Side Bending Practice

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needsmorecowbel
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Side Bending Practice

Post by needsmorecowbel » Sat May 21, 2016 10:03 pm

I'm toying with the idea of using 2 mm oak edging that you'd use on an edge bander in a cabinet making workshop for making some laminated sides for a hollow body electric. I'm using a bending iron/ heat gun with a spritz of water to do the bending. Surprisingly the pieces are even fairly stable when you bend them on the finger joins that are spaced every 150-300mm.

Am I best off trying to get the edging to fit the mold exactly (as you would when bending an acoustic set) or, as my intention is to laminate two or three pieces together, can I afford for there to be some small 1 mm gaps here and there prior to laminating?

Or would I be better to just thin them down to 1 or 1.5mm and try laminating after bending those thinner pieces

I'm just finding it difficult to get the bends right at the moment but will have another crack tomorrow. It's not that I'm getting any cracks but rather I've overworked areas in frustration and am as a result getting some slight rippling / distortions in the sides (perhaps applying too much water?).

Stu

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Re: Side Bending Practice

Post by kiwigeo » Sat May 21, 2016 11:29 pm

What sort of glue to you plan on using? If there is any chance of gaps between the laminates then use epoxy resin glue. With thin laminates and a proper mold and clamping caul you can get by with Titebond. I'm just finishing work on a parlour guitar with laminated sides. The sides were about 1.5mm thick and I glued them up with Titebond but used an internal mold with a flexible caul to ensure even clamping of the sides against the inside of the mold.
Martin

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Re: Side Bending Practice

Post by needsmorecowbel » Sun May 22, 2016 8:47 am

Cheers Martin, I was thinking of just using titebond

Stu

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Re: Side Bending Practice

Post by blackalex1952 » Sun May 22, 2016 1:17 pm

artin wrote:
I glued them up with Titebond but used an internal mold with a flexible caul to ensure even clamping
How is the flexible caul constructed? Cheers!Ross
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needsmorecowbel
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Re: Side Bending Practice

Post by needsmorecowbel » Sun May 22, 2016 2:55 pm


youtu.be/

Approx 1:45

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Re: Side Bending Practice

Post by kiwigeo » Sun May 22, 2016 3:27 pm

blackalex1952 wrote:artin wrote:
I glued them up with Titebond but used an internal mold with a flexible caul to ensure even clamping
How is the flexible caul constructed? Cheers!Ross
Pretty much as in Bogdanovich's video below except I used 3mm MDF thinned to around 1.5mm with my drum sander instead of masonite.
Martin

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Re: Side Bending Practice

Post by blackalex1952 » Sun May 22, 2016 4:59 pm

Thanks.That's how I have been vacuum laminating my sides,same kind of thing to hold the bagged veneers onto the mould.I like the use of multiple layers of masonite, which I'll try. But the reason I asked is because I am looking for a good way to laminate without the vacuum bag using HHG, which gells faster than titebond. So there is limited time to get all those clamps into place before gell stage, I don't have a heat blanket to include in the pressing.Neither HHG or Titebond go off easily in a vacuum. One issue is that it's not easy to see how well aligned the veneers are once bagged up and covered in release fabric and breather. Also I would rather use HHG than epoxy resin. Another issue I have found is that when laminating a tight, small radius cutaway bend as in a Selmer for example, the caul which clamps that particular bend has to a be pretty accurate match with the mould, even allowing for the veneer thickness in it's radius or there are voids between the laminations at that point...at least that is what has happened to me on a couple of bends. I know many would disagree, but I think that HHG has the best properties for instruments...easily undone, re joined, can be heated to repair voids in the veneers if they happen for some reason, and I think that hide glue has good acoustic properties. I made three moulded lumps the same size, one from hide glue, one epoxy and one titebond. When well hardened, I dropped the samples onto the cast iron saw bench...Hide glue pings! The others thud!Cheers! Ross
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Re: Side Bending Practice

Post by kiwigeo » Sun May 22, 2016 5:51 pm

Ross, if you're laminating you want a glue with a bit of tack time or you're going to have a hell of a job on your hands. From your comments it's my impression that the only "advantage" in using hide glue is it's (IMO debatable) superior acoustic advantages over other glues. On my builds I want as little energy as possible leaking from the top and down the sides.....if non-hide glues do indeed have inferior acoustic properties then they'd be the glues I'd be choosing for laminating sides.

