A New Take on the Bowsaw....

[jimi43]

Hello again everybody.

Over the past few months, having been forced to sit still and convalesce, to keep myself from going mad....I decided to work on some more prototypes for KT Tools...a project I plan to expand when I retire in a few years.

I know I will be making reproduction vintage infill planes...possibly cutting tools, screwdrivers etc...but I thought it would be interesting to look at making a bowsaw...following the traditional design but with a new twist.

I have always been fascinated by the technical advantage of the English Self Longbow....the famous weapon which was instrumental in winning a few battles with our dear friends over the Channel....

Traditionally made of English Yew...this weapon was also responsible for the Urban Myth (?) of the gesture unique to the English....and hence the name of my version...

The TWO FINGERS MARK BOWSAW.......

Still in the prototype stage and with the assistance of Steve (Orcamesh) and Douglas (condeesteso) who provided the stock (thanks guys!) and Ian at Tuffsaws who kindly gave me some offcuts from bandsaw blades...it is slowly coming to fruition...

The concept of the traditional yew longbow is the use of the lighter coloured sapwood on the "back" (which is strangely the front facing wood)...and the beautiful orange heartwood, forming the inside curve of the bow....a kind of natural lamination.

The idea is that one wood stretches and the other is compressed and they both want to do the opposite so when released...the bow has much greater forward power than other bows. The Two Fingers Mark bowsaw symbolises this wonderful invention and makes a more attractive bow...but to some extent...the same principle applies...

The traditional bowsaw works by having two "cheeks"...the bow bits...separated by a "stretcher"....

The thin blade which would snap if bent is put under pressure between two pins by the counteraction of the twine which is twisted between the horns of the cheeks....

This is then locked into place by simply slipping over the stretcher when the tension is at optimum.

The handles at each end of the opposite cheeks....have steel shafts which are split to accept the blade...and a hole is positioned halfway along to accept a pin to secure the blade before tension is applied....

One end is larger than the other....

...and is the end that is held when in use.

I chose to use steel for longevity over brass which is traditionally used...and at some point in the future, a locking mechanism will be incorporated to prevent the handle twisting when in use. The handles are made of rosewood...yum!

In order to match the contrast of light and dark wood in the handles...I have laminated the stretcher with some American walnut and yew sapwood....

...this sandwich being much more resilient to shattering or splitting than the primary woods alone...this part is under immense pressure!

Overall finish is with cellulose sanding sealer...followed by Tru-Oil...an amazingly tactile finish for a hand tool.

There is still quite a bit of work to be done on the blade technology.....and the next prototype will be a larger version...with rip and crosscut ammunition...but for now...it's coming along just fine....

A huge thanks to my friends here for their help and guidance.....

Jim

 

[AndyT]

Very pretty. I especially like the use of lobelia!!

I do like the idea of exploiting the different properties of the wood. Is that the same bog oak on the handles that you used for your special screwdrivers?

I'm a bit puzzled by your comment "and at some point in the future, a locking mechanism will be incorporated to prevent the handle twisting when in use" - this sounds like a complication to solve a problem which is not there. You need to be able to twist the blade round, to get clearance, and then you want it to stay still in use. I have a nice old model which I use with a coping saw blade, and also a couple of school woodwork productions with longer blades on. None of them rotates in use - the tension on the blade is enough to keep it set. There is a complicated American patent model which links the two ends with a loop of chain to keep the ends in step, but that's just an oddity.

If you do get on to making more - and I hope you do - you could extend the principle to larger european style saws. You could also try the sort of kinked blade that Frank Klausz uses to saw dovetails automatically. (video here)

Good luck with this!

 

[jimi43]

Thanks Andy.

To take your point about locking...the thing I want to do is to lock both ends at the same position...whether this be straight cutting or an angle...up to 90 degrees to vertical.

Even with tension on....I find that when using the saw, the handles tend to drift out of line a bit...I noticed this on the Marples I have and in discussions with Douglas...I believe this happens on his Gramercy too.

I am a bit nervous about tensioning this saw up too far at the moment as I haven't quite got the right blades for it yet and I don't want to end up snapping anything having just finished it. In theory...I can see that the tension would tend to keep the handles in line...I am far from an expert on these things...learning all the time!

The handles are Indian Rosewood I'm afraid...I may make a special edition one out of bog oak....I didn't want to waste it on a prototype if it were not to work....maybe the next one! 8)

Jim

 

[woodbloke]

Jimi, this is a nice variation on a very ancient (possibly 2000 year old) saw. The most glaring and obvious thing that I can see is that you appear to be using leather for the cord to apply the tension. Leather in itself will have a lot of 'stretch' in itself so the tension on the blade that you thought you might be able to obtain will be considerably less than you originally intended. What's actually needed is a cord made from a virtually non-stretchy material. Fwiw the Romans used animal sinew in their catapults and other engines of war.
I made a bigger frame saw variation on one of these a couple of years ago and used a length of 6mm studding to wind on the tension and like you I used a bit of one of Ian's bandsaw blades, in my case a lump of 25mm stuff. The tension that can be wound on without damage to the saw or other components is truly staggering so I wouldn't worry unduly about fine tuning the design...it's worked well for the last two millennia :lol: - Rob

 

[jimi43]

Hi Rob

Well spotted my friend...I realised after I used it that it stretched too much...even though I appear to have taken all the stretch out of it now...

It is for the photos actually...I liked the look of it...but I have some yachty stuff that Douglas also gave me.. (a mine of stuff that guy!).....which I will spend the afternoon making into a cord....and I have some French Dacron (how cool is that!) coming....which I thought would be a touch of fun...given the name!

I looked at the studding design...which was used quite extensively with a toggle thingy in the middle...but I kept the twine in the end...closer to the bow analogy!

