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Performance difference between RV-12 and RV-9

B

benika

I'm New Here
Hi everyone, i'm from the UK and I'm looking into getting my first kitplane. I'v been digging in VAF forums for a while and here is my first post.

I'm looking at the RV-12 mainly because of its removable wings. As I will store it in a garage and a lack of local hangerage.

Ideally I'd like an RV-9 (115hp) with removable wings as I would use it to travel 500miles to family and do so economically.

But the RV-12 is quite a bit slower even though there is only 15hp in the difference. Why is that? I know it is because of the LSA requirements. But why structurally?

What modifications could be made to make the RV-12 faster and more economical over longer distances. What effect would they have?

Thanks
Ben
 
Random thoughts - -

I built an RV-12. I feel it cruises best by myself at 108 knots, or 125 miles per hour, on premium auto fuel. Without knowing fuel cost, and type, and availability in your area, hard to say. There are just too many things to take into account here. What amount of your time will be on that 500 mile trip compared to local flights ? Do you want the plane sitting outside at an airport ( not my choice for sure ) ? I can tell you in the USA, I doubt many people take their wings off regularly. The wings coming off is a good feature if desired. Maybe a point or so can be taken from this. Good luck.

John Bender
 
Reduce drag for more speed

the RV-12 is quite a bit slower even though there is only 15hp in the difference. Why is that?
Click to expand...
It takes a certain amount of power to maintain level flight. Any additional power can be used for more speed. The RV-9 has more additional power.
What modifications could be made to make the RV-12 faster and more economical over longer distances. What effect would they have?
Click to expand...
The steps can be removed for less drag with no effect on aircraft control.
Wheel pants can be added.
Gear leg fairings can be installed on all 3 legs.
Transition fairings like these can be added:
http://www.vansairforce.com/community/showpost.php?p=560685&postcount=11
A lower drag canopy could be made with more of a gentle slope on the forward side. But if the months of canopy construction time is added to the time en-route, cruise speed will be very slow. :D
Joe Gores
 
benika said:
Hi everyone, i'm from the UK and I'm looking into getting my first kitplane. I'v been digging in VAF forums for a while and here is my first post.

...

What modifications could be made to make the RV-12 faster and more economical over longer distances. What effect would they have?

Thanks
Ben
Click to expand...
Ben,

As you're in the UK I take it that you have heard of the Light Aircraft Association. If not have a look at their website, you'll need to contact them if you're planning to build an aircraft in the UK, as they oversee the process. Any modifications you want to make to a design will have to be approved by them, this isn't a trivial process - espically if you want it to go faster.

In short, if the RV12 isn't fast enough for you build something else that is.

The first RV12 to fly in the UK was built by Keith Boardman, who is based (as far as I know) at Perth, which isn't too far from you. He also posts on these forums as Gblwy.

Brooklands
 
I'm just thinking aloud at the moment. I still have to build a shed before I can start building a plane. It just looks like awfully good fun, the building of the plane from what i've seen in all the build logs.

Lets put the question another way, if you had the same engine in the RV-12 and the RV-9 which one would fly faster? Which has the more efficient airframe?

The only other plane I'm considering is the europa xs which seems to be able to cruise at higher speeds than the RV-12.

I would primary want to use the plane out of grass strips and store the plane in my (future) garage.

Cheers for the responses.

Ben
 
I wouldn't consider modifying the RV-12 to increase cruise speed without considerable engineering assistance. The aircraft was designed to fly within LSA speed limitations.

There are many things that must be considered with an increase in speed. Among other things, the stabilator attach could be a real factor at increased speeds.
 
The RV12 will fly 500 miles in about 4 hours, and the RV9 with 118hp will do it in about 3. Add in the preparation and travel time either side of takeoff and landing, and the total trip time probably won't be that much different.

Every aircraft choice will involve compromises, so the best thing is to be realistic about the kind of flying you will actually be doing most of the time, and then choose the aircraft that suits your aspirations and budget the best. I wouldn't suggest trying to modify the -12 to make it do what a -9 will do. On the other hand if I was going to build a -9, I would want more than 118hp.

I considered the RV-12, -7, and -9 and for me the best all-round choice was the RV-12. I expect most of my flying will be local, but I also intend to fly it across Australia, and I'm quite sure it will get the job done. But as they say, YMMV.
 
I started on a Europa...

...in the early years of its existence. I started having some build/performance concerns and put the project on hold. A while later I was talking about it with a friend who had built a beautiful LongEZ. He said "no matter what plane you choose, you're going to spend a LONG time building it. Are you SURE that when it's done it will be able to do what you want it to do?" In my case, with the Europa I was now sure it would NOT fill my mission.

