I can't believe this worked- 3rd bow

[Rufledt]

Here's yet another red oak board bow.  This one I decided to make for myself and figured if it broke i'd still have fun making it.  Entirely red oak from home depot:



It's Micmac-ish, 71" ntn, about 45# @ 28".  The back bow is about 30" long.  It's made from 2 1/4"x2" boards glued together with some reflex, and then thinned a bit but it's still fairly stiff.  I think it takes about 80lbs of force to bend them back down flat.  I figured 30" because that's about where it would have to be for the string to lay down along the main bow when being drawn as per a design I saw in TBBv3.  I don't have a f/d curve to support the idea that it increases energy storage, but the bow does pull fairly smoothly with no stack.

I tried to make the tips as light as possible and had some fun trying my hand at carving the complicated string groves:

The last 7" or so don't bend at all and are as light as I dared to make.  the limbs on the main bow are actually narrower than the last board bows I made (which were significantly lighter draw) but the board has a much better early/late ratio.

After seeing coaster500's locator grip, I wanted to try one.

I held the unfinished handle where I wanted and used a pencil to mark my finger locations and it feels super comfortable.  you can also see how I attached the short strings.  I had a different way of doing it that looked much nicer but it didn't prove reliable, so I just drilled into the handle and mounted 2 1/2" oak dowels that I had left over from making some planes.  It's not as nice looking, but it holds up.  I forgot to get a picture of the other side of the handle, i'll do that later.

Here's the string grove on the back bow:

I can adjust the back strings when braced by pushing this down and moving the string out of the grove.  the string is then loose enough to remove from the dowel and retie/twist to adjust. 

I was trying to figure out a way to keep them balanced, and here's what I came up with.  A string with the same mass, length, and tension will resonate the same frequency.  I made both these strings at the same time with the same number of dacron strands, tried waxing them the same amount etc... and the length is the same.  This way, the only variable is tension.  If I pluck the strings and they have a different pitch, the higher pitched one is tighter.  i don't know how good this method is compared to other ones, but it's all I could come up with (thank you physics of music class in college!).

Here's my full draw at 29.5":

The tiller didn't end up perfectly even.  The upper limb bends a little more (it measures about 1/8" more bend at brace height) and a slight twist makes the difference appear worse when viewed from the side the photo was taken.  That limb took just under 1 1/2" set compared to the lower limb's 1 1/4". 

Most of the set seems to be in the mid to outer limbs, and if I were to make another I would make the limbs wider mid limb and outer limb.  Next time I guess.  It's by far the fastest shooting of the 3 red oak bows, but it also has the lightest tips, least set, and the highest draw weight by a good margin so it's probobly not the 2nd bow design which did it. 

I wonder why this bow is thinner and yet took less set, if it has to do with the denser wood or the design.  I had a slight theory that the 2nd bow and small strings takes a lot of tension load, making the main bow do more of the compression in comparison to a normal longbow.  This might mean the compression load is spread more through the thickness of the limb, making more wood do the work and therefor ease the compression load on the surface of the belly.  Just an idea, proboby not accurate because i'm a noob. 

I'm finishing it with the same linseed oil as the others, and i'm thinking of doing another wrapped handle like I did on the last bow

It'll probably hide the formed handle, but at least it'll still be comfy. 

More target practice soon, i hope and then I can report more on how it shoots.  I've only been shooting at my own little target from 5 yards or so, so it's hard to judge if it is truly as inconsistent as a guy at an archery shop around here told me micmac bows are.  I am inclined to believe him since it's a bugger keeping these extra strings balanced and at the same tension from one brace to the next.  Only time will tell if it ever settles and if the bow even survives. 

More pics coming when I get the handle done!

[AJMag]

In the words of the little neighbor kid... "That thing is sick!"  Really cool bow, like the tips.

[soy]

  cant wait to jear how it shoots for you...cool beans man!

[toomanyknots]

Friggin awesome. 

[Rufledt]

I finally wrapped the handle:

It's dacron.  It kinda reduces the form fitting nature of the handle, but not entirely.

Also I noticed a problem:
 
By the time I noticed the checks, It had already reached just under 1 1/2" of set and it hasn't gotten worse with shooting today.  I may have caused the problem by bracing and drawing without letting the short strings settle in.  When braced, the strings make a much higher pitched ring when plucked and I have to do a bunch of short draws and progressively longer ones until they settle in.  Once the pitch is lower and both strings match, then I do full draw.  I wonder if the checks were also caused when I was playing with different tensions on the short strings to raise the draw weight. 

When I noticed the problem I loosened the short strings a bit (when unbraced they now hang very limp) and wrapped the limbs like shown:

It's just artificial sinew tied on so it doesn't add any draw weight, i'm just hoping if the bow does blow this will stop hunks from flying. 

