Van's Air Force
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Are Fastbacks Faster ?
- Thread starter mvs163
- Start date
wrongway john
Well Known Member
On the 4?s it seems a 5 mph pickup is realistic. Talked to Sam James last year at Oshkosh, and IIRC, that?s the figure he used, or it might have been slightly higher. Anders picked up some speed too, but I think he added paint at the same time he did his fastback option, so don't recall what he thinks the fastback itself added.
Neal@F14
Well Known Member
An RV-4 built as a fastback and equipped with the James cowl can definitely be quite fast.
The RV-8 in my avatar makes perhaps just slightly better than Van's book speeds... and a friend's fastback RV-4 equipped with James cowl, carbureted O-360 and CS prop walked off and left me behind, and he even had a passenger in the rear seat and I was solo.
The RV-8 in my avatar makes perhaps just slightly better than Van's book speeds... and a friend's fastback RV-4 equipped with James cowl, carbureted O-360 and CS prop walked off and left me behind, and he even had a passenger in the rear seat and I was solo.
Alan Carroll
Well Known Member
The fastback sure looks fast!
I did do some tuft testing with my standard RV-8 and saw no obvious evidence for separation of flow from the canopy. I used pieces of yarn taped to the canopy, and they all laid down flat and pointed aft.
I did do some tuft testing with my standard RV-8 and saw no obvious evidence for separation of flow from the canopy. I used pieces of yarn taped to the canopy, and they all laid down flat and pointed aft.
I think I gained speed
I transformed my RV-4 from a standard turtle deck (finished in 1992) to a fastback over a 90 day period during the winter of 2009. I think I gained as much as 5 knots, but can't say for certain, since I didn't keep accurate records in its original configuration. If I didn't gain any speed, I'm still happy I made the conversion, if for no other reason than the "looks".
With an 0-360, regular constant speed (not blended airfoil) I consistently cruise at 9,500 ft. with 7.5 gallon/hr fuel burn showing 174 knot TAS.
See before and after photos:
https://picasaweb.google.com/jaknjoan/20100415RV4FastbackModification
On my flight to and from OSH last year, I was flying with a friend with a well done RV-4 running an 0-320 with a Sensenich prop. Each fuel stop I used less fuel than he did. Bottom line, in my opinion there are speed benefits in the conversion.
Jake Thiessen
Independence, OR
I transformed my RV-4 from a standard turtle deck (finished in 1992) to a fastback over a 90 day period during the winter of 2009. I think I gained as much as 5 knots, but can't say for certain, since I didn't keep accurate records in its original configuration. If I didn't gain any speed, I'm still happy I made the conversion, if for no other reason than the "looks".
With an 0-360, regular constant speed (not blended airfoil) I consistently cruise at 9,500 ft. with 7.5 gallon/hr fuel burn showing 174 knot TAS.
See before and after photos:
https://picasaweb.google.com/jaknjoan/20100415RV4FastbackModification
On my flight to and from OSH last year, I was flying with a friend with a well done RV-4 running an 0-320 with a Sensenich prop. Each fuel stop I used less fuel than he did. Bottom line, in my opinion there are speed benefits in the conversion.
Jake Thiessen
Independence, OR
FASTER!!!
Of course it is faster, otherwise it would be called a Slowback! And with the same reasoning, you don't have to see behind you because you are going so fast no one can get or stay back there!
Seriously, I can't explain why but I do know my -4FB is faster than the average stock -4, -6, -7, -8, simply because I have been faster than anyone I've flown with over the last couple years. Just a carburated O-360 but I consistantly get 180 KTAS at cruise at 8,500 to 10,500MSL...really!
Rear viz will be affected by your design of the canopy. I put a curve in mind and when tail chasing I can still more than adequately 'check 6'. Another big advantage is more volume area in the baggage compartment and a nice head rest area for back seat riders.
I do like the way it looks better and further modded my -4FB with a front seat 4 inches further after and canopy starting 6 inches further aft giving it a long nose look, especially with the Sam James cowling.
