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13brv3 10-19-2017 07:40 PM

How tall is your plane?

I have an RV-3B that I bought already flying. The previous owner told me the motor mount had some cracks, and they replaced it with an RV-4 mount because they were told it was stronger. First, does anyone know if there was any difference in the -3 and -4 mount? Mainly I wonder if the gear sockets are at a different angle since the fuselages are not the same length.

The next question I'd have is if they used new gear from a -4, and if they're the short or long variety. The reason I'm questioning this is because I had an RV-3B before, and this one seems much higher in the nose than my old one was. I actually have to S-taxi to see forward, and I can't land it worth a ****, though that might be a different problem :-)

For reference, I took a measurement today which hopefully someone can compare to their plane. I measured 28" from the bottom of the firewall straight down to the ground. I'll be really interested to know if that's close to what others measure, or if I have a unique long gear RV-3B :eek:


Ironflight 10-19-2017 09:03 PM

If I was home, I'd have this for you in a heartbeat Rusty - but I won't be back with Tsam until Sunday or Monday. Ill get it then if someone else doesn't measure theirs first....

13brv3 10-20-2017 09:47 AM

Thanks Paul. No real hurry, and if I get multiple answers, that will be interesting too.

One other variable I thought of is that my old plane had a custom engine mount for the rotary engine, but it was based off the stock RV-3 mount. The landing gear sockets may have been slightly abnormal on that one compared to a stock mount though.


13brv3 10-25-2017 12:52 PM

I asked the owner of my old RV-3B to measure the height at the firewall, and he came up with 25.5" compared to 28" I measured on my current plane. Since that one had a custom motor mount, I still don't know if that one was short, or the new one is tall. I'd still be interested in some measurements if someone can measure an existing RV-3 or RV-3B for me.


RussellT 10-25-2017 09:03 PM

The measurement from bottom of firewall to floor on my 3B is very close to 29 1/2 inches, length of the gear leg from top to caliper mount flange is approx 40 1/4 inches. This is on a build in progress, standing on her own legs with new tires but without the engine fitted, the tail supported to level. Circa 2008 kit.

13brv3 10-26-2017 09:03 AM


Originally Posted by RussellT (Post 1213998)
The measurement from bottom of firewall to floor on my 3B is very close to 29 1/2 inches, length of the gear leg from top to caliper mount flange is approx 40 1/4 inches. This is on a build in progress, standing on her own legs with new tires but without the engine fitted, the tail supported to level. Circa 2008 kit.

Thanks for the measurements. The engine will make a big difference in the height, but I couldn't guess how much. The length to the caliper mount could be helpful, and I'll take a look next time I have the cowl and wheel pants off. The plans show measurements for the gear legs as well, so I could also compare to those.

I looked back through the logbook entries to see if there were any more details, and in fact there were. The mechanic said he removed the engine, mount, wings, and replaced the lower firewall weldments with the heavier RV-4 WD-403 left and right. He then noted that he reinstalled everything, with no mention of replacing the engine mount. It was a few years ago, and the owner wasn't a builder or mechanic, so he probably got the story wrong, or didn't understand what really got replaced.

Along the way, I read through a bunch of RV-4 threads regarding short vs long gear. What I learned is that the gear leg angles were different, so you had to have the correct engine mount as well. I also read that the short gear version was discontinued, likely a long time ago. It might be that the RV-3 was built using the short gear combo before the model was discontinued, then after the RV-3B came out, perhaps they all got the long gear version? This is all total speculation of course. I checked the plans to see if there was a WD number shown for the engine mount, but I don't see one.

I also ran across a number of reports of cracking lower firewall weldments, and I guess they made 3 version, with the last one being thicker. That must be what the mechanic installed.

At this point, still kind of a fun mystery though.


dacronwall 10-27-2017 03:53 PM

RV-3 landing gear
I bought my RV-3 with a cracked engine mount. It was built in 1984/85 and was the original. It had cracked and been welded 2 times before, probably because was then equipped with an IO-360 and a Hartzell CS prop which is heavier than it was ever intended to handle.
We ordered a new RV-3 engine mount and gear legs from Vans,(in 2014) and had them powder coated and then installed. It has the new mount with an IO-320 and Catto prop on it now.
I have to do S-turns when taxiing to feel comfortable, but I have a slider canopy which gives me room to crane my head out of either side for view. As far as landing, it was hard at first coming out of a Citabria. I learned to carry a bit more speed over the numbers and fly it on, I wheel land it 95% of the time....and it looks cooler too.
I am going down there this afternoon, I can throw a tape measure on it and let you know.

13brv3 10-27-2017 04:08 PM

Thanks for the info Dave. Your measurement should be a good comparison, because mine also has an IO-320 and Catto.


dacronwall 10-27-2017 07:59 PM

RV-3 height
I just flew it.
Full fuel, measures just over 28" to bottom of fire wall.
My plane is 842 lbs empty, I have 22 gal fuel in a fuse tank (no wing tanks) and I have done the CN-1 and CN-2 wing mods.
Nothin fancy as far as instruments, but do have ADS-b in/out.

Best flying RV of them all. Keep it light, keep it fast.

13brv3 10-28-2017 07:48 AM

Thanks Dave. I think I'm about ready to accept that my current plane is the normal height, and the old one was shorter for some reason.

Mine was built heavy, including full upholstery and duel electric system. I'm working on a long term diet program for it, including replacing those two 15 lb batteries with a single EarthX battery. Sadly, it's in a hangar 1.5 hrs from home, so I'll wait until space opens up closer before I do too much work to it.


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