RV-4 Fastback Question

A couple of years ago I saw a photo on the VAF website of a fastback modification done on an RV-4. Does anyone know if drawings and descriptions are available for this modification and if so, where can I get them?

Thanks

Chad Eyanson
Austin, Texas

John Harmon has the parts to modify the turtledeck. The rear of a Harmon Rocket is just an RV4 with a turtledeck. I believe poeple just cut the rear of the canopy frame to make it fit the turtledeck. I don't think a Harmon canopy would work for you, but you may contact him about getting the hoops for the rear of the canopy to graft onto yours.

fastback

My -4 is fastback. My website has some information on it.

http://www.precision3d.com/rv4/rv4fuse.htm

The usual way to do this is to take a stock RV-4 fuse kit and buy the harmon components for the top-aft section. But I was told that there are some difficulties mating the harmon parts to the stock fuselage. So I did the whole thing myself from scratch with 0.025 aluminum. It came out ok, If I could do it again, I probably would do the same but be a bit more careful about drilling the F-407 bulkhead to the sheet. It's makes an awkward double-bend angle that I didn't check for a nice flat true face. So it's a little squew.

As for the canopy. Again, the standard way is to mangle the stock canopy. Again, I decided to do it custom for the following reasons:

- For PIC head clearance, I pushed the canopy forward so the tip of the canopy is about 1/2 way down the glare shield. (like an RV-3)... vs. right at the panel (like an RV-4).
- I angled the panel about 25 degrees. Typically -3 or -4 instrument panels are almost square to the longerons.

My canopy is tip-up. I bought the 6061 stock, layed it out (with the canopy jigged in place, bent the tube. I then gave the lot of bits to a professional welder. It came out shockingly [to me] well. I mated the standard Todds HR canopy to the canopy frame using the Sika adhesive system.

Todd's Canopies:
http://www.toddscanopies.com/

Todd's instructions on using Sika:
http://www.toddscanopies.com/bondrv8.htm

This Sika thing went really well. Relative to the old soft-rivets; Sika is far superior.

With some ingeniuty, I could have done a slider, and still could. But I dont really want it. I'd nead to fabricate a RV-8 like rollbar and a track system. There's also an issue with this HR canopy having clearance sliding past the pilots head. It's a low-profile canopy with marginal head-room. Pushing the canopy forward that foot really helped a lot though, so maybe it's not that big an issue, if you did that too.

-Bruce

That fastback look is like a P-51 D to what a early model looks like. just looks right.

Bruce I couldn't find hardly any picts of the fastback on that link. Are you flying yet?

Also-- I went and checked the old defunct RV-4 group and the picts I posted of a friend of mine's fastback are still in the photo section. title-- Mean Green.

In my humble opinion, one of the all time best looking RV's is Mean Green. If you toss out interior room etc. the RV-4 fastback is IMHO the best looking RV design of all time.

edit-- even if the Fastback design wasn't their idea-- Van's should take credit for it anyway. (it looks that good)

Fastback RV-4

Thanks to all for the info.

The reason for the question is that fast back is a great looking mod that I expect wouldn't add much weight. I am still in the planning/dreaming stages and have narrowed my plane choices down to an RV-4 or the Nexus Mustang. I am leaning toward the RV because it is a proven, attractive design.

The help is much appreciated.

Chad Eyanson
Austin, Texas

Mean Green Pics

I know exactly the airplane you are talking about. Could you please post a link or photo of "Mean Green". Wasn't it an Austrailian airplane?

Also, do you fastback types expect/experiance any speed/performance increases? I'm not quite sure the "looks cooler" factor is enough to move me off the keep it simple beaten path.

Mean Green Photo

Here it is

P-51's

mark manda said:

That fastback look is like a P-51 D

Click to expand...

I believe you ment P-51B. The P-51D (besides adding the HUGE Rolls Royce Merlin engine) added the bubble canopy. P-51D is what everyone thinks of when you say "Cadallac of the Sky".

To my knowledge (and there are many P-51 experts out there who may know) there where no fastback P-51's with the big engine. That should have been a bit faster than the bubble canopy variant. The bubble canopy was at the pilot's request for improved visibility.

-Bruce

More on the fastback mod

knifeman said:

Thanks to all for the info.

The reason for the question is that fast back is a great looking mod that I expect wouldn't add much weight. I am still in the planning/dreaming stages and have narrowed my plane choices down to an RV-4 or the Nexus Mustang. I am leaning toward the RV because it is a proven, attractive design.

The help is much appreciated.

Chad Eyanson
Austin, Texas

Click to expand...

First thing... I installed the canopy last night and put the cushions in. I did my very first cockpit ergonomic analysis. I have WAY more headroom than I thought I would have. The top of the stock rollover bar is about 3" bellow the crest of the canopy. My cusions put the top of my head (I'm 5'6") about 6" bellow the top of the canopy. So I will have to add A LOT of booster cushions and under-cushion foam to get my head up high enough. I'm pretty pleased with what I have. I nead to get a decent digital camera so I can post some pictures.

Here's my personal overal analysis on the mod:

1 - I should be one of the lighter RV's ever made (for many reasons) so when I weigh mine in a few weeks, I can put up or shut-up about weight. Whatever is gained in more aluminum top-deck matrial should easily be lost in canopy weight (it's a smaller canopy).

2 - I should be 5-10kts faster than a similarly configured bubble canopy RV-4. This has been said to me by other fastback -4 owners.

3 - In the tip-up configuration, the canopy arrangment is functionally identical to the bubble canopy RV-4.

Despite the drastically different look, this modification is IMHO, a very minor one entirely cosmetic with the only drawback being poor 6-o'clock visibility. But when I dog fight in my stock -3, with all four points of my harness synched as tight as I could get them, I couldn't crick my neck to see in the dead 6-o'clock anyways. If you let up on the seatbelts, you can bend your back around to see there, but I got motion sick in about 5 seconds.

Images

Hey Bruce
How about some images of you RV4 project!

Fast Back vs Coupe...

The P-51A was originally designed as a Recce (reconiassance) aircraft with an Allison engine and was named the "Apache". The first few shipped to England were flown and later modified with the Rolls Royce Merlin and a bubble attachment over the sliding glass portion of the fastback called a "Malcom Hood". It was designated the P-51B "Mustang". The Factory began modding the P-51 with the Merlin, more firepower, fuel and armor.Thus the P-51C was born. Later in 1943, engineers began working on improving the C model based on inputs from pilots about rearward visibility, range and several other small mods.They built the bubble canopy P-51D. Amazingly efficient, the lower cooling scoop to this day is a low drag coefficient marvel. Hard to believe a piston engine fighter was running around at 300 knots at 30K feet in the 1940's...

As far as RV4's go, I like the bubble canopy. The F16's bubble canopy is slightly bigger but basically the same shape and I can see the top of the rudder inflight with no worries, the same as in my RV4. Like the Harmon Rocket, rearward visibility is less than the bubble canopy but if you don't do alot of acro or dogfight people, who cares? I do, and I think the bubble canopy on the RV4 (and the P-51) looks alot sexier and I like to look over my shoulder once in awhile for wiley Lancair Drivers...

When you get past the dream stage and if you like a fastback, build one!
(Just don't dream too long, it may never be a reality...)

Good Luck!

RR

Since I'm going to paint mine eventually, this might be a worthwhile mod for me. They sure do look good...I contacted John Harmon to see if he'll sell a kit to make the mod. I'm not crazy about my canopy fit anyway . No word from him yet.