I guess now all there is to do is keep shooting and see what happens.  Like I said it had already stopped taking more set by the time I noticed, so i hope it just stays like this.  If it does get worse I guess i'll just have to make another!

Do any of you guys have a trick to stops checks once they begin?  Is this a terminal problem?

[Jodocus]

Cool piece, the tips look awesome! Hope it lasts!

[Rufledt]

Random thought-  Has anyone ever tried making a continuous string version of something like this?  Something that just connects on the back near the handle and goes over the main bow tips like it goes over the short bow tips, it might be interesting to try.  Maybe for the next one...

[Badger]

  The bow came out very nice!

[Rufledt]

Update!

I shot about 100 shots today and it took a little more set.  It's almost 1.75" just unbraced set, and what it took was mostly in the outer limbs.  It appears to want to be whip tillered, so the next one will have to have a bit more wood further out where there is more stress.  Despite the set, it hasn't lost as much early draw weight as I suspected.  I'm guessing it has to do with the back bow which is already under some tension when braced, though not as much now that i loosened the strings to reduce some strain.

I may make the next one (when I get to it) out of some other wood, since I can't bet on finding another red oak board that's quite as good as this one was.  There's a local lumberyard I'm gonna check out this week and their website shows a lot of variety.

[JW_Halverson]

Crazy stuff.  I used to want to make one of those...but I got lazy.  Kudos to you for taking on such a complex project, and more kudos for pulling it off.

[Del the cat]

That's some funky wood work. Looks very 'Arts and Crafts Movement' almost surprised there isn't a carved mouse on it.
(Dunno if that makes sense on your side of the pond)
Nice work, big project.
Like JW H says, kudos
Del

[DarkSoul]

Those aren't "checks" but chrysals. Those occur on the belly of a bow, when the belly is doing too much work and basically collapses to some extend. If the chrysals remain as small as pictures above, you may not need to worry. But if they progress, or if there are only a few per limb, if may be fatal. Run a search for 'chrysal' on this forum, or possibly 'fret', which is a synonym.

The bow came out really cool! I like your ingenuity on those tips. I'm surprised the bow takes set in the outer limbs, because those parts are hardly bending in the full draw picture. A bow can't take set where it isn't bending...did the tiller change, or is the set located midlimb after all?

[Rufledt]

Thanks!  I've read a good deal on the arts and crafts movement (part of my recent foray into furniture making) so maybe some of it bled over?

JW-  Make one! don't get lazy!  this thing is pretty sweet, and before this started failing (my fault) it shot real nice.  It still does, just not super awesome.

I did a good deal more shooting today with it.  It took no additional set, and the chrysals have stayed the same.  I should also mention this is with considerably less tension on the back strings, taking pretty much all of the preload off of them.  It still has a fairly stackless draw of a 71" ntn bow, but not the early draw weight it had before the chrysals occured.  I guess I can leave it as is and have a shooting bow, or raise the weight and risk breaking it.  Like I said when I made my wife's bow, sluggish is better than broken, so i'm gonna leave it and start a new one.  I guess I'll have to live with an average shooting, cool looking bow with very little hand shock.  I think I'll live. 

Here's a tiller shot I just took now:

Does it look much different to you guys?  with so few bows under my belt i'm still not confident in my tiller eye.
this is after the few hundred arrows from the last couple days of shooting.  I think if i had started with the back strings this loose, it wouldn't have taken as much set, but it kinda makes the back bow less important (except for looking really cool, which I think it still does quite nicely).  Looking at the limbs now, the crysals seems to be spread evenly (and lightly) over the outer half of the bending portion, and the worst few of them didn't get any worse today.  only a few per limb are bad enough to see with out looking too hard, most are only 1-2mm long.  I guess the set is outer-mid limb, it's the outer half of the bending portion.  I guess I just overpowered the belly wood.  I don't know exactly why, but the next one I make will be significantly wider.  This was only a 1.5" wide board and the taper starts way too early.  Just not enough wood for this design/weight.

I read what I can find about this design and it seems pmost eople say the back bow forces the outer limbs to do more work, and it appears to be mainly compression stress.  I'm guessing a lot of tension is taken over by the back strings?  I don't know for sure.  Another thing I read said to tiller the main bow slightly whipped because the back strings pull the inner limbs into bending, but that's the opposite of what I've found here.  That may have been the penobscott design, though. 

I'm still wondering if anyone thought of doing a continuous string version?  Just one long string wrapping all the way around?  I'm thinking of making the next one like that (and wider limbed) and if it doesn't work well just cut it down and make conventional tips for 3 strings.  Maybe i'll try 2 strings, one for the main bow and one for the back bow, just suspended over the top?  Has anyone tried any of this?

I'm hoping either of these ideas would help eliminate my problem with uneven back strings.  Right now for the first couple dozen shots I have to keep checking and balancing, and then once every few dozen check again.  If it wasn't so freakin cool looking I wouldn't bother with this design!