Crossbows - Everything about Building, Modding, and Using your Crossbow Gear

Latest topics

» Wooden Crossbows - Seeking Info
by Franck Yesterday at 4:16 pm

» crossbow prod material/what type of steel
by Franck Yesterday at 4:11 pm

» Ball shooting Crossbows worth the bother
by septua Thu Jul 19, 2018 11:07 am

» my composite crossbow lath project
by stuckinthemud1 Wed Jul 18, 2018 1:35 pm

» Limb harding\ tempering ?
by ragumup Wed Jul 18, 2018 2:03 am

» how made homemade (reverse) crossbow ?
by Ricardo Sat Jul 14, 2018 3:56 pm

» Pump action crossbow (powerful)
by Ivanhoe Fri Jul 13, 2018 7:50 am

» nut from antler
by OrienM Thu Jul 05, 2018 8:50 am

» Nut from a pool que ball?
by drawknife Sun Jun 17, 2018 5:29 am

» Trouble with my Gafa
by drawknife Fri Jun 15, 2018 2:56 am

» Do all triggers Have claws - what types and claw or no claw
by globalmark Thu Jun 14, 2018 12:19 am

» For Sale: Masai Crossbow
by TonyU Mon Jun 11, 2018 1:15 pm

» Medieval composite bows
by juanjo Fri Jun 08, 2018 5:10 am

» yew and sinew prod help needed
by stuckinthemud1 Thu Jun 07, 2018 1:34 am

» Small gothic crossbow (with wooden lever)
by OrienM Fri Jun 01, 2018 10:35 am

» Binding on the stirrup
by Geezer Sat May 26, 2018 7:26 am

» horn inlay and veneer
by OrienM Thu May 24, 2018 8:44 pm

» Presentation
by c sitas Wed May 23, 2018 4:31 pm

» My latest crossbow
by drawknife Tue May 22, 2018 3:13 pm

» The Arbalist Guild - Around the World
by stuckinthemud1 Sun May 20, 2018 5:32 am

» angles and rivets
by Geezer Fri May 18, 2018 1:16 pm

» morticed nut blocks
by Dark Factor Wed May 16, 2018 12:02 pm

» Crossbow triggers
by Croftage Mon May 14, 2018 1:41 pm

» Cocking lever
by c sitas Fri May 11, 2018 8:09 am

» Late roman crossbow
by Dark Factor Wed May 09, 2018 10:27 am


    How to know you went too heavy

    Share
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    How to know you went too heavy

    Post by actionbow on Mon Jun 08, 2015 7:45 am

    Laminate recurve. 31" nock to nock. I left it at around 230lb @ 14". It was shooting like a beast, crazy hard. I was just getting the red dot sighted in. About 60 shots in blam!

    https://docs.google.com/file/d/0B4Dp009Fgn7KaGRwVE4zaEVjMjQ/edit?usp=docslist_api
    avatar
    kenh
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 769
    Join date : 2012-08-03
    Age : 70
    Location : Living Aboard a Sailboat in Fort Myers, FL

    Re: How to know you went too heavy

    Post by kenh on Mon Jun 08, 2015 8:09 am

    Too bad -- nice looking prod.   Looks like the fades were too steep.  It broke right where the fade ended.  I don't think I'd have made the "riser" so thick...
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Mon Jun 08, 2015 9:22 am

    You are half right. Mostly I left too much at the tips. I made the fade work too hard. Sometimes it works out...other times...
    problem with a laminated bow is you can't change your mind after you glue it up. I got greedy. I was shooting at around 340 fps, it's kind of addictive.

    This is why I wear safety glasses religiously.

    c sitas
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 477
    Join date : 2012-11-24

    Re: How to know you went too heavy

    Post by c sitas on Mon Jun 08, 2015 11:49 am

    You know speed is nice. What you were shooting is about an average for most compound crossbows. Possible you weren't taking enough energy out of the bow on the shot. Maybe the bolt is to light. That could act almost like a dry fire. The results would be the same. I've both seen and heard this happen. It is quite unnerving,eh.
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Mon Jun 08, 2015 11:56 am

    If I can get "average" compound bow speeds from a home built recurve I will be more than satisfied.

    shooting 440 grain bolts. I just needed to lighten the mid-limb/tip area more.

    c sitas
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 477
    Join date : 2012-11-24

    Re: How to know you went too heavy

    Post by c sitas on Mon Jun 08, 2015 1:39 pm

    How many pounds are you pulling?
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Mon Jun 08, 2015 2:16 pm

    230# @14"
    avatar
    Alan Case
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 14
    Join date : 2015-05-08

    Re: How to know you went too heavy

    Post by Alan Case on Mon Jun 08, 2015 2:37 pm

    Did the limb fail as the bow was drawn, or did it fail on the shot?

