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  #1  
Old 12-10-2011, 12:30 PM
t4tango t4tango is offline
 
Join Date: Nov 2011
Location: Bedford UK
Posts: 22
Default Fastback RV-4

The installation of a fastback conversion might be something I could do as part of the repair to my -4 fuselage (top torn up by unfriendly Chipmunk) are there any implicationsf on performance and C of G?

Thanks for any advice
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  #2  
Old 12-10-2011, 02:17 PM
Jaknjoan Jaknjoan is offline
 
Join Date: Jan 2005
Posts: 239
Default RV-4 conversion to a fastback

First off, I undertook a conversion of my 1992 RV-4 to a fastback two years ago, and would do it again in a heartbeat. I had my airplane down for 90 days during the process.

I purchased bulkheads 407, 408 and 409 plus the enlarged turtledeck skin from John Harmon in Bakersfield, California. Then I ordered a Harmon Rocket canopy bubble from Todd's Canopies in Florida. I purchased a new standard RV-4 canopy frame from Van's and modified it as necessary to fit the aircraft and the new turtledeck. Since there are no plans for this conversion, you just do what needs to be done to accomplish the desired outcome.

If you are interested in any of the finer details, you can contact me at <jaknjoan@minetfiber.com> and I will be happy to share pictures and my experience with you.

I can't tell you the exact increased speed I gained, but I can tell you that I can fly all day at 8,500 to 9,000 feet at WOT leaned to just less than maximum EGT and show 174 kts. TAS. This is with an 0-360 carbureted Lycoming and standard Hartzell C/S prop.

I actually did the conversion for the appearance but believe the increased performance in cruise is worth it.

Jake T
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  #3  
Old 12-12-2011, 09:43 AM
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smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,891
Default Fastback FOUR, the best RV ever?

Tim,

You have chosen wisely, the Fastback RV4 is arguably the best RV of any type, ever. You need only look back a few threads to AXO's very nice project and Jake's comments above to see the merits of the FRV-4.
Having flown several F4's and owned an HR2 I can tell you the speed gained and ergonomics of more back seat head room and slightly more baggage space alone make it worthwhile. Dave Anders built one of the first ones back in the mid 90's. Dave's masterpiece in horsepower vs weight and drag reduction attention to detail was the CAFE efficiency winner 15 years ago and is the fastest RV on the planet, still to this day.
Considerations would be to purchase the parts from John Harmon, then AXO, JJ and others can help you with exactly what you need.

Good call!


Dave Anders masterpiece FB RV-4


My buddy JJ's gorgeous FB-4
Smokey

Last edited by smokyray : 12-12-2011 at 10:00 AM.
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  #4  
Old 12-12-2011, 11:26 AM
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longranger longranger is offline
 
Join Date: Mar 2007
Location: 45G, Brighton, MI
Posts: 1,867
Default

Quote:
Originally Posted by smokyray View Post
... Dave Anders built one of the first ones back in the mid 90's. Dave's masterpiece in horsepower vs weight and drag reduction attention to detail was the CAFE efficiency winner 15 years ago and is the fastest RV on the planet, still to this day....
I thought so too, until this morning when I read Bob Axom's post in the "best RV" thread:

Quote:
Originally Posted by Bob Axsom View Post
I went to the downloadable file of 1162 race flights at www.sportairrace.org under records and stats, deleted all the rows that were not RVs, resorted by speed, and kept deleting columns until it would fit the 8000 character limit of this forum. The results with a ranking column from 1 to 297 are copied below. The only data that would fit are Aircraft Type, speed ranking, Engine by color code (Red = 320 cu in or smaller enginees, Blue = 360 and Gold = 390s or (for RV-10s only) 540s) and speed in knots.

Bob Axsom

RV-8 1 Blue 217.17 (John Huft)
RV-4 2 Blue 209.06 (Dave Anders)
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  #5  
Old 12-12-2011, 03:18 PM
t4tango t4tango is offline
 
Join Date: Nov 2011
Location: Bedford UK
Posts: 22
Default Fastback RV-4

I always thought the fastback conversion looked good, but these photos are fantastic, a credit to the builders thats for sure. I'm not sure whether anyone has done the conversion over here from an existing RV-4, and noted that on AXO's thread that the Harmon frames were cut and rivetted to the existing RV-4 ones which is pretty much what I will have to do to get rid of the damage - were there any issues with your EAA that I could take on board when I speak to our regulator?

