Questions on Penobscot bow design...

[halfseminole]

I've been doing a fair bit of research on bows that offer a "let-off" but aren't wheelie bows, which has led me to two forms-the horse bow, and the Penobscot.  My horse bow, while it needs tuning, does actually offer a small amount.  However, all of my research on the Penobscot has shown me that it does offer the let-off, but it also can be tuned over a wide range of draw weight by manipulating the front strings.  This would help me immensely, as I could start low and work up on the same bow, as well as tune down if my arthritis is really eating me up, without having to change bows.  Familiarity helps my accuracy, generally speaking.

There are Penobscot kits available, or I can design and build my own.  Bow geometry isn't exactly new to me (that horsebow works, after all) but I wanted to see if anyone had built one and if they had any advice.  I don't expect to get this done in a month by any means, but an adjustable weight bow with my health problems is a seriously good idea, and one that I don't have to go buy limbs for would be even better.

 

 

From what I've read, this is referred to as a Micmac war bow.  It seems to be the most easily tuned.

I'm thinking hickory would be appropriate.  I'm keeping clear of osage, its price is way out of what I can afford and I don't have the tools or place to work it down to a single ring for a pair of bows.  I've seen a few of red oak, as the overall weight of the primary bow is not high, but I'm not sure I'd trust it anyway.  Shooting my board bow drove that point home for me.

Feel free to tell me I'm insane, or to buy a kit and do it, but I can't find a kit with the Micmac long strings in front.  If I could, my dilemma would be over.  Any other advice (such as wood selection) would be most welcome.

[Pete W]

I think you will be disappointed if you expect let-off , as in the holding weight gets less as you draw farther.

[halfseminole]

Certainly not like a wheelie bow.  In fact, I don't need what little my horse bow can do.  It's a nicety, but the real interest is in making an adjustable weight bow without buying an ILF, which will never be in my budget.  Either I learn to make bows that suit me, or I do without, as buying is just completely beyond my budget.  Same with osage, I can get completed bows from many places for what a stave would cost me pre-shipping from what I've seen.  

With being on a fixed income because of disability, what I lose in money I make up for with time.  So, I figure being willing to sit and work on this will do me better than not shooting because I can't afford it.  Currently I make everything I use-strings, points, fletching, quiver-all of it.  It's nowhere near as good as what I see here, but I learn more every time.  One of these days it will get good.

[Pete W]

Now adjustable draw weight from a Penobscott is definitely a real thing that comes easy by twisting the back bow strings. if you can track down John Large from Nova Scotia, he goes by Ironfist on forums, he is a wealth of knowledge on the Penobscott and Mic Mac bows.
 Pete

[MoeM]

You shall take a look at whitewolve`s  max P    series!
Sometime ago I emailed with the bowyer and he already agreed to help me with some information bout the bow but one day he didn`t answer and I had/have little time so I put the projekt besides.
(but I`ll bring it back on my desk soon...)

[LittleBen]

Just a thought here, btu if you're drawing 34", you could probably shoot a long (maybe 66 or 68") target recurve bow. For example Samick polaris makes 33# @28" limbs. They should be around 42# @ 34". That would give you plenty of speed and power to shoot deer or whatever. I think the polaris is about $120.

Also a long target bow will have very little stacking compared to a straight limb bow or shorter recurve.

I know you were talking about going up and down in weight, but honestly, I don't think you need to go up much at all if you're drawing that far. You'll have alot of speed at just 40#.

[halfseminole]

I didn't know about the target recurve thing, so thanks a ton.

The issue for me is that for one, this is done as physical therapy, so I'm wanting to go up in weight so as to strengthen my arm.  For two, what's wrong with my shoulder is a very complex issue.  I have arthritis, I have rotator cuff tears, I have atrophied muscles and I have a brachial plexus tear.  If I'm having an off day right now, I can't shoot my bow.  

Because I know I'm not as physically strong as most, I'm trying to be smarter to make up for it.  This search was actually sparked by my rheumatologist, who asked "if it's too much one day, isn't there a way to make it a little less so I don't miss a day of practice?"  I know she didn't know, and honestly I didn't know the answer, either.  So I searched until I did.

I know there are other bow styles possible, but this seemed to be the easiest with the tools accessible to me.  I saw an awesome one made from a whole 3-4" stalk of bamboo (split but leaving the internodes) that I want to try on down the road but I thought that this would be easier.  Found it    here  in the TBB.  

Can someone explain to me the speed with my draw length thing?  My horse bow doesn't seem to show that, but it's a short thing.  

I have a custom bow ordered (barter is great) but I want to give myself some options for when the pain is too much.  I know it's not a normal problem, but it's one I have pretty badly.

