J

JDRhodes

Well Known Member
Just curious - and I don't what to start a horsepower debate - But...

How would a low powered RV-4 do? And has anybody had any experience? Just thinking that to create a fun, putt-around airplane and economical local hamburger getter, an RV-4 with a C-90? or O-200? would be cool.

I know that it would not climb 1000 fpm, and probably wouldn't cruise more than 120 or so. That's not the point. Think low and slow. What could you expect from <100HP?

If you think a Cessna-150 Aerobat is fun - a light, simple C-90 RV-4 would be a blast!
 
1/2 throttle

Get a 150HP RV-4 and just push the lever in 1/2 way. It will do pretty well, be economical to run, be WAY more fun to fly than a 150 anything, and be much more reliable than a C90.
 
I have a -3 with an 0-235 (108 HP @ 2,800 RPM) burns 4.4 GPH and I do about 150 MPH. I think if that is what you want to build go for it.

Performace is limited due to a cruise prop, but once it gets going the fun factor is just fine. :D
 
Exactly Dale

If you build one with a C90 your resale is zero in my opinion. You could buy/build one with an O360 and keep fuel costs way down just by throttling back. Then when you need power you have it.
 
throttle back

I new that was coming!

1) NOBODY would have the self control to run around at 1/2 throttle. :D
2) This is an excercise in what would happen and has anybody done it. Up to the builder to decide if it's worthwhile or not.
3) Re-sale - who cares?
4) C-90 with minimal accessories (no gyro, elect, handprop) looks like it would weigh 100 lbs less than a typical O-320 installation (with all that stuff). CG issues, I know. Might need a long mount.

These are expirimentals. OK to experiment. I just like noodle out the concepts. I'm not building one.
 
Geico266 said:
I have a -3 with an 0-235 (108 HP @ 2,800 RPM) burns 4.4 GPH and I do about 150 MPH. I think if that is what you want to build go for it.

Performace is limited due to a cruise prop, but once it gets going the fun factor is just fine. :D
Click to expand...

Bob Each is building a RV-4. He hasn't decided on an engine yet. It's between a Cont. O-200 or a Lyc. 235. Bob is concerned that the Lyc. 235 will have to much power.

We refer to his RV-4 as a LSA-4, or sometimes as a Harmon Rocket 1/2. Bob is concerned about the 120 knot restriction for an LSA.

Regards,
Jim Ayers
Modified RV-4/Harmon Rocket 2 Lyc. IO-540 engine & MT 4 blade propeller

PS The third plane being built in my hangar is Mark Swaney's F-1 Rocket with a Lyc. IO-540 engine with a 4 blade MT propeller.
 
Put on a climb prop, and a J-3 cub style open cylinder cowl! That'll help slow it down. And look pretty different.
 
Jeff,

I understand what you are thinking about.

Having spent a number of years racing Miatas it was always fun to talk to Vette guys because they would talk about HP. The Miata guys would talk about weight and suspension.

Depending on the course, sometimes the Miata would just smoke the high HP Vettes. And contrary to what most people think, the short courses favored the Vettes but if the course was set up so the Miatas never had to slow down, the Vettes owners would be crying.

Just remember, and this applies to airplanes doing acro, the secrete to going fast is never slowing down.

PS. and build the -4 with an open cockpit option!
 
JDRhodes said:
I new that was coming!

1) NOBODY would have the self control to run around at 1/2 throttle. :D
Click to expand...

I guess I should start believing what every one is always telling me...I really am a nobody!

I fly around at low power all the time (I do use full power for takeoff though).

When fun flying in our local area with my kids, we are in no hurry to get to nowhere so we cruise our 180 HP RV-6A at 5 - 5.5 GPH.
 
I say go for it. In my kitfox I slow it down all the time to about 80mph, sometimes slower. Very fun to weave in and out of trees in the boonies, we have that here. I go into the mountains all the time and fly through the channels, very fun also. Don't know if I want to do those things with the RV, can't see straight down, no I don't think so. That's why I'm keeping the kitfox.
 
A little OT.....but...

allbee said:
.............. I go into the mountains all the time and fly through the channels, very fun also. Don't know if I want to do those things with the RV, can't see straight down, no I don't think so. That's why I'm keeping the kitfox.
Click to expand...

.....powerlines have claimed quite a few. From my Ag experience, if you're going to fly down a river or canyon, look left and right continuously, since the towers or power poles will show up and THEN you'll more easily find the powerlines in advance.

Be safe,
 
It would be quick!

JDRhodes said:
Just curious - .... What could you expect from <100HP?
Click to expand...

I am still on my flight test here in the UK. All the testing is done so I am just building to a required 25hrs. I just spent a good half hour this morning burning about 5.5USG/hr. Not sure what power that is from a carburated 160hp O-320 but 2130rpm and 22.5". My guess is well less than 50% rated power but I will let you work that out. That gave me between 160 and 165 mph at around 3000'.

