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  #81  
Old 08-24-2007, 01:28 PM
gmcjetpilot's Avatar
gmcjetpilot gmcjetpilot is offline
 
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Default EAA mag 1997 & RV's the greatest Kit plane of ALL TIME?

Quote:
Originally Posted by doneil
Ross

You mentioned "CFD plots on a 6A at 0 alpha". David Roberts
David I mentioned the reference above, April 1997 EAA article with the RV-6A CFD plots. Ross said he has his own CFD program he plays around with.

Quote:
Originally Posted by Kahuna
Boy do I disagree with this. There are MANY things he has not spent the time to consider and there are thousands of these flying with incredible mods that Vans has neither contemplated, nor implemented to improve his design. Van brought a basic design to the table which is a tremendous platform to improve upon. He is spending little time doing that. Good on all you guys who are making it better. Best,
Well I think we are looking at it differently.

"There are MANY things he has not spent the time to consider and there are thousands of these flying with incredible mods that Vans has neither contemplated, nor implemented to improve his design. He is spending little time doing that."

I am not challenging you but what specifically are you talking about? What mods are so great that they have changed the basic design or performance significantly?

Many mods I see builders make have nothing to do with the basic airframe kit, like engine/prop mods or the mods are trivial and have little affect on the plane. The exception, in my opinion, is the James cowl inlet/sealed plenum type set-up, which I see as worth while. Not a must but worthwhile.

Most mods are frosting on the cake. Sure builders like Dave Anders RV-4 is an example of taking a 220 mph RV and making it go +250mph. If you follow his work its beyond what most are willing to do, like using a highly modified engine with short engine/prop TBO's.

You say Van is not improving his design? Well the RV-7 and RV-8 are the improved versions of RV-6 and RV-4 respectively. That was some thing. Producing a value priced kit plane with more bang for buck is doing something. He could continually change the design but at some point you have to freeze the design.

Heck he came out with the RV-10, pretty much a success from what I hear. It uses new construction techniques (composite/metal hybrid structure) and new airfoils, plus a 260 hp engine. The RV-9? In about 10 years he has come out with the RV-8, 7, 9 and 10. How many manufactures do you know who have made as many innovation. Now he's working on the RV-12. I don't think Van's aircraft is resting on their laurels and past reputation and not innovating all the time.

Van has gone back to the RV-3 and redesigned significant parts like the main spar. He has gone back to the RV-4 and made improvements to the engine mount, longer gear and elevator. The RV-6 got top hinged rudder pedals and the RV-7 got a big rudder and so on.

Van does improve the design adding safety and efficiency when needed. He has released 3 wing tips: Horner, shear and symmetric. Clearly Pre-Punch is a quantum leap in kit value and construction. Also cowls are now epoxy/nomex. Van has made significant progress over the years in my opinion.

You could call me on the RV-6A/7A nose gear controversy. Van has changed the nose gear design recently (the new fork). Some think he should change the whole nose gear, kitandkaboodle. Another debate for another time.

Airplane designs as you know are a million compromises. I know you have done cool and extensive mods to your RV, like a 540 in a RV-8. Is it better? Sure more power is better, but in the big scheme of things a IO360 or now IO390 +200 HP RV is no slouch, even with 180HP or 160HP, you're faster than 90% fixed gear single engine cert GA planes (and many retracts). It's not that Van can't design a 540 RV-8, it's just he felt the "sweat spot" was with the 4 banger. Van is an engineer and like a Chess master thinks 20 moves ahead. Sure we see a mod as improving something, a no brainer, but he sees the affect overall. His conclusion of a mod's value may differ.

Van has been known as the "Flying Dutchman", where Dutch means cheap. Van is also a frugal designer, not one to make elaborate complicate designs when simple work's. His personality comes out in his design. I think you're addressing personality or preference more than a lack of Van's design skills or thoroughness. I still contend its hard to improve on the basic airframe design or performance, and most "Improvements" are really frosting not the meat of the design.


Not sure specifically what you are talking about, but in regards to cooling drag & cowl flaps I know Van has explored and tested them. I'm a huge proponent of the Barnard/James/Holly Cowl sealed inlet/plenum design. Why does Van not change his cowl and baffle kit? I don't know, but you can delete the cowl from your kit and buy a SJ cowl. Other factors may be involved, including inertia of manufacturing, why fix what ain't broke. To change major parts adds cost. Van's cheapness is good for us, other wise he would need to charge $40,000 like Lancair charges for their kits.

