Another longbow build-along...

[red]

Looks like you'll have a great second career when you retire...wish I had those skills.

[ghost]

smj:

To bad Illinois is not closer, I have more Osage than I can use in my lifetime. Long, straight logs up to 18' is dia., cut boards, and of course living trees. Even though it is nasty on tool edges it is one of my favorite woods to turn.

Ghost

[royden]

smj - we have trucks heading east every once in a while. If I hear of someone coming back empty I'll give you a shout and see if you want to schedule a delivery somehow.

[smj]

That would be grand! I would certianly be interested. Thanks very much guys!!!

[smj]

Back to red's bow...

So, let's get to putting a string on this thing! I start out by doing a trim job on the limbs as mentioned and shown a few entries back. These facets you've made on the belly will now be used to control the tillering process. To change the tiller, remove wood from the center of the limb. To change the draw weight, remove wood in equal amounts from both of the side facets created on the belly stock. The next step, I floor tiller a bit. By this, I mean to say that I put the limb tip on the floor, or my bench, and flex the limb. The limb has to flex, or more belly wood has to be removed from the side facets until is starts to flex a bit. Looks like this -

Here is the limb unloaded, no flex, but in position -


Now I lean on the limb, supporting the bow at the grip and then also at mid-limb on the other limb, just enough to see that the limb will flex -


At this stage - I use a sander to help adjust the limbs to where they flex a bit. I take wood from both side facets and also a bit from the middle of the limb. I try to do this in equal amounts, quickly, but only in small amounts! WARNING - high speed belt sanders take off material very fast. If you pause for even a 1/4 second, you will get a non-even result that will cause additional problems for you. This needs to be done evenly, without forming thin spots in the belly wood. Play a bit with this tool before using it, or use a very fine sandpaper that won't allow for large operator errors! Of course, then you might as well use something else -


So, you now have a limb that moves, wiggles, shows some flex. Once the bow is ready for the tiller tree, you have to cut nocks in it so that a string can be used. Here are the steps I use -

Mark a 45 degree angle line where the limb measures at least 1/2 inch in width -


I use a hacksaw blade to cut the marked line out, and then also measure the depth of the cut to 0.1 inch or a bit more -


Then with a chain saw sharpening file, I cut the nock out. You can watch the hacksaw cut that was made, when the cut from the blade goes away then you know what depth you've filed down to. Or you can just eye-ball the whole deal like most do! I like to measure a few things out -


At this point, I put the bow on the tiller tree... I must apologize to all of you - the pictures I took of this part turned out so badly I will have to redo them. For example -


I do not have a clear spot to take these photos handy and the backgrounds are so distracting that, as you can see above, they are of little worth. However, at this step, I use a spokeshave to try to get the limbs to appear close to the same flex and strength. I think it important to get the limbs close to being the same strength before you string the bow for the first time. If one limb is way strong it can put a most unusual flex in the other weaker limb. I gage this by looking at the two limbs and eye-balling the flex of each limb - do they look equal? It is hard to see what with the clutter in the background, but in the above photo one limb is almost straight out while the other seems to bend at the mercy of the first! So, again, a spokeshave is the tool of choice for removal of some belly wood to match this up better. Again, remove wood from the two side facets, then a bit from the middle to keep the limb balanced and to reduce the strength of the limb and increase flex. As the strong limb begins to appear to match the weak limb, I get rid of the spokeshave and go with a cabinet scraper. To give you an idea of the difference, here is a photo with a sample of the results of a spokeshave and a cabinet scraper -


The thicker shavings (on the right) are from the spokeshave. Of course, this can be adjusted as well, but I really like the scraper for fine adjustments, and will use it and a palm-sander for the rest of the job here!

Very important here - as you remove wood you must flex the limb. I continue to flex the limb on the bench and well as doing 20 or 30 short flexes on the tree before pegging the bow to check what the effects were of removing some wood. Wood has a memory. When I am doing the fine tune, every time I remove some wood I shoot the bow 30 times and then check the tiller changes. At this point, since we are not yet shooting the bow, you can still flex the limb. However, I don't like to flex the limb much more than it will have to flex to be strung at a standard brace height. Again, wood has a memory - you don't want to over flex the limb and introduce unwanted memories!

If one limb seems way stiff, or strong, when compared to the other, you can remove a bit from the length of the weaker of the limbs if you have enough length to do so. In this case, red has a shorter draw length than I so I knew I'd want to reduce the nock to nock length anyway so it was a natural thing to do. I take about 1/2 inch off of the weaker limb at a time, no more. After adjusting, both appear to be very close in strength now. Again, if the limbs are not close to the same strength one can over-power the other and put some rancid bends in the weaker limb. When I put a string on for the first time, I like a long string that will allow the bow to go back to the relaxed shape, but under tension. This allows me to make sure that the string is in the center of the bow - which I think important! If it is not, then you need to adjust your tips and nocks to make it so.