    It was a nice looking effort. It looks like the glass may have failed in compression on the belly side.  What is the thickness stack used along the working limb?  Does the limb continue to gradually taper from the fades to the tip, or does the thickness remain constant?  What is the thickness of the glass laminations?  It is asking a lot of the materials to get the high draw weight at the 14-15" draw length, and with such a short prod length, but it I believe it should be possible.
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Mon Jun 08, 2015 2:41 pm

    Ahh...good questions.

    It failed on draw.

    Normally I will laminate the riser between wood lams but this time I tried it behind. I think you are exactly right, the belly glass failed right at that fade.

    It's an extreme bow so I am not surprised it failed. I learned a couple things and I have already bought the lumber and made some adjustments to the fades in the press.

    Great observations everyone. This is helping.

    c sitas
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 477
    Join date : 2012-11-24

    Re: How to know you went too heavy

    Post by c sitas on Mon Jun 08, 2015 4:53 pm

    Giver Action; this kind of thing is really fun. Both for the builder and the watchers.
    avatar
    Gnome
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 409
    Join date : 2011-10-16
    Age : 54
    Location : North Georgia

    Re: How to know you went too heavy

    Post by Gnome on Tue Jun 09, 2015 5:31 pm

    An impressive experiment, Actionbow- I'm especially impressed that no arbalists were injured in the production of this display of skill. Seriously, it's cool to see somebody pushing the envelope with a laminate recurve prod. Hope to see the next iteration soon!
    Gnome
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Tue Jun 09, 2015 5:46 pm

    I'll press it this weekend.
    avatar
    twedzel
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 47
    Join date : 2014-01-08
    Age : 45
    Location : Vancouver Island BC

    Re: How to know you went too heavy

    Post by twedzel on Tue Jun 09, 2015 9:55 pm

    Alan, Excalibur's limbs probably have less working limb than actionbows failed prod, and they draw 220lbs@14"ish draw length and 290lbs@ 16"or17"ish draw length. They are all fiberglass but it proves that it can be done.

    I was just putting together one of my first prods with a riser almost identical to this one thick with short fades. I did this in hopes of avoiding hinging off the fades and getting more working limb. Anyways it popped off when I was testing the wood. But I really liked how the wood alone was bending so I have decided to leave it off and see what happens after laying up the fiberglass (kind of like a bendy handle bow but in prod form). I wouldn't be surprised if the very slight bend in the middle will loosen everything up after binding it in place. But some part of me is hoping that the binding block will reinforce the center section enough to minimize movement.
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Tue Jun 09, 2015 10:55 pm

    There is a big difference between all fiber limbs made in a  commercial compression mold and what I do.

    I'm not worried. 60 shots is enough to convince me it is possible.

    I'll post chrony vids when I nail it. Fingers crossed for 350 fps.
    avatar
    Alan Case
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 14
    Join date : 2015-05-08

    Re: How to know you went too heavy

    Post by Alan Case on Wed Jun 10, 2015 12:56 am

    Actionbow,
    I am pretty sure you are on the path to making it work. I bet the failed limbs did shoot well while they lasted.  I look forward to see how your next ones turn out!

    I am building and testing similar draw weight glass & wood composite bow limbs for flight archery (distance shooting). I would actually be happy with 60 shots, but I push them pretty hard.  The arrows are tiny at around 110-120 grains, so each shot is almost like a dry fire. 

    Twedzel,
    I don't have any experience with the Excaliber crossbow limbs.  Are they solid glass?  It seems like they would be pretty heavy, but they seem to perform pretty well regardless.
    avatar
    hullutiedemies
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 178
    Join date : 2012-07-03
    Location : Fennoscandia

    Re: How to know you went too heavy

    Post by hullutiedemies on Wed Jun 10, 2015 4:24 am

    Karpowicz was getting 350 fps with Turkish horn bows
    http://www.atarn.org/islamic/Performance/performance_table.htm
    But energy efficiency was only 50%.

    What was the efficiency here ?
    avatar
    twedzel
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 47
    Join date : 2014-01-08
    Age : 45
    Location : Vancouver Island BC

    Re: How to know you went too heavy

    Post by twedzel on Wed Jun 10, 2015 9:03 am

    Actionbow

    Its probably not as different as you think. This link gives a good overview of the process for compound limbs. The process of making crossbow limbs will be much the same. Also consider the outer 10% of the limb is taking 90% of the force. If you are using Bo-tuff then you are using the same stuff that most of the major manufacturers are using in the areas of your limbs that taking the most strain. Don't get me wrong, I also think this is getting to the edges of what the design is capable of, but we agree it is doable.

