67" Red Oak Lam Bow, 50lb @ 28"

[mmattockx]

Apparently I am going to post one bow every fall... Hopefully this picks up now that I am done with building a house, moving and all the other upheaval of the last year.

I designed the bow using David Dewey's spreadsheet for the limb thickness and back profile. This bow is a Perry reflex experiment. It was glued up in 2 stages with the first glue up being the core and belly lams pulled into ~6" of deflex, then that assembly was glued to the back lam while pulled into ~2.5" of reflex. The goal was to minimize set while using a fairly mediocre bow wood. It finished all the gluing with ~1/2" of reflex. That pulled out while working it out on the tree and it has taken ~1/2" of set since so I figure that was pretty successful for a 50# bow from red oak boards.

I did no tillering at all, just cut the back profile to shape, glued on the handle and then exercised it out to 28" of draw. On the tree at first it looked very decent but the bottom limb has come up a bit weak when drawn in the hand after final sanding. I didn't bother checking tiller until it was done and it has a bit under 1/8" negative, so a bit of adjustment should have been done to make it optimal. Considering this was a quick and dirty experiment I am pretty satisfied and the bow shoots very nicely with no hand shock. Perfection will have to wait until the next round...

The tips are 5/16" wide for the outer 3" or so. A 0.100" underlay was added to the tips to stiffen them up a bit extra. Finish is tung oil, nock overlays are walnut and maple.














Mark

[RyanY]

Looks great Mark. Where does the handle/arrow pass line up in relation to the limbs?

[Hamish]

Looks like the spreadsheet works really well.
How does it feel, re handshock?

Not a fan of how the handle looks, but that probably doesn't effect performance, and it needs to be pretty deep to keep the shelf area strong.

Successful experiment, well done.

[mmattockx]

Looks great Mark. Where does the handle/arrow pass line up in relation to the limbs?

Pretty much the same as most around here. The deep part of the grip is the center of the bow and the arrow rest is not quite 1.25" above center. I did the channel to get the rest a bit lower but I'm not that crazy about the result and I don't think I am going to bother with that on the next one.

Looks like the spreadsheet works really well.
How does it feel, re handshock?

Not a fan of how the handle looks, but that probably doesn't effect performance, and it needs to be pretty deep to keep the shelf area strong.

Successful experiment, well done.

No hand shock that I can tell. Of course, I am a hack that is not particularly sensitive but it is smooth for my hands. I am not crazy about the handle, either. It was an experiment as well and is too clunky looking and feeling for me to be satisfied with it. The next one will be less blocky.


Mark

[mmattockx]

In replying to the questions, I realized I didn't put any pics of the grip area up...






Mark

[Will B]

Very nice bow!  I really love the pyramid design and not so muck the handle but I bet it shoots nice. What do you like better…building houses or bows?  Thanks for posting your bow.

[mmattockx]

Very nice bow!  I really love the pyramid design and not so muck the handle but I bet it shoots nice. What do you like better…building houses or bows?  Thanks for posting your bow.

Thanks. We had a contractor doing the house but it was still more work than the bow. This winter we are finishing the basement so bows will look even better after that is done.


Mark

[willie]

Mark
I like the width profile leading into the slim tips, and also where you distributed the bend in the side profile. ill bet she shoots smooth

[bownarra]

That is a great example of tiller shape matching limb profile Nicely done.
With red oak to help avoid the set trap the back quite severely. like up to 40% less width than the belly!

[mmattockx]

I like the width profile leading into the slim tips, and also where you distributed the bend in the side profile. ill bet she shoots smooth

That is a great example of tiller shape matching limb profile Nicely done.
With red oak to help avoid the set trap the back quite severely. like up to 40% less width than the belly!

Thank you, gentlemen. bownarra, I achieved a similar result with the Perry reflex preload I put on the belly during the glue ups. Trapping is something I will keep in mind as an addition to the Perry reflex for future bows, there is nothing wrong with using multiple techniques to help the wood out and maximize performance.


Mark

[bjrogg]

One good one a year will work.
Bjrogg

[willie]

In replying to the questions, I realized I didn't put any pics of the grip area up...
Mark

after seeing your  handle pic in this post I was curious if the bottom lam is the same thickness from tip to tip? ie the entire fade is contained in the lighter colored handle piece?  some bowyers dont have very much success with the glued on handle arrangement. Was the short lam on the back of handle purposely designed to help spread the stress in the fade area?

nice glue lines! 
tb3?

[mmattockx]

after seeing your  handle pic in this post I was curious if the bottom lam is the same thickness from tip to tip? ie the entire fade is contained in the lighter colored handle piece?  some bowyers dont have very much success with the glued on handle arrangement. Was the short lam on the back of handle purposely designed to help spread the stress in the fade area?

nice glue lines! 
tb3?

You're making me go way back in the memory bank here...

1) The bow is 3 lams full length and the ~0.080" thick power lam under the handle area. I don't recall the main lam thicknesses, but the core is thicker than the back and belly lams. I think the back and belly lams were the same thickness. They are all constant thickness, though, with no taper. All the tillering was done by designing the pyramid profile to work with constant thickness limbs. The pyramid shape isn't a true straight sided triangle, it has a bit of an arc to it as that is what you actually need for correct tiller with constant limb thickness.

2) I glued the power lam in towards the back side of the bow because it simplified my layups during the laminating. Structurally it doesn't matter where the power lam is in the stack, just that the overall stack thickness in that area increases as intended.

3) Yes, the lighter wood has all the fade in it and is a glued on piece. The colours vary because I used oak pieces from a number of boards.

4) Yes, TB3 for everything. I think it is a bit soft for laminating like this and is part of the reason the reflex pulled out during shooting in. I am going to try smooth on for the next one.


Since you have asked, I will add a bit more detail. I gave a very basic description of how I did the glue ups, but here are some pics.

Glue up #1 - Belly and core lams glued into deflex:






Glue up #2 - Belly/Core lam assembly pulled into reflex with the back glued on. The back of the bow is up in this pic:



This pic shows how far glue up #1 had to be reflexed for the second glue up:




The end result, something like 1/2" or so of reflex but with the belly pulled into tension like there is 6+" of Perry reflex:




The handle pieces. The thin one is the overlay on the back, the other on the belly side:








The handle pieces glued on and part way through shaping. I liked using the drill press with Forstner bits for hogging off the majority and will definitely use that again on big, chunky grips:





Mark

[superdav95]

Very interesting set up jig for your glue ups.  Looks adjustable and sturdy.  I like it!   

[willie]

Mark,
thanks for the detail pics on the fade pieces. As I thought, the power lam helps distribute the load better over the fade area.

Curious about the perry part of the experiment. Did you collect force draw data when the bow was fresh off the form?
My guess is that if there was a measureable benefit to the pre stressing of the lams before glue-up, then there might be a higher string tension at brace and early draw weight, (when compared to a non perry reflexed of the same design).

since you dont mention a control bow for comparision, would you comment if the bow has lost any draw weight, or specifically, any early draw weight, in the few years of use?

My thought is that if the bow, fresh off the glueup, has internal stresses even when unstrung, then
perhaps over time the wood might creep back towards an unstressed condition similar to the way a thin board leaned up against the wall will take a permanent set or "belly" over time.