TEST -----Static Tips

[Mad Max]

I DID PART OF THIS TEST BEFORE I STARTED MAKING MY BOWS THIS WAY


.030 Glass 1-1/2" x 12" (17 Grams)
.060 Quarter sawn Osage 1-1/2" x 12" (17 Grams)
.115 Quarter sawn Sitka Spruce 1-1/2" x 12" (17 Grams)
ALL pieces are 17 Grams
  

Bend Test
The block on the scale is taped in place, the end of the piece being bent is at the edge of that wood block.
The block of wood on top of the stack of tape is pushed down making sure it is at the edge of a line on the piece being bent. Read grams of force

Glass 63 grams force
Osage 175 grams of force
Sitka 650 grams of force        I checked all of these several times
  

  
A--The limb tip in the back (or right)is a conventional tip Look
B--The one in the front ( or left) is my static tip
Both have the same stack
A-- has a .030 tip wedge
B-- has a 1/4" Sitka Spruce tip wedge (by the way I don't like the way my wood wedge turned out) any way, for the test
A-- 67 Grams Total weight
B-- my way 47 grams Total weight
Both are the same length
I all so did a bend test with both clamped to my work bench
A-- bends with little force, so it needs thicker wedge or under lays,  over lays
B-- mine is very stiff as is
  

I WANT YOUR INPUT
WHAT DID I PROVE


After some other test on my 64" static recurve T/D
I had too much angle on my static tip so I took 10 degrees of angle off

[fujimo]

hey Mark,
back in my shop today, went over all the drawings, comparing the one piece to the three piece etc.
laminated my plywood together, and will start on cutting the form out etc when all is dry
also made the 1/4"plywood router form.
this post sure grabbed my attention!
good job!
isnt there some formula about twice the chord= 8 times stronger/stiffer??
where are the engineers??

[Mad Max]

Bowyer's bible

narrow and thicker is stronger than thin and wide

[fujimo]

how do you think the osage would compare to the spruce, if it were the same thickness?- and i know vastly heavier!
i see your test is orientated around weight!

[Mad Max]

Sitka was .115 thick
osage was .060 thick
Sitka 17 grams divided by .115 x.060 = 8.87grams

so sitka and osage the same thickness
sitka =8.87 grams
osage 17 grams

Sitka = 650 grams of force
osage = 175 grams of force
650 divided by 175 =3.7
So sitka is 3.7 times stronger for the same weight

I think I did all that right?


The less fiber glass you use in the tips, the better off you will be.

All my self bows had narrow thicker tips. ALLWAYS

[snapper1d]

Twice as wide = twice as strong.  Twice as thick = 8 times as strong.

[Mad Max]

Yea.       What he said

[savage1]

I would like to try that on my limb sometime.
Never built a tip up like that.

Lou

[bornofmud]

Nice, very cool, thanks for all the testing and info!  I'd imagine that the thicker stack and the way you brought the tip wedges all the way through the hook will help with stability.  Also liked the idea of using a softwood for the tip wedge, keep the weight down and the strength up, so long as it stands up to long term use.  Definitely a cool idea!  You should make a bow with it and see how it does!

[Mad Max]

Like this
I have been working on and off on this one for a month

Waiting for the finish to cure

   

[savage1]

Mark did you post a build along on this tip?
I would like to try it on my limb.

I notice on the osage bows you made the bridge was outside the glass and this one is laid in the glass.
What's preferable or easier if it dont matter.

If you share this, please show the profile and size of string loop to make it work..

Thanks ,
         Lou

[monterey]

Mark, thanks for this ongoing report.  Very interesting.

[Mad Max]

savage1   I PM you

Thanks guys