Official Luthiers Forum!

Hey guys, just want to pass along. Being me to this hobby, I find myself looking for a different approach to what's out there.
I've been looking at the gobar clamping system and three best deal I found for fiberglass rod is at Harbor Freight.
They have a special on a wire running kit right now, $10 for 10 rods that are 39” long, normally it goes for $15.
Same kit at Home depot is around $35. I know we have sponsors that sell the gobar kits, so I'm not sure if my post is bad form, if so, shoot me a PM do I don't do it again!!:grin:
So now I'm contemplating whether to cut the 39” rods in half and make two 19.5” rods or just cut them diem to 24” like the rods are sold from the luthiery shops. Any suggestions? I've never used them, do I'm not sure if cutting them shorter will drastically change the pressure. I'm assuming that the height of my deck will play a huge factor, but then again,.you know what they say about assumption
Anyway, just wanted to share, in case you're looking for some fiberglass rod....
Cheers!
Raul

Shorter rods will exert more tension. You have to decide how long your rods will be, how tall you want your deck and how thick your rods are. I use the fiberglass driveway markers from Home Depot. They are thicker than typical go bar rods but I don't use a deck. I have plywood reinforce event on the ceiling above one section of my bench. I cut the rods to the correct length and the heavier rods work out to be about right because they are much longer than 24 inches. I like this system because there is plenty of room to work in and I don't have a deck to move around (I can just stack the rods up in the corner when not in use.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

You can order several fiberglass rods from any kite building supply online for $10-15. My gobar deck is about 3 feet tall. I found the 1/4" rods to be slightly too stiff for soft tops and braces. I recommend smaller.

Not all fiberglass is the same. But if you can get 8 to 10 lb of force your good. be very careful when cutting it as the dust is not good for you.
I only use reinforced fiberglass this helps to hold the fibers together so they don't give you splinters.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I have been using them for years, cut t 24 inch lengths, if you cut them properly the lengths with the connectors can be screwed together and cut to length to make rod..work perfect, get a couple packs of the 33 ft length rods.

_________________
MK5acoustics.com

I have a build in the doc u build section, under new build for 2015, scroll down to the bottom of the first page and you can see these rods in use..

_________________
MK5acoustics.com

I buy mine from https://goodwinds.com. 3/16 x 72". Black fiberglass. Dremel cutoff wheel. Buy the end caps from them too. 100 pack

I have a 36" tall deck and use 3/4" X 1/4" scrap wood (fir works good). I like using wood because its already around and you can cut them to what ever length you want.
I have shorter ones I glue the tops and backs to the rims with.

I bought these 3/16" fiberglass rods and end caps from IntoTheWind.com and cut them in half. Looks like they're $4 now. I don't remember paying that much!

Hesh did an experiment a long time ago using different lengths of rod and a scale to see if the amount of deflection (bend) made a difference in the amount of pressure exerted. The results were negligible. I wonder if the same principle would apply to different lengths? In general, we want something like an inch of deflection.

Length does not matter. The elastic modulus (E) does. And the diameter. It's not intuitive. It's called buckling column theory. Once a column buckles (bends) under a normal load, additional deflection will not result in additional normal force. It will, however, make the column or rod more dangerous. If you doubt this, put a small scale on your go-bar deck and test different loadings or deflections. You could basically bow a rod almost to the fracture point and the normal force will remain constant. But... Wear safety glasses

A typical 3/16" fiberglass rid will exert about 7 pounds force

That is only part of the story Mike. Length does not effect the force clamping force exerted if the deck height remains constant. As you say further bending of a longer rod will have a negligible increase in force exerted. BUT. . . A taller deck (and the associated longer rods) will decrease the clamping force applied. Take a 10 foot length of PVC pipe and try to buckle it end to end; pretty easy to do. Now try that with a 2 foot long piece. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Would these do the job? http://www.ebay.com/itm/4mm-Roman-Blind ... 3a4fa5d9d1

Agreed Andy. What is usually left out in these discussions is the issue of constraints. How the ends are held. It matters, but is too hard to explain.

Got some of this.
They're pretty floppy. 5 mm is a bit better. Cheapest I could find is http://www.ecfibreglasssupplies.co.uk/p-644-white-polyester-fibreglass-rod-5mm-dia.aspx but postage is a killer to Scotland. Try phoning, they were helpful. If you are near South Shields, pick-up is possible. Other wise Kite suppliers, for end caps too.
Off the top of my head, with the roman blind rods, 600 mm gives a bit short of 1 1/2" kg force.
I used 400 mm, gives 3 kg.
Short length means more awkward to get in normal go-bar decks, basically difficult for access, remove glue, etc.
(For me this was OK, these are for a built in go-bar deck over a Solera, not braces etc. I have 600 mm for that.
I'm using it to glue on the back, so the level comes up 100 mm anyway, and no glue to remove that I can't reach)

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

It puzzles me that I don't often see people recommending spring tension curtain rods for go-bar decks. They have several good features:
1) They are only 2 - 3 dollars each.
2) They come with end knobs.
3) They can be easily adjusted to just the right length and force within a relative broad range, i.e. from around 2.5 to almost 4 feet.
4) They don't bow and you can mount them perfectly vertically so there is no side force on the item being glued.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Pat, can you show a picture of what you're talking about? I hate my go bar deck with furious passion and really want to find something better...

I think John Arnold uses some sort of spring loaded go bars. IIRC there was a picture on one of the forums. Maybe John will show up and cast some light on his approach.
Tom

_________________
A person who has never made a mistake has never made anything!!!

Here you go, Ed. Like Bryan, I use some plywood attached to my ceiling above one of my work benches for a go-bar deck. I got the cheapest spring curtain rods available and, to be honest, if I had to do it again I'd spent the extra dollar per rod to get higher quality ones. Never-the-less, these do the job just fine. Here are a couple of pictures:





I guess I should also mention that the sign you see on the wall was given to me by my wife and is about golf....

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.