Primitive Archer

Main Discussion Area => Bows => Topic started by: Rowan Bows on December 25, 2021, 09:07:35 am

Title: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 25, 2021, 09:07:35 am
Hey Bowyers!
The Møllegabet bow is made from elm and the backing from black locust (heat treated). The bow is 166cm ntn unstringed.
It has adjustable draw weight in 3 positions. 56# 62# 75# are possible. At my draw it has 68# highest level.
Very easy to string and adjust the cables.

Shooting session: https://www.youtube.com/watch?v=wJj5Vylefgw

Sorry for the compressed pictures but Im only allowed to load up 4.
There are better Fotos here: https://imgur.com/gallery/6VznfqB

I wish you all a very nice Christmas, Peace, Health and Harmony with your family.

Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Selfbowman on December 25, 2021, 09:28:44 am
Interesting bow but lots of mass. Fun project I’m sure.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 25, 2021, 09:47:00 am
Mass seems to be a problem with these bows thats why I heat treated the black locust. I think it became much lighter. Its fun to shoot.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on December 25, 2021, 11:28:08 am
Cool bow.Nice work.Never seen one of this kind adjustable but it makes sense.A veritable type bow.You've definitely got the bow making bug.You'll have to educate your neighbors to stay out of trouble.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: bownarra on December 26, 2021, 03:29:05 am
These bows are wacky!!!
To gain some more efficency you can reduce those levers quite a bit. Even with the sharp reduction in width they don't need much increase in thickness to keep them stiff. I rough them out at 1/8ths thicker than the thinnest part of the working limb. Same with recurve thickness. Just think how little extra thickness is needed to produce a stiff spot on your working limb :)
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on December 26, 2021, 08:29:04 am
To get the look of these type bows is actually easy.Elm is an excellent wood for it because of its interlocking grain.The benefits from them is ease of draw because of low string angle and dead in the hand release.To appreciate the shooting & performance benefits takes a little more time.It's a final fine balanced tillering process on these types of bows removing material from these levers but still keeping them relaively stiff to see it happen.Length of levers can vary also with a shorter working limb.A person has got to remember stress gets less out towards the tip on all bows also so less will still hold up fine.
There comes a time though to know when to quit as a few grains [under 20] won't make much difference and will jeapordize the durability of the bow too.
Removing material from these levers a little at a time while testing it will slowly reveal the benefits 1 fps at a time.I've made them so narrow and needle like they almost bow a bit sideways.That's when you know you've gone too far.
Once a person gets familiar with different woods enough times I immediately know how deep and narrow to start with to reduce time in making them.

Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 26, 2021, 10:58:34 am
my english is not sooo good. you mean the needles of the mollegabets?
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 26, 2021, 11:13:50 am
One more nice bow  (-S
Very good execution  :OK I like it
Probably bownarra is right about the heavy tips - they could be made less thick. But the excess weight does affect speed less than one would may think; I once made this experiment with a 38# moellegabet: I removed 50 gramms of wood from the levers and only gained 5 fps. According to this 10 gramms of mass removal will provide 1 fps. But shooting comfort definitly was much better...

I have not done a penobscot myself and I dont fully understand how it really works. According to my understanding the secondary bow itself cannot store a lot of energy.....1 due to its tiny dimensions and 2nd due to the very bad string angle it has to work with; it has to work more like a cable backing...

I would be very curious to see te tiller of the main bow without the secondary bow and compared to the tiller with the secondary bow attached...how does the tiller shift??? Would there maybe more bend close to the handle without the secondary bow attached???? could you provide this pic?  :D

Also I would be very interested in the fdc of these different bows. You see my rough estimation in a drawing  ;) of course the curves  wont be so linear and I guess I got a too big difference in early draw weight in my drawing.... maybe I'm completly wrong...

Cheers and merry X-mas!

