Yew Composite prod:help needed

First topic message reminder :

Hi there

I am new to posting in this forum but have used it in previous builds. I am looking to build crossbow prod useing  Yew and sinew only. Horn seems too time consuming. 

I would like to follow a build I have seen by the user OrienM:

https://thearbalistguild.forumotion.com/t1655-yew-and-sinew-prod-help-needed

However i would like the draw weight to be at least 250lbs. I know this is a lot to ask without useing horn but is anyone able to give me a guess as to the dimensions for what that might be before tillering.

On a side note the design of the crossbow is very unique as it allows the crossbow to cocked in under 3 seconds with a draw weight of 400lbs and utilises this speed of draw with a magazine of bolts. The materials used were available to anyone living in the period of when crossbows were still used on the battlefield and so from a historic sense this build is very interesting. The design is relatively compact and very easy to use with minimal effort in the loading process. 

I'd very much appretiate any advice/help, and would be happy to reveal the design in a PM

Regards

Ed

Ok, so, here is my lath, it is a yew branch with the sapwood left on, one course of sinew, buffalo horn nocks v-spliced on 4 inch long splices which is why the ends of the bow are a bit too stiff.    Made last summer, I covered it in freshly cut birch bark about a month ago, the bark is still not dry but I only know this because the oil paint reveal coat is still not fully dry - the oil in the bark is keeping the paint wet. The lath is bending to a string movement of 11.5 inches, somewhere in the region of 115 pounds.

  Dimensions are 28 inches from nock to nock, width at centre is 1 3/4 inches. Width at nocks is 1 1/4 inches. I should have gone a little shorter but I don't think I would have gone under 26" for an 11" draw length. 

The one-year drying time for horn-bows is because the wood is still green - horn bows use un-seasoned timber to cope with the extreme reflex they pull into the bow when they "pretzel" it.  If you are using dry timber then a much shorter drying time is ok. - carefully monitor its weight, it will lose weight as it dries, once the weight reaches a stable minimum it is dry then add a bit more time to be safe.

Incidentally, the photo shows the main reason for removing the sapwood - by the time I'd finished tillering, most of the heartwood had gone - you can see the darker heart-wood as a stripe running along the centre of the lath- but the bow still hits really, really hard.  Next time I do this, I intend to go with no sinew and only the yew with the sapwood reduced to no more than 3mm but if I do go with yew and sinew I will completely strip off the sapwood

That looks nice stuckinthemud1! I bet it is fast, a long draw and no deflex added...

I got out a ruler this morning and measured my crossbows' prods...both bows have osage/sinew prods, similar in design but differing in size and draw weight. They are full compass tillered (no stiff central area), deflexed to relieve compression forces and aid in stringing, and asymmetrical (the upper edge of the prod is a straight line). I tend to use conservative draw lengths, more like 1/3 than 1/2 of NTN length.

Prod #1 is 35" NTN, measures 2" x 1 1/8" (including backing) at center, 1 1/4" x 9/16" at tips, and is deflexed by 4"; brace height is 5", power stroke is 9" and it pulls about 150#.

Prod #2 is 30 1/2" NTN, measures 1 3/4" x 1" at center, 1 1/8" x 9/16" at tips, and is deflexed by 3"; brace height is 4", power stroke is 6 1/8", and it pulls about 200#.

For archery bow-style draw length measurements add the brace height and power stroke numbers together...prod #1 draws 14" (9 + 5).

If you wanted to get a faster shooting bow with white woods specifically wouldn't you heat treat the belly?

banuvatt wrote:If you wanted to get a faster shooting bow with white woods specifically wouldn't you heat treat the belly?

You certainly could; I've found heat-treating very effective on whitewood archery bows.

I tried it on a crossbow prod it certainly worked as far as I'm concerned.

I definitely would heat treat, I heat treat all my bows, irrespective of wood-type and they all improve dramatically, yew included.  I didn't heat treat my yew/sinew lath as I tillered it after sinewing and you can't heat treat a sinewed bow, but if I had it tillered before applying sinew I would have heated it.

Are you going to paint the birch bow backing like how the Turks did? I do like how decorative their bows look they often are painted with like this gold gilding and have like flowers or some other type of design.

Not in the Turkish style, the Europeans painted their bows in their own styles. Just got to find an image of a pattern I like that's clear enough to copy. Most bows are too badly damaged or too badly photographed to be of use.

How about this? 

Anyone of these that I shared above? Search up Andreas Bichler, as far as I could tell he looks like a renowned crossbow maker. His work is pretty impressive especially with the painting designs of composite crossbow prods.

Hi there.

