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Repairing Tip Mortise?


Regis
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I'm "restoring" a bow that has a relatively large piece broken out on the front side of the tip mortise. The cheeks are fine and you can not see anything from the outside but, there is no wood under the plate for about 3mm (and jagged).

What is correct? I can drill/cut out evenly and plug the hole. Then cut new mortise. Or, I can use a filler? Or?

The value is probably only $750-$1000 but, I still want to restore it correctly as if it were a very valuable bow.

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do you mean its sort of broken off where the undercut of the mortice is?

If so i always think its best with bows to replace the wood with similar wood grain direction etc.(i have 100`s of junk bows to use for repairs)Removing as little wood as possible in the process. Then just tidy up the mortice. I wouldn`t fill the whole mortice unless it over size.I don`t think stress will be a problem like making pin or splice repairs.

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This has been bothering me, so I thought I'd mention it.

Whenever pernambuco is used, I like to clean any surfaces that are to be glued with a q-tip and denatured alcohol or acetone, until there is no more color coming off of the wood, and the wood surface becomes dull, otherwise, the glue may have a hard time adhering to the wood permanently - I'm not sure if it is simply an abundance of resin or a combination of resin and wax, but the raw wood doesn't always glue well otherwise.

You'd think that eventually the wax or resin would re-permeate the cleaned area, and cause problems in the future, but apparently, that isn't the case.

I've talked to other repairmen (who repair world class bows) who have recommend very light scoring or abrading the surfaces that will be glued slightly also - this in regard to tip gluing where ebony and pernambuco meet or where ivory/bone and ebony join together.

The whole scoring issue can be a touchy subject as the glue experts often recommend a perfectly smooth wood to wood interface. My compromise is not to have really smooth or shiny surfaces, and not to score, but to have dull or abraded surfaces and to make sure that the joint isn’t starved..

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"...other repairmen (who repair world class bows) who have recommend very light scoring or abrading the surfaces that will be glued..."

What type of glue do these 'world class' repair shops now use for pernambuco repair?

Also, what did the best shops use to repair broken pernambuco sticks before modern epoxies and Cyanoacrylates were available?

I understand from this forum that there are many old repairs still holding up well on famous maker bows, which I find somewhat amazing considering the oily nature of the wood.

Jimbow

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I sure agree with the "not shiny" surfaces and thoroughly clean. I don't know about minor scoring as I always thought that was for non-porus material such as metal or synthetics. To me, of most importantance to acheive a strong/permanent glue joint is a perfect fit and clean. Then using enough glue to cover surface (after any soaking-in that is). Other things are important also like immobilizing while drying and using fresh glue.

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Certainly cleanliness of the surfaces is very important.

I have used both epoxy and C/A glue on pernambuco but lean a bit toward Epoxy particularily SystemThree T-88 which is expressly recommended for oily woods. It is used extensively for teak and other boatbuilding applications. Do not use any of the 5 minute cheapo types... only 24 hour type should be used and even then, requires a full week to fully cure.

SystemThree recommends coating hardwood surfaces and let them stand for 30 -40 minutes before pressing them together with minimum pressure.

The one bad experience I had with epoxy was my first bow head spline about 10 years ago. I was super cautious to get a perfect and tight fit of the pernambuco spline, using another brand of epoxy. A real tight fit was the wrong thing to do with epoxy and it gradually broke loose a couple of years later and I re-did it.

I have had no problems with SystemThree T-88 on many pernambuco splines and a variety of other material applications but I am careful to always clean surfaces with acetone, scuff the areas, and to allow a slight glue clearance so as not to starve the joint.

Jimbow

I would still like to know how the old experts repaired bows. I expect they used hide glue but I have never done that. Maybe it would be worth a try!

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"What type of glue do these 'world class' repair shops now use for pernambuco repair?'

and

"I would still like to know how the old experts repaired bows. I expect they used hide glue but I have never done that. Maybe it would be worth a try!"

OK, I’ll got out on a limb and give you my opinion about the state of modern bow repair. Just keep in mind that I said “opinion ‘, because, I certainly am not in that class of bow repairmen who would be considered “world class”. I am merely a work-a-day hack...

In every case I can think of, talking to them personally, they have not hesitated to recommended ca or epoxy for repairs. (and for tip attachment in the case of new bows, or tip replacement in the case of old bows... If you can see that hide was used, probably hide is a better choice, but if you can see that it has been repaired or re-repaired in the past with god knows what, or white or yellow glue, then I wouldn’t hesitate to remove that and switch to ca or epoxy.)

Usually, they are not shy about naming specific brand and strength glues either.

(Be forewarned, especially if they don't know who you are, they will balk about saying that such glues are traditional, though, or even that they are used in the shop, if the subject comes up. Often, it is more difficult to get a bow maker to commit to a specific statement regarding repair technique, than it is to get a violin maker to commit to one (guffaw!) I suspect that it is because they are equally in the dark about what "everybody else uses", plus, talking about specific techniques that are commonplace in the shop, isn't really information it behooves a shop to divulge. I don’t blame them. If I wasn’t posting here, I wouldn’t be saying THIS.

Many people intentionally seek to retain that aura of uncertainty, wherein the average guy on the street almost certainly isn't sure about which glue to use. That can be a very good thing - the worst repairs I ever (EVER) encounter is where the bow owner attempted to repair the bow first before bringing it in.)

Please no one get offended - this is humor...

I've used (hot, not the Franklin bottle stuff) hide glue for bow repairs before - and it IS capable of being used with no problems..., but, I think that it (hide) has certain properties that make it somewhat less attractive for bow repairmen.

Like set (not cure) time, gap filling capabilities, carve-ability, etc. I find that ca can fix a split or break quickly, invisibly, and permanently - it's a pretty attractive glue for some applications in bow repair.

Often one problem is that amateurs don’t clamp and then let the repair be until long after the glue has cured... Thirty seconds later they are pulling it apart and are surprised that the “instant” glue hasn’t even bonded yet (because the wood is not porous at all) and the pristine break starts to get mucked up with super glue. With superglue you often get one chance to have it exhibit it’s superior characteristics, then you are going to be fixing what it has made difficult.

None of them (or us) knows what is going to happen to these glue joints in fifty or a hundred years, but I think that they are much more willing to make a non-traditional glue "standard" than violin makers are.

Probably for very good reasons.

"Also, what did the best shops use to repair broken pernambuco sticks before modern epoxies and Cyanoacrylates were available?"

To be honest, I don't know, I didn’t work in one. But I always used hide glue - same as for violin wood repairs, before I became convinced that the (at least some of the) bigger shops don't hesitate to use epoxy or ca.

Splines, pins, pegs, and whatnot are also common in bow repair - since the gluing area is always so small, and such things are still in use today. Often the use of a spline will dictate which type of glue to use.

Please, if anyone encounters a very fine, very expensive bow to repair, and is not certain how to go about fixing it, do not take my advice as gospel - take the bow to someone who is a bow expert before you proceed, or let them do the repair.

I LOVE bow repair, but I will warn you, it is much easier to mess up a bow with a bad break than it is to restore it.

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Hi Craig,

WOW! What an informative response!

Wish I could rate you 5 stars for that knowledgable and helpful post.

Even though you may have put yourself a bit "out on a limb", as you said, this type of information is of great assistance to many of us in weighing options and will certainly keep many from Elmers glue experimentation in the future.

Thanks for your gutsy, humorous, candid, and thorough explanation! You certainly answer our nagging questions on trade secrets that are sometimes shied away from.

Jimbow

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