PS: https://www.deepl.com/de/translator  (https://www.deepl.com/de/translator) works very well for translations - bow-building specific terms maybe not always  ;)
PS: I like your videos too - very cool music jingle you have there  ;D ;D ;D
 
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 26, 2021, 12:12:50 pm
No problem this is the tiller without the backing connected and a picture from the needles. I dont know how to show it but maybe you can get an imagination of the thickness. I had many problems with this bow before. First backing was way to weak. I tried to tune it with a sinew backing wich gained only 5lbs. So I thought you have to attach a really strong small bow. I gained much more draw weight but of course the backing was very heavy now. So I heat treated the black locust and the whole bow was much lighter and had not this handshock anymore.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 26, 2021, 12:17:36 pm
thank you! I dont have a picture of the profile from same angle to compare. But anyways: I mean when the bow is fully drawn....
In your full draw pic - secondary bow attached - the bend is concentrated on the outside. I expect it to be more towards the handle without the secondary bow...
I dont think the mass of the secondary bow does affect performance a lot. This mass does not need to travel very far...
The levers look like 18-20mm thick. 14-15mm would be enough...
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Selfbowman on December 26, 2021, 12:51:32 pm
I see what you are saying Simk about the mass of the second limb. How does moving the string father out on the lower limb affect the tiller of both limbs. Maybe a braced look at all three weight limits would be interesting to me. Arvin
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 26, 2021, 01:58:28 pm
You think they could be even thinner? I know what you mean with the tiller. The backing defenetly affects it in the outer limbs. Maybe I can get some time to make a good tiller foto without backing connected these days. Merry Christmas !
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 27, 2021, 05:05:52 am
Selfbowman: I dont think moving the string on the lower limb affects the tiller a lot. But I think there's a noticable difference when you attach the secondary bow to the main bow... Also: How does the secondary bow change distribution of stress on the bow: Inners vs outers - back vs belly...?   To me it looks like it stiffens up the inners. I could also imagine the secondary bow relieves stress from the back of the main bow, but not from its belly. Of course also neutral plane is shifted somehow. Also I would expect a very progressive (not linear) increase of drawweight - that's why I was interested in the fdc's. I'm just tryi'n to understand how the system works.

Rowan Bows: It's about the love for bows. It's not about a few gramms +/- or a few fps +/- ....these really are details  ;)
nevertheless optimizing never stops of course. I checked a bow from mine that I recently tillered. Also a reflexed lever-bow. Also from elm. It initially was 55#@28" ...now tillered down a little...
cheers   
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 27, 2021, 05:33:49 am
7mm  :o thats brave.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 27, 2021, 06:11:12 am
the mark actually shows 9,2 and 14,2mm  ;)
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on December 27, 2021, 07:13:21 am
The full draw picture as mentioned definitely shows more bend in the outer limbs just ahead of the lever fade.An area of the limb that does'nt store as much energy as the inner limbs,but does relieve the work the inner limbs do.It's good that you extended the width all the way to the lever fade.
I personally think the inventers of such type bow did what they had to with the wood they had around them to get what they wanted.
All in all you did a fine job.
Took a few pictures of the widths of 2 different bows on the levers.Osage and elm.Measured 9" back from tips and at tips.
The devil can be in the details when reducing these.
The fps gain from testing from removal of material I've found too is right in the perameters of what simk posted.Right around 140 grains of removal[70 grains from each outer limb to tip] gains a person 1 fps.As said earlier too the benefits of a smooth draw and dead in the hand release is noticeable.
mm measurements.
osage
(https://i.imgur.com/HJhqpkO.jpg)
(https://i.imgur.com/2pVcFDS.jpg)
(https://i.imgur.com/dMEfymz.jpg)
elm
(https://i.imgur.com/pza86sU.jpg)
(https://i.imgur.com/X6hjmRl.jpg)
(https://i.imgur.com/HxpvtRB.jpg)
longer levers/shorter working limb like this on elm will make both aspects more noticeable.Thickness and width of lever 1 foot from tips is just a shade over 1/2".A 3" fade at the bottom of lever extends the stiffened portion to around 15" altogether on the bow limb.The bow is 62" TTT.There is around 9" of working limb.
(https://i.imgur.com/e1QEVeL.jpg)
(https://i.imgur.com/v9hzLyZ.jpg)
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Don W on December 27, 2021, 09:47:24 am
Interesting bow. I like it.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 27, 2021, 09:50:14 am
simk: oh yeah 9,2 :fp
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 27, 2021, 11:01:08 am
Tiller with and without the backing attached.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Selfbowman on December 27, 2021, 01:10:58 pm
That’s a cool bow. The full draw pics with the second limb working and not working was very interesting to me. Just as Ed said about the second limb taking on the stress at inner limbs. Ok sorry guys but what kind of speed are you getting? It does not matter to anyone but me maybe but I’m curious. Arvin
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 28, 2021, 08:34:26 am
I don´t know it cause after the heat treating I didnt scale it yet. Also I think my Chrony is not reliable. Before the HT the best shot was 52,4m/s with a 28gram arrow but as I said I think these datas are not reliable.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 28, 2021, 03:43:12 pm
thanx for the pics Rowan Bows! It's how we assumed - secondary bow stiffen's up the inners :OK
the longer I'm thinking about this "2-bow system" the more I think this little secondary bow must cause something like a visible stacking in the fdc. How does it feel to draw? If you give me the drawweights of the 75#-version every 2" from 10"-28" I will generate the fdc...?!  (-S It would be very intersting for sure.
Thanx Ed as well. I notice your levers are a 2mm thinner than mine. What cross section are the levers? Mine are kinda trinagle. Glad you got the same numbers for weight/speed correlation. Always dangerous to post any numbers here  ;D