In this case, since I wanted to shorten the bow to 66 inches nock to nock anyway, I removed a bit of length from the upper, weaker, limb. My design is for a 2 inch longer upper limb at 68 inches, I want the limb difference to be less than that at 66 inches, so this played very well for me this time. Redo the nocks, and cut off the extra.


Now that the limbs are a better match, we can string the bow to check the centerline of the string -


Looks good - I think we are about to have a bow here!

I will now string the bow, and tillering takes on a different feel... I'll explain in my next posting!

[red]

Very impressiive work. Certainly a book in the making here. I always wondered how the draw weight and tillering was accomplished. This is actually better than Christmas...it's like getting to see Santa making a toy just for you.

[smj]

red said:

Very impressive work. Certainly a book in the making here. I always wondered how the draw weight and tillering was accomplished. This is actually better than Christmas...it's like getting to see Santa making a toy just for you.

I don't know about "impressive work," I like to wait until the bow is done before passing judgment on anything! Believe it or not, something could still pop up that might make this a less than perfect bow, maybe a no-bow-at-all... This part of the bow making process is slow. You can not hurry it. If you take one swipe to many off of the belly wood, the draw weight will end up very low - you can not add back wood once taken away. Period. This is why I like to use the scraper, it only takes a small amount of wood off with every pass and you have very good control of where wood comes off and where wood remains. It is possible to get it wrong, but the odds are in my favor! When the limb wood is thick and the limbs are not flexing much, the sander is fine as there is a long ways to go. Even to then use the spokeshave is fine as you can afford to remove some wood. However, now that the bow is strung, every little bit removed needs to be checked with care, and the bow flexed a bit to ensure that the modification to the belly is registered correctly. As we continue along this path, what we really need is a means of registering just how much the limb is flexing - at which part of the limb... Once we glued the bamboo to the belly board, we have increased the homogeneous character of the bow limb. With a self bow cut from a stave you really need to check tiller, or flex, all the way through the draw length. What I mean to say is that it may be that strung but at rest the bow will look off, but at full draw the bow might be perfect! Once the bamboo goes on, the bow will pretty much reflect the tiller when strung and at rest as it will when at full draw. Hence, I string the bow at a low brace to begin with, just to make sure that the string is centered and that the limbs are somewhat balanced weight wise. Here is a look at the limbs, you can see that the lower limb is still very strong to the upper limb -


As a matter of fact, at any lower a brace height the lower limb over-powers the upper limb and returns to the reflexed unstrung posture! Hence, by using the low brace, we keep from putting a lot of unnecessary stress on the upper limb.

Once the limbs appear more balanced, we will look at the use of a tool to help us figure out this whole limb flexing stuff!

[smj]

So, it took a while, but compare this photo to the last - note that the upper limb does not look as stressed, and the lower limb shows a bit of curve to it now -


We now have a brace height of 4.25" at the grip, bow center. The tiller, if measured, where the lower limb hits the grip block at 4 7/8 inch, where the upper limb hits the grip block of 5 1/8th inch. This is still a nice stiff bow, too. Keep in mind that we still have to shape and clean up the grip area, the grip is at least an inch more thick than where the limbs hit the grip block. I gave the bow about 80 half draws before taking these measurements. I will not draw the bow any further until I get the next step done - match the limbs curve all along each limbs length. This means taking the block of wood you see in the picture, and dragging it along the length of the limb on the belly, and using it to gage the amount of flex in the limb while strung, but at rest. When I have good curvature all along the limb, I will check the draw weight - lets hope it is still above 55 pounds at 28 inches!

To start to see some flex in the lower limb, I probably took 40 or 50 strokes on both side facets with the scraper, and probably 25 to 30 strokes down the middle of the lower limb belly. I also flexed the lower limb a lot on the bench, and then when it started to balance out, half draws to flex both limbs. They need to learn to work together, so this is the time to start working them.

From now on, we have to use the block to check limb flex, the eye alone can lead you astray! Also, small amounts of wood will be removed, then string the bow and flex it 30 to 50 times to see what the result really is once the wood takes note that it lost some thickness... It really does remember!

Keep in mind, that this is the cross-section of the limb (call it mid-limb) and where we are removing material along the limbs length -


By the way, with a glass bow, you have to thin the limb to affect tiller - you can not take off belly material at all! You'd grind right through the glass! This is only for laminate board bows and self bows from a stave.

[smj]

skipmaster - what do you think? Is any of this making sense to you? I'd really like to see you make a bow!

[smj]

Here is a look at my tiller check tool -

It is red oak, about 1 3/4 inch square and just under 7 inches long.

I used sandpaper on glass for a flat surface, sanded each side until I knew for sure it was flat -


Then I put some finish on it, sanded it smooth, put a little more finish on it, and added a different single screw to each side - but each screw is of a different sized head.


To use this little fellow, you simply run it along the belly of the bow and watch the gap between the bow and the tool. You can use the different head sized screws to help keep track of the measured gap. Keep one side without any screw in it so that you can measure flats and also when curves go in the other direction -


Now you can mark on the limb "stiff" spots and "hinges."

These pics were posted before in "Tools and Stuff" so if they look familiar, they probably are!