In summary I think acoustic properties of hide glue are debatable and not nearly as important as tack time for laminating work.
Martin

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Re: Side Bending Practice

Post by Nick » Mon May 23, 2016 6:09 am

blackalex1952 wrote:Neither HHG or Titebond go off easily in a vacuum.
Both glues rely on moisture evaporating which doesn't happen in a vacuum too well, my understanding (and forgive me if I'm trying to teach grandma how to suck eggs, apart from gluing bridges on, I've never used a vacuum bag clamp) is a Urea based glue (such as this one), one which goes off chemically, is the best glue to use in a vacuum situation. But to that end an epoxy would achieve the same?
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Re: Side Bending Practice

Post by blackalex1952 » Mon May 23, 2016 2:29 pm

Yes Nick. I have used the urea formaldehyde glue in a vacuum bag. I didn't really like it and the Selleys one, which was readily available locally, is off the market now. It's also expensive for the quantity that they sold it in. I find that the epoxy is better, and this time of year I have been using a fast hardener. I have glued in a vacuum with HHG, the trick is to put lots of dry absorbent paper in the bag to take up the moisture. But, due to glue tack time and alignment problems with such a short time available it's a hassle and I didn't get the best results. The laminations, if using the method in Michael Collins Selmer book, need to slide relative to each other after bagging when they are placed in the side moulds to bend properly and not get any voids, particularly on the tight bend at the cutaway, I have found this to be a problem if the glue is not viscous enough. The original Selmers were laminated using HHG in a mould. If they did it ,I can, hopefully. There are some high end European makers who glue this way, it seems to help with sales, perhaps? Regarding the comments I made about the acoustic properties of glues, to my way of thinking the brace gluing I have done with HHG seems to get a better, albeit subtle, tonal improvement. If there are any voids in the laminations with HHG when the sides come out of the press, they can be easily repaired with heat. My impression is that boutique drum makers use heavy rim liners for the same reason as luthier might use solid liners or added side mass. The drum makers all talk about the tonal differences between the timbers that the drum shells are constructed from. I might be splitting hairs re guitars sides and the glue used, but to me, titebond has a damping factor, the reason for the thud! So even if I want all the energy of the fundamental in the soundboard to be reflected from a solid rim, if that solid rim is sitting on sides which dampen high frequencies, it is quite feasible that the tone of the instrument could suffer. I need to do a few more builds before I can know for sure. But many makers prefer HHG. I think it is a fun glue, I always enjoy using it. Epoxies and other chemical substances are unpleasant to handle. The other concern, although I seem to have succeeded, is gluing to the laminated timbers because the epoxy usually wicks through thin veneers, so the HHG can only bond with the epoxy surface and not penetrate the timber as it should, eg back braces on laminated back liners on sides.
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Re: Side Bending Practice

Post by kiwigeo » Mon May 23, 2016 3:09 pm

blackalex1952 wrote:The original Selmers were laminated using HHG in a mould. If they did it ,I can, hopefully. There are some high end European makers who glue this way, it seems to help with sales, perhaps?
I suspect the original Selmers were laminated using HHG because modern glues like Titebond and epoxy either weren't around or weren't as well developed as they are today. Just HHG was used by the masters in years gone by doesn't necessarily mean it's still the best choice in the modern day when better products are available.

As I've pointed out I think you need to carefully evaluate your reasons for wanting to use HHG for laminating.
Martin

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Re: Side Bending Practice

Post by blackalex1952 » Mon May 23, 2016 7:10 pm

As I've pointed out I think you need to carefully evaluate your reasons for wanting to use HHG for laminating.
Thanks Martin for your input. Always to be respected.I am still curious, so by the time I have tried a few different methods I will know what works for me.It's possible that Selmer used casein glue for the side laminating, many of the French luthiers from that school of guitarmaking used casein..I'm only guessing, never used casein but I don't think it is a hot glue and it might have a longer life before gel stage. I haven't done a Selmer with solid sides, which is much less mucking around I reckon. I will soon to compare the effect on tone. They are finicky guitars in some ways, about as much in common as a Holden and a Peugeot to work on and also drive! The players are also fussy, looking for a special combination of musical/acoustic properties and playability. Long scale but easy action, projection and cutting power in a crowded room, that unique Selmer GJ sound but with strong bass,a particular balance in the mids and thick trebles-all that and not tinny sounding like the Chinese versions I have played (I own a high end Chinese Selmeroid, no pliage), even the high end Chinese ones I have played. The sound is a jazz sound, cutting amongst horns in a small ensemble, with tight percussive throbbing rhythm power-it is easy for GJ rhythm players to sound rattly! My thinking is to chase my own unique quality tone and mojo within the subtle boundaries of the needs of the genre and it's modern evolution. Otherwise, there are plenty of factory guitars made by the main exponents in France to compete with. I also really love the 3D nature of the builds, as well as being a jazzy player myself. Same reason I don't like making Martin style dreds, I prefer OM and similar sizes...the good ones sound really balanced to me. The market is saturated with drednoughts and people have been "earwashed" (brainwashed) to accept only that sound. Well, they are dominating the market, there are enough people producing them. I am hoping to get into archtops pretty soon also.
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