 
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 28, 2021, 05:40:25 pm
the draw is quiet hard with the 75# attached. I always thought like of course its because of the draw weight and the leight of the bow 166cm ntn unstringed. Actually I didn´t even think about the affection of the mainbow tiller untill you brought up this fact. I simply tillered the mainbow and then like "ok lets attach the small one"  :OK
I adjusted the cable leigh so that the whole tiller looked good and shot it and Ive shot it a lot. there are still no compression cracks.  Cant tell something about the force transmitting among this tillershifting but everything seems to be in balance. The levers are stiff till 29cm from the nock then the limb begins to bend.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: bassman211 on December 28, 2021, 06:26:55 pm
Nice conversation piece, but a well built selfbow performs just as well ,or better. I have made a dozen ,or so of them with different lengths, thicknesses, widths from Elm, Hickory, Bamboo, White Oak, and Ash, and have chrony tested each one. Best example I have seen of one was made by Marc S L. He concured with my findings They are fun to make ,and shoot, and they do have adjustable draw weight. Every bow builder should take a crack at least one. You mixed,and matched yours which makes it unique
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 28, 2021, 06:47:25 pm
Thank you sir
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on December 29, 2021, 12:04:59 am
I got the converted numbers stated at 172/fps with a 431 grain arrow[or an 8.3 grain arrow] @ 52#'s? I'm assuming before heat treatment of secondary bow?I don't believe it would have much relevance on outcome though.Main bow maybe yes.
Using a 10 grain arrow[531 grains] I figure the speed to be right around 160/fps.Very respectable.This bow Rowan made should never develop string follow over the years from shooting and shoot the same.
I like to follow up on bows I've made years later and shot a lot every year for durability reasons to see what they perform like.It reveals to me how well I tillered the bow.
Most bows perform best when freshly made.Not everyone shoots the same through the chronograph.Some pause more at full draw than others which can bleed full draw weight a little.Snap shooting usually produces the highest fps readings.Some people are very good at it.Not uncommon to see a 5fps difference between shooters.
simk....Lever depth difference on mine measured at same spot[6" from tip] between osage[1/2"] and elm[9/16"] is 1/16" deeper for elm.Elm is more V shaped.Less depth on osage because of it's density.
 