Did you know the first RV-6 prototype had an annular cowl inlet under the spinner (smiley face), verses the previous RV-4 axisymmetric dual inlets on each side of the spinner. Yep he tried to make the annular inlet work, but after much flight test he went back to the RV-4 design, as used on all current models today. Sure all his planes share common design characteristics, but so do Boeing jets. I don't think he is lazy but again why fix it what ain't broke.

Van wrote a series of articles in the RVator about cooling drag, cowl flaps and ways to improve the design for speed (in the 1993 time frame). He is a trained engineer and clearly his choices are well thought out? I know people complained about drawing inaccuracy or inconsistencies in the early days. Now that dwg and part fit is excellent. There will always be "WHY DID HE DO IT THAT WAY?" Some love Cam-Loks for the cowl verses the piano hinge. So what, its really an insignificant mod and the piano hinge has advantages, not the least of which is cost/weight.

Van is not here to defend his design. I'm sure 9 out of 10 times he would have good reasons for doing what he did. The 1 out of 10 times he may nods and says, good idea, but to get into the kit, it has to contribute a significant improvement with out adding cost, weight & build time. At air shows Van cruises the RV flight-line, when no one is watching. He appreciates SOME mods. Some mods make him shake his head. The KISS and KILL (keep it light lad) principals have their own rewards. Van's way is not the only way. I know that, and the joy of kit planes is modifing them, in part because we can. Nothing wrong with that.


Some mods have negative affect of adding weight, build time and cost.

Is there really a better kit plane on the market? Opinions will vary. With +5,000 flying, they all can't be wrong. I can say without reservation, RV's are the most popular and numerous high Perf kit planes in the sky. There really is no competition on the "total performance" horizon. Van has a fair and balanced design in my opinion even in stock form. Is it a perfect or optimal design in your opinion or mine? No but what's perfect.

We can agree GO forward and modify (carefully and safely).
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Last edited by gmcjetpilot : 08-30-2007 at 04:37 PM.
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  #82  
Old 08-24-2007, 04:37 PM
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Nuisance Nuisance is offline
 
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Quote:
Originally Posted by F1Boss
As soon as I get your deposit check!

Seriously, the side panel idea has been kicked around here for quite a while. The exhaust would be dirt simple (3 short pipes), but would sound really weird, as you would hear only 3 cyls at a time from the ground -- kinda like a T28 or Wildcat...

I think it's too easy to ignore, as the cowl mod would take minutes, the outlet panel would be easy (some of it would have to be stainless of course), and the exhaust could be mocked up out of steel for testing purposes.

Maybe John Huft will try this idea before I can get my plane in the air??

Cheers
Mark
Mark, quit playing on the computer and get to work! I want to see that 550 powered EVO flying!

I am not so sure that the bottom of the cowl (actually the beginning of the fuselage) is such a high pressure area...the bottom of the wings, yes; the front of the cowl, yes. I think most of the fuse is a freestream pressure area. That is why we put our static pressure ports on the sides.

Meanwhile, the mechanical complexity gets harder. And, I am not sure I want to fly in that plane! It is loud enough in a big airplane!

Maybe this thread will inspire some innovators out there. And, with the new SARL race series, we can get some independent verification of all the claims.

John
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  #83  
Old 08-24-2007, 05:47 PM
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Mike S Mike S is offline
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Default

Quote:
Originally Posted by doneil
Ross

You mentioned "CFD plots on a 6A at 0 alpha".

Can you tell me if this information is available in the internet and where?

Several years ago I think I remember a picture or a drawing of the high and low pressure areas on the 6A in Kit Planes or Sport Aviation or maybe the RVator. I have spent quiet a bit of time looking for it and have not been able to find it again.

Do you or anyone else know about this? Or maybe I just dreamed it up?

Thanks

David Roberts
This was done on Steve Barnards plane, it was done in Redmond Washington, by a company called "Analytical Methods Inc.".

The author was Dave Lednicer.

Google it???

Hope this helps.
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  #84  
Old 08-24-2007, 06:28 PM
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RV8RIVETER RV8RIVETER is offline
 
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Default

I was kidding earlier, but there is some interesting reading to be found about a custom designed aircraft that uses updraft cooling here.
http://www.melmoth2.com/texts/Cooling%20flow.htm

I have not been able to find any RV plots, but my search did remind me of the above link.

Actually has a CFD plot, that while not the same demonstrates the front end pressure. The low pressure area is very near the front of the cowl as to be a difficult choice to deal with. And then the pressure builds again at the windscreen. I agree with John that the lower exit is not in a high pressure area. I guess if you really wanted to use a low pressure area you could build a duct to outlet over the top of the wing, but that is alot of fairing to hang out there or alot of fuselage modifications.

