Wood species for Falcate braces

[colin north]

Hi Trevor
do you think that Mediteranean Cyprus (Cupressus Sempervirens) could be suitable as an alternative wood for construction of Falcate bracing?
I can obtain tonewood grade of it much more readily than any of the other possibilities mentioned in the book.
Any general recommendations or caveats on using it, if potentially suitable, would be welcome.

[Trevor Gore]

I'd be inclined to have a go with spruce (sitka), first, and see if you can get that to bend how you want. Some will and some won't! Such is wood.

[ozwood]

Hi,

I've used Sitka for 3 lots of falcate bracing , and 1 set in King billy , the spruce works fine I just applied a little heat and moisture I't bent just fine.

Cheers,

[colin north]

Thanks guys, guess I'll buy some sitka (I have only euro spruce, and it's very stiff!)

[ozwood]

Hi Colin ,

I would give it a Go, the worst that will happen is you will waste a bit of Spruce , as Trevor said It either will or it won't , The peice of Spruce i have been using is perhaps a nice compliant peice , just bend it as you would any other timbers , a bit of heat and moisture , as long as it does not split or crack your home and hosed . I have a Mould made out of MDF in the shape of the brace I want to acheive with Dowel pegs spaced every 40 mm in 40mm from the edge , one for the centre bace and one for the outer brace with some celo tape along the edge to avoid gluing the braces to the mould, I bend the slats pretty close to the shape , then apply glue to one side of the slat , Start at one end and use 4mm shock cord to criss-cross the mould wraping around the pegs as I go this seem to provide enough pressure to give a nicely glued brace , I leave it there over night .

Cheers,

[colin north]

Thanks guys.
Look like even stiff euorospruce will bend - built and tried out my new (first actually) pipe today while waiting for my Sitka...

[colin north]

Hi Colin ,

I would give it a Go, the worst that will happen is you will waste a bit of Spruce , as Trevor said It either will or it won't , The peice of Spruce i have been using is perhaps a nice compliant peice , just bend it as you would any other timbers , a bit of heat and moisture , as long as it does not split or crack your home and hosed . I have a Mould made out of MDF in the shape of the brace I want to acheive with Dowel pegs spaced every 40 mm in 40mm from the edge , one for the centre bace and one for the outer brace with some celo tape along the edge to avoid gluing the braces to the mould, I bend the slats pretty close to the shape , then apply glue to one side of the slat , Start at one end and use 4mm shock cord to criss-cross the mould wraping around the pegs as I go this seem to provide enough pressure to give a nicely glued brace , I leave it there over night .

Cheers,

Can I ask what kind of glue you are using??

[Allen]

For laminated linings I use HHG. I'd hazard a guess that these would be similar. The heat and lubrication of the glue helps get the pieces to slide into place, Plus it dries hard.

[Trevor Gore]

Colin asked "What glue?"

I find it easier to use epoxy, Techniglue in particular. The water based glues tend to make the laminations curl across their width, making them more difficult to clamp.

[colin north]

Techniglue not available in UK.
Widely available here is Araldite epoxy resin glue, (1 to 1, but still pretty runny if it gets a chance).
Never heard any of that failing on anything, unless with heat.
I also have some West 105 epoxy resin - not sure now which to use now. Glue?/Resin? - ah well, back to the book (Resin was bought for bonding the CF)

What IS the difference between Epoxy resin and Epoxy Glue anyway?

Anyway, just wondered what Ozwood was using.
I like the sound of a former and dowels with the "rubber band" - I'll probably back up the laminations with flexible steel banding (Pallet banding stuff).

[Cookie man]

[quote="colin north"]
What IS the difference between Epoxy resin and Epoxy Glue anyway?
[quote]

I can't really help you with the bracing issue:mrgreen:, but I'm 99% sure that epoxy glue
is the combination of Resin and the catalyst/hardener. Araldite is a typical epoxy and comes in the two parts as you can see. once they are mixed you then apply it to whatever you're gluing. (being a miniature model hobbyist I know a little bit about glues) I often use Kneadatite which is an epoxy putty, and the resin and hardener are two different colours (blue/yellow) so I'll be able to tell when they're fully mixed.

[Trevor Gore]

Techniglue is a 2:1 mix and is handy because it is thixotropic. Araldite (1:1) is fairly viscous if not too hot. Not sure whether it is truly thixotropic, but at room temperature (20C) it should work fine.

[ozwood]

Sorry Colin been away for a few days.

