Bending Aluminum Tube Around Elliptical Arc

[Andrew Herrick]

Yup, that Little Guy is fairly similar to what I'm envisioning, but with one big difference:

A bent tube for the ribs rather than a truss.

Why? Well, I'll definitely grant that the truss rib is easier to manufacture, and naturally stronger. The problem is that the galley lid has to be almost flat. You can't use a truss-style rib (or a triangular block of plywood) for a super curvy galley. That's why the lid stops before the profile starts to really curve. (I know you know this, Aggie79, but it might not be apparent to everybody). And I'd rather not sacrifice the user-friendliness of a galley lid that extends all the way to the rear of the camper.

By the way, so far, I've heard that bending 1.5x1.5x1/8-inch aluminum tubing to an elliptical arc isn't a standard request and would require 8k in tooling So I'm waiting to hear back how large of aluminum tubing can be bent with standard equipment.

[aggie79]

You can't use a truss-style rib (or a triangular block of plywood) for a super curvy galley. That's why the lid stops before the profile starts to really curve. (I know you know this, Aggie79, but it might not be apparent to everybody).

I agree that a truss-style rib would only work for a "half-galley" hatch. I was just "thinking out loud" to keep the creative thoughts coming.

And I'd rather not sacrifice the user-friendliness of a galley lid that extends all the way to the rear of the camper.

My hatch is about 6' long and curvy. It was a bear to make but does open up tall enough to easily access the galley.

I've been fortunate to not have spring-back even though my hatch was framed with 1-1/2" deep plywood ribs. It is skinned both sides so I guess that helps to strengthen the hatch.

[Philip]

If you end up going with the bender I linked to. Let me give you a warning. You won't make the curve in one pass most likely. Plan on making a few passes. Run all material threw in each setting. Do not run them one stick at a time. Then change settings on the roller. You would end up with sections with different radius on them.

BTDT on sheet metal rollers.

[QueticoBill]

So, I was touring a factory today, one that makes platforms, orchestra shells, chairs, and related products, and sow the perfect tool for your elliptical aluminum ribs. Not in my price range I;'m sure but really cool to watch it pop out odd identical unusual shapes.


And just for teh heck of it - THE way to glue stressed skin panels - a roll coater filled with moisture cured urethane, does up to 5 x 12 every 5 minutes, which includes vacuum bagging till set (special 3M 20 minute curing adhesive).



It was hard not to think of being able to build a tear in an hour or two with all the gear in the plant - robotic welders, powder coating lines, all kinds of CNC machines. Oh my.

[Billy C.]

Andrew. Use a buck. A buck is used all the time in fabrication. What you do is build a form to match the inside of the tubes that follows the shape of the finished product. Make it from two pieces of plywood glued and screwed together. You can then bend the metal to the shape and you have the buck to compare it to. You could even clamp it on one end and bend it around the buck but you will have some spring back with that method. So using that method you would have to over bend it to get it to stay in the shape you want. Go slow and compare it to the buck often and you will be surprised at what you can do. This method is used in many areas from boat building to hot rods to airplanes. Do a little research online and you will see what I am talking about. I hope this helps bill

[Syberia]

I made mine out of steel, not aluminum (don't have the equipment to weld alu.), but I did it the old fashioned way - fire and a hammer.

[Andrew Herrick]

Andrew. Use a buck. A buck is used all the time in fabrication. What you do is build a form to match the inside of the tubes that follows the shape of the finished product. Make it from two pieces of plywood glued and screwed together. You can then bend the metal to the shape and you have the buck to compare it to. You could even clamp it on one end and bend it around the buck but you will have some spring back with that method. So using that method you would have to over bend it to get it to stay in the shape you want. Go slow and compare it to the buck often and you will be surprised at what you can do. This method is used in many areas from boat building to hot rods to airplanes. Do a little research online and you will see what I am talking about. I hope this helps bill

Bill, you read my mind. Great idea. After talking with different turnkey manufacturers, I think a "buck" is how these hatch ribs would have to be fabricated in limited volume. With a little math, I should be able to design two bucks: One for the final form, the other as a form. Ideally, metal bent around the form should springback and match the final form. Sounds good in theory?