To comb or not to comb your sinew

[Wallski]

I’ve installed sinew by pencil size strips, and combed strips of sinew using a dog bush and I can’t tell the difference in shooting the bows.   When I comb the sinew, it’s more work and I lose about 25% of the sinew when processing it.   I’ve seen Superdave’s horn bows, and his sinew looks super smooth but don’t get those results.   The smoothness results I got was adding sawdust/glue as a topping.

[Eric Krewson]

I am not a sinew expert but have used it on a few bows, I have never combed sinew, just processing it from a dried tendon to fibers is enough work for my arthritic hands.

Once I get the layers of sinew on a bow, I wrap it tightly and neatly with Saran wrap for a few days until the glue starts to set up. This smooths the sinew surface somewhat, after the glue cures, I sand it smooth.

[superdav95]

Thanks wallski!   I would agree on the reduction of at least 25% when combing the sinew vs not combing it.  I’ve noticed an improvement on performance and appearance/asthetics.  The performance improvement is slight in the instances I’ve seen but I suspect it has something to do with reduction of unnecessary mass on the limbs yet doing same work.  The sinew can be an improvement/enhancement on a selfbow or horn bow because of its ability to resist under tension very well despite it relatively lightweight contributing mass.  Too much sinew however can be counterproductive.  This includes excess glue.  I have found that with more glue then needed not only adds mass but cracks a bit when drawing the bow.  Sinew is extremely strong in tension and you will not likely break it but it can still fail as a backing if there at large inclusions or gaps due to uncombed strips.   This happens as the sinew dries and shrinks.  The crossed over fibers create these voids which can if large enough be a problem.  Little ones not likely a problem but if large enough I’ve had them also create a hinge on the core and break the wood while the sinew remained together.  So long story short it’s very unlikely your sinew will fail or break but what it’s doing to the wood or horn underneath it can cause a break elsewhere.   I’ve also had test bows  become too unstable due to excess sinew in relation to the belly of the bow and it’s ability to balance in compression to the sinews tension.  Relative thickness on a horn bow is important and also with backed self bows for example.  I’ve not had great success with a 50/50 split on thickness with wood to sinew on some bow woods.  I generally shoot for 1/3 sinew to 2/3 wood.  This will give really good performance too.  Just some hard lessons learned along the way for me anyway.   

[StickMark]

went to search the site on this very question.
Thanks

[WhistlingBadger]

On my most recent attempt, I tried combing the sinew wet, right before I dipped it in the glue (I always soak mine in warm water for a few minutes to soften it up before I apply it).  Running a plastic comb over it makes all the fibers nice and parallel, and removes any loops or snags.  It seems to go on a lot cleaner that way. 

[Wallski]

Hey Eric, I’m going to try wrapping my next bow with Saran Wrap.   I thought of about using fabric tape but, assumed it would stick to the sinew, creating another problem.
Thanks for responding Superdav, I’ve always admire your craftsmanship.  My first couple of sinewed backed bows, were slow due to excess glue, I use Titebond 3 watered down, if that makes a difference, from watching Ed Scott’s YouTube, mentioning he doesn’t use hide glue anymore.

WhistlingBadger, I only combed the sinew that I ran through a dog brush, using a hair comb once placed on the limb to keep the fine fibers straight.

I have a addiction to building bows, and from the number of bows some of you build, I was wondering how some of you are still married, because my wife has complained multiple time about how much time I spend in my shop.