I agree my b50 strings does not last very long!

[beachbowhunter]

I think you are on the right track to reduce the wedge angle of the riser. It would also smooth out the hump that there seems to be just after the fade now. That with some more reflex would be worth trying out. Very few fast bows have a BH of 8" or over.

[LittleBen]

Two otherwise identical bows:

The 1st with brace height 7" and drawn to 50#@28"
The 2nd with brace height 8" and drawn to 50#@29"
Should shoot nearly identical in speed.

So yes lower brace will give you faster speed, but only if you're keping the gpp the same. If you lower the brace on that bow, it probably won't make much difference for your 490gr arrow because even though the power stroke gets longer, the draw weight will come down slightly.

[wcdurand]

beachbowhunter, that's the idea. A little change in the angle of the riser should help me getting a lower brace height without string slap on the curve at limb tips.

So I will start on the riser angle, little bit of recurve and lots of attention to tip weight. (new form of course. and then see what difference does it make to the bow, and so on till I am happy.
 
Fujimo gave me an idea on using spruce as wedge material which is a lot lighter.

I must say I enjoy the current bow because it is really quiet so much so that guys at 3d come over to see why my bow is so quiet!

[mikkekeswick]

Brace height doesn't affect draw weight at full draw. A lower brace height will give you a longer power stroke = more speed.

[wcdurand]

Thank you mikkeswick, it is the extra speed that I am after. As the bow is now, I cannot bring the brace height down because then the noise goes up because the string touch the lams at the tips.(string slap that you hear)

[PZee]

Hey Willem

How about looking at Terrys bow hush product. You wrap the string at the tips with wool to quieten it like recurve shooters do...

Pete