It sounds like you have identified your mission and the RV12 will NOT fill that mission. With the trip length, your desired time enroute and your need for off-airport storage, maybe more research into the Europa or other removeable/folding wing designs might be warranted. Or re-analyse your mission...

Not trying to be a kill-joy, just food for thought:eek:

Jeremy Constant
RV7A
 
Apples to Oranges comparison

Ben,
It sounds like having removable wings is an economic "must have" for you. That eliminates the RV-9. While the wings can be removed from a 9, it's really the sort of job to only be done because you have to [Like after an off airport landing, where the ship must be broken down and trucked [a lorry to you] back to an airport. Wing removal on a 9 would be an all day job.
The RV-12 uses conventional, pulled rivets [more drag, less time to build]. The 9 uses flush, conventional rivets. The 9 has a much more streamlined fuselage, by design. The build time of the 9 would probably be double that of the 12.
As Mel mentioned earlier, cleaning up the airframe of a 12 would probably be illegal, especially considering the additional regulations you face in the UK [relative to the USA].
Unless you have enough room at home for a private airstrip and a bigger "shed" I think the 9 is a deal breaker. Consider sharing a hanger with a high wing aircraft if you really decide you want the 9.
Charlie
 
chaskuss said:
The RV-12 uses conventional, pulled rivets [more drag, less time to build]. The 9 uses flush, conventional rivets. The 9 has a much more streamlined fuselage, by design. The build time of the 9 would probably be double that of the 12.
As Mel mentioned earlier, cleaning up the airframe of a 12 would probably be illegal, especially considering the additional regulations you face in the UK [relative to the USA].
Click to expand...

Excusing my ignorance, I'm presuming that the conventional rivets would have higher strength than the pulled kind so how would strengthening the airframe be illegal. I wonder how much difference this would make in the cruise speed.

I'm a mechanical engineer so I am generally more interested in why the performance for the aircraft differ not necessarily that I want to change them.

Because of non removable wings I do agree think that the RV-9 is not ideal for my situation plus fuel economy would be of greater important to me than outright speed.

I have looked at the Europa xs and it does seems to tick all the boxes, the removable wings, speed, economical and range. However the build time is a good bit longer than the vans, smaller active build community, and somewhat tricky ground handling (Monowheel) which may not be ideal for a low time pilot.

But the major downside is the low resale value of the Europa, it is cheaper to buy than to build the xs. For this reason it has pushed me more towards the RV-12. I've also seen a few Europa kits for sale indicating that it would be more likely for me to finish the Vans kit over the Europa

Ideal case would be the Vans with the performance of the Europa.
Maybe with conventional rivets, wheel pants, fairings, and maybe a CS prop. If this makes the RV-12 too fast I could always put the 80hp 912 in it instead.

Thanks for all your input so far, its been plenty food for thought. Cheers
 
benika said:
Excusing my ignorance, I'm presuming that the conventional rivets would have higher strength than the pulled kind so how would strengthening the airframe be illegal. I wonder how much difference this would make in the cruise speed. snipped
Click to expand...

Ben,
General rule of thumb is that the drag reduction achieved by using flush rivets only shows benefits in aircraft which cruise above 150 mph. You are correct that conventional rivets would be stronger. They are not needed for strength. The RV-12 uses 1/8" diameter pulled rivets for the skins. The other RVs use 3/32" flush conventional rivets [AN426-3-x] to attach the skins. The reduced strength of the pulled rivets is compensated for, by their larger diameter.
Switching to AN470-4-x conventional rivets will require more labor. Using AN426-4-x flush rivets would add even more labor, as you would then have to dimple countersink all your parts. I can make no knowledgeable comments on how much speed you would gain from doing that.
Charlie
PS Good luck with selling your regulatory inspector that story that you went to flush, conventional rivets for strength. :rolleyes:
 
Regulations

benika said:
Excusing my ignorance, I'm presuming that the conventional rivets would have higher strength than the pulled kind so how would strengthening the airframe be illegal. I wonder how much difference this would make in the cruise speed.
Click to expand...

If you're contemplating modifications, you need to start with what the regulations will allow you to do, rather than what seems OK from an engineering viewpoint. The RV-12 is intended to be an E-LSA category aircraft, and therefore may not be modified from the manufacturer's plans.

If you modify it, it will become something else, such as AB-E (Amateur Built Experimental). Even replacing the pulled rivets with stronger conventional rivets is not allowed for an E-LSA that is designed with pulled rivets (unless you get the manufacturer's written approval). As one of the previous posters suggested, check with the LAA first to find out what the rules are.