[IMG]F:\My Pictures\My Pictures\Aeroplanes\RV4\DSCF0062.JPG[/IMG]
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  #6  
Old 12-12-2011, 03:40 PM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Is this a pricey modification? Sounds like the canopy and the paint are the big ticket items.
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  #7  
Old 12-12-2011, 06:00 PM
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smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,891
Default FB4 price tag

Cost to an existing 4? Since Dave told me the FB mod increased cruise roughly 5 knots, figure $1000 per knot

BTW I am a skeptic when it comes to speed claims, but the CAFE foundation provides real data collected by experts and calibrated instruments. The prototype HR2 couldn't match Dave's original 4, he has changed props to a WW 151 since Cafe.
Check this out:

http://cafefoundation.org/v2/aboutca...rfromchaos.php

Smokey

Last edited by smokyray : 12-12-2011 at 06:21 PM.
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  #8  
Old 12-12-2011, 06:18 PM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,544
Default

Tip for Harmon bulkheads:
Cleco the bulkheads in place with two or three clecos on the sides and at the top. I forget it they are one piece or two pieces but it they are one piece then cut the bulkheads in half at the top. In that case make a little patch to join the top halves together and hold with a few clecoes. Drill the holes for the skins in the bulkheads. Now put the skin in place and back drill and clecoe it to the #7 and the aft small bulkhead.
The next step is to take the clecoes out of the top center of the remaining two bulkheads and then drill them to the skin. After they are drilled to the skin you can then make the final holes in the patch that joins the top halves of the bulkheads together.
The point is that you want to make the bulkheads FIT THE SKIN, NOT THE SKIN FIT THE BULKHEADS. You may also have to replace some of the lower flanges on the number seven bulkhead to get it to fit the skin properly.
The Harmon bulkheads, by today's standards, could be considered a good place to start.
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  #9  
Old 12-17-2011, 12:43 PM
Jetj01 Jetj01 is offline
 
Join Date: Mar 2005
Posts: 337
Default I LOVE my RV-4FB but.....

Smoky,

Thanks for the compliment but YOU CAN'T HAVE MY -4FB!

Anyone contemplating a RV-4 fastback should realize it won't be as easy as a 'standard' RV kit. Van's takes most the quess work out of the build when you follow the plans. Most of it. Deviations, such as a fast back, different cowl, etc, creates many a head scratching moment. Case in point is the Harmon bulkheads. They are designed for the longer Harmon fuselage. So when placed in a standard -4 fuselage they must be cut, and in my case, widened to fit. This is trial and error since there are no 'plans' to follow. Furthermore, the fiberglass fairing on the tail juncture won't fit: the fast back changes the shape. Another biggie is the canopy frame. Not even close to Van's standard. And...And...And...

I made several changes on mine: Moved the front seat back 4 inches. (two weeks ago I had a 260 pound, 6'2" guy in the back, not comfortable but doable still!) Moved the canopy frame back 6 inches to give it a longer nose look, added a Sam James cowl....love the look! Etc Etc etc.

Every change you make to Van's standard will add exponentially to your build time. I hated it during the process but love the results. My plane turned out light and fast, which is purely by luck and chance since I went with looks before science. But I love my RV and it will stay with me 'forever'!

Good luck in your endeavors and most importantly, work on it a little every day and soon....nah, three years from now it will be done...or not!
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Last edited by Jetj01 : 12-17-2011 at 12:46 PM. Reason: Can't spell!
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  #10  
Old 12-17-2011, 02:05 PM
Jaknjoan Jaknjoan is offline
 
Join Date: Jan 2005
Posts: 239
Default Empennage fairing when converting to a fastback

In case you are unaware, the empennage fairing from Van's for an RV-8
fits an RV-4 fastback empennage with literally no modifications.

[quote] Furthermore, the fiberglass fairing on the tail juncture won't fit: the fast back changes the shape. Another biggie is the canopy frame. Not even close to Van's standard. And...And...And...[quote]
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