Advice needed for bending conduit: convertible top content

Resurrecting this 2020 thread at the end of 2024. I still don't have a convertible top for the '32 phaeton, and would still like to make one.  This thread made me abandon the conduit idea for a few years....But I'm back to thinking that is a method worth trying. - JoeyM

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I have been looking at threads at locostusa the HAMB where folks are building frames for convertible tops out of conduit, and I'm feeling inspired enough that I am considering trying to make my own frame for a folding phaeton top.

https://www.locostusa.com/forums/viewtopic.php?f=23&t=18512&sid=5713d35aa1aef012161deaaffaca2c14

https://www.jalopyjournal.com/forum/threads/building-a-29-a-roadster-top.1090592/

Some of those bends are pretty tight. 

What method and or equipment should I be using if I want to make really tight bends like that?  I've heard about filling the tube with sand.  How well does that work with conduit?  Would a Harbor Freight/Northern Tool bender be capable of producing those narrow radius curves?

Just get a conduit bender at home depot

for the super tight ones i might try sand and leverage around something round

The radius shown is too tight for an EMT hand bender.   Even a short radius bender has a 3" radius bend.  A standard hand bender is around 4 1/4" radius bend.

The bender from the Hammer Store won't work, either. 

Your Link said:

The Klutch® Manual Metal Bender with Floor Base makes duplicate or one-of-a-kind parts in the shop, in your truck or on the jobsite! (Will not bend conduit or exhaust pipe). You get 1in., 1 1/4in., 1 1/2in., 1 3/4in., 2in., 2 1/2in. and 3in. round dies plus a right angle die.

EMT is extremely thin walled.   And not a very high quality steel.  Bending any sort of thinwall tube requires a mandrel (the bender) and a folow bar (the floor in this case)  It won't like incredibly tight radiuses, and packing it with sand will likely only serve to blow out the seam.      If you can make it work with a 3" radius, then it can work for a frame for a top, but it's still pretty lightweight.  (I built a top frame for a friend's '78 Z28 homemade roadster decades ago)     

I wouldn't plan on welding EMT, either.  

Cooter said:

The radius shown is too tight for an EMT hand bender.   Even a short radius bender has a 3" radius bend.  A standard hand bender is around 4 1/4" radius bend.

Good to know. That explains a comment in the HAMB link above saying, "there's nothing wrong with using EMT, that just becomes the thing that determines the shape of your roof"

Now I need to decide if that's problematic or not

I am revisiting this idea 4 years later: 

This thread scared me away from conduit frames for convertibles...for a while.  I drove the Datsun without for a few years, but recently ordered a convertible frame kit from speedway.  It is a kit for the frame of a roadster top,

...do I knew it would need a bit of modification to fit on a phaeton-type body.  How much modification? It'll need to be taller, wider, and longer.  Oh, and most interestingly, the radius on the side pieces for the kit's bows/irons is no tighter than what can be achieved with conduit 

JoeyM said:

I knew it would need a bit of modification...How much modification? It'll need to be taller, wider, and longer.

The distance from my windshield to my roll bar is 42 inches.  The Speedway kit for roadster tops is a lot shorter than that.

Looks like you lost some toes between the last two posts. 😳

In reply to AngryCorvair (Forum Supporter) :

He only had four on the right foot so he can't afford to lose many.

AngryCorvair (Forum Supporter) said:

Looks like you lost some toes between the last two posts. 😳

Nope. Still have five digits on each foot.

The only garage-related injury recently was getting some skin removed from my hand by an angle grinder

JoeyM said:

AngryCorvair (Forum Supporter) said:

Looks like you lost some toes between the last two posts. 😳

Nope. Still have five digits on each foot. The only garage-related injury recently was getting some skin removed from my hand by an angle grinder

Been there. Flap disk will wreck a knuckle in no time flat.

Just an observation, but the none of the tube bends in those other threads look to be particularly tight radius, and the one in the first picture here actually looks more like square tube to me. Pie cut, welded, and ground smooth will make pretty much any radius you want. The main thing I saw in those threads that could be used for sharper curves would be wood.

Driven5 said:

The main thing I saw in those threads that could be used for sharper curves would be wood.

Good point. I'm wondering about the wood.... Some tops have it, some don't. Should I run a wood strip along the top of each metal bow?

The original 1932 Datsun type 11 did have wood. I know that a lot of YouTube videos Show people folks stapling their top material onto wooden parts of the frame   on the other hand, the Bimini boat cover folks Don't seem to ever use staples, instead making a sleeve to run a length of tubing through. 

I was thinking about using sunbrella fabric, like the Bimini folks, but have no experience with it. Can staples be put through sunbrella without causing it to fray?

Driven5 said:

The main thing I saw in those threads that could be used for sharper curves would be wood.

Good point. I'm wondering about the wood.... Some tops have it, some don't. Should I run a wood strip along the top of each metal bow?

The original 1932 Datsun type 11 did have wood. I know that a lot of YouTube videos Show people folks stapling their top material onto wooden parts of the frame   on the other hand, the Bimini boat cover folks Don't seem to ever use staples, instead making a sleeve to run a length of tubing through. 

I was thinking about using sunbrella fabric, like the Bimini folks, but have no experience with it. Can staples be put through sunbrella without causing it to fray?

So it turns out that an ordinary conduit bender can achieve the same bends as the bows in the speedway Kwik top kit for top irons