Given the speed at which the RV-12 is designed to fly, using conventional flush rivets is not likely to reduce drag enough to make a major difference to its cruise speed. The wheel fairings add 4-5 kts by all accounts, so I doubt that the rivets would more than a knot or two (but they will add much more than that to your build time).
 
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Rivets and mission

Changing from pulled blind rivets to bucked solid (flush) rivets is not a trivial matter. The RV-9 (4,6,7,8,10) design has had to consider access from both sides of the skin, and a method for closing out the structure. In the case of the RV-9, the lower wing skins are put on last and the sequence of riveting is to start at the trailing edge spar, gradually work forward along the ribs, then finally close out using the three inspection panels to stick your arm through to hold the bucking bar. The RV-12, may or may not have this provision, you would have to research it thoroughly before trying. It's also possible to use flush pulled blind rivets, but you would still have to dimple the skins and underlying structure.

You should know that modifying an aircraft for more speed, even if it is allowed by the airworthiness authorities, is also not a trivial matter. If you look at a performance envelope (a V/g diagram) for an aircraft you will see the right hand vertical line is Vne, that is the never exceed speed of the aircraft. This is the speed beyond which structural damage can occur. By "hotrodding" an airplane whether by drag reduction, or increasing engine power, it is possible to push the cruise speed up to or maybe beyond Vne. Not saying this will happen, but you need to be very careful and research the Vne of any aircraft you intend to modify for extra speed.

The Europa was on my short list before I bought an RV-9A kit. In the end the RV-9A had more room, the kit was cheaper (but probably not the finished airplane), and I was more confident with sheet metal construction.

You are probably aware the Europa is available with tricycle gear. However your desire to operate from grass may make the monowheel preferable. Be aware there have been several accidents, especially in the UK with RVs with nosegear on grass. I will not be operating my RV on grass unless it is golf course putting green smooth. Others may have a different opinion.

The tradeoff between storage, speed, and ability to land on a variety of surfaces is a difficult one. I would suggest that you get some flight time in each of the aircraft on your short list and prioritize your mission needs more fully before making a selection.
 
jjconstant said:
I stated building the Europa... in the early years of its existence. I started having some build/performance concerns and put the project on hold.
Click to expand...

Maybe a little off topic but

Jeremy,
I was wondering, as you are one of the few people that have built or at least partially built the both a composite plane and an sheet aluminium plane.
How do you compare building of the two, in terms of enjoyment and satisfaction gained.
Open question to every one as well.
Is a Rv-12 more satisfying to build than an Rv-9 or other. Or is it too short? too easy?

Because I primary want to build the plane and the flying is a nice bonus.
 
Come take a look

Come to Perth and take a look. My RV12 is there and took a year to build. My friend's monowheel Europa is also there. Took 10 years to build, is fast (probably the fastest Europa), and is MUCH less comfortable than the RV12. Oh and the Europa is on its third prop ;-)

Cheers...Keith
 
Keith,

That sounds great I will definitely take you up on that offer, I wont have a chance to pop down until September though.

You make a good point however, any fuel savings that the Europa has over the RV-12 are negated by the cost of replacing the props.
 
First, you need to know that I packed in the Europa project while on the tail section. I enjoyed the work but the instructions kept changing, the Internet user group was just getting started and there were problems with some aircraft performing up to spec and others weren't even close and nobody knew why.

Comparing my experience with both projects I have to tell you that I did more fiberglass work on the RV than on the Europa! While I enjoy aspects of fiberglass work I've come to the realization that even though I can do structurally sound fiberglass, getting it as beautiful as it should be was something that I needed help with. I didn't have the eye or the patience. I had committed early on to using a professional painter. After the initial fitting and structural work on the fiberglass and being only marginally successful in attempting to make it pretty I decided that the final finishing on the glass was "pre-paint":D

I also must confess that I REALLY like the fact that with metal planes, the soundness of the structure is reasonably easily verified. I was rather spooked when one of the early, looked-up-to builders in the Europa community crashed when his plane suffered an in flight break up. It was later established that he had done glass on foam layups while heating his shop with a kerosene heater. Apparently some unburnt airborne kerosene contaminated the foam and caused delamination.

So I would say I prefer metal.

All best

Jeremy Constant
 
From an earlier post --

The RV12 will fly 500 miles in about 4 hours, and the RV9 with 118hp will do it in about 3. Add in the preparation and travel time either side of takeoff and landing, and the total trip time probably won't be that much different.

Two questions...

1. What would be the expected total fuel consumption of the -9 and the -12 for the trip mentioned above?

2. The poster is in the UK - does the E-LSA even exist over there? I thought it was FAA unique about midway between two EU weight classes.
 
Mission

What you need to do is get a flight in a 12 and a 9, the rally would probably be the best place to arrange this. You would be welcome to fly my diesel 9.

