In brief: I finished rehairing a cheap fiberglass bow by making and installing a version of the tip wedge from this YouTube series by Gilles Nehr.
It’s crude. I used low-grade poplar wood from Home Depot, and shaped it using sandpaper.
But it works. My cheap bow is now (inexpertly) rehaired, as shown below.
The one thing I can say for sure is that this goes a lot faster once you have a little experience with it. Making and fitting the tip wedge took less than an hour.
Blah blah blah recap
The frog is done. As noted in Post #1518, rehairing the frog of a violin bow is the easy part. The frog has multiple redundant systems to keep the horsehair in place, and the newly-carved wooden wedge fits into a well-defined oval cavity.
Getting the internal wedge cut and placed in the frog took me about three hours. A lot of that was what I would call fumbling time. That is, guessing how to go about it, with the tools and materials I had on hand. And screwing up and starting over.
To see how to finish off the frog, by cutting and installing the ferrule wedge, this video (YouTube, Gilles Nehr) seemed quite clear. I used regular Titebond (yellow wood glue) instead of Elmer’s (white wood glue), but I otherwise did as he did.
Now I need to do the tip. Unlike the frog, the system for attaching the hair to the tip has zero backups. A tiny friction-fit wooden wedge is all that keeps the hair in place. As a bonus, if you cut the wedge too big, it’ll split the tip of the bow when you press it in.
As a further bonus, this is also the end of the bow where you need to bind up the loose ends of the hank of horsehair. And cut the hair to the right length.
So it’s an altogether different ballgame. After a couple of failures that I won’t go through, this is what I learned.
Tip wedge, in theory.
First, for the life of me, I couldn’t understand how the tip wedge was supposed to stay in place. Other than gluing it, as mine was glued originally.
A couple of failures did wonders for focusing my attention. That, and carefully watching this YouTube presentation by bow maker Gilles Nehr.
Terminology of the tip wedge. For purposes of discussion:
- Tip mortise is the hole in the tip of the bow.
- Top and bottom of the wedge are obvious, I think. Top is the part you can see.
- Sides of the wedge run parallel to the bow stick.
- Front face of the wedge is nearest the tip.
- Rear face of the wedge is nearest the frog.
As with the frog, you first try to stuff the bound end of the hank of horsehair, into the mortise as far as it will go, so that the bound end sits flat on the bottom. Or as close as you can get, to that.
Then you make the wedge as thick as possible, from top to bottom. So long as, in the end, you can push it in until it’s flush. That deep fit is the key to keeping this wedge in place, as shown below.
Here’s a schematic of what (I think) is going on.
Under tension, the horsehair wants to pull the front face of the wedge up, and so rotate the wedge out of the hole. (This is precisely how my first attempts failed.)
What prevents that is the “critical distance” above. That is, the distance from the lower edge of the front face to the upper edge of the rear face. If the wedge fits tightly from front face to back face, that diagonal is too long to be swung through the opening of the mortise.
Which means that, as long as the upper edge of the rear face is stuck firmly in place, you shouldn’t be able to dislodge the wedge by pulling up on the hank of hair.
And so, you cut this wedge to ensure that those two places are where the wedge binds. That’s why, in this cross-section, the tip wedge is almost a parallelogram. Top and bottom are parallel. The front and rear faces are roughly parallel, but slanted. This is intentional, and this is the tip wedge shape shown by Gilles Nehr.
To insert the wedge, you drop it in with the front and rear face more-or-less vertical, until the top of the front face is flush with the tip (guard). Then you finish by pushing the rear face of the wedge down until it is flush. The slanted rear face of the wedge provides leverage, and so ensures that you produce significant pressure against the horsehair. And that the wedge can’t be popped out by pressure on the horsehair.
That’s the theory, anyway. Other re-hairers somehow manage to use a relatively thin wedge, but I have no clue how that stays in place. By contrast, the Nehr tip wedge, I think I understand.
Tip wedge, in practice.
1: Watch videos one and four, by Gilles Nehr
You definitely want to watch the first and fourth episodes in the YouTube presentation by Gilles Nehr. He carves the tip wedge in the first one, he sets it in the fourth one.
I didn’t use the same tools. Lord knows I lacked both his skill and precision. I didn’t even make my wedge in the same fashion that he made his.
But that wedge, carved in episode one, was what I was aiming for. In particular, I note these features of his tip wedge:
- Front and rear faces are just slightly slanted, in the direction shown in the diagram above.