[MoeM]

Hm I guess you can have a lot of fun with light arrows on a 20# target bow- if you have better days you can shoot more instead of pumping your bow`s weight up!
The draw length thing is generally quite easy- the longer the draw the longer the acceleration way!

[LittleBen]

MoeM hit it on that one. The longer the draw length, the more energy stored at a given draw weight.

the power stroke of th ebow is the draw lenght minus the brace height, so at a brace height of 7" a 25" draw gives you 18" of power stroke, and a 34" draw gives you 27" of power stroke.

So I draw 25" ... a 40# @ 25" bow might shoot a 500grain arrow at 140fps or so.

You draw 34", so a 40# @34" bow might shoot that same 500 grain arrow at 180fps.

you would be storing roughly 50% more energy which is released into accelerating the arrow.

I totally understand the physical therapy aspects. If it were me I'd get one solid bow at a weight I can shoot all the time, maybe it's 40#, maybe it's 30# ... whatever it is.

Then I'd say if in the future you wanna go to a heavier weight bow, make or pickup a second one.

Then if you wanna do some physical therapy, do standard rotator cuff excercises to strengthen. I had alot of trouble with my rotator cuffs resulting from wrestling injuries and I found that alot of your basic rotator cuff excercises were very helpful, even using just a .5L bottle of water held in the hand.

[scars]

Enjoy

 

[paoliguy]

I saw an add that shows a longbow with multiple string nocks. The further out nock would give lower draw weight and the one further in would give higher. Same idea as piking a bow for draw weight.

[Ironfist_Canada]

Just  got back on Tradgang and saw this post. Hi Pete.  The gentleman in the Pic is Judson Bailey from St Albans Maine. I used to chat with him about Penobscots and Mik Maqs and he sent me some really useful info on these bows.  He also has articles in at least two Primitive Archer issues.I would be happy to answer any questions you might have  about these bows. I have lost count  on the number I have built. The Mik Maq  takes longer to build but in my opinion is easier to tune and adjust weight. Hope to hear from you  I do have lots of pics of some of my bows and also a build along.  John.

[Pat B]

Have you done a force/draw profile for either the horn bows or the Penobscot bows so you could actually see if there is any let off or reduction of draw weight as the draw increases?

[Ironfist_Canada]

I have never experienced let off, there is none. There is however a high early draw weight which does not increase much as the draw is made. The big bow tries to shorten by bending away from the archer allowing compensation to occur.I imagine the F/D  graph would start at the full draw weight or near to it and then proceed as a straight line.Bailey sent me some F/D graphs but I cannot find them as I moved home and things got lost.I vaguely remember the line being almost straight up.

[Ironfist_Canada]

Pat B  there may be some F/D graphs  in the articles that Bailey wrote for PA magazine. He had articles in two issues .It would be 10 or 12 years ago now.   John.

[KellyG]

So for changing draw weight wouldn't a cable back bow be the easiest? I have only seen one but the builder said if he wanted and increased the weight he twist up the cable and lower weight untwist.

Just a thought.

[halfseminole]

Yes, a cable backed bow can be adjusted just that simple.  I have one that is now way oversized for me to shoot (try wielding a 6' bow from a wheelchair) but braiding the cables is really long work.  It's six of one, a half dozen of the other on adjustable weight bow designs.  The issue for me is now gonna be the fact that I am not only wheelchair bound, but it's a small chair made for those who can still push themselves and it's lower to the ground to make falls easier on you.  I'd love to build one of these if I could get it the length of say a horn bow or a horse bow.  I'm planning an experiment, but I have a lot of math in front of me to parse...

[Pete W]

Hi John, been a while. I hope to get down east again this year for the Hampton shoot and pick up some NB Hop Hornbeam staves while I am there .
 And of course a feed or 2 of Fiddleheads.

[Ironfist_Canada]

I took a look at Baileys F/D readings tonight on his #65 Penobscot. The bow was braced at 6inches. It drew #5 per inch until it reached 12inches where it required #4.5. at 14 inches it was at #3 and at 16inches it read #2.5. It stayed at #2.5 until 24 where it dropped slightly to maybe #2.25 until #65 at 28 inches. It was hard to read the chart but this is some idea of the F/D chart. it took #5 to move the string one inch at the beginning of the draw and #2.25 to move the string at the end.At roughly half draw this bow became easier to draw and probably would not stack at all if drawn beyond its tillered length of 28 inches. The F/D chart was sent to me by photo copy from a gentleman at Primitive Archer magazine.Like I said its not the easiest thing to read but it is accurate enough to explain the above. This is the research of Judson Bailey of M aine.

[Ironfist_Canada]

Hello Pete  I do not get to the shoots much these days. A friend of mine here in N.S. found a nice area to pick fiddleheads in a river valley. Lots to pick each spring. Hope you are well .