All fired up

[Mad Max]

so I decided to shelve it for a spell and build a more mild mannered bow. 

?

[onetone]

Because I suspect the bow’s dry fire and crash damaged one of the limbs and I don’t want to spend the time now chasing a lost cause.    I will save that for the dead of winter. 

[Kirkll]

Quite honestly….. I don’t see how you guys keep these these together so long in the first place with all that hinge pressure coming right off the fades. This  type of bow design always has amazed me.

Your latest riser shape with longer fades looks much better to me. But…. I’ve never tried building anything like this before. So take with a grain of salt….  Kirk

[onetone]

Kirk - I agree they are surprising bows. I used to think such radical reflex was possible only with sinew/wood/horn composite bows, but there are currently many fiberglass/wood laminate bows with extreme reflex being made in Europe and Asia. They seem to be durable. I am encouraged to work out a lasting design because they are a blast to shoot.

Hey that was a snappy form design with the hinges! Was that a one-off form?

[Kirkll]

Back in 08-09 I built several hinge forms including some full length one piece bow forms. I think this is the last one I’m still using a lot. The recurve forms don’t work as well with hinges…So my updated forms I quit using them.  Kirk

[Mad Max]

11-1/2" reflex nock to belly of riser

[onetone]

Outstanding Max!    If you go for any more reflex you are going to have to bump your shelf up a few inches!

[Mad Max]

Yep

[Kirkll]

I’m curious how You determine the string length on one of these Max.

 I’m amazed how you can get that tight of bend right off the fades without them letting go.       Kirk

[Mad Max]

I’m curious how You determine the string length on one of these Max.

 I’m amazed how you can get that tight of bend right off the fades without them letting go.       Kirk

I used the sheepeater 50" bow string to brace it and then made a string for 6" brace , then work your way up on the brace. (brace as low as possible without slapping your wrist) Also .175 stack = 32#@28" so a .200 stack will make a 48# bow.
Fiberglass will take a lot of abuse

I'm pretty sure the bow met it's maximum

[mmattockx]

I used to think such radical reflex was possible only with sinew/wood/horn composite bows

I find that surprising since fibreglass can withstand far more strain than either sinew or horn. It should be possible to build a much more radical FG lam bow than with traditional materials.

MM, just a question on that bow. Have you tried starting the bend an inch or two farther out off the handle area and/or increasing the amount of limb that is bending? Another question, how do you manage to get a string on that out in the field? Or do you string it at home and leave it strung the whole time out hunting?


Mark

[Mad Max]

I would not say that fiberglass bows are more radical.
Read all of this and the Draw force curve ( A DFC is not very accurate pulling to 1" at a time on HORN BOWS) the DFC would be much better (accurate ) if you could read all the data in one draw cycle like you are shooting it.
http://www.manchuarchery.org/bows
Stringing the bow in the field--step threw method, just make sure you are pushing and pulling on the correct places.

This is James Parker's design, he makes horn bow also so I believe it's a good design.
He changes lam taper or width or what ever accordingly to what he gets on his 1st bow off the form to make it bend like he wants.
All of the limbs are work but the knee's work the most.

Someone on here a few weeks ago quoted some horn bow maker saying something like bending out of the riser and drawing back as far as possible and a few other things. (can't find the post).

When the bow is braced there is a gap(concave) in the center of the limb at the knee from the tension of the fiberglass.

[Kirkll]

Are you saying that cup in the glass isn’t there without a string??? Now that’s a brand new concept ive  never heard of….

Now I have played with building limbs with a cupped cross cut profile before coming out of the forms, and it’s incredible how much the draw weight it increases doing this.

Of course the first time I did it, it was a boo boo. I had the gap in my form above the air hose too far apart and all the pressure went to the center of the limbs and caused a cup shape limb…. I came in 15# over draw weight on those limbs, and sanding glass was tricky on a cup shape limb.

You remember OL AdCock?  Built those long bows with a cupped limb and even spent a lot of money to patten that limb design….. the dad burn things were pretty fast too…. I can’t remember what he called that design….   Kirk

[garyschuler]

I believe Adcocks design was called the Adcock ACS limb. Which stood for ( Adcock cross section )

[Mad Max]

yes it's flat when un braced.
Tension trumps compression, My opinion the tension over rides the compression and the belly convex and the back concaves   

James Parker made a boo boo too and that OL guy said something about suing him.
James said you can't  sue me for making a mistake on gluing up a bow.
He told me that back in January when I went to visit him.