Sorry just seen that there is a second page. I don't seem to get notifications for this. 

Been in the workshop all day. I wanted to practice on a bit of yew that wasn't perfect as i'm in short supply. got it bending evenly with the dimensions Andrew suggested but leaving on a few mm just to get it to a rough size before I add the sinew. just waiting for a spring scale to measure its draw wieght. At a guess I'm well over 350lbs at only 6 inches draw so i have left enough to get it down to the right amount. I know I shouldnt tiller until the sinew is added but I guess theres no danger in flexing it a bit.

I have reduced the sap wood to about 25% of the thickness and i have at least 3 untouched growth rings still there. 

Not sure If i want to waste time actually sinewing this piece as there are two knots that are really making me worried.

Also I dont think the wood has been seasoned enough. Is it ok to add sinew to unseasoned yew - There is definitely too much moisture on this piece. 

My good stave has been seasoned for 5 years... I can get a moisture reading but the person i bought it off said it was perfect moisture and hes a bowyer.

P.S did you see my video of the first working prototype Orien. I sent you a DM

Maybe try heat treating it? Just an idea if it seems like there's too much moisture left over.

Yes i thought about that but lots of people say that you shouldnt try and heat yew as it splits easily.

Don't force dry it, can you post a picture pf the lath?

stuckinthemud1 wrote:Don't force dry it, can you post a picture pf the lath?

Here is the untouched good piece of yew. was going to be for a longbow but will make 2 crossbow lathes. 

No picture of the current lath but here is a drawing of our set up for tillering. very elegant as you can see. the top right shows from memory the bend we got.

If you can post a photo of the lath, we can see the knots and advise you how best to deal with them.  Are they solid or do they have a black ring and are rotted out?  Do you know what a differential winch is?  They are very easy to make

Can you not leave it out to dry? Maybe strap it to a board so it doesn't warp. I have seen people do this with bamboo arrow shafts leave them out in the sun to dry but also tie them in a bundle together to avoid warping. It's just an idea, since supposedly maybe using a heat gun or a fire would be too aggressive.

If you can then buy a moisture meter, if not then weigh the wood every day and see if the weight changes, if the weight is stable the wood is dry. Lovely lookin stave by the way. Can you post a photo of the knots you are worried about, from above

stuckinthemud1 wrote:If you can post a photo of the lath, we can see the knots and advise you how best to deal with them.  Are they solid or do they have a black ring and are rotted out?  Do you know what a differential winch is?  They are very easy to make

yes so here is a picture of the worst knot on the good seasoned stave. 

the second pic shows how the bottom of the stave is perfect with no knots

The uploader has broken.. here are the links


https://scontent-lhr3-1.xx.fbcdn.net/v/t1.15752-9/65738971_634884817010990_4612507018605887488_n.jpg?_nc_cat=109&_nc_oc=AQnTkFaMY8UfqCr08zlhaCkncrveqrLDXqnZ18W76ifYnC2OWwtm48MndOMgpNFCSdg&_nc_ht=scontent-lhr3-1.xx&oh=5fa006b58de0eac4068b20c3cd5371c6&oe=5DE66F59

https://scontent-lhr3-1.xx.fbcdn.net/v/t1.15752-9/67847993_2227010830943428_1760950773342011392_n.jpg?_nc_cat=111&_nc_oc=AQlwCS0sK4ZaolRtiTrGWGvZAu0_7Ad3_LOpQLnxpjQYfyWQjaCVF8Pq15BuEpxPQY0&_nc_ht=scontent-lhr3-1.xx&oh=86667b9b3f708f71cefb6c0fdb11efa6&oe=5DA0EB5B

How far along the lath is the knot? It is a problem but not if it is right at the centre. If the underneath is good then just use the heartwood and sinew it might be best

stuckinthemud1 wrote:How far along the lath is the knot? It is a problem but not if it is right at the centre

So the second from the left shows the stave ive got. you can see the knot 3/4 of the way up

https://scontent-lhr3-1.xx.fbcdn.net/v/t1.15752-9/s2048x2048/66176967_420051755517406_8906411937265352704_n.jpg?_nc_cat=107&_nc_oc=AQnWToAbr6wGHZP3jLxi9vTf2YzSuo69YgH4O8CjSvtwwM4KQJAJXLic0mdL-Dvtuww&_nc_ht=scontent-lhr3-1.xx&oh=c1a015231fca1801a274d25aa6e1cf4e&oe=5DDF4BCB

Dont forget im adding sinew to that should help with the strength right?

also dont forget im able to get a whole lathe from the bottom of the stave with no knots at all