RV-12 - What if??

As I read through the info on a 12 from the Vans website, I began to wonder....what if someone built a 12 like we build our planes. You know that someone is going to do it that way!!!!!!

How fast would cruising speed be????

Ditch the blind rivets, dimple and do hammered rivets. Put a set of fairings on the gear and pants on the wheels. Keep a keen eye on things that slow a plane down. I might want more than 20 gallons though.

Vans lists the cruise speed @75% power @8,000 as 118 kts.

Imagine a 12 pulling up alongside and blowing away the boys in a Cessna!!

My guess is that an RV-12 with wheel pants, gear fairings and a ground adjustable propeller could cruise close to 130 kts. How fast you would want to cruise would, for me at least, depend on Vne. A 130 kts cruise would need a Vne of about 145 kts for me to feel safe.

I don't know what percentage of the structure could be built with bucked rivets because it was designed for pulled rivets and access for bucking, squeezing etc. may be limited in some areas. I don't know what increase in performance using flush rivets would achieve for a airplane cruising at130 kts. It may not be worth the effort.

I would like to see more fuel, in a tank running full width of the baggage area, but no more that 12" or so front to back. It would, of course, depend on weight and balance considerations so the rear CG limits are not exceeded. Until Van's lets us know the specifications for the RV-12 all of this is pure guess work. Still it's fun to dream.

I think you'd find that going with flush rivets would be extremely hard unless you went with flush pop rivets in a lot of areas. All of Van's existing aircraft are designed in such a way as to ensure you have access to be able to buck the rivets as you build. The RV-12 was not, and if I remember correctly, Van stated that this gave them much more flexibility in design and assembly because they didn't have to worry about the builder being able to get access to the inside of the structure to buck the rivets. On the other hand, if you built entirely with flush pop rivets, that might work out pretty well.

PJ Seipel
RV-10 #40032

Guestimate

Once upon a time, I read that the landing gear produced more drag than the wheels. Seems like it was mentioned in percentages. Memory is vague here but it seemed it was something around 15% together (DON'T HOLD ME TO THAT NUMBER). My old A&P mentioned on a Beech Muskateer he owned, if he replaced all the standard rivets with flush rivets, it was worth 20-25 knots so I'll call that 15% for a conservative number.

Together, you get 30% (in theory). If a 12 is listed at 118 knots, then a 30% increase would give you 153.4 knots (176.4 mph).

What's the realistic chance that a 12 would be scooting around the sky at 175 mph?!?!?

Fuel burn on the Rotax engine at 75% according to Vans is expected at 5.8. The 3.5 to 4.5 was economy cruise.

If usable fuel is 19 gal (just guessing), 30 min of reserve taken out, you have an endurance of just under 2.9 hours or a range of 507 miles at a smidge over 30 miles per gallon. And 2.9 hours not be a bad thing when you start reading the thread on bladder range (LOL). At that kind of economy, what a great puddle jumper for those little 300 mile trips.

Since a person may not be able to hammer all rivets, use flush blind where you can't get a bucking bar. Fair up the gear and wheels, look for other opportunties which might cause drag.

Then, could you get 175mph at 75% cruise? I guess we'll find out one day when someone lets us know.

I would have to question your A&Ps numbers.

Not sure how he figured this. I don't think flush rivets will buy you much speed in the 100-120 knot range. They would make the airplane look nicer and easier to paint, but not much help in the speed department. We built a Zenair CH601HDS with flush rivets and didn't see any speed gain at all.

Who knows

Mel said:

Not sure how he figured this. I don't think flush rivets will buy you much speed in the 100-120 knot range. They would make the airplane look nicer and easier to paint, but not much help in the speed department. We built a Zenair CH601HDS with flush rivets and didn't see any speed gain at all.

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I'm just messenger on the rivet drag. You have to admit it's a interesting "what if" I'm sure we'll find out in year or two when one of the brave experimental builders does the experimental thing.

I do find it interesting on the Zenair numbers. Thanks for the info.

So you do all of that and still have the medical issue. Every thing that you ask for can be had in a 6A with a O320 FP and EI. Keep the A/C lite. and it will exceed all of the above numbers and look good doing it. A 7A will also work, but it is a bit heavier.

Remember the mission of the 12. And if it does not fit your needs, then don't try to make it work. Van does make a model that will fit your needs. You might just want to wait for his powered ............ well that's later.........

On the cheap side

gasman said:

So you do all of that and still have the medical issue. Every thing that you ask for can be had in a 6A with a O320 FP and EI. Keep the A/C lite. and it will exceed all of the above numbers and look good doing it. A 7A will also work, but it is a bit heavier.

Remember the mission of the 12. And if it does not fit your needs, then don't try to make it work. Van does make a model that will fit your needs. You might just want for his powered ............ well that's later.........

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Only 1 mission? I was just thinking outloud what one might see in performance changes on a lower cost model with lower gas use.

I will also lay you odds that we will see a 12 with pants soon.

WE WILL SEE.....

Webb said:

Only 1 mission? I was just thinking outloud what one might see in performance changes on a lower cost model with lower gas use.

I will also lay you odds that we will see a 12 with pants soon.

