R

RV-4

Well Known Member
Hello everyone

I sometimes think about converting my RV-4 short legs to the long ones and I'm wondering how hard of a conversation and how expensive it might be..

Is there anyone who has done the job who could share info?

Thanks

Bruno
[email protected]
 
I was just talking to my wife about putting the longer gear legs on our 4 when this post just came up. It would be good to have that bit extra prop clearance . Was just looking today at someones 4 with the longer legs and while mine is apart at the moment would be a good time to change them . Any comment's for or against ?.
 
Bruno,
I did a conversion several years ago on a freinds airplane. He had purchased it, not built it. He had a hard landing and bent the gear up bad enough that it needed to be replaced. You really need to take everything into consideration before making this mod. It may go very smooth and it may be just the oposite. In his case he had the old style cowl with a 4" prop extension. When we put on the new motor mount and legs we came up with several problems. The first problem was that the baffling and engine no longer fit right in the cowl. No amount of work seemed to right the situation. To make a long story short the baffling was shot and needed replaced anyway. Without completely reworking the cowl it wouldnt fit right. Ended up with a new cowl and of course that ended up needing a 2" extension, we had to rebuild the filtered airbox, let us not forget that this also leads to needing a different spinner, not to mention bolts, hardware ect. The gear angle is different and the brackets for the wheel fairings and brakes are different. New brake lines (no big deal here)
I am not trying to discourage you from doing it just making you aware of some of the things that may come up.
I have flown both the short and long leg versions and saw no great advantage of the long gear legs. I will say that when one sits next to the other that the long legs look a little nicer. I never had a prop strike with my short legs in over 1100hrs of flying so I dont see prop clearnace as an issue. If your are flying with an 0360 with a longer prop it may be.
I would have to say if your tires wear evenly and everything works the way it should I personally would leave it alone. Good luck either way ;)
Ryan
 
She got Legs...

Bruno,

I have performed the "switch" twice. To do it right requires a new engine mount as well since they are match drilled by Harmon Lange. Big job. I flew my RV4 for 10 years with short legs out of my 1100' rough turf strip in AL. Also have many hours in friends Long-legged RV4's.

Adding to Ryan's, here's my pro's and con's list from the cheap seats.

LL Advantages: Slightly shorter STOL takeoff. (higher AOA)
Slightly better 3 point STOL landings (less TW first)
Better prop clearance (fewer rock dings, if you venture off road alot)
Better looking "curb appeal"(in my humble opinion)

LL Disadvantages: Poorer forward visibility during taxi
Slightly more drag :)
Lots of work and $$$ to convert (wallet stress)
Longer moment arm on engine mount/firewall stresses.

My advice:"If it ain't broke, don't fix it"

V/R
Smokey

PS: On inspections I see many more buckled firewalls and cracked engine mounts on Long Gear airplanes, mainly from poor pilotage. (The Short gear have less moment arm and less shimmy). I guess Bob Axsom would even tell you the Long Legs have more drag, which they should.
 
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smokyray said:
I have performed the "switch" twice. To do it right requires a new engine mount as well since they are match drilled by Harmon Lange.
Click to expand...

Not to pick nits but you absolutely have to have a new engine mount, regardless of drilling, the long leg mount has the gear sockets at a different angle so that the wheels remain in the correct place relative to the C of G and the long legs are larger in diameter and will not fit in the old mount.
 
Short vs long legs

Hi Guys

Thanks a lot for all the feedbacks...greatly appreciated

There are no special reasons for wanting the long gears legs except the sex appeals that is all..

With a 3 bladded Catto, prop clearance is not a factor and I mostly do main gears landing first rather than 3 pointers anyway ..

I was curious at the work and expenses involved in the process but with all your good advises, I will stick with what I've got..It has been working fine for the last 12 years ..

Like Smokey says :"If it ain't broke, don't fix it"

Thanks again

Bruno
[email protected]
 
... some additional points to consider

Bruno

We replaced the on our RV-4 the shorter gear by the longer new one.
Background: We bought the 4 from a previous builder that had it not completely finished. We wanted to have a new O-360 instead of the old O-320 that came with the project. Additionally the landing gear legs were not finished (needed heat treatment). -> Yes, he did even the landing gear legs on his own!

We found some additional points that you might consider:
You will need a new engine mount as mentioned by Russ and Smokey.
The center bolt holes that attach the engine mount to the firewall will not line up with the existing holes, because of the changles angle. We also had to fabricate some washers because the engine mount did not contact the firewall. And of course, the washers needed to be slighly conical as well, because firewall and engine mount were not parallel.
6962709246_0de58e6549_z.jpg


On our airplane the lower corner bolt holes did not align completely as well. We solved that by fabricating some special bushings from stainless. A hole story of its own...
7108782979_d0a5bc7e8a_z.jpg


Just some additional points, if you want to make the trade off the cooler look against the work to be done.
 
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Vans has the instructions

Contact Vans for a .pdf on how to fabricate a backing plate to fix the engine mount firewall hole mismatch. It is a known issue.
 
Long legs issue

Thank Andreas

It appears to be way too much work just for a better look..

Having a 3 bladded Catto on my RV-4 solved the prop clearances isues so I will stay with what I've got.

Thanks to all for the replies.

Bruno
 
NOW........to switch the question up (don't mean to high-jack the thread):

I have cracked lower weldments on my built & flying RV-4 (original weldments -> cracking is a known issue). I already purchased the new motor mount, longer gear legs, new leg fairings and new wheel pants.

Question is: Should I switch everything over when I'm in there to replace the weldments, or should I just replace the weldments? I'm not retired so I don't have buckets of free time, but I'm tired of renting a C-172 to fly while I try to find time to work on my RV-4 (I won't fly my RV-4 until the weldments are replaced).
 
RV4

I had the lower weldments crack on my first RV4. I figured an easier way to repair them. Give me a call if interested. Evenings best. Jim 317-718-3415
 
Robert,
Depending on the vintage of your RV there were 2 different kinds of weldments. The old style had a split between the horizontal and vertical legs of the weldment. The newer style are one solid piece no splits. The old style tended to crack. I would say if you have the old style it would be a good idea to replace them and if you dont have gobs of time I would stick with the repair and keep the rest of the airplane the way it is.
Ryan
 
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