Two years and two hundred hours and going to OSH for the third in it in two weeks. No regrets!
JAKE: Great looking =4FB! Nice work!
Of course it is faster, otherwise it would be called a Slowback! And with the same reasoning, you don't have to see behind you because you are going so fast no one can get or stay back there!
Seriously, I can't explain why but I do know my -4FB is faster than the average stock -4, -6, -7, -8, simply because I have been faster than anyone I've flown with over the last couple years. Just a carburated O-360 but I consistantly get 180 KTAS at cruise at 8,500 to 10,500MSL...really!
Rear viz will be affected by your design of the canopy. I put a curve in mind and when tail chasing I can still more than adequately 'check 6'. Another big advantage is more volume area in the baggage compartment and a nice head rest area for back seat riders.
I do like the way it looks better and further modded my -4FB with a front seat 4 inches further after and canopy starting 6 inches further aft giving it a long nose look, especially with the Sam James cowling.
Two years and two hundred hours and going to OSH for the third in it in two weeks. No regrets!
JAKE: Great looking =4FB! Nice work!
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Neal@F14
Well Known Member
I've got some great pics of JJ's -4FB from the 2009 Oshkosh trip, taken at Wautoma.
JJ's if you don't mind, I can post them. Just let me know if it's ok with you.
JetJ01 said:
Brings to mind that quote from the Ferrari driver in the movie Gumball Rally... "What's behind you doesn't matter"
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The Wizzard
Well Known Member
inflight detachable canopy
does anyone know of a quick release system for either the standard or fastback canopy? In other words, wear a parachute and the ability to shed the canopy and get out!
does anyone know of a quick release system for either the standard or fastback canopy? In other words, wear a parachute and the ability to shed the canopy and get out!
Sure - lots of us have installed PiP pins instead of bolts to attach the forward roller mounts to the canopy frame with the standard slider. the idea is that if you are wearing a parachute, you close and latch the canopy, then pull the pins before flight. If you need to get out for some reason, you unlatch and pull the canopy back an inch to get it out from under the windshield overlap, then push up - the airflow will catch it, and it's gone!
Of course, that is all theory - no one (that I know of) has every tried it in flight to see if it works.
Go head Neal!
Neal, post away. You can also see my -4 Fastback by using Google.com in the image section and my tail number: N234JJ.
In the -4 construction, the piano hinge pin on the right that holds the swing over canopy is designed to 'Wrip off" if opened in flight if you need to egress the aircraft, which you will need to after doing so since there will most likely be associated damage to the emphanage section.
Neal, post away. You can also see my -4 Fastback by using Google.com in the image section and my tail number: N234JJ.
In the -4 construction, the piano hinge pin on the right that holds the swing over canopy is designed to 'Wrip off" if opened in flight if you need to egress the aircraft, which you will need to after doing so since there will most likely be associated damage to the emphanage section.
AX-O
Well Known Member
Kahuna,
here is a old picture of mine. I flipped the locking rods (top rod on bottom, and bottom rod on top) so the canopy locks in the foward direction vice aft (per the plans). The rods go into the intrument panel and the bulkhead for the aft seat.
John Clark
Well Known Member
I'm amused...
...17 posts and no one has answered the question. I would be interested in some (scientific) data on the trade out between a possible drag reduction from the shape and the drag increase from the added wetted area.
John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
...17 posts and no one has answered the question. I would be interested in some (scientific) data on the trade out between a possible drag reduction from the shape and the drag increase from the added wetted area.
John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
wrongway john
Well Known Member
You added ?scientific data? which I'm sure he would have appreciated as well, but two of the three questions in the OP were general questions that he requested info and data on, and which he got answers for. One was as simple as to ask if Dave Anders went faster after the fastback conversion. The other was any data on the speed after the fastback conversion. He did request some tuft testing on the aft portion of stock canopies which no one has covered. There is some detailed data on various aspects of Dave Anders plane including the fastback model can be found here:
http://www.sacrvators.com/Aircraft Efficiency N230A.pdf
GusBiz
Well Known Member
Got your PM Neal...