    Alan

    I am pretty sure Excalibur limbs are solid glass, but I also do not have first hand experience with them either. I did a fair bit of research on them for design inspiration. The added weight of all glass vs glass and wood core would be much more of a factor in a longer limb. You can use heavier materials in shorter limbs shooting heavier arrows. Its the same reason why steel is almost unheard of as a longbow material but workable for a crossbow prod.


    Last edited by twedzel on Wed Jun 10, 2015 4:58 pm; edited 2 times in total (Reason for editing : man I shouldn't try writing in the morning)
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Wed Jun 10, 2015 3:26 pm

    Twedzel I typed a long response pointing out the differences but in the end it basically proved you right.

    They have R and D  and production tolerances I can't approach but I also have a attitude toward risk and a desire to do things that a large company doesn't. 

    Also, I'm determined. Money isn't my motivation. Excellence is.
    avatar
    actionbow
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 139
    Join date : 2012-09-18
    Age : 45
    Location : Portland, Oregon

    Re: How to know you went too heavy

    Post by actionbow on Wed Jun 10, 2015 3:29 pm

    My idea is that with wood lam cores I can hopefully get the best of both worlds. The speed of wood and the durability and draw length of glass. Maybe, just maybe my penchant for deep recurve shapes and the beauty of wood will result in something wonderful and deadly.

    c sitas
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 477
    Join date : 2012-11-24

    Re: How to know you went too heavy

    Post by c sitas on Wed Jun 10, 2015 4:11 pm

    Well Action; at any rate , your workmanship is second to none. The thing looked beautiful  before it went south.You definitely  have a rare  talent and a masterful eye. Good job
    avatar
    twedzel
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 47
    Join date : 2014-01-08
    Age : 45
    Location : Vancouver Island BC

    Re: How to know you went too heavy

    Post by twedzel on Wed Jun 10, 2015 5:04 pm

    actionbow wrote:Maybe, just maybe my penchant for deep recurve shapes and the beauty of wood will result in something wonderful and deadly.
    I like your thinking!
    avatar
    Alan Case
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 14
    Join date : 2015-05-08

    Re: How to know you went too heavy

    Post by Alan Case on Thu Jun 11, 2015 2:15 pm

    Hullutedemies,
    50% efficiency is pretty good for an all-natural material bow that is shooting such a light weight flight arrow. The efficiency really drops with lighter arrows and faster speeds. Also, as Twedzel pointed out, at very high speeds, longer hand shot bows are at a disadvantage compared to short & heavy draw weight crossbow designs. 


    I there is some pretty good test data on the Arrow Trade Magazine site. Excaliber crossbows have efficiencies in the low-to-mid 70% range for arrow speeds ranging from 320-380 fps. That is pretty good for a solid glass limb. The Middleton is right up there too. I would expect a well made laminated glass/wood prod should do even better. 


    Alan
    avatar
    hullutiedemies
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 178
    Join date : 2012-07-03
    Location : Fennoscandia

    Re: How to know you went too heavy

    Post by hullutiedemies on Sat Jun 13, 2015 1:27 am

    Alan Case wrote:

    I there is some pretty good test data on the Arrow Trade Magazine site. Excaliber crossbows have efficiencies in the low-to-mid 70% range for arrow speeds ranging from 320-380 fps. 
    Found it - 348 fps was the 73% bolt
    http://arrowtrademagazine.com/articles_pdfs/jan_13/Jan13-MatrixCrossbowTest.pdf

    So Matrix should cast 470 fps with 50% efficiency-
    and this is why one should allways record the energy efficiency. Because it immediately tells the potential maximum performance of a bow.
    avatar
    Alan Case
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 14
    Join date : 2015-05-08

    Re: How to know you went too heavy

    Post by Alan Case on Wed Jun 17, 2015 11:21 am

    I really like how the arrow trade magazine conducts their tests.  They are very thorough and measure the stored energy and arrow kinetic energy for different weight arrows.  They even use two chronographs.  I also figure around 470-480 fps for the Matrix 380 at 50% efficiency (using the virtual mass model) although the arrow would only be around 155 grains in order to achieve this.  It isn't bad performance for solid compression molded glass limbs.  On the other hand, a determined prod builder should be able to exceed this performance level by a good margin using laminated wood & glass construction. 

    Alan
    avatar
    hullutiedemies
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 178
    Join date : 2012-07-03
    Location : Fennoscandia

    Re: How to know you went too heavy

    Post by hullutiedemies on Thu Jun 18, 2015 1:47 am

    155 grains is about 10 grams . I consider that heavy. If I want to go fast I use couple gram kebab-sticks with my inswinger compounds. My "heavy" target bolts weight about 10g.

    Sponsored content

    Re: How to know you went too heavy

    Post by Sponsored content


      Current date/time is Sat Jul 21, 2018 5:48 am