recommended rubber for rib pressing

[fairchild]

Hi all---
I am making nose ribs in my hydraulic press with a thick rubber pad.
They are coming out very nice except the my lightening hole flanges are
not quite turning over (bending) quite enough. I THINK my rubber isnt
quite extruding down into the hole far enough to full bend the flange to
30 degrees. I am thinking I need a slightly softer rubber. I think my current
rubber is some kind of carbon type rubber----- but I have read that a
polyurethane version is the best performing kind for this application.
Can some one advise me what durometer and thickness that is good ?

(Im actualy building a bearhawk--- not an RV---- but dont tell anyone ! )
Bob admits that he "stole" the RV's wing construction style because he
he must have thought it was so sensible....

Thanks ahead of time for any guideance.
Tim

[dpansier]

I have used sections of Truck inter tube with success, flows into the smaller areas and gives good part definition.

[vfrazier]

Originally Posted by fairchild

Hi all---
I am making nose ribs in my hydraulic press with a thick rubber pad.
Tim

How many tons are you needing for a nose rib?

[rv7charlie]

What dpansier said, on top of the rubber block. I assume you've seen these?
http://www.eaavideo.org/detail/video...t-hydroforming
and
https://www.youtube.com/watch?v=xw5yEMsDxR8

[fairchild]

yes I have watched both of those videos-----

I have 2 rubber chunks--- each 11 by 14 inches and 2 inches thick.
My jack is 20 tons---- but I may go bigger----
It is working really good except I need a tiny bit more extension of the rubber
through the lightening hole cavities to roll the flange a bit more.
My rubber is unknown hardness but looks like very close to car tire durometer-

Tim

[vfrazier]

I haven't tried them, but farm supply stores often sell thick rubber mats that sure look like a cheap source of easily sized rubber.