66" T/D shallow LB....but modified a bit

[bjansen]

I put the final coat of finish on this one today. It is a 66" T/D longbow...kind of an experiment in several ways.  

I started with the bingham "shallow" design, but I created a shallow arced cross section.  To do this I first took my dremel tool with the drum sander crearted an ever so slight dip in the middle of my form.  I then tool the cabinet gooseneck scraper and scraped and scraped to achieve the desired arc.  I started the arc just after the fade and continued to the end. I then filled in the dips and valleys, holes etc with wood filler.  Then I wrapped sand paper on a drum (with the same arc) and sanded smooth.  Finially I attached a piece of rubber which bent right into the arc.  

For the lams I used Maple S/A and a walnut core, Brown S/A wedges and Botuff (with scrim), to keep it from breaking when bent into the arc....it worked pretty well.  After the glue up it was a noticable arc (however you cant really tell in the finished pic even when i put a straight edge on it as the finish sanding rounded the corners about even with the middle of the lam stack.

 

 

 

Next, the riser....I tried to create some nice waves live I have seen in others...it took some time but worked pretty well.  I dont have a pattern sander..but I just cut and sanded a piece, traced it on to antother and cut and sanded to fit.  I used maple and brown S/A.  Overlays consist of walnut, white and brown glass.

 

[bjansen]

Tip overlays are phenolic and I also tried to trap the back a bit.

 

 

[bjansen]

Another experiment was the finish..I typically use TB epoxy and just frost the last coat..But I saw a Black Widow the other day with quite a bit of texture...so I thickened up the mix and opened the spray pattern a bit..and I did get a little more texture....(I think I like the light frost better though).  

 

 

 

 

[bjansen]

 

So, how did the arced crossection work..not bad...I suppose..The bow came out to only 39#...and in the final finishing stages (prior to the finish) it shot a 500 grain arrow 161 fps.  Nothing too spectacular..but not too bad I suppose.  I know I am deliquent on the full draw pic...but I need to make a new string and let that finish cure a couple days.

I am going to experiment a bit more with these specific limbs by creating a riser with straight limb pads.  I am thinking this will raise the poundage a bit, but probably not too much.  I will add to the post and some final data once that gets done.

[B M A]

Great work.  You did a very nice job on the riser.

Brock

[White Oak]

Another beautiful bow Brad.Love that riser!!!  

[Igor]

Very nice

Thanks for sharing


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[jess stuart]

Super job, I love the riser.  What was your intended weight?  I would think that is good speed at 13 grains per pound.  Again good job.

[bjansen]

Thanks guys...I intended to make it 45#, I was thinking the arc would require less lam stack, which it did but it did not stiffen it up as much as I expected.  Im not even sure what I deducted from bingham's chart to achieve that desired weight..but overall, I think I need a bit more arc.  

I had a couple questions on design theory that I would appreciate any of your thoughts.

1.  If you were to add arc to the cross section, do you think the back being convex or concave would be better.  I thought concave, thinking that drawing the bow would require the crossection to flatten (and this would occur more evenly through the limb).

2.  If you were to add arc to the cross section, all other things being equal...would that require more or less taper in the lams.  I go back in forth on this, but I used the a total taper of .002 on this bow (same as suggested in the "shallow" design by Binghams.

[4est trekker]

Heck yeah!  That's a great looking bow!  Awesome job, Brad.

[Broken Arrow 1]

wow thats a  beauty. absolutley one heck of a job. Wow!!

[Diamondback59]

damn brad after our talk this a m  i relley do like it   tell ya what bulid another 70 #  ill take it give it a try on the water buff come march haha  but man this is ur best one yet i think  brock

[Innocente]

the lines in your riser are hypnotic.  nice work man.

[Furtaker]

This is an experiment I was going to try later this winter.
I was going to go with a concave cross because I thought of a way I could do that with out making perminent modifications to my form just in case it didn't work.
As far as taper I would think you would need more because building a cup in your cross section would add stiffness and in my mind the whole idea is to add stiffness and reduce limb weight at the same time witch would increase preformance.I think you are on the right track though.160 out of a 39#bow is pretty darn good.

Great looking bow by the way,that riser is a beauty!
Good luck on your adventure.

[kennym]

Nice work Brad!!  Gonna bring it to Mojam so I can shoot it? LOL

Think of the convex/concave like a venetian blind slat,much stronger one way than the other.....

[Apex Predator]

I like that a lot!  I want to know what it will do at 10 gpp 28" draw.

[Scott F]

Great timing!  I have one limb done on a Bingham's 3 piece t/d but I doubt that it will look anywhere near as nice as your bow does.

Very inspirational.  I'd be interested in reading about what type of jig (in any) you used to drill the limb bolts.  Also, did you drill your index pins all the way through your limbs or did you use a jig for that as well?

[bjansen]

Thank you...I used the Bingham jig..it is a bit touchy but if you take you time you can get them lined up pretty good...I have had alignment problems before, and have not yet tried drilling all the way through the limb for the allignment pin. I do think drilling all the way through for the allignment pin is the way to go though and will probably do that in the future.

I took that picture (the one where it looks right down the limb) to show the alignment...i got pretty lucky on this one...but that picture looks like the bolts are a bit off center..i went back and checked, i think it just may be the way i took the picture.

[JJB]

Beautiful work!

[rkmnt2]

Another beauty Brad!
  And I think you are thinking right about the concave on the back. Definitely the way to go.
   Don