Rocket Wings

Hello to the group.

There is an RV project for sale locally that I am interested in. I know it would be hard to improve on Vans RV 4, but I would like the expert opion of this group to advise me on a few ideas I have.

Has anyone installed Rocket type or clipped wings to a standard 4 ?.
I think it would be neat with a few extra MPH and faster roll rate.

Some may ask why not just buy a rocket kit but I love the 4's bubble canopy and do not want a fast back or the fuel burn of the extra 2 cylinders.

Something like the first Harmon rocket but 2 seats

Any thoughts ?

Clipped wings do not do good at altitude.

Good point. Whats is the service altitude of Rockets ?

Paul,
I had the same idea. Watching this thread. Clipped wings and the 180 hp engine with MT prop and B and C alternator.... Maybe a fastback too...

Dennis

Hi Paul,

I don?t know about Rockets service ceiling but they don?t count as they have lots more power on essentially the same airplane (essentially the same only for the discussion of how high can they fly) your RV-4 will have a 320 or 360 engine and will benefit from the extra/standard wing area. My 200hp -4 likes to travel in the teens, 15-16k? but my Dads 160hp is better served at 8 to 10k?. YMMV

Cutting the span down on the already short RV wing will primarily hurt slow speed performance, and will only improve top speed at lower altitudes. At typical cruise altitude of 10000 MSL or so, it won't add anything. Rolling velocity is about the only thing that will improve with span reduction.

See this thread for an extended discussion of induced & parasite wing drag:

http://www.vansairforce.com/community/showthread.php?t=56141

Rocket vs RV4

Paul.

Horsepower helps up high, but to a point. I found my Rocket would begin to "plow through the air" around 14,500'. My 150HP RV4 with wing-tips removed during the test phase (roughly the same span as an HR2) fell off the step at 10,500 but went faster down low. It did climb all the way to 20,500 once with tips on, pretty amazing for a wood prop and 150 horses! With tips removed it rolled much better, like the HR2. I reinstalled the tips and liked the compromise. My HR2 had "Bat wing" tips which I really liked, mainly for aesthetics. My RVX (RV6 fuselage with RV4 wings and tail) performs somewhere between a stock 4 and my HR2.

My HR2 friend Dale fabricated a set of extension wing tip tanks that attach to his outboard wing at the spar. They increase his Rocket span back to stock RV4 span. He told me he immediately noticed better performance up high but slower roll rate, final approach and cruise speed reduced.

Most likely the higher percentage of your flying will be below 10K. Therefore I think it to be a great mod. Add the fastback parts and a light sump, Lycon engine and you will have a winner.

Smokey

I put my wingtips on with hinges for the exact reasons Smokey mentions. My intent is to make a set of wingtips from scratch that I can quickly change over to depending on mission profile...long high X/C, use extended tips, stock tips for local flying, cut-off tips for low altitude short races....

My ideal 4 is the standard conapy, rocket type wings, heavier beefed up empenage, Io 340 of 360- 185hp with composite FP prop.
Fun little plane i think.

Further more, does anyone have a 340 in thier RV 4 ?. What is the weight advantage over the 360 ?. Is the 340 idenenticle in weight to a 320.

Looking for the best power/speed/weight/handling option regarding engine prop combo for project.

Paul

Fastback conversion

I did a fastback conversion on my -4 about 2 years ago, and think it did justice to my -4, in both performance in cruise, and in the looks.

I'm currently stuck in a little city of Merritt, B.C. due to weather just south of me in Hope. I'm trying to get to Chilliwack before heading back to Oregon on Saturday, July 9th. Spent the night on a sofa in the terminal building. Fortunately was able to tuck the -4 away in the only hangar on the airport.

With the fastback at 9,500 feet I consistently show 174 knots true airspeed burning 7.5 gallons/hour. At 8,500 feet I do 170-172 true burning 7.5/hr. I did not check those numbers before the conversion, but I believe I gained 2-5 knots.

Attached is the link to the before and after look.

https://picasaweb.google.com/jaknjoan/20100415RV4FastbackModification

Jake Thiessen
Independence, OR

Wingtips are easy to experiment with

I am currently tied to more important duties but I have 10 wing tips (5 sets) for our RV-6A and another change is is in my mind. I originally built the plane with 9" span tip tanks inboard of the stock Horner tips (1996 vintage) resulting in a span of 24.5' and 55 gallon fuel capacity. This was intended to compete in the Aircraft Spruce Great Cross Country Flying Race from Denver to Oshkosh in the 360 cu. in. class. I flew our Archer II in the race that year and refueled in Cherokee, Iowa so I knew something of the actual demands of the race. Before the plane was done that race was discontinued and the AirVenture Cup Race was being flown from Dayton to Oshkosh. I had plenty of range but the speed was not competitive. In 2007 the Sport Air Racing league started sanctioning short cross country air races (100-300 miles) and in 2008 the AirVenture Cup Race start point was changed so that every other year the race starts in Mitchell, South Dakota (east bound and tailwinds typical). Both of these changes gave the opportunity to increase the speed for competition by changing the wing tips. I built the plane so that the tanks are removable and the tips are removable. I developed streamlined 3" span tips for the wing without the tip tanks, streamlined tips with the tip tanks, semi-flat fiberglass tips without the tip tanks and flat metal tips without the tip tanks. The wing span in the original configuration which I still use for travel is 24.5'. The subsequent configurations are 21.5', 23', 21.125', and 21' respectively. The fastest configuration is the streamlined tips without the tip tanks. The difference between that and the original configuration is 3 kts at 6,000 ft density altitude. All of this is spread around this forum in various threads with photos.

My current thought is to reduce the basic wing span to 19.5' convertible for use with the tip tanks and a cruise or racing tip or no tip tank with a racing tip with spans of 23', 21.5' or 20' This requires shorted ailerons. I am strictly interested in racing with no aerobatic or supplemental oxygen altitude operation so conceptually this seems like a good way to go.

If I were in your shoes I would establish the conceptual design of the features you are interested in (your requirements) so you don't do something in the build that conflicts with what you need to do to satisfy your requirements in another area. Detail design and implement each area as your hardware gets to the point where you can deal with it hands on. Always think of how you can back out of a mod that does not yield the performance you are looking for.

Bob Axsom

no wingtips

I have a 4 with no wingtips, just flat plates at end of wing. I also have a set of vg's on it. I don't have any comparison as it is the only 4 I have ever flown and was built by my neighbor. He built a rv7 with tips. He reports more "float" on landing and a slower roll rate. I don't have specific numbers but I don't fly high often. It seems to land faster than his rv7 but still very easy to place where I want and make the first turn off with no problem. I don't seem to have a picture on this computer but will post one in next few days if you are interested.

For sure please post these photo's

Paul

tipless rv4

here is a pic. sorry it is too large. I have tried to resize at photobucket but still comes up too large.

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Hi Piere,

I to have a RV 6 with an O-360-A1A with a fixed pitch Sensenich metal propeller, 72" dia x 83" pitch.

I was wondering if you have the Catto standard 74 inch pitch ?.

I will get a Catto 3 blade very shortly, just have to work with Craig and get the correct pitch for cruise .

Paul

short wings on rv4

I was at the Vetterman flyin in Hotsprings SD this fall, Larry told me he took his rocket and changed engines from the 540 to a 360 with extended engine mount to fit the cowl, said the rocket now handles better,
contact Larry he can give you the details
Ken
Flying RV_6
Harmon /f1 in progress