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WE WILL SEE when the numbers start to come in on finished 12's that they will be very close to a low end 7A...

My point is.... if you don't want a medical, or you do want removable wings or you DO WANT TO pop it togather, then a 12 might be just right for you.

AND YOU ARE RIGHT.......... There will be someone that will shove a MAZDA under the hood and retract the gear just because they will have extra build time left.......

BUT IF YOU WANT A CHALLANGE....... of a low priced 12 then fly it on 80 hp and pocket about $8000.00 http://www.aeroconversions.com/ Now you can build a lighter 12 and clean it up to reach the speed limit. Then you will have economy and a FUN CHEAP aircraft...........

Van did not have this option. But you do!.......

Got to tell you...

Gasman - Got to tell you that if petrol keeps on course, we might all be turning in our others for a 12!!!!!!

I'm interested in seeing the 12's performance numbers starting to show up.

My hat is off to Van's for their efforts in this arena. This is one of the times that a manufacturer did the right thing before they were forced to.

Next thing you know, they'll figure out the equivalent of Doug's new ride for a single seater that only uses a 60 horse engine. It will be the RV14 cuz no one wants a lucky 13. Wouldn't that be sweet.

First - I am not an engineer... and definitely not an expert. With that caveat, it is my understanding that aerodynamic cleanups have an impact that is proportional to speed... and that flush rivets at LSA speeds may only produce a 1 or maybe 2 knot speed increase. Likewise... I believe that adding pants to a 7 or 9 adds somewhere around 6 or 7 knots.? But one of you 7/9 builders could confirm or correct. I would guess that an RV-12 would then gain 3 to 5 knots maybe with pants. I'd sure be nice to see some numbers from Van's. I am really surprised at how long it has been and it doesn't appear that they are done with testing even now. Makes you wonder the difference in validation between Van's and all the other kit manufacturers.

As far as the RV-14... I think it should be an LSA taildragger version of the RV-4 with matched-hole, pulled rivet construction... powered by the Jabiru 3300. Sign me up!!!

DJ

Ran across the numbers last night

Phyrcooler said:

First - I am not an engineer... and definitely not an expert. With that caveat, it is my understanding that aerodynamic cleanups have an impact that is proportional to speed... and that flush rivets at LSA speeds may only produce a 1 or maybe 2 knot speed increase. Likewise... I believe that adding pants to a 7 or 9 adds somewhere around 6 or 7 knots.? But one of you 7/9 builders could confirm or correct. I would guess that an RV-12 would then gain 3 to 5 knots maybe with pants. I'd sure be nice to see some numbers from Van's. I am really surprised at how long it has been and it doesn't appear that they are done with testing even now. Makes you wonder the difference in validation between Van's and all the other kit manufacturers.

As far as the RV-14... I think it should be an LSA taildragger version of the RV-4 with matched-hole, pulled rivet construction... powered by the Jabiru 3300. Sign me up!!!

DJ

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I ran across the numbers last night when working on the wheel pants. Van lists 8 for the gear and 3-4 for the wheel fairings. I don't remember if it was in knots or mph but did state it would take 27 hp to add 12 (I think it was knots) on to cruise speed. This was for the RV7. I expect you would be able to 8 or 9 more from a RV12. If knots, then you would be pushing it up towards 130 knots cruise.

I would be inclined to hammer rivets where I could and then use blind ones where I couldn't.

As far as the RV14 goes -
- It would be a single seat tail dragger
- Skins prepunched and use both combo blind and pulled rivets
- Wheel fairings and gear farings
- Cowl would be a molded fiberglass nose with aluminum top, bottom and sides that have a single hinge on top that you could open on either side. Landing light in cowl nose
- Canopy would be an aluminum frame (rollbar inside) that had panels that would drop in place, seal with rtv, and place a cover strip frame on top. Door would be side of canopy and part of side.
- Engine Rotax 912S since Van's is using and has mounts
- Shoot for as smooth a design as possible for the best speed vs fuel flow that Vans has ever made.
- Make it the lowest cost kit Van's has also produced by the changed cowl and canopy design.
- Increase the amount of fuel you carry so you can have a 4 hour range with 1 hour reserve.
- Ski / golf bag tube

Webb said:

I ran across the numbers last night when working on the wheel pants. Van lists 8 for the gear and 3-4 for the wheel fairings. I don't remember if it was in knots or mph but did state it would take 27 hp to add 12 (I think it was knots) on to cruise speed. This was for the RV7. I expect you would be able to 8 or 9 more from a RV12. If knots, then you would be pushing it up towards 130 knots cruise.

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I really don't think your numbers will work at these lower speeds. Drag means a lot more at the higher speeds of the RV-7/8 than they do at the speeds of the -12.

According to the POH for a 1978 Piper Warrior II, wheel fairings add 7 knots to the cruise speed. Pre-1978 wheel fairings only add 2 knots. I would guess that the Warrior and RV-12 cruise at similar speeds.

FWIW the folks at Glasair said that the sportsman 2+2 has flush rivets only on the leading edge because that is where the most benefit is realized. Once you get too far aft the airflow becomes more turbulent and flush rivets are not worth the effort.

Ryan