How do you explain the penobscot bow's performance?

[medicinewheel]

Nice bow!  Thanks for posting, but I must say that deserves a separate thread.  You should post it so it can be eligible for bow of the month.

            J. D. Duff

hi guys!  -  yes PE-LEEEAAAASE! - a penobscot-thread would be great; this thread already had new info about the design. thanks!

bowmo! - that's a really nice bow!

question: would this be considdered a 'selfbow' or a 'backed bow'?? 

frank

[DanaM]

Good question Frank, I think its a selfbow as long as both bows are one piece. If someone
makes the bows for instance boo backed then we have a backed bow.
Actually I think its really a type of early compound

DanaM

[Marc St Louis]

Actually Dan's Penobscot was included in a BOM vote before, last year I believe.

[tyler]

the performance comes from the compound action of a properly made penobscott. meaning if you had someone who is very good at math you could figure out the right geometry to make a bow that literally lets off something like a modern compound. i think this design is very complex and would take some r&d to make anywhere near potential. perhaps a penobscott with recurves that lift off just as the strings of the back bow start to wrap onto the limbs........ just a thought

[jkekoni]

Is it possible for penobscot bow to be Perry reflex?

I do not mean by gluing 2 pieces of wood together to make the arcs, which of course can be done,
but by using the small arc to draw the long arc backwards when not pulled.

Or is this actually the normal way to make such a bow?

I mean this design is too complex for just making the bow narrower, a non bending handle is easier to make and to invent.

[Judson]

     I guess I was the one who got this Penobscot bow stuff started with my first article in Primitive Archer.    It seems to me that I should explain how the bow works.
    At brace height the string angle between the back bow and the main bow is very shallow.    This means that there is little mechanical addvantage that the main bow has when drawn to bend the back bow.    As the bow is drawn the tips of the main bow do not bend back very much at first.    The string angle on the back bow forces the main bow to shorten putting strain (stored energy) on the lower and mid limb areas of the main bow.    Once the main bow tips bend enough to create enough mechanical addvantage  (String angle between the back bow and the main bow) the back bow will start to bend.   It is at this time in the draw where the force draw curve will flatten out.
      I am in the house  not the shop now so I can not give you the issues of Primitive archer my articles on this bow were in however I will post them in the future.    By the way if you read the articles ignore the tillering info there is a better way o do it that I will also explain.

[JackCrafty]

Thanks for reviving this thread.

I've made one penobscot bow of ipe (both parts) for my nephew.  Both parts are self bows and are D-bows with no reflex.  The bow has a surprisingly long draw and the ipe does not seem to be stressed very much.  I need to go back and take measurements....I made it back before I read the bowyer's bible series.

As far as I can tell, the originals were made of hickory with rawhide strings.  And the smaller bow barely bends at all.  I don't think it behaves like a cable-backed bow because those bows depend on the springiness of sinew.....rawhide is not nearly as springy.

When I built the bow, I noticed it could be left strung for long periods without loss of power.  I think that is the main advantage....that and the fact that you can make the bow more narrow than a regular D-bow.

I'm going to build several more this next year (cross my fingers) and I should be able to give a more educamated opinion later.

[son of massey]

  i have wondered about this too.   the neutral plane argument seems reasonable enough, but that would mean that the mini bow isnt adding anything that a thicker bow, or some other backing, wouldnt add.   the design is certainly harder than a cable backing, so why not just use a cable backing?   
   this is just a thought, i have not made nor have i studied any of these bows myself.   however, i was thinking that based on microscopic reversibility, the micro steps you take to get from A to B are the opposite of the steps from B to A-what goes up comes back down in a symmetrical fashion.   The mini-bow flattens out against the big bow early in the draw, and at that point it can add weight but it seems liek it would be stacking weight-in other words it shouldnt add much in energy storage.  the big bow doesnt start to bend at all from the tips until relatively late in teh draw.   this means that the bow tips of the big bow would stop moving early in the release as well.   as the opposites all happen, the tips would hit home well before the string is finished moving forward thrusting the arrow.   the little bow now starts to pull off the big bow and snaps the string taut using the long bow tips as leverage.   it would be the energy storage benefits of a short bow with a longbows mechanical advantage-same idea as a holmegaard.   the energy curve would be steep early in the draw as you pull the short bow into stacking mode but that would be translated over a longbows length, so late in the release you should have the same steepness of energy released.  SOM   

[mitchman]

wow you guys rule if someone would get me in the right direction i can get halp from my math teacher and physics teacher and we could form a hypothetical model of the best way to make a "recurve compound."  i think it would be sweet
         will someone make a flash video/slideshow of how the draw is supose to work like how son of massey described it.  that would be way cool and a easy to grasp. i want to make one

[Judson]

     If you people want to read the articles I wrote on the Penobscot bow  for Primitive Archer they are in volume 3 issue 4,volume 5 issue1, volume 5 issue 4, volume7 issue 1.   
   Did you know that there are six distinst variations of the Penobscot bow which should in reality be called the Abnaki bow as the basic design was found with all the members of the Abnaki Confederacy.    Probably the most distinctive variation was with the Micmacs, this is also the only Penobscot variation that was specifically a war bow.    (If you go to Web shots you will find pictures of these bows)    Reasearching these bows has been lots of fun and shooting them even more.    One hint that I have found is to tiller the main bow to what ever you want for a final draw weight.   After you have done this then add the back bow and retiller until you get back to your desired draw eight.

[Kegan]

From what I understand...

The main bow is about 10-20# less than the bow's final weight. It doesn't feel all the extra stress because the smaller back bow does. It is, in effect- well overbuilt without all the extra mass. Which Comstock and Baker and anyone using Osage has discovered. The smaller back bow is pretty heavy and should be highly reflexed or stiff (to give it lots of power), to give it the desired weight. If it's wayyyyyy too overbuilt, it doesn't matter so much, because it's jsut a weight-adder, and only functions in small movements. It's close to the handle, and therefore doesn't have to slow the arrow.

What all this adds up to is a bow with the phsycial weight of just slightly more than, say, 40#, but shooting with the power of, say, a 60# bow. It's mroe of a primitive sort of fiberglass than a primitive compound (which is why it shoots heavy arrows better- all that extra energy with less mass, instead of just mechanical leverage without storing mroe energy).

DANG IT- NOW I WANT TO BUILD ONE!!!!

[koan]

As to why this design was used, could it be because of the wood/materials they had to use ie...poor quality wood in tension? Or compression? Just curious, maybe it wasnt to build a better performance bow...but just a bow that would survive..just thinkin out loud...maybe we should build this bow from willow or doug fur and see what happens ....Brian

[Kegan]

As to why this design was used, could it be because of the wood/materials they had to use ie...poor quality wood in tension? Or compression? Just curious, maybe it wasnt to build a better performance bow...but just a bow that would survive..just thinkin out loud...maybe we should build this bow from willow or doug fur and see what happens ....Brian

Hickory in the North East. The semi- green hickory would have pretty poor compression strength by comparison. Which would be a perfect example of my delusional ramblings .

[koan]

  Sorry, aint familiar with the history of the P. bow...I just remove wood till it bends or breaks,lol....Brian

[mitchman]

so would it be possible to have a super heavy mini bow and a light say 35 pound bow and reach a weight of like 60 with very little mass on the large bow and it is all on the small one. i guess what i am asking is what are the limits to this cool design and does anyone have some good web pages on this stuff.