[wrongway john]

I like speed as much as the next guy, but I?ve always enjoyed gas efficiency even more.

I?m sure the present low fuel prices are not going to last long, which is even more reason I would like to concentrate on this.

With gas miser type mileage, who can claim the King?s seat here?

I think everybody on this forum is already familiar with Kent Paser and the amazing speed and efficiency he got out of his Mustang II with the modifications he did.

This could as easily be applied to Van?s RV?s. And actually we already have a leg up on the Mustang crowd simply because we already have the fastback versions, which is something the standard Mustang II?s don?t have.

I think it?ll be worth noting what modifications others have done with their RV?s to increase gas mileage.

Would our RV wing verses the Mustangs laminar flow help, hinder or neither in our quest for great fuel efficiency?

Kent lists in his book that at 2,200 engine rpm, he has a true airspeed of 173 mph, fuel consumption of 4.0 gph, which comes out to 43.3 mpg. How do the best of the fuel efficient RV?s series fare?

wj

 

[RVAddict]

Kent lists in his book that at 2,200 engine rpm, he has a true airspeed of 173 mph, fuel consumption of 4.0 gph, which comes out to 43.3 mpg. How do the best of the fuel efficient RV?s series fare?

wj

See HERE.

This is in an RV-3. Hard to imagine a two seater doing better...

 

[bhassel]

fastback

I know I've seen some 4 & 8 fast backs, but does the shape of canopy on the side-by-side count as a fastback?

Bob

 

[wrongway john]

See HERE.

This is in an RV-3. Hard to imagine a two seater doing better...

Thanks for the link. Gotto love than panel too. Yeah, I'm sure the one seaters will have the advantage here.

I know of a guy that swore his one-seater Mustang was only burning 3.0 gph at 150 mph cruise, and he said he knew this because that is what his monitor showed. He was also trying to sell me a plane, but I still figured he was probably telling it straight. That plane is still for sale, btw, if anybody is interested. He's down to $14,000, and not a bad looking Mustang.

wj

 

[wrongway john]

I know I've seen some 4 & 8 fast backs, but does the shape of canopy on the side-by-side count as a fastback?

Bob

I suppose the 4?s and 8?s wouldn?t probably qualify as a fastback model since their bubble canopy?s rise up considerably from the back, but dunno. I used the terminology that Kent used, and still would enjoy hearing about their efficiency as well. I was thinking more of 6, 7?s and 9?s as the fastback models for the two-seaters, but maybe others would describe them differently.

I also think the RV-3 would benefit by going to a fast back model as well.

I recently re-read up on Kent?s two-seat Mustang, and took note that when he did his first test flight after his fastback conversion his top speed had increased by 12 mph.

wj

 

[bhassel]

fast back

Boy that's enough speed increase to make anyone take notice.

Yeah, I'd be curious if anyone has fastback'd a side-by-side. I've seen a couple of 8's & 4's (of course the HR).

Bob

 

[hevansrv7a]

Speed vs. $$$

You will get the best mpg at your best L/D but that's pretty slow for an RV. Around 96 kts/110 mph for a 6 or 7, give or take. You should use about 3.3 gph at that speed for about 33 statute mpg. This is based on the CAFE 6A and is quite close to the actual readings for my 7A.

If you want to go faster you will get good mileage but not as good. Of course, if there is a HW or TW, these calculations will vary, sometimes a lot.

The best trade-off speed is 1.316 times best L/D, also known as Carson's speed. The CAFE 6A will burn about 5.0 gph at 139.5 mph, its Carson's speed. That's about 28 mpg.

These speeds and fuel flows are at standard conditions where TAS and CAS are equal. My understanding is that you can do a lot better at higher altitudes. I typically cruise my 7A at 8.0 gph doing 155 kts KTAS or better at density altitudes between 5,000 and 8,000, but it's just a personal preference.

I suspect a 4 or an 8/8A can do a little better because of the narrower fuselage, but the difference will not be huge.

You may see claims that greatly exceed these numbers, but I'd be wary of accepting them at face value, given the verifiable source of this data.

 

[zav6a]

Kent's Mustang

Is in my hanger. The contrast in wing thickness and chord to an RV is remarkable. That alone probably dictates that we won't get our RV drag down to where his is no matter what we do. Lots of other neat features on Kent's plane too.

 

[wrongway john]

You may see claims that greatly exceed these numbers, but I'd be wary of accepting them at face value, given the verifiable source of this data.

I appreciate the info about the L/D, carson?s speed and such. It will give me some general guides to go by.

