Stainless Tube Bending Bimini Top Construction

[rustnrot]

Relax, this is for my toyota-engined, surface drived, Chris Craft XK18...I want to make my own bimini frame stainless 7/8" tubing with fittings tigged on. Do not want to use aluminum and I gotta do it myself...and I am willing to get the correct tool...are these tools ok for tubing or more "pipe oriented"? In other words the "holder prongs" look like they might dent thinwall tubing during bending?

Aluminum tubing for biminis is I think .058" thick. I trust the same would be plenty for stainless? I am simply going to weld-up the hole where the set screw is on the fittings once satisfied with the fitup. Probably drill another hole in the fittings 180 deg from the existing one and weld there also.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=001&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=110128102572&rd=1&rd=1

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=003&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=130117919522&rd=1&rd=1

If it goes right I think I have a way to lift the rear hatch and have top fold down inside hatch and then close rear hatch over it. There is no bulkhead behind rear seat in this boat so I think a couple of "notches" on either side of the rear seat should allow this. I will want relatively tight radii bends and there probably will be no or little crown on the top of the bimini to reduce space folded-up.

[yeller]

Those will work if the tubing fits it properly. Any gaps between the tubing and the cradle walls will cause the tube to 'flatten' until it makes contact with the side walls. 7/8" SS tubing, electrical conduit (EMT) and rigid pipe are not the same outside diameters.

I made a top once with 1" SS and used an electicians conduit bender. The SS was smaller than 1" conduit so I first bent a piece of conduit then cut it in half (lengthwise) on the bandsaw. By placing the 'inside' half of the conduit in the bender, it made the cradle small enough to work with the SS.

I used one like this:
http://www.mytoolstore.com/klein/51211.html

[rustnrot]

Thanks! I trust you had enough manual "oomph" to make it bend ok? Did you just use the "standard-issue" marine polished stainless tubing (not sure what the wall thickness is?).

Sounds like it is not going to be as hard as I thought....

[MOP]

I don't know I am scratching my head on this one, I ran a cable and tubing shop in the USAF. I don't see you bending marine grade which is not near the quality of the military stuff without a "mandrel bender". Marine tubing is not seamless, look inside the end you will see the black line. Give it a try but make sure the seam is centered against the bender, good chance it will split if you have on the outside.

Phil

[gcarter]

I might would think you'd have a fairly long cheater on that handle w/SST.
The fit and seam ideas seem like good suggestions.

[mrfixxall]

this is the kind i use when im building a rol cage..little over kill but i know my nadds wont be hurting after im done...cheep too

http://www.etoolcart.com/browseproducts/12-Ton-Hydraulic-Pipe-Tubing-Bender.HTML

[rustnrot]

fixxall, I have seen those kinds of benders before but web lore seems to indicate that they are for pipe not tubing, the difference being that pipe (sch 40) has a much thicker wall than tubing and does not dimple against the (relatively small) stops of this kind of bender (ram-type) vs. a draw-type bender.

Have you bent actual tubing without dimpling and if so what wall thickness on this type bender?

Lastly, as all of you know pipe and tubing are measured differently. On this type of 'pipe' bender when they say 3/4" die, do they mean a die for .75" outer diameter tubing or a " die for 3/4" pipe which has an O.D. of 7/8" to 1" depending on schedule and material?

[mrfixxall]

fixxall, I have seen those kinds of benders before but web lore seems to indicate that they are for pipe not tubing, the difference being that pipe (sch 40) has a much thicker wall than tubing and does not dimple against the (relatively small) stops of this kind of bender (ram-type) vs. a draw-type bender.
Have you bent actual tubing without dimpling and if so what wall thickness on this type bender?
Lastly, as all of you know pipe and tubing are measured differently. On this type of 'pipe' bender when they say 3/4" die, do they mean a die for .75" outer diameter tubing or a " die for 3/4" pipe which has an O.D. of 7/8" to 1" depending on schedule and material?


if your worried about kinking the tube you can always fill the tubing with sand and weld the ends up...ive never needed to do that but i heard it works..
that hyd bender has a set of wheels that the pipe rides on and its a slow process so i dond think it will kink the tubing..It also refered it as a tubing and pipe bender..the thinest i bent was .024 and didnt have any issues but that was steel and not stainless which is a mo fo to bend anyways..

good luck

[yeller]

I don't know I am scratching my head on this one, I ran a cable and tubing shop in the USAF. I don't see you bending marine grade which is not near the quality of the military stuff without a "mandrel bender". Marine tubing is not seamless, look inside the end you will see the black line. Give it a try but make sure the seam is centered against the bender, good chance it will split if you have on the outside.
PhilA mandrel bender isn't necessary. The most important thing is to make sure the tubing fits the bender properly. If it doesn't contact the sides, the tubing will kink. That is why I bent a piece of EMT 1st and put 1/2 of it in the bender (as mentioned in my 1st post). I usually can't contribute much because you guys alway know more than me, but this one I am sure of. I used to do marine upholstery for a living. :)

Rustnrot, yes I had enough 'omph' to bend it...and yes it was just 'standard issue'. The SS tubing is no tougher to bend than EMT and the 7/8" will be easier to bend than the 1" that did.
I'm not sure where they measure the .75 from, but you can be sure that the SS tubing will be smaller than the .75 rigid or EMT bender. If you have a piece of the tubing, I suggest you go to Homedepot electrical department and see how it fits in the benders. You may have to do as I did and put a piece of 3/4" EMT in it to make it fit properly.
Lastly...I know you want to do it yourself, but it may be easier and cheaper to get a marine upholstery to bend it for you.

[yeller]

Did a couple quick measurements for you. The marine tubing is measured to the OD and EMT is measured ID. Don't know if this helps, because I don't know how rigid is measured. My guess though would be ID.