Wood Prods

First topic message reminder :

Hi All,
I "carved" the beechwood down to about veneer thickness and it's still 'stiff as a board'.  That's okay because I've set it aside and a hazel stave is coming along nicely . . . I think; I'm nearly at the point of needing a tillering stick (has to be a milestone in the life of a crossbow builder).  I'm going to try, if it doesn't become too time consuming, to work in a wippe-like addition to it.  It will provide some measurements for when the time comes to make the one for the finished crossbow. 

Anyway, Mac, I'm looking forward to what you have to say about prod width vs. thickness; I think it will be an issue very soon - if not already. 

If anyone has experience with cutting new wood in the forest any thoughts would be much appreciated.
Godwin

This one pulls about 100 kg or bit more with 123mm power stroke ( 220#-250#/5" imperial)


String is 48 cm.
Bow is yew branch stave, 33x23mm mid-limb spread out legth about 60cm . Stave is steamed to brace-height deflex.

Just scale that up about 35% and you get 26" wide bow with power stroke just under 7". Draw weight for same limb width could be up to 300lbs . So 180#/7" should be trivial exercise.

Wood prods really benefit from high deflex. For given power stroke limbs can be about twice as thick as they would for a low braced, reflexed longbow type tiller.

hullutiedemies wrote:This one pulls about 100 kg or bit more with 123mm power stroke ( 220#-250#/5" imperial)

Some updates


3 axle lock, a rollernut/claplock hybrid ( a classic design, there are drawings somewhere in this forum)
Carbon fiber lock plates, delrin nut, tickler shaft has aluminum tube extension.
Maple tiller.

Some excuse of a finish:

I tried to cast epoxy resin over the carbon to make it a bit nicer. Did not go very smooth.

The black goo behind the clap is silicone filler shock absorber.
Bridling is jute, nut is held with cotton line.




Still have no chrony.
But at distance test a 21gram bolt went 190m
and 32g bolt 150m
when launched at 50 degree angle.( Might have gone further with a bit shallower elevation, but I wanted to make sure the bolts land upright so they can be found.)

This was expected as the potential energy is ca. 60J and calculated virtual mass couple grams. So this handles heavy bolts like a 50#-60# longbow.
Optimal bolt mass should be about 4g.
I have lost a few 4-7gram bolts into a lake in calm weather, but they went too far for the splash to be seen.

I use a sonic timer on the phyphox app. It measures the difference between 2 sounds, like a bowstring going “twang” and a bolt hitting a target.  If you shoot a measured distance, say 20m, you can calculate speed.  It’s a crude measure but will give you a ball-park estimate

I am familiar with that method.
And I know how fast my bows shoot. But I am not telling.
I do not have "The Interne Bragging Rights", since I cannot post pictures of a chrony screen.

Fair enough.

Interested to know your thoughts on deflex now that you have been shooting a heavily deflexed bow for a while

Not much to add to my previos posting almost decade ago:

https://thearbalistguild.forumotion.com/t1113-observation-about-brace-height

But since then I have left several of my bows permanently strung for several years, and there has not been any observable reduction in draw weight. So that is one more benefit.
This is superioir way to make a wooden prod. Easier, faster, more durable, more powerful.
And historically accurate. As everybody has been using them.

Thank you, that is really useful information

For what it’s worth, here are my thoughts on early medieval  wooden crossbpws in Europe.  There are lots of advantages to deflexing and I am really greatful for the work done by Hullu as he has shown that deflexing cures the biggest problem with wooden laths - you can't leave a straight or reflexed wooden lath strung without damaging it.  I have no doubt that some makers absolutely would build their laths with deflex.  There are very few wood laths to have survived from the period.  None that I know of can definitely be said to have been deflexed.  I know of 2 that were sinewed and 1 that was reflexed.  I know of three more that show a lot of set and one or more left strung for centuries that became permanently deformed so much that we can't say what the original shape was.  All told that's about ten survivors out of perhaps several million laths.... I imagine that, like nowadays, every maker/guild/region had their own preferred approach the outcome depending on the client budget and the purpose of the bow - a hunting bow being different from a war bow or a target bow. A cheap bow being quickly made from low grade timber, a more expensive bow being top grade wood and the highest even being sinewed and able to pass for horn bows.  I imagine that many wood laths for war bows would have been heavily deflexed , art from the period showing apparently wood laths shows them with very thick sections and deep brace heights and deflexing would allow such bows to b easily braced and be braced for weeks or months if necessary