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 29, 2021, 05:22:18 am
I shot it with 70#-74# but like I said these numbers are not reliable - I dont trust that chrony. It also says Error everytime. 1 of 5 shots only counts and then it shows really weird numbers too - I wish I did´nt post them. The reason could be anything but I know one thing - all my customers are happy with my bows since 2012. A few shoot competitions with them and since Im so busi at building I became a very bad shooter myself so maybe thats the reason.
But hey I was county champ in 2014 ahh those times :)
Elm is a great wood. Once I had a bug and was almost ready with the bow. The back was clean but I realized a little hole on the side. The result was a labyrinth of bug channels underneath 2 rings from the back. This bow was messed up so I made a breaking test. It behaved almost as if there has never been a violation.
https://www.youtube.com/watch?v=_h7rLImiaIs
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on December 29, 2021, 06:37:57 am
Yes those numbers at 70-74 pounds do not seem right.Perhaps a new chronograph is needed now.It's ok to be curious of a bows' performance.To me it's just a measurement of my own bow making capabilities.Just because an arrow hisses does not mean it's going fast.That's a different thing causing that.It is like said the chronograph is the unmerciful extractor of truth.I've found years ago shooting in 1 bow after another is'nt good for a persons' form for target shooting either.
Like you said though as long as your customers are happy and they can get accurate with one of your bows.I get follow up communication from people shooting my bows many times.
My main beef is with the FG bow making industry.These self,simple composite,and complex composite bows can and do perform and out perform the FG bows.I personally like seeing owners of FG bows scratch their head when we shoot together.Natural bows will never out perform the compound bows.Neither will the FG bows.
The reliance upon technology IMO hurts the archer in a way to not understand exactly what's going on with a bow and arrow.It does help the industry line their pockets though.Excuse me but I am a very independant cuss.
Good thing about elm is that it does'nt explode.If that were red cedar or cherry or many other woods it would have gone boom.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: bradsmith2010 on December 29, 2021, 03:09:01 pm
  sometimes if the light is not right, you will get error readings,, try testing at different time of day,, moving backward or forward a bit till results are consistant,,
if i am in question, I will have someone else shoot with me,, that has a good release,, results can be consistant,, and give you information on what might be improved on,, I use the chrono to hone my skill but it is not the main factor in a good shooting bow,, but I like having the information,,one of my main hunting bows it not great through the chrono,,, but the accuracy makes it my favorite,,, (-S
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Selfbowman on December 29, 2021, 10:29:10 pm
Yep
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 30, 2021, 06:18:59 am
do you think the tiller shifting is an advantage or maybe a disadvantage? I mean both limbs are still equal after connection but the bow has less bend in the inner limbs. this problem (if it is a problem) would be so with every double bow except you make an akward main tiller. there must have been a logical reason for the natives to make those.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: simk on December 30, 2021, 06:52:50 am
Hello  :) I don't think you can say the tiller shifting is an advantage or a disadvantage.... its just the consequence of attaching the second bow.
There's little documentation about these bows and various explanations why this design has been choosed. Maybe this double-bow- concept wasn't very successful in bow evolution because there in fact are not many advantages. You will find several threads to read about this concept on this site or paleo planet as well...altough I didn't find a fdc of one. The fdc will tell you a lot about function and theoretical performace. 
I personally am very critical about the general concept and do not see any advantages. I think it's performance is worse than from a "normal" bow of the same drawweight. Just think about under what bad string angle the secondary bow has to work and the consequences. this theoretically could be seen in the fdc chart (i'm still interested in). Practically you could test it by shooting your bow though the chrono and shoot the same arrow with a "normal" bow of similar drawweight....but still many other factors to affect the results  ;)
cheers
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 30, 2021, 12:34:23 pm
true story but I just could not resist the temptation to build it  (lol)
