Hysol ??

[southwind32]

I'm replacing my front spar on my project. Taking the hysol off is time consuming, but making progress.
My question is, can you put a new mixture of hysol over old cured hysol? OR do I need to remove every little bit of the old hysol. I'm only concerned with hysol on wood. I'm able to remove 95% free the ribs from the spar, but if there's any left, do I need to go back remove any remaining on the wood, or will it bond ok?
Thanks
Brian

[Esser]

Hey Brian, I think you could be ok, my only concern would be did the heating of the hysol affect its integrity. I think false ribs would be ok but remove all hysol off the ribs

[efwd]

Hey Brian. You should make good time at cleaning off the Hysol from the ribs by using a sanding wheel on a dremel.

[Slyfox]

when I went from long wing to short I needed to remove some ribs and hysol. I found if I heated up the hysol it scrapped right off. I used my 1500watt gun. . Now I don't know if I just got lucky or it will work for you, it did for me.

[jiott]

I agree, if it was me I think I would try to sand off most of the old Hysol on the wood. However, I wouldn't stress too much about it because the bond of ribs to spar is not a critical structural joint. The ribs only serve to space the spars one from another and to provide an airfoil shape for the skin (fabric) to adhere to. The Hysol is only there to keep the ribs from sliding around and getting out of position. Your critical structure is the spars, diagonal cross braces, and the lift struts.

[jiott]

As was stated, the false ribs are a little different story because the Hysol is the only thing holding them in place, so I would be more concerned about a good Hysol to wood joint on them, even though they are not critical to flight. On the main ribs I would bet that if all the Hysol to wood joints were loose you would not notice a difference as long as the Hysol to spar joints were intact to keep the ribs in position.

[David47]

I have to respectfully disagree with the comment that the rib to spar joint is not structurally critical. A significant amount of the airload applied to the wing fabric is transferred to the ribs, which in turn transfers the load to the spars. In our particular rib to spar joint geometry, the ribs interlock with the spars which forms a large part of that load transfer, however the Hysol provides stabilisation of the joint (eg prevents rib rotation) and also provides additional load capability. So I would say that the rib/spar junction are important to the manner in which loads are shared between covers, ribs and spars.

[Slyfox]

I remember reading once that you don't need the glue. ha, yes that's what I read. that the glue is mainly to hold things together until you get the covering on. I don't know if I would feel comfortable with that or not, but that's what I read. I think it might have been the original designer of the kitfox. but I remember reading such a thing is all I can say.

[jrevens]

I have to respectfully disagree with the comment that the rib to spar joint is not structurally critical. A significant amount of the airload applied to the wing fabric is transferred to the ribs, which in turn transfers the load to the spars. In our particular rib to spar joint geometry, the ribs interlock with the spars which forms a large part of that load transfer, however the Hysol provides stabilisation of the joint (eg prevents rib rotation) and also provides additional load capability. So I would say that the rib/spar junction are important to the manner in which loads are shared between covers, ribs and spars.

I absolutely agree, David.

[Esser]

Just to clarify in my post, I thought you might be ok leaving hysol on the false ribs as they aren't structural but to remove it all from the ribs.