Then if the your preferred mount see if you can find a farm nearby where you can out a strip. Farmers will do almost anything for money in my experience. We set up a strip locally for 6 aeroplanes which only costs us ?500 a year, and built our own hangars.
 
Gil

Q1. I'm guessing 24l/hr for the Lycoming and 18 for the Rotax so say line ball for the trip.
Q2. I'm not sure about the UK, but E-LSA exists in Australia

az_gila said:
From an earlier post --

The RV12 will fly 500 miles in about 4 hours, and the RV9 with 118hp will do it in about 3. Add in the preparation and travel time either side of takeoff and landing, and the total trip time probably won't be that much different.

Two questions...

1. What would be the expected total fuel consumption of the -9 and the -12 for the trip mentioned above?

2. The poster is in the UK - does the E-LSA even exist over there? I thought it was FAA unique about midway between two EU weight classes.
Click to expand...
 
benika said:
I'm just thinking aloud at the moment. I still have to build a shed before I can start building a plane. It just looks like awfully good fun, the building of the plane from what i've seen in all the build logs.

Lets put the question another way, if you had the same engine in the RV-12 and the RV-9 which one would fly faster? Which has the more efficient airframe?

The only other plane I'm considering is the europa xs which seems to be able to cruise at higher speeds than the RV-12.

I would primary want to use the plane out of grass strips and store the plane in my (future) garage.

Cheers for the responses.

Ben
Click to expand...

Ben,

Keep in mind that the 12 has easily removable wings, allowing your future garage to be considerably smaller (assuming you're planning to store the plane there). The removable wings and vastly shorter build time are what sold me on the 12.

Jerre
 
Sounds to me that what he needs to consider is an RV12 with a Viking engine with a constant speed prop.
 
Viking Engine

Th5s would pose a lot more problems in the Uk as I doubt any have been fitted here. Its not impossible but a it would be more time consuming getting a new engine/prop/mount combination through the system.
 
Ben, I don't know if you're still mulling this issue. I had to go 'walkabout' for several weeks and couldn't follow the thread until now. Perhaps more for emphasis than to offer new info - and because I feel our 2 years in England helps me appreciate your circumstances - here are both of my two cents:

-- Contrary to one comparison above, I think you'll find build times to vary greatly (between the 9 and 12) if the range of build times I've researched for those two a/c are a fair indication. Perhaps build time is less significant to you than most others (you did say you were looking forward to it), bu another aspect is that 'life happens' and one's circumstances can change over time. Completion of a 12 in a single year is, by most accounts, quite do-able for the committed builder. That means - if you tackle the shed this Fall - that could be flying your own plane early in 2013 vs. perhaps 2015 or later for a 9.
-- I missed the amount of actual flying time (especially, distance flying) you've done, so let me repeat the point several others have made that 'enroute time' is only a piece of the time it would take you to fly 500 NM. That range means a fuel stop. Fold in (no pun intended) getting the plane's wings on and ready to fly, along with the pre-flight wx brief, and tucking the plane in at the other end and a 9 is unlikely to be meaningfully faster than a 12. More fun? Hard to say. More expensive. Absolutely.
-- In that regard, I think about those LSA pilots I met down in Australia who were jugging autogas and great operational savings (and not just in the price of fuel but also maintenance). Before committing to a 9, if I were back in the UK, I'd be exploring how easily one can burn autogas with a 9.
-- Contrary to Don's enthusiastic (tongue in cheek?) endorsement, the last thing a new builder needs is to ignore a proven European-sourced engine and its absence of trade barriers for follow-up parts sourcing. OTOH I would carefully investigate whether there are differences between the European & N American 912 engines. It's been surprising how the 'same engine' in other engine products has varied between those two geographic regions.

Good luck on the mulling!

Jack
 
As someone who has built a 9A and is supervising the build of a 12, I can agree with Jack on times. The 12 is much simpler/quicker! I find I rarely fly my 9A as fast as it can go. I expect to fly the 12 more nearly at high cruise. I will say that the 9 is a gas miser, but I only run 100LL. The 12 will be cheaper to operate. Cost wise, I have less in the 9A, simply because I bought a used engine. Either way you go, you won't be disappointed. the whole thing is, the later you start, the later you finish.

Bob
 
WAM120RV said:
Th5s would pose a lot more problems in the Uk as I doubt any have been fitted here. Its not impossible but a it would be more time consuming getting a new engine/prop/mount combination through the system.
Click to expand...

If I was in the UK I'd take a good Look at Installing an UL Power Engine on either the 9 or the 12 myself.....Seems to be a few of them fitted to different A/C over there & in Europe! Seems to bea very Nice Engine!
 
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