Another great thread for ideas and learning!
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Last edited by RV8RIVETER : 08-24-2007 at 06:30 PM. Reason: Oops
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  #85  
Old 08-24-2007, 08:23 PM
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rv6ejguy rv6ejguy is offline
 
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Default

Quote:
Originally Posted by doneil
Ross

You mentioned "CFD plots on a 6A at 0 alpha".

Can you tell me if this information is available in the internet and where?

Several years ago I think I remember a picture or a drawing of the high and low pressure areas on the 6A in Kit Planes or Sport Aviation or maybe the RVator. I have spent quiet a bit of time looking for it and have not been able to find it again.

Do you or anyone else know about this? Or maybe I just dreamed it up?

Thanks

David Roberts
Peter Garrison ran ads in various magazines for Loftsman/ CMARC under his company AeroLogic years back. http://www.aerologic.com/. Be forewarned that the lofting program part to define the shape of an object is very complicated to use (for me at least) I ain't no engineer.

Fortunately, the RV6A had already been lofted by someone a lot smarter than I and I conned Peter into giving me those files when I purchased the programs.

Once you get the shape, the rest runs pretty easily in DOS.

Like I said, there may be better, cheaper stuff available today.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 08-26-2007 at 10:45 AM.
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  #86  
Old 08-27-2007, 12:40 PM
doneil doneil is offline
 
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Default April 1997 Sport Aviation

George

Thanks for the information. This was the article I was refering to. Guess I didn't dream it up after all. I found your earlier reference and the fact there was no belly plot. I still find it useful.

To Mike and Ross thanks for the replys. Ross I can see from your reply I would not be able to use the software even if I could afford it.

David Roberts

Last edited by doneil : 08-27-2007 at 12:42 PM. Reason: Change Name
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  #87  
Old 08-29-2007, 11:39 PM
ksouthar ksouthar is offline
 
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Default Exit Area Too Small ???

RV9-A
Lycoming 0320-E3D (150hp)
Sam James Cowling with Glass Plenum

OAT ~ 80 degrees

CHTs - 350 +/- in climb 320 in cruise

Oil Temp 190-200 climb, cruise - doesn't seem to care... Never seen it break 200.

S/W Oil cooler mounted to the rear baffle (firewall mounting will cost you higher temps!)

Keith
N355RV
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  #88  
Old 08-30-2007, 04:39 AM
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gmcjetpilot gmcjetpilot is offline
 
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Default You can make the firewall Oil Cooler mount work

Quote:
Originally Posted by ksouthar
RV9-A
Lycoming 0320-E3D (150hp)
Sam James Cowling with Glass Plenum

OAT ~ 80 degrees

CHTs - 350 +/- in climb 320 in cruise

Oil Temp 190-200 climb, cruise - doesn't seem to care... Never seen it break 200.

S/W Oil cooler mounted to the rear baffle (firewall mounting will cost you higher temps!)

Keith N355RV
Thanks for the info, but I'd disagree about your last comment, "firewall mounting will cost you higher temps!"

I'd say you are right if uisng Van's standard brand of coolers and firewall mount kit, which are not great. However using a SW cooler and making proper ducting of proper size (larger than 3"), makes the OT a non-issue ,even if mounted on the firewall.

If done right, than OT's can be as good or better with a firewall or engine mounted cooler. The baffle location works fine temp wise, but it has a nagging tendency to crack the baffle on many installations, at least if you don't reinforce it and brace it (a lot). Than some times the cooler cracks.

The 360's don't do as well with the cooler on the baffle, crack wise. The O-320 are better suited for baffle mounted oil coolers, I think. The 320 coolers are smaller, weigh less and the O-320 may not shake as much as 360's. Trying to support the weight of the cooler, oil lines and the oil inside them, while the engine shakes like a wet dog, is hard on the flimsy sheet metal baffle. That's my opinion any way. Just stay away from cheap coolers and Vans remote mount cooler kit. Search the forum archives for proper remote cooler design.
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  #89  
Old 08-30-2007, 02:50 PM
Bill Palmer Bill Palmer is offline
 
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Talking Firewall Mount is Okay

George,

As far as I can understand from various threads, a firewall-mounted oil cooler works fine if: (1) it is fed by a 4-inch-diameter duct and (2) it's an appropriately-sized Stewart Warner. Note: Van's RV-10 firewall-mounted oil cooler plenum is fed by a 4-inch duct. I know you have a negative opinion about the less-than-optimal angled flow inside Van's RV-10 oil cooler plenum, but Van's plenum volume appears to be adequate, if not better, than most oil cooler plenums, and plenum pressure (differential pressure across the oil cooler) and mass flow rate across the cooler are arguably more important for oil cooler efficiency than the flow path itself. Flow path seems to be somewhat important in delivering air to the plenum, however, so the 4-inch-diameter SCAT duct from the baffle to the firewall-mounted oil cooler plenum should be as straight and short as possible. Also, the downstream face of the oil cooler needs to "see" a low, or ambient, pressure area in order to achieve the maximum possible differential pressure across the oil cooler.