I use titebond to glue the laminations , But a Trevor Pointed out It does make them Curl a bit because it' water based, and then I have to Tidy the Sides up un the Drum samder, So In future I'll try some Techniglue , You should be able to Find something Similar, try a Marine suppliers . It's best Described as Gel Like, and Does not Run everywhere one part is a Honey Colour the other looks a little Like vaseline ..

Cheers,

[kiwigeo]

Techniglue not available in UK.

Colin, these guys might be worth check out: http://www.epoxy-resins.co.uk/

[colin north]

Taken to another thread

[weslewis]

adirondack spruce ..bent at 300 degrees...sprayed with supersoft ..
my first shot at falcate bracing!!!

[Trevor Gore]

Neat! Well done!

[woodrat]

Hi Wes, Thanks for Posting yr pics...I will make a form for my bending machine now and use my electric blanket just like sides.

Best of luck with your falcate...I just finished my first a couple of weeks ago and was glad that I grasped the nettle and got over my fear of the whole CF thing. The guitar is definitely noticeably louder than my x braced ones and that is with all things being equal like string height and top at 180Hz. It is definitely the way of the future for my steel stringers....

John

[weslewis]

I have a OM body style that I started months ago that I decided to try my hand at putting in an armrest , and now it has become my test guitar for using carbon fiber ,with an x brace design simular to picture 11-29 in Trevor's book, using carbon tow on the braces and cloth on the bridgeplate. I used system three resin with the #2 hardner which gives plenty of open time to set up...

This stuff is Fun!!!!!!

[Dave M]

I realise this is a very old thread but I have just started trying out the idea of falcate bracing and the spruce that I tried bending, for the slow curves on the primary braces, just laughed at me and split.

So I wonder if anyone has found a more consistent timber available in the UK for this use? Our usual tonewood suppliers don't seem to offer much range in this area.


Dave

[Trevor Gore]

The best advice is probably to source some more spruce until you find some that will bend. It's a bit of a lottery, but the stuff that won't bend makes great back braces!

Other than that, for The Shed Guitar I used Oregon Pine (Douglas Fir) which bent fine. It's denser on average than most spruces, though. If you're really stuck, you could try something like Euro Beech. Most of the native British hardwoods will heat bend, too.

[GregHolmberg]

This is an old thread, but I thought I'd pass on the results of my search for a brace wood. Note that this is just calculations, and I haven't actually tried any of these species.

First, the species must be bendable. I found this report that lists steam-bendable species.
Machining and related characteristics of United States hardwoods
By E. M. Davis, 1962.
Technical Bulletin No. 1267.
Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.
Steam bending starts on page 39 (PDF page 41).

This lists 25 North American species and the percent of samples they found to be bendable. This list is not complete, so just because a species isn't listed, doesn't mean it's not bendable. It just means we don't know. If you know that some of these species are in fact steam bendable, let me know--I'll update the spreadsheet.

I then used data from the wood-database.com for density, Young's modulus, and modulus of rupture. These are, of course, only averages for each species.

I re-created Gore's calculations as in Table 4.4-2 Brace stress, and added these bendable species and many other light-weight species. 80 species, altogether. See this Google spreadsheet. Bendable species are highlighted in orange. Sorted by mass. Feel free to copy this spreadsheet and change dimensions to match your project (you'll have to unhide the first 10 rows). I just used the dimensions from the book.

Very few exceeded the allowable stress. Bendable species in order of weight (lightest first):

• King Billy Pine
• Black Cottonwood
• Black Willow
• Sitka Spruce (bendable?)
• White Poplar
• Yellow Poplar
• American Chestnut
• Alaska Yellow Cedar (bendable?)
• Silver Maple
• Sycamore (US)
• Bigleaf Maple

The list goes on from there. Take a look.

Now, exactly where one can buy Black Cottonwood, I'm not sure. It's native to Northwestern North America, and is a fairly large and common tree. Used for plywood and boxes, but not commonly available as lumber.

Hope this helps someone,

Greg

[GregHolmberg]

To answer the original question: Mediteranean Cyprus was one of the few species that exceeded the allowable stress. It's at 130% of the allowable stress.

The other species that exceeded the allowable stress are:

• Balsa
• Paulownia
• Gore's Western Red Cedar (but not average WRC according to wood-database.com)
• Northern White Cedar
• Sugi (Japanese Cedar)

Has anyone tried to steam bend Obeche? If it were bendable, it would be the next-best thing after King Billy Pine.

Greg

[kiwigeo]

Thanks for the info Greg.

[Dave M]

I think I have said this before but for the tightly bent secondaries in Sitka I use 4 thinner laminations rather than 3, bent over a hot pipe. Still get some failuires but mostly that works.

West system epoxy with some filler to increase viscosity gives a nice relaxed time to clamp up.

Cheers Dave