- Sides appear quite slanted, to fit within the slanted tip mortise.
- He gouges a channel in the bottom to give more room for the hair/allow the wedge to be deeper.
- He rounds off the lower edge of the rear face, to allow the wedge to be inserted into the mortise more easily.
What you don’t get a good sense of, from the video, is exactly how tiny that wedge is. Under a quarter-inch (say, 6mm) in every dimension.
2: Cut and bind your horsehair.
This is the point where you:
- Wet and clean the hair
- Put the frog on the bow, in the position that leaves the hair as loose as it can get (i.e., with frog pushed fully tip-ward).
- Comb out all the tangles.
- Measure and bind the hair.
- Cut the hair and seal the end.
Note how imprecise the hair-cutting step is. Wetting the hair allows it to stretch. How much it stretches depends on how hard you are pulling on it.
That said, I followed Nehr’s advice. Measure the depth of the tip mortise, and begin binding the hair at that distance beyond tip mortise. As shown above. I.e., lay the hair across the mortise, and begin binding it about a quarter-inch past the tip end of the mortise. (Other sources gave a vague “just beyond the tip mortise” as the location for the binding and cut.)
In theory, you are supposed to bind the hair with thread, in the same fashion as you might whip the end of a rope to keep it from unraveling. Then cut the hair, and seal the end with by melting rosin dust into it.
Doing that on the fly looked to be beyond my skill level, so I dumbed it down to something I could handle.
First, I used a simple kitchen twist-tie, to start, as shown above. I used this to gather the horsehair where it was to be bound, and to mark that spot. You can slide the twist-tie on the hank of horsehair to adjust exactly where you want your binding to be.
Then I used superglue (cyanoacrylate glue). Once I had the twist-tie on, and slid into the exact right place, I super-glued a short section of the horsehair together. Originally, I thought that superglue alone would do, but the blob of superglued hair lacked strength under pressure. It failed, in the function of being a “stopper” on the end of the hair hank. So …
Then I bound it with thread. After the fact, I wrapped it with thread, as one is supposed to. Then superglued the thread in place.
Then I cut the hair just past that. And superglued the cut end of the hank of hair.
Functionally, I think this ends up being more-or-less exactly the same as if I’d had the talent to do the thread-binding on the fly.
Note: You really want to get all the horsehair equally taut, before you bind it. If you don’t — if you bind it up with some loose and some taut, that’s largely how it’s going to stay when finished. Pull your fingers down the length of it a few times, and clamp in in your fingers. If possible, do not let go until the hair is fully bound. E.g., if you use the superglue method, don’t let go of the hair until you’ve applied the superglue, and it has set.
3: Cut and fit your wedge.
Unfortunately, I have no pictures here, as I was fully occupied trying to get it to work, at all. See last paragraph. Again, see Nehr’s video on the shape you are aiming for.
A few pointers.
Track the grain. As with the frog wedge, the grain of the wood of the tip wedge must align with the direction of the bow stick. Mark the top of your piece of wood so that you don’t lose track of which end is which.
Aim for the thickest wedge that will fit. My wedge ended up being just under a quarter-inch thick, from top to bottom. Call it 5 mm. I think that’s consistent with, but at the high end of, what I’ve seen elsewhere.
I chiseled out a little sliver of 1/4″ thick poplar. Then I mostly used sandpaper to shape the wedge, rather than knives, as Nehr does. As with the frog wedge, the first thing you do is thin it from side-to-side so that the end of your piece of wood will fit into the mortise. Then you continue shaping it. Then you cut it to length, and continue shaping it.
A long-nosed Vise-Grip worked well for holding that tiny wedge for sanding. Just tighten the screw on the end of the tool until the block of wood is held firmly in the jaws.
A Skil knife (razor blade utility knife) worked well for gouging out the hollow in the bottom of the block. You can also use that to shave down the block, but I lacked the knife skills to control that well enough. (Remember, the block of wood is less than a quarter-inch on a side.)
The final fitting has to be done with the hair in place. As a result, there is not necessarily any distinct point where you stop fitting the wedge, and begin the final assembly of the rehaired bow. The only way to know that it fits right is to put the hair in place, push the wedge into place, and see if it fits tightly enough to hold the hair. But once that’s true … you’re done. You don’t really want to take that wedge out any more.
That last point is why I have no pictures. I considered removing my tip wedge so I could photograph it. But on the whole, I’d rather just have the bow rehaired, and not risk having that tip wedge fail if I had to remove it and re-insert it.