I know so many people say the RV4 is a pitch to build and its yesterdays model etc but it such a cool little aircraft. Being 5'7" it would fit me nicely.
The less that CAD plans, the undrilled parts and the general 1970s production approach of the -4 really is keeping me from doing it but its still such a nice plane.
Thanks for the picks Neal.
I know so many people say the RV4 is a pitch to build and its yesterdays model etc but it such a cool little aircraft. Being 5'7" it would fit me nicely.
The less that CAD plans, the undrilled parts and the general 1970s production approach of the -4 really is keeping me from doing it but its still such a nice plane.
Thanks for the picks Neal.
Not much, if any
Would not appear to be much, if any speed differencefor the -8. Reference this thread.
http://www.vansairforce.com/community/showthread.php?t=52038&highlight=rv-8+fastback
Two "nearly identical" -8's flown for comparison, info posted on page 3.
Would not appear to be much, if any speed differencefor the -8. Reference this thread.
http://www.vansairforce.com/community/showthread.php?t=52038&highlight=rv-8+fastback
Two "nearly identical" -8's flown for comparison, info posted on page 3.
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Fastback Conversion - Giving credit where it's due.
I have followed this thread since its origin. I provided my comments, noted above, about my fastback conversion results, but wanted to add something.
My inspiration for the fastback started years ago when I first saw the results on Dave Anders'-4 conversion. I finished my first -4 before Dave Anders was flying his in the conventional form. I then saw several other conversions, or original builds that incorporated a fastback. The one feature that appealed to me most was a fastback that had a straight fastback line, from over the roll bar to the intersection with the vertical stab. I like Jj's -4 a lot, but didn't care for the slight low spot where the canopy meets the turtledeck. Where I have to give the credit for my straight line is postings in these Forums made by (AX-O) Alex Alvarez. The key being to move the canopy bubble, made by Todd's Canopies, about 4 inches forward from the conventional position, and making the canopy frame fit the bubble. Not try to fit the bubble to the canopy frame. I used a new canopy frame from Van's, removed all the 7/16" tubing, then followed Axel's example in dropping the side attachment 7/16th tube to enhance rear passenger visibility. I purchased new 7/16 inch 6061T6 tubing, and had it welded where necessary. I like the appearance of a straight line in the side skirt, but the dipped line like I did on mine (see photos attached to original post) made more sense from rear passengers standpoint. I made my own side skirts from .025 material I had on hand.
In my opinion, rearward visibility was not compromised, I see no difference in flight.
This really is a simple conversion, and worth the effort. The canopy work is much easier than the original Van's canopy.
JT
I have followed this thread since its origin. I provided my comments, noted above, about my fastback conversion results, but wanted to add something.
My inspiration for the fastback started years ago when I first saw the results on Dave Anders'-4 conversion. I finished my first -4 before Dave Anders was flying his in the conventional form. I then saw several other conversions, or original builds that incorporated a fastback. The one feature that appealed to me most was a fastback that had a straight fastback line, from over the roll bar to the intersection with the vertical stab. I like Jj's -4 a lot, but didn't care for the slight low spot where the canopy meets the turtledeck. Where I have to give the credit for my straight line is postings in these Forums made by (AX-O) Alex Alvarez. The key being to move the canopy bubble, made by Todd's Canopies, about 4 inches forward from the conventional position, and making the canopy frame fit the bubble. Not try to fit the bubble to the canopy frame. I used a new canopy frame from Van's, removed all the 7/16" tubing, then followed Axel's example in dropping the side attachment 7/16th tube to enhance rear passenger visibility. I purchased new 7/16 inch 6061T6 tubing, and had it welded where necessary. I like the appearance of a straight line in the side skirt, but the dipped line like I did on mine (see photos attached to original post) made more sense from rear passengers standpoint. I made my own side skirts from .025 material I had on hand.
In my opinion, rearward visibility was not compromised, I see no difference in flight.
This really is a simple conversion, and worth the effort. The canopy work is much easier than the original Van's canopy.
JT