These are my personal observations/conclusions/opinions ("2 cents") anyway!

Best Regards,

Bill Palmer
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  #90  
Old 08-30-2007, 03:57 PM
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gmcjetpilot gmcjetpilot is offline
 
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Talking I agree 100%

Quote:
Originally Posted by Bill Palmer
George,

As far as I can understand from various threads, a firewall-mounted oil cooler works fine if: (1) it is fed by a 4-inch-diameter duct and (2) it's an appropriately-sized Stewart Warner. Note: Van's RV-10 firewall-mounted oil cooler plenum is fed by a 4-inch duct. I know you have a negative opinion about the less-than-optimal angled flow inside Van's RV-10 oil cooler plenum, but Van's plenum volume appears to be adequate, if not better, than most oil cooler plenums, and plenum pressure (differential pressure across the oil cooler) and mass flow rate across the cooler are arguably more important for oil cooler efficiency than the flow path itself. Flow path seems to be somewhat important in delivering air to the plenum, however, so the 4-inch-diameter SCAT duct from the baffle to the firewall-mounted oil cooler plenum should be as straight and short as possible. Also, the downstream face of the oil cooler needs to "see" a low, or ambient, pressure area in order to achieve the maximum possible differential pressure across the oil cooler.

These are my personal observations/conclusions/opinions ("2 cents") anyway!

Best Regards,

Bill Palmer
No offense about the RV-10 set up Van is selling (supplied only for the RV-10 kit I guess?). They should make it avaiable in their accessory catalog. 3" v 4" is 77% more area for the latter.

I'm talking about their standard Van's 3" remote kit not their RV-10 kit, which sounds better, just from the fact they went to 4" dia. When the duct/tube starts to get as big as the cooler, than the shape of the cooler air-box transition matters less, since there is little transition. An optimal shaped duct transition is frosting on the cake, if the duct is at least close to the **proper area.

Sure better shapes always help with flow, but if overall volume and pressures are high enough, it overcomes any little less than elegant shapes. The RV-10 kit works it works. Also the RV-10's are using larger or better SW coolers I suspect, so air is used more efficiently used.

The standard 3" remote oil cooler kit, in my opinion, is what my gripe is about, too small except for may 150hp or may be 160hp coolers. It's not only the poor shape of the cooler air-box (flat shallow square box) but other issues as well. When a less than efficient clone cooler is mated to an under-sized 3" SCAT, with hot climate and/or +180HP engine, you have an OT problem. That's a proven fact. Just trying to keep people from making the same mistake over, not trying to kill Vans remote cooler kit sales.

** Getting the engineering data out for a cooler, any cooler (if tested and published) it tells you the kind of pressure (inches of H2O) and flow (CFM) is needed to achieve the design cooling capacity of the oil-cooler, which dictates the size (area) of hose/duct needed (for a given pressure)........ The size of tubes and fin spacing on the cooler affects what kind of air flow it needs to work best, low pressure / high flow or high pressure / lower flow. The cooler needs to be optimized for the application and installation. The SW units tend to work better in our application with the kind of pressures and flow we can supply the cooler. Example, the SW 8406R, needs more than 3" to feed it at typical differential pressures we see under the cowl. It's just better quality cooler. However just using it with 3" scat is kind of a waste and a band aid on the real issue, the area of the 3".

When you take the 3" remote kit and use a less than ideal brand of clone cooler you make the problem worse. This recent post is excellent regarding Pro/Cons of brands and models of typical coolers we use in RV's (for the smaller Lycs):

http://www.vansairforce.com/communit...794#post150794

I agree with you about the cooler exit area. An exit shield or short duct can promote or improve flow out of the cooler, no debate, but baffle mounting the cooler is not a MUST to get low OT's if done right (SW cooler, duct area sufficient and exit area is shielded). I try to keep the cooler higher up on the engine mount than down and low on the firewall where air is gathering and swirling around the cowl exit. The key is putting the cooler on something that is not shaking, i.e., the engine.
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Last edited by gmcjetpilot : 08-30-2007 at 06:05 PM.
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