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RV-12 Questions

L

lakespookie

Member
So I know I want to build an RV-12 but I am contemplating going EAB and making some modifications, primarily Fuel tank size and engine choice, I was wondering if anyone had an info on the following items;

1. flutter analysis
2. CG limits
3. Structural loading Limits in particular when it comes to the wing spar.
4. Wing/Empannage Loading Design Limits.

Although I will probably end up jumping on a Stock 12is build lol :rolleyes::rolleyes::rolleyes:
 
lakespookie said:
So I know I want to build an RV-12 but I am contemplating going EAB and making some modifications, primarily Fuel tank size and engine choice, I was wondering if anyone had an info on the following items;

1. flutter analysis
2. CG limits
3. Structural loading Limits in particular when it comes to the wing spar.
4. Wing/Empannage Loading Design Limits.

Although I will probably end up jumping on a Stock 12is build lol :rolleyes::rolleyes::rolleyes:
Click to expand...

Have you ever built and airplane before? If no then I recommend you build as directed by the kit builder. If you go faster than the recommended Vne then make sure you life Insurance is paid up.;) if you hang an engine heavier than a Rotax then you are going to have CG problems:eek:. If you are out of CG then you will exceed the structural limits as stated by the manufacturer. :( But all things concidered the 12 was designed around LSA specs and is not really a good kit to build as a EAB. You might want to build an RV9 if your heart is set on an EAB. The stats bear this out, in my honest opinion only about 1% of completed kit are build as an EAB. Good luck on your new adventure.:)
 
So short answers to some of your questions

1. I have assisted with a previous kit build just not a vans product,
2. I have no intention of exceeding Vne, however the reason for the flutter analysis info is to correlate it with increased performance of a different power plant choice affecting Vne Limits especially at higher altitudes.
3. Life insurance is paid up however I have no intention of getting myself in that kind of trouble hence the questions for feasibility and the most likely outcome of building a stock 12is,
4. My interests are in hanging a 15is of the nose so while I do anticipate some weight/cg considerations its not crazy out of the ball park to imagine that a different engine in the same family is possible.

That being said the biggest concerns would be flutter at altitude with the greater performance of the engine, and structural design limitations.
Overall the biggest limitations I see with the 12 is the fuel capacity, of course everything in engineering is a compromise so addressing that faults as far as my mission parameters go has secondary impacts that can potentially be addressed with the other power plant options already available from Rotax.

FWIW, I am an Engineer in aerospace, and was just looking to do feasibility analysis if the data was available, I am pretty sure the CG limits I can find from the weight and balance sheets then I can just do calculations with my intended changes.

But really my larger concerns would be structural load/design limits given the additional fuel and engine weight, and flutter analysis at altitude given the improved engine performance.

Then again who knows what vans has down the line with the upcoming Proposed LSA changes, it would be really nice if they ever got the IMC change through although I don't know if they are really pushing that.
 
I was wondering if Vans may eventually rework the -12 for the 915 when the LSA rules change? In any case it looks like the weight difference looks like 46 pounds according to the Rotax web site. That would seem to be a great deal of additional weight on the nose. One other thought that came to my mind was the addition of the turbo on the 915. Vans says they have worked out the additional cooling issues associated with the 912iS. I suspect that would be a bit more of a design consideration with the turbo?

Disclaimer, I am not aero engineer :)

Carl
 
Yeah its a constant balance between things with every decision, The move to the 915 presents the most problems but the added performance give a higher overall gross weight with larger fuel tanks is hard to not look at, but there are so many things to consider with that change (Vne limits at higher altitude are the scariest, closely followed by structural design/stress limits, then CG impacts, followed by heat management, airflow impacts due to the heat management/packaging changes, changes to the engine mount, etc. it goes on and on everything impacts something else I can go on for a while down this rabbit hole lol.

Of course all of those issues can be solved but the biggest safety issues boil down to cg due to impacts on controllability of the aircraft and engine performance especially without the drop off with a turbo engine vs flutter performance of the airfoil, and structural load limits of the airfoil as designed. I suspect a large part of the structural limits will be driven by the design of the attachment points of the wings given that they are removable more so than the inherent structural strength of the airfoil, which impacts all of the above lol.
 
Of course the more I think about this the more I want to see how achievable it is, and at the same time lean more and more to building a stock 12is and then jumping down a rabbit hole lol
 
I can think of roughly 25000 reasons lol but yeah you are probably right other than those 2 extra seats I don't need it looks like a fantastic platform, But if I were to go 4 seater ideally it would be a different kit I would want. A certain dinosaur related kit that is currently vapor ware lol
 
lakespookie said:
So short answers to some of your questions

1. I have assisted with a previous kit build just not a vans product,
2. I have no intention of exceeding Vne, however the reason for the flutter analysis info is to correlate it with increased performance of a different power plant choice affecting Vne Limits especially at higher altitudes.
3. Life insurance is paid up however I have no intention of getting myself in that kind of trouble hence the questions for feasibility and the most likely outcome of building a stock 12is,
4. My interests are in hanging a 15is of the nose so while I do anticipate some weight/cg considerations its not crazy out of the ball park to imagine that a different engine in the same family is possible.

That being said the biggest concerns would be flutter at altitude with the greater performance of the engine, and structural design limitations.
Overall the biggest limitations I see with the 12 is the fuel capacity, of course everything in engineering is a compromise so addressing that faults as far as my mission parameters go has secondary impacts that can potentially be addressed with the other power plant options already available from Rotax.

FWIW, I am an Engineer in aerospace, and was just looking to do feasibility analysis if the data was available, I am pretty sure the CG limits I can find from the weight and balance sheets then I can just do calculations with my intended changes.

But really my larger concerns would be structural load/design limits given the additional fuel and engine weight, and flutter analysis at altitude given the improved engine performance.

Then again who knows what vans has down the line with the upcoming Proposed LSA changes, it would be really nice if they ever got the IMC change through although I don't know if they are really pushing that.
Click to expand...

Not to throw a wrench into you Van?s build, but have you thought about building a Sling 2 kit? Unlike the -12, it MAUW everywhere but in the USA is 1540lbs, rather than 1320lbs. Also, with full fuel it holds 39.6 gallons. I don?t see mounting the 915iS a problem, as it can already be had with a 914 if you like.

I think an EAB Sling 2, with a 915iS, Airmaster constant speed prop and Garmin avionics would be one slick plane. I think a RV-9 or even and eight better, but if your looking for a Rotax equipped bird, the Sling might fit the build.

Good Luck!
 
I have noticed a lot of people pushing the 9/A over the 14/A, I am assuming this comes down to the wing and the more cross country focus of that wing + significant cost increase of the 14 vs the 9 kit
 
The 9A is limited, by Van's to about 160 HP. Lot's are built with OS 360 motors. The Vne is higher, but again, you put too much HP into it, and you exceed the safety margin envelope, rather easily, at higher elevations.

Van's built the 9 around a 118 HP OS 235. Some have run OS 320's, some have run OS 360's.

A better understanding on the limitations on engine size on a RV-9A is here:

https://www.vansaircraft.com/pdf/hp_limts.pdf
 
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