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Would you worry about this in a potential purchase?

C

CATPart

Well Known Member
So the spinner is off center from the cowl. Could this be indicative of anything other than a poorly fit cowl? Having never built one of these I can only assume a few possible ways this would have happened. I personally would have tried hard to avoid this. Probably a dumb question. The rest of the aircraft looks great.

Off-Center.jpg
 
Age

Just like old people sag, so do old engine mounts. :eek: Fix is easy, new engine mount rubber shock mounts, and perhaps a washer or two for adjustment.
 
Engine sag? If so, there are a bunch of different threads about it, including this one and a bunch of others.

HTH.

--
Stephen

Edit: my post crossed with Pete's while I was searching for the old stuff. Great minds stink alike! :)
 
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Check before parting with cash.

The Guys are probably right that its engine sag, but I would want to pull the cowl off and make sure there is no deformation of the engine mount or firewall before parting with cash.

I have seen a number of 4's with bent engine mounts and firewalls caused by hard landings on rough strips. There are a number of mods for this like welding a gusset on the lower engine mount he and a gusset at the rear of the firewall on the weldment.

There is a photo of that on my blog.

Like I say they are probably right that its sag, but that lower engine mount area takes a beating on every landing, in fact that completely collapsed on our Tailwind on its last ground loop. I fitted the Tailwind with RV4 gear some years ago.
 
Or... the cowl could have just been built that way, I see this quite often where the builder just did not take the time to trim and fit the cowl properly.
 
A lot of builders allow for 3/16" to 1/4" engine sag and adjust the cowling accordingly while trimming. I allowed for 3/16" and the spinner to cowl have settled in nicely after 180 hours.
 
Good look over

If you have checked the engine mount and all is good and safe, and the isolators are new and properly installed (washers etc)..look for a good glass guy. Pay him to work his magic and what bugs you today will be almost unnoticeable after a pro works his voodoo.
Enjoy the plane.
 
RickWoodall said:
If you have checked the engine mount and all is good and safe, and the isolators are new and properly installed (washers etc)..look for a good glass guy. Pay him to work his magic and what bugs you today will be almost unnoticeable after a pro works his voodoo.
Enjoy the plane.
Click to expand...

It would be cheaper, quicker and just as effective to add some spacers under the two lower engine rubber mounts...:)
 
This is from a relatively inexperienced point of view so take this FWIW, but it occurs to me that it would be important to know if it's cosmetic or structural. If it has new isolators 80 hrs ago it's probably not age or G induced sag. So it is either bad cowl fit or structural. The RV4 guys or Van's must have a way to determine if the engine is on the correct thrust line. For me, that would be item 1. Item 2 would be to make sure the engine mount is structurally sound. If those 2 check out, it's cosmetic and you can fix it or not.

Jeremy Constant
 
A friend of mine has an older RV-4 that used to have a sag like that. It also had a curious airframe vibration at certain engine RPMs. Turned out to be cracks in the lower weldments behind the firewall that the engine mount itself bolts to, and are riveted to the fuselage & longerons. After replacing the weldments, no more engine sag and no more weird vibrations either.
 
BE SURE TO CHECK WELDMENTS INSIDE OF FUSELAGE ALMOST ALL OF EARLIER RV-4'S HAD THE LIGHT ONES AND WOULD CRACK STARTING AROUND BOLT HOLE. GET SOMEONE FAMILIER WITH THIS TO CHECK IT OUT AS IT IS HARD TO SEE SOMETIMES. THESE WELDMENTS CAN BE CHANGED BY PARTIALY REMOVING FUSE. SKINS. THE REPLACEMENT WELDMENTS ARE MUCH HEAVIER MATERIAL. LOOK AT THIS BEFORE YOU BUY.
 
Thanks for replies everyone. Now I know "sag" is the proper term. FYI this bird has conical mounts. I did read the posted threads about sag and they made me feel a bit more comfortable with the issue. If I find nothing structurally wrong, then assume it is cosmetic or sag, makes sense.
 
Conical Mounts

If everything checks out I would bet that it has a conical engine mount. I've seen them move/sag after just a few hours. FWIW.
 
Looks familiar

That RV4 looks like the one I owned for 3 years and and flew for 250 hrs. Is it 870MC? If it is, PM me.
 
the 80hrs on the mounts is meaningless, how many months or years ago were they replaced. if it was years ago, that's probably normal sag, if it was just months ago, a more detailed inspection is a must.
 
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