It does help to have much of this verified as possible which is I feel like Kent Paser?s data is accurate, and I don?t mind quoting from him. He documents his work well, has a degreed aeronautical engineer background, and has much of his results also documented in the Oshkosh Pazmany efficiency contests, CAF? races and other events; and has won numerous awards for the modification he has done with his Mustang.

wj

 

[wrongway john]

Is in my hanger. The contrast in wing thickness and chord to an RV is remarkable. That alone probably dictates that we won't get our RV drag down to where his is no matter what we do. Lots of other neat features on Kent's plane too.

I'm aware of many of those neat features, his "Speed with Economy" is a must read for any plane enthusist, and is a great inspiration to all builders. I figured most around here have already read it.

I've often wondered about that wing, and wondered how much that may have helped him. But I also understand quite a few that go with that laminar flow wing don't get it right, and few realize it's true potential. It's obvious Kent got it right.


wj

 

[osxuser]

I often wonder about some of the posted gains in the book... like Microlon. I just can't see that happening. FWIW, the side-by-sides are already fastbacks...

 

[wvshooter]

I'm building a Mustang II and I can vouch that the wing is very thin in comparison to anything other than the canard on a long ez. Not only is it thin but it is also tapered giving it a much shorter chord at it's outer reaches. It is also thinner at it's outer reaches than it is at the wing root. That's less drag than what a constant chord wing produces, but how much less. I don't know.

I read the Kent Paser book and was astounded by the performance improvements that resulted from his mods. In the area of fuel economy his addition of reversion cones in the beginning of the header exhaust tubes had the biggest effect. I forget the numbers but when I first read it I was very surprised that that one mod could produce that much fuel savings. If you read the book you'll find the claimed performance improvements are very difficult to challenge because aircraft performance was carefully measured prior to and after each mod was done. It's been awhile since I read it but I think Paser himself says he had trouble believing some of the data at first sight.

 

[hevansrv7a]

Microlon comment

I often wonder about some of the posted gains in the book... like Microlon. I just can't see that happening. FWIW, the side-by-sides are already fastbacks...

Notwithstanding Kent's well regarded testing, I also have trouble with this one. Just for the sake of easy math, a 6 mph gain on 200 mph is 3%. That means that the hp would have to increase by about 1.03 to the third power or 9.3%. If Microlon produced a 9.3% increase in net HP at the top end then I suspect there was something wrong with that engine to begin with. Also, Microlon's claims to be an engine treatment as opposed to an oil modifier are absurd. If you removed almost all the friction in a well lubed engine running at rated HP you would likely not see this kind of gain. A 3-5% gain in max HP would be very good and I doubt that Microlon would do it.

FWIW, I once did extensive research and testing on Teflon oil additives for cars. Microlon, IMHO, is junk. It has large, unevenly sized particles which do not resist Teflon's tendency to clump; it won't stay in suspension. DuPont has been very clear that, in general, Teflon oil additives don't work. There is one, however, that they had to admit in writing "might" work.

Tufoil, a little known additive, however, is excellent. Google for web site. Multiple patents, Guiness Book of Records, scientific testing, etc. HOWEVER, Microlon is FAA approved and Tufoil is not and will not be. The inventor/manufacturer of Tufoil flies a Bonanza and knows that the economics are just not there to produce a low-ash version for aircraft. I've discussed it with him more than once. You can PM me if you want to discuss my experiences with Tufoil in experimental aircraft or in cars and trucks. I don't want to say more about it in public. There is some potential there.

 

[wrongway john]

Perhaps one can dispute a discrepancy with one individual modification or more. Some of his methods for testing the Microlon were maybe not the most idea testing conditions. He says he can?t verify all of the claims the manufacturer makes of it, but in his book his felt quite comfortable about his data which showed an addition of 6 mph increase. This aspect should be able to have others getting similar results too, I would think. It?s certainly worth looking more into it, before one committed to this part.

But I do think it would become difficult to fudge the final numbers of all of his modifications because of results he has got by entering his Mustang in many popular contests.

wj

 

[osxuser]

Perhaps one can dispute a discrepancy with one individual modification or more. Some of his methods for testing the Microlon were maybe not the most idea testing conditions. He says he can?t verify all of the claims the manufacturer makes of it, but in his book his felt quite comfortable about his data which showed an addition of 6 mph increase. This aspect should be able to have others getting similar results too, I would think. It?s certainly worth looking more into it, before one committed to this part.

But I do think it would become difficult to fudge the final numbers of all of his modifications because of results he has got by entering his Mustang in many popular contests.

wj

Oh I have no doubt of that, I've been reading and re-reading the book, and have make some modifications to some aircraft based on his research. Overall, he definitely made astounding improvements to the design, but I don't think that RV's have as many flaws at the original Mustang II or as much potential for gain because of the high lift wing.