good morning. i screwed up my rv-7 rudder trailing edge a couple of months ago (it was badly bowed). later i built it again with excellent results.
some people just follow van's instructions and have no problems at all but don't know why. some people (like me) have problems here and don't know why too. so i tried to figure out how i could do it better the second time. i would like to post it here... maybe somebody else can benefit from it.
van's instruction says: drill and deburr everything, glue the trailing edge with proseal together, cleco it with a straight aluminum angle, let it cure a couple of days, remove the angle and backrivet everything together.
i believe that the weak point here is that, after removing the angle, the prosealed trailing edge is still flexible. when you rivet it, the forces which lead to a bending are greater than the "pro-seal". so it would be cool to have a still straight clamped trailing edge during riveting. here's the process:
- when i removed the aluminum angle after the proseal cured, i took a unibit and drilled carefully every other in the angle to a larger size (3/4 inch or so) so that the back riveting set "goes through"
- after deburring the new large holes, i clecoed it again to the trailing edge
- as a backriveting plate i used a cheap metal bar, to allow the trailing edge to sit flush against the bucking bar, i drilled small holes in the bar so that the "cleco-nipples" disappear in them.
- now you can backrivet every second rivet in the trailing edge from one side while the hole edge is still forced by the angle to straightness. (follow the suggested rivet pattern in the instruction)
- the rest of the riveting you have to do without the aluminum angle but most likely the trailing edge tends to bow now nuch less.
it turned out great with no measurable bowing, bending, banana shape or whatever. the additional effort is maybe 15 minutes or so.
so that were a lot of words for a simple process. i don't want to play the mr. know-it-all here but i feel this could really help somebody to avoid frustration.
Happy Buliding and Safe Flying!
Kay Stecklum
RV-7 dealing with bottom skin riveting
Munich-Germany / Huntsville-Alabama
some people just follow van's instructions and have no problems at all but don't know why. some people (like me) have problems here and don't know why too. so i tried to figure out how i could do it better the second time. i would like to post it here... maybe somebody else can benefit from it.
van's instruction says: drill and deburr everything, glue the trailing edge with proseal together, cleco it with a straight aluminum angle, let it cure a couple of days, remove the angle and backrivet everything together.
i believe that the weak point here is that, after removing the angle, the prosealed trailing edge is still flexible. when you rivet it, the forces which lead to a bending are greater than the "pro-seal". so it would be cool to have a still straight clamped trailing edge during riveting. here's the process:
- when i removed the aluminum angle after the proseal cured, i took a unibit and drilled carefully every other in the angle to a larger size (3/4 inch or so) so that the back riveting set "goes through"
- after deburring the new large holes, i clecoed it again to the trailing edge
- as a backriveting plate i used a cheap metal bar, to allow the trailing edge to sit flush against the bucking bar, i drilled small holes in the bar so that the "cleco-nipples" disappear in them.
- now you can backrivet every second rivet in the trailing edge from one side while the hole edge is still forced by the angle to straightness. (follow the suggested rivet pattern in the instruction)
- the rest of the riveting you have to do without the aluminum angle but most likely the trailing edge tends to bow now nuch less.
it turned out great with no measurable bowing, bending, banana shape or whatever. the additional effort is maybe 15 minutes or so.
so that were a lot of words for a simple process. i don't want to play the mr. know-it-all here but i feel this could really help somebody to avoid frustration.
Happy Buliding and Safe Flying!
Kay Stecklum
RV-7 dealing with bottom skin riveting
Munich-Germany / Huntsville-Alabama
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