Quote Kirk "Now I have played with building limbs with a cupped cross cut profile before coming out of the forms"
Tell me how you made the form?

[onetone]

I think this is the post you mentioned Max. It is a quote, more or less from the book Ottoman Turkish Bows by Adam Karpowicz:

“We can now summarize the design characteristics of a fast bow … 1. make it as short as possible and the limbs, including the bending section, as thick and narrow as possible 2. draw as far as possible 3. reflex the limbs as much as possible 4. keep the bending as close to the grip as possible for the longest limb path. All four requirements can be met, but only within the constraints of material properties, the skill of the bowyer and by the strength of the archer.”

[Mad Max]

Bingo that's it

[Kirkll]

yes it's flat when un braced.
Tension trumps compression, My opinion the tension over rides the compression and the belly convex and the back concaves   

James Parker made a boo boo too and that OL guy said something about suing him.
James said you can't  sue me for making a mistake on gluing up a bow.
He told me that back in January when I went to visit him.

Quote Kirk "Now I have played with building limbs with a cupped cross cut profile before coming out of the forms"
Tell me how you made the form?

Yup… that was it ACS .   Sometimes I wish I could just re boot the hard drive in my mind. There is a lot of info in my head I have a hard time accessing at times. It’s like all my memory got shifted to the cloud, and I have internet connection issues periodically… it’s frustrating knowing I know something, but can’t access it instantly.

The forms I was getting a cupped cross section were std 1.75”  in width, and no different from any other forms I’ve built. but I was using 2” width glass in an attempt at taming down a radical recurve limb shape with extra width. I had over inflated the hose to about 70# and rounded out the hose too much. And that pretty much put all the pressure in the center of the limb and created the cup….

The whole project was a complete abortion, and the limbs I had wasted were way to curvy to even use for tomato stakes much less fit in my wood stove.

I tried a similar attempt on a long bow limb to purposely come up with a cupped cross section using 1.75” glass on a 1.5” form . Oh I got a cupped limb, but it wasn’t consistent enough to get both limbs with the same cross section just using an air hose, and the bow was off tiller almost 2” and bending in different locations….. I promptly threw in the towel shortly after that trying to replicate a cupped crosse section, and started experimenting with wedges and taper rates to get what I wanted.

Even the AdCocks ACS was considered somewhat vertically unstable in my opinion. Especially the lower draw weight models. Over 50# were ok… but less than 45# were kind of floppy at the tips.

Btw… that patent  has long since expired, so if you feel so inclined to play with it , fear not any legal retribution. But It’s not worth the frustration in my opinion.

OL AdCock was an accomplished flight shooter for many years and attended the national flight shooting competition in Utah every year, but I never met the man personally. I have no idea whether he is still kicking or not.

Kirk

[Mad Max]

There is a guy in Germany that makes self bows and he use a rounded scraper on the belly to tiller with high crowned staves. He calls it hollow limb

[mmattockx]

Are you saying that cup in the glass isn’t there without a string??? Now that’s a brand new concept ive  never heard of….

Take a flat wood lam and bend it to a pretty sharp radius. Not enough to damage it, but a lot of bend. Now lay a straight edge across it, it will be cupped just like MM shows.

Tension trumps compression, My opinion the tension over rides the compression and the belly convex and the back concaves   

It's not tension trumping compression, it is the change in width that does it. When you take a rubber band and stretch it, it becomes narrower as it gets longer. All materials do this. It is the lateral change in width that accompanies any length change. This effect is called the Poisson Effect.

The effect is quantified by Poisson's Ratio. For example, Poisson's Ratio for carbon steels is 0.29. For every 1% strain longitudinally the lateral strain will be 0.29%. Under tension materials get narrower, under compression they get wider.

The cupping is caused because the tension side of the limb is getting narrower while the compression side is getting wider. To accommodate these changes the limb cups toward the tension side.


Mark