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: bassman211 on December 30, 2021, 12:44:04 pm
I have made the so called Mic Mac double bow with a sliding nocks, and the loops attach at  the riser on the shorter back limb. Much easier to adjust poundage that way, but no improvement in performance. My brother has a pro shop with a large, very expensive, and accurate chrony. That is were I did my testing. Take that bow to a shoot, and shoot it, and archers will gather around like flies on a sugar cube out of curiosity. It's  very design is a sales point, but no advantage in performance, and more time consuming to make. Still nice to build, shoot, and have fun with.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on December 30, 2021, 02:01:41 pm
Nice, do you have a link or a foto? Id really like to see this solution. Mine needs 10 seconds to attach the cables on highes level, think thats quiet comfortable but Im always open for improvement.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: M2A on December 31, 2021, 09:09:12 am
Cool build! Enjoyed the read on this thread. Bow looks great.
Mike
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on January 01, 2022, 08:07:40 am
Hey guys happy new year!
I have some speed scalings for you   ;) the problem could have been my release.
I shot a 474,6 grain arrow with and without the backing. Let me point out that I really dont know if that is fast or not - ok but I think that arrow was quiet heavy.
the first shots went out stupid and mr. chrony has let me know maybe a 100 times that he has an error. but after a little release practise I could get the bow ~5m/s faster. I practised more and more and shot the bow without backing 49#on my draw with a 474,6gn arrow - 49,25m/s or 161,5fps
The backing attached gave me 68# on MY draw - same arrow 53.80m/s or 176,5fps
So... I dont know if thats good or not but I am a man of science  )P( I gave you those numbers although I know now posting numbers is really dangerous here.
I had very much fun with this bow and I mean no matter if its worth it or not I couldnt resist to build it. cheers!
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on January 01, 2022, 09:26:49 am
Happy New year back at ya.Glad you worked things out with your chronograph and it's still usable.
Most bow makers,not all,who never concern themselves with testing their bows and then do usually are disappointed.Which leads them to ignoring it altogether in their bow making process.Many times it's just a matter of release.That type shooting can actually hurt accuracy though with many.Hitting what your looking at counts.
Nothing really dangerous about testing process if all done legitemate.
Most designs of bows are pretty efficient if fine tuned while tillering from 1 bow to the next.
Your numbers fell in right where I figured after seeing your initial testing.Interesting your added bow almost adds 20#'s to the draw weight.Starting out with a highly efficient main bow should transfer like numbers with the added second bow and draw weight IMO,but it would be interesting to see.
In time I will show a test of a different bow I'm making again on video good or bad.Deer season and accumulating snow of over a foot with high winds here will keep me busy for a while.I need to keep a 3/4 mile long lane open plus my yard and I live in the sticks.Plus my non heated tractor shed/bow making shed will be pretty cold to work in.Below 0 F. weather coming here for  while.The dead of winter is upon us here.
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: Rowan Bows on January 01, 2022, 09:52:11 am
Chrony session: https://www.youtube.com/watch?v=RK8QcY_vU88
Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: BowEd on January 01, 2022, 10:57:52 am
Looks like the test was legitimately done.
Your release looks fine to me.I have a different looking type chrongraph though.
It has hoods for shadow casting I think and I shoot through the V about 3' in front of chronograph.
(https://i.imgur.com/csCl0b5.jpg)
When diagnosing bows it's important draw length is the same and starting out at least with a standard.Using a 10 grain arrow on all bows.50#' with a 500 grain arrow.60#'s with a 600 grain arrow.It levels out all the bows on the same playing.
If number is odd like 53#'s it gets a 530 grain arrow.
It can get a little more confusing using an over draw then too.Then you see how much the added inch gives you.
An old timer said to me once when I showed him my findings.Makes sense he says... if you want the bow to go faster pull it farther back....ha ha,but in reality which I failed to get across to him was that the sustained freshness of limbs gained with good tillering is
 really where it's at.

Title: Re: Adjustable Penobscot Møllegabet 52#-75#@28"
Post by: superdav95 on January 03, 2022, 02:35:48 pm
Great looking bow.  Love the concept!