Fuselage crack RV4

Hi and seasons greetings. I recently bought an RV4 with O-360 and the newer style fuselage weldments. Wish I could post a picture but there is a vertical crack in the right fuselage skin that extends about 2-3 rivets above and below the lower edge fibreglass cowl cheek extensions. It is JUST aft of the cowling . Of course looking to fix but wondering how extensively ( if at all ) I should extend the patch (.040) past the standard 3 rivets beyond the crack . The fibreglass cheek extension will have to come off and be modified to go over the patch .
Once again. Wish I could post a picture but I thought that given the perpensity for hard landings to wrinkle firewall maybe something that goes a bit lower picks up the rivets that tie skin to lower weldment might help ? The minimum upper limit will be about 2/3 of the way up inside the cowl cheek extension to extend 3 rivets past the end of the crack .But maybe higher to balance load .... structure still needs to flex for sure . Obviously will be stopdrilled .
I have a picture of problem and outline of my proposed fix that I can gladly email to anyone willing to offer an opinion and again apologies for not being able to post that picture.
Could be just overthinking this but I believe that overkill is right where I like to be !�� Many thanks in advance Stew. [email protected]

Many thanks

Much appreciated Carl. Merry Christmas

Stewbronco said:

Hi and seasons greetings. I recently bought an RV4 with O-360 and the newer style fuselage weldments. Wish I could post a picture but there is a vertical crack in the right fuselage skin that extends about 2-3 rivets above and below the lower edge fibreglass cowl cheek extensions. It is JUST aft of the cowling . Of course looking to fix but wondering how extensively ( if at all ) I should extend the patch (.040) past the standard 3 rivets beyond the crack . The fibreglass cheek extension will have to come off and be modified to go over the patch .
Once again. Wish I could post a picture but I thought that given the perpensity for hard landings to wrinkle firewall maybe something that goes a bit lower picks up the rivets that tie skin to lower weldment might help ? The minimum upper limit will be about 2/3 of the way up inside the cowl cheek extension to extend 3 rivets past the end of the crack .But maybe higher to balance load .... structure still needs to flex for sure . Obviously will be stopdrilled .
I have a picture of problem and outline of my proposed fix that I can gladly email to anyone willing to offer an opinion and again apologies for not being able to post that picture.
Could be just overthinking this but I believe that overkill is right where I like to be !�� Many thanks in advance Stew. [email protected]

Click to expand...

A doubler three rows past, doubler one gauge above repaired skin is standard. It has been a long time since I had my RV-4. I would lead to replacing the whole cracked panel. Again it's been awhile. So I understand your steel weldments are OK? On VAF forums there is at least one excellent thread showing extensive repairs in this area on an RV-4. You are not the builder of the plane. I assume you are comfortable doing sheet metal and drilling fasteners out.... etc. If not you can learn... My main advice is inspect they **** out of the firewall, adjacent fuselage structure, engine mounts to make sure there is no hidden damage.

Firewall

Yes firewall is pristine as is engine mount . Weldments all good . I actually doubt this is from any hard landing or abusive handling as I knew the builder and the second owner ( I am the third) and they were excellent professional pilots of long standing.I also had 3 very experienced RV gurus look at plane prepurchase We are planning an .040 doubler and will do both sides on the basis that symmetry is important and who knows if left side is about to have same problem . Just doesn't seem like any kind of common problem I saw on forum or on planes I looked at ...but want the fix to solve problem not just be a patch if possible. Many thanks.

Check your cowling installation

Those cracks are between the rivets that secure the cowling via hinges/hinge pins. I suspect they are developing because of excessive vibration/loads from the cowling movement. The engine/gear loads are carried through the heavy angular structure behind the firewall which tie directly to the upper and lower longerons. A repair to what you have could possibly be made with a trim out of the damaged skin and a repair doubler put on the inside. At my day job, I do structural repair and mod design for heavy jets, so its simple in my eyes, maybe not so much for others. If you do the internal doubler, use flush rivets, seal the joint with proseal and it will be almost invisible. I did build my -4, so I am familiar with the area you are working with.

Agreed

Thanks Bill ... that was an opinion offered by a very experienced local RV fellow also as to the cause . I value his opinion greatly and it is to me it is the one that makes the most sense as all else ( firewall / engine mount is good . Problem is not much room in behind there to make the repair you suggest if I am following you . That structural angle is very close in behind but will certainly give that one another look . Plan on adding 4 nut plates ( 2 on top part of the cheek and 2 underneath) to secure cowl to the " cheek " extension to help with this one also .Many thanks and appreciated your advise on the gear intersection fairings and the pictures ... definitely going to follow your lead there. Stew

On my old RV-4, I never had cracks but I did have smoking rivets. My IA suggested replacing the rivets with #4 screws, and that solved it. Don't know how relevant that might be when you attach the doubler...

Ed

RV expert living in Langley-Bryan Carr

Stew,

If you're based in the Langley, B.C., you must know who Bryan Carr in Langley is. He's a multi repeat RV builder of many models.

If you don't know him or haven't communicated with, I suggest that have him look at what you have, and if anyone can provide excellent guidance, I'm sure Bryan is the man.

Jake Thiessen
Independence, OR

Aileron brackets..

While were talking all your issues, the RV-4 is completely "hand built" with zero predrilled parts for the most part. The aileron brackets are often different left-to-right. The key is making sure the ailerons sit even with the wing and not high or low. it will make trim issues if so, and you will be back to drilling new hinge brackets. Think, check and rethink before making any corrections to the "mismatch" you have if the plane was flying true before.

I see Speedy One has gone to a new home... Good to hear!

One of the ways to correct for a "heavy wing" was to slot the aileron mounting bracket and raise/lower the aileron slightly relative to the rear spar. Speedy One used to fly pretty true, at least George never had trouble holding position in formation... So whatever he did building it has been working so far.

Good eye Rob

Yes ... new owner and George built a good plane and I am leaning very heavily to just replicate what George had with brackets ( I have another thread on that exact subject ) but on the " measure twice and cut once " theory I thought getting some educated experienced second opinions would be in order . Good thing about cold is it slows you down enough to rethink things without getting impatient.