Cheers for the comments mate...most useful...especially the confidence on the tension!

Jim

 

[Harbo]

Jim, sorry but I think your longbow concept is wrong in this situation.

The longbow was designed to recover very quickly to transfer momentum to the arrow.
In the bowsaw the cheeks are acting as a lever - the pull from the tightened cord acting in the opposite direction to keep the blade tight - the stretcher acting as the fulcrum. Any strong type of wood (or metal) would achieve this.

Don't get me wrong it really looks good and a very nice piece of work.

Rod

 

[jimi43]

Hi Rod

I know mate....it is more symbolic than technical but it looks better than beech and I can always say "quick blade change design"....can't I!? :mrgreen:

I have a feeling that this might generate some interesting discussion!

Cheers

Jim

 

[Harbo]

Jim

"quick blade change design"

I like that - if ever you market it I am sure our cousins across the pond will love the English Longbow theme?

Rod

 

[jimi43]

Jim

"quick blade change design"

I like that - if ever you market it I am sure our cousins across the pond will love the English Longbow theme?

Rod

Indeed my friend.

The concept of robbing the rich to give to the poor is alive and well mate! :mrgreen:

Jim

 

[pedder]

Hi Jim,

this is a very fine saw, my friend. Congrats to the great work.

the knobs would be nice in yew, too. And I do like steel over brass for light woods. (for dark woods, too.)

Cheers
Pedder

 

[Richard T]

Absolutely cracking, that, Jim. Love the use of Yew like that.
I know that Rosewood is gorgeous an awl ..... but it's not that English ... and American Walnut?
[-X

I heard from Robin Williamson (the bardic Harper late of The Incredible String Band) that the pieces given to the most pressure in a harp frame (a lot of pressure) are made from Hornbeam. Not so pretty maybe but a bony - fido native.

 

[MIGNAL]

I had the very same problem with the Bow saw that I made i.e. a tendency for the blade to turn or spin too easily. Fortunately I had a very well made and rather elegant old Bowsaw that had tapered rods. Obviously someone had experienced the very same problem and the tapered rods (and matching holes) was the solution.

 

[Klaus Kretschmar]

Jimi,

many congrats on a beautiful saw. It is that nicely done, I'm hooked with it! To my eye it hits the perfect balance in all senses. Extremely well done!!

Klaus

 

[Racers]

Hi, Jimi

Very nice, Love the Yew

Pete

 

[dunbarhamlin]

That is a fine looking beast.
One thought that springs to mind is, that whilst there are four (more?) commercial makers of bow saws, I can't think of anyone offering frame saws. Perhaps something to add to the quiver.

the knobs would be nice in yew, too. And I do like steel over bras for light woods.

Hey, this is a family show :lol:
Wunderbras I am familiar with. Steel over bras bring to mind images of Madonna.

 

[pedder]

And I do like steel over bras for light woods.

Hey, this is a family show :lol:
Wunderbras I am familiar with. Steel over bras bring to mind images of Madonna.

#-o #-o #-o #-o #-o #-o #-o

(corrected the typo.)

 

[bugbear]

I had the very same problem with the Bow saw that I made i.e. a tendency for the blade to turn or spin too easily. Fortunately I had a very well made and rather elegant old Bowsaw that had tapered rods. Obviously someone had experienced the very same problem and the tapered rods (and matching holes) was the solution.

All the fixings I've seen on old saws are taper fit.

I don't blade rotation is a big issue - if you use the traditional grip; very little torsion on the big handle, and none on the small.

BugBear

 

[AndyT]

BB - thanks for scanning that photo - I was going to refer to the same one. It's from Charles Hayward, Tools for Woodwork.

It also shows the importance of nicely chamfered edges where you need to grip round the side piece (not just the handle) and that ideally the saw securing pin or whatever is short enough not to scratch your fingers.

The Frank Klausz video also shows that the larger framed saws are gripped by the frame, not by the turned handles.

This all makes sense if you try and use one - I find the turned handle on its own too small to be comfortable.

 

[jimi43]

Cheers for the feedback and comments guys!

To the two lawyers...Pedder and Klaus...I am humbled...it did enter my head that trying to make a saw amongst such fantastic artists was going to be a big call....but at least it is fantastic to have a forum where so many craftsman assemble and are high targets to reach for (some day! Yeh right!)

The complexity of what appears to be a simple tool is amazing and furthermore...the knowledge of members about the little nuances that make it work properly. I shall try the tapered rods and sockets on V2! Thanks MIGNAL for that gem!

Yes Richard...I felt a bit bad using American walnut and if I had a long piece of another native wood I would have used it. I want it to be dark...I suppose I could stain hornbeam...mmm idea!

dunbarhamlin...frame saw....great idea...stored for future thoughts and research.....

BB...thanks for the photo on use...that was something that was confusing me but makes sense....I am not so worried about the locking mechanism now...but it is still in the tuit drawer! Thanks for the confirmation Andy....I shall seek out that reference too!

And last but not least...thanks Peter for the kind words...I love the yew transition too...blinking nightmare to work with though...and I still haven't got over the fact that I am probably now terminally poisoned!!! :mrgreen:

Cheers all!

Jim

 

[Richard T]

A friend of mine - another tree surgeon - once stashed some long straight Yew he cut just in case he ever became aware of a bow maker (what's the proper word? Fletcher is arrows ...) who would, of course, jump at it. Years later he saw a guy advertising himself as the last English longbow maker. He rang him up and couldn't give it away to him. He said that using English Yew (T. Baccata) was too much like hard work and that he used something else - I forget - maybe something American ....
So anyway Jim, you're not the only one to find it hard going. I also remember seeing R.Underhill having great trouble making the bi - sap/heart strip for a spring pole powered toy car. I think we can safely say this stuff ain't easy.