So in answer to your question it would perform quite well in level flight. However I think there would be two issues:
- resale value as others have mentioned.
- the CofG would be rather impractically far aft I suspect.
 
JDRhodes said:
Is there such a thing? I've got pencil sketches of that, too!
Click to expand...
Jeff,

Some time back someone posted a picture of an open cockpit RV-4 (I know there is an open cockpit RV-3 flying in Hawaii as well.) but I couldn't find it in a quick search.

The guy had it set up as convertible so he could put the bubble back on in the winter. In the summer he had two windshields. The rear one would be removable but I don't know if the front one remained in place when using the bubble canopy or not.

I suspect, but don't know, that he might limit his cruising speed to keep from getting pounded by the wind.
 
RVjim said:
Bob Each is building a RV-4. He hasn't decided on an engine yet. It's between a Cont. O-200 or a Lyc. 235. Bob is concerned that the Lyc. 235 will have to much power...
Click to expand...
Jim,

It is my understanding that it is easier to put an inverted oil system on a Lycoming. If negative G's are important to him, this might impact his selection. Other than that, there is nothing wrong with the O-200. Well, other than he will have to build a custom engine mount for it. Yet another reason to go with the Lycoming.

Besides, too much power translates into a great climb rate with the proper prop.
 
throttle stop?

You could put a -320 on for good resale value, but fabricate a throttle stop, limiting you to only 2/3 throttle or so? Seems like something like a stop directly on the throttle might be easily removeable in case you do want to have all the power, but try to keep it on there to limit your hp and fuel burn. :cool:
 
If fuel flow is that important put in a fuel flow gauge. Once you approach your limit don't advance the throttle more.
 
aerobatic LSA-4

N941WR said:
Jim,

It is my understanding that it is easier to put an inverted oil system on a Lycoming. If negative G's are important to him, this might impact his selection. Other than that, there is nothing wrong with the O-200. Well, other than he will have to build a custom engine mount for it. Yet another reason to go with the Lycoming.

Besides, too much power translates into a great climb rate with the proper prop.
Click to expand...

Empty weight has been our primary concern. You point about using the Lycoming 235 engine with an inverted oil system brings up an interesting point related to aerobatics. The LSA gross weight limit of 1320 pounds is below the RV-4 maximum aerobatic weight of 1375 pounds.
Our current challenge is to have a high enough useful load to still be a two place aircraft. And the empty CG location plays a big part in this, also.
Maybe an inverted oil system will be required to keep the CG far enough forward. :)

I heard recently that registering an existing homebuilt design as a LSA can increase the value of the homebuilt. However, this could have beed idle speculation, because of the current selling price of LSA's. Anyone know about this?

Regards,
Jim Ayers
 
Can't be done!

RVjim said:
I heard recently that registering an existing homebuilt design as a LSA can increase the value of the homebuilt. However, this could have been idle speculation, because of the current selling price of LSA's. Anyone know about this?

Regards,
Jim Ayers
Click to expand...
You cannot register an existing homebuilt design as LSA unless the kit manufacturer offers it as an E-LSA kit. You would have to register it as "amateur-built." It can still be flown by a sport pilot if it meets light sport parameters.
 
pierre smith said:
.....powerlines have claimed quite a few. From my Ag experience, if you're going to fly down a river or canyon, look left and right continuously, since the towers or power poles will show up and THEN you'll more easily find the powerlines in advance.

Be safe,
Click to expand...


I never fly low if those things are there, what I do is pick an area that I like, then fly no lower than about 200ft and check real close for power lines and such. I ain't stuppiiid. After an area is checked real good than I put it as a low and slow fun spot. Out west these areas are real easy to find. I have mountains near by and when the winds are good and the weather is clear I fly into them. I've taken mountain flying classes and the first thing they teach ya is to go slow and off to one side, the right side works best, this does two things, it allows you to have an out by being able to make a turn and go back out, and it allows you to hang wide and look into your next turn. On that one you can be hanging wide left or right. thanks for the concern.
 
RVjim said:
Bob Each is building a RV-4. He hasn't decided on an engine yet. It's between a Cont. O-200 or a Lyc. 235. Bob is concerned that the Lyc. 235 will have to much power.

We refer to his RV-4 as a LSA-4, or sometimes as a Harmon Rocket 1/2. Bob is concerned about the 120 knot restriction for an LSA.

Regards,
Jim Ayers
Modified RV-4/Harmon Rocket 2 Lyc. IO-540 engine & MT 4 blade propeller

PS The third plane being built in my hangar is Mark Swaney's F-1 Rocket with a Lyc. IO-540 engine with a 4 blade MT propeller.
Click to expand...

Jim,

Can you give us an update on your friend Bob's RV-4 LSA? How far along is the project?

Regards,
 
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