Thinking about Building an RV-7, but I have a few questions

[svanarts]

Originally Posted by cgrossl

I do plan on getting my tail wheel endorsement along with some tailwheel time after I get the endorsement. My concern is how much harder is a taildragger RV to handle than say a Cub or Citabria during takeoff and landing. I know that the RV7 is a sport plane and I also know that there are some planes out there that low time pilots have no business in. From what I have heard, the RV7 isn't one of these plane, but I wanted to get some more opinions before I decided what I am going to do.

I haven't flown the RV-7 specifically but I have flown the RV-6, and my RV-4 and have about 800 hours in my old Aeronca Champ and the RV-6 and -4 were both much easier to land in my opinion. They handle crosswinds much better and track fairly straight down the runway. The RV is fairly docile as taildraggers go but it will still bite you if you don't watch it. If you can handle a Citabria you won't have any problem with your RV.

[rjsflyer]

Another budget item to consider while building: you stated you'd likely put 100-200 hours of flying in before your finished building. If your renting a spam can at, say $75/hr, you'd spend $7500-$15000 on flying during the build. For me, it's a compromise right now, getting ready to lay out large chunks of cash on items like avionics, instruments and an engine. Paying for the kits is pretty easy as you go. I haven't flown much recently due to putting more $$ into the plane for the large ticket items.

[4kilo]

Cameron,

As far as aerobatics goes, the engine doesn't really care about the attitude of the aircraft, it is only affected by the loading. You can have a positive G load even while inverted. If you only want to do the usual sport aerobatics, you will never unport either the fuel or the oil unless you make a goof (which will only last a second or two - not enough to cause any problems other than to dump some oil on the belly of the airplane).

Serious negative G aerobatics does require inverted fuel and oil systems, but since that is not the mission you intend for your airplane, you really do not need to spend the weight or money.

Pat

[Mel]

Your idea of a mid-time engine is also a good one, especially if you plan to do your own overhaul. I started with a high time first run O-320 (2500 hrs), but with good numbers on oil consumption and compression. I flew the airplane for 300 hrs before OH, and even then, it was running great and all parts were within acceptable limits. The surprising part of this scenario is that you won't save a lot of money going this way. Overhauls are expensive, even when you do them yourself. You do save a little money and gain a ton of experience.

[cgrossl]

Pat,
I understand what you mean by keeping the plane positively loaded, but I'm just wondering how steeply you can climb, or dive and still not uncover the oil or fuel pickup. If you are climbing very steeply, there is only 1G on the aircraft, but all of the oil would be at the back of the sump. The same would be true during a steep dive, only the oil would be at the front of the sump. In either of these situations, I would think that after you exceed some climb angle or dive angle, the oil and/or fuel pickups will be uncovered. I would think that bank angle would have the same affect, as long as you aren't turning while you are banking, like during a roll. Isn't there some point during a roll where there are some negative G? Is it just not enough time to affect anything? My line of thinking is coming from my automotive background because I know almost nothing about the internals of a Lycoming engine. I guess I'm trying to figure out more about how these things work.

Mel,
I thought my line of thought was sound on the engine. I was hoping to save money by doing the overhaul myself, but if I don't save money, I still want to do it. I've built many car engines including several air cooled VW engines, which look very similar to a Lycoming. Overhauling an aircraft engine would be a great learning experience. I think that's the biggest reason that I want to build a plane. I'm bored to death if I don't have something interesting that I am learning about.

By the way, are there any other things that I need to consider before I decide to build?

[Mel]

I think you are thinking of "slow rolls" where you would have 1 negative g at some point. The typical rolls done in RVs are "aileron rolls". An aileron is so named because you only use aileron control as opposed to rudder input. This is similar to a barrel roll where you will keep 1 positive g throughout the maneuver. This is an over simplification, but the idea is that you can do them without inverted systems.

[cgrossl]

Mel,
When doing an aileron roll, or barrel roll, what is the center of rotation? I am guessing that since the plane is experiencing positive G-forces through the entire maneuver that the centerline of rotation is slightly above the fuselage? If the roll rate is high enough, I am guessing that centrifugal force during the roll is what keeps the plane under positive G loads throughout the manuever? Please correct me if I'm wrong.

Obviously, aerobatics are a long way down the road for me. It is starting to sound like I have a whole lot to learn.

[szicree]

A barrel roll is pretty much what a "corkscrew" type roller coaster does. An aileron roll is more or less the same deal, only less coordinated.

[flyeyes]

Originally Posted by cgrossl

Mel,
When doing an aileron roll, or barrel roll, what is the center of rotation? I am guessing that since the plane is experiencing positive G-forces through the entire maneuver that the centerline of rotation is slightly above the fuselage? If the roll rate is high enough, I am guessing that centrifugal force during the roll is what keeps the plane under positive G loads throughout the manuever? Please correct me if I'm wrong.

You've got it right, except that the axis of the roll is more than "slightly" above the fuselage. A typical aileron roll consumes 50 or 100 feet of altitude (You pitch up initially, resulting in a climb, and lose altitude while inverted). The slower roll, the more altitude you need.

There are a couple of rolls here from two different angles. Looking over the tail makes it a little more obvious, I think.

James Freeman

[Spindrift]

James,

Great video! I'll definitely be reviewing anytime I need a little extra motivation to work on my plane.

Cameron,
I went through much of the same questioning before buying my 7 tail kit last week. Just to be sure I wanted a 7 i/o 9, I dropped the big bucks for an aerobatics lesson in a T6 Texan about 3 weeks after passing my checkride. Not only was it incredibly fun -- no doubt on the 7, but I learned a ton beyond just doing loops and rolls -- which were easier than I thought. We did unusual attitude recovery(similar to under the hood -- eyes closed, get disoriented, open eyes, my airplane...) but instead of mild stuff like during training, I was recovering from well past 90 degrees. Because of the positive G load, you have no idea how far over you are until you open your eyes. We also did a full stall -- which in a Texan means a MAJOR snap to an inverted dive (stick slammed so hard and fast it bruised my thigh). Obviously in the hands of a great instructor, not a big deal, but it definitely got my attention and gave me a much better understanding of some of the comments I've read on this and other boards about stall/spin accidents.

Long story, but the moral is I learned enough to know that I don't need an inverted system, but I definitely will be taking more aerobatics lessons in "3-5 years" when my 7 is done!

bill
RV7 (A?) -- working on HS rear spar!