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 Post subject: Re: RV-15
PostPosted: 16 Jul 2022, 23:01 
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USAF seems to be okay with oil canning.


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 Post subject: Re: RV-15
PostPosted: 16 Jul 2022, 23:22 
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Location: Ontario, Canada
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[quote="M Turner Billingsley"
Well of course the Sportsman wing doesn't look like that in flight - it's composite construction - [/quote]

The Sportsman flying surfaces are all conventional riveted aluminum, not composite. It's hard to have an informed conversation when the basics like this aren't understood.


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 00:50 
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Username Protected wrote:
Unfortunately I've had some involvement with RVs which were operated from non-paved strips and I got to see the labor which went into repairing the gear attachment points as a result of the non-paved field operations.


Keep in mind that Van's training RV-6A has about 20,000 hours and at least as many landings from a grass field. And again, this is their training airplane, where the technique is bound to be less than perfect. And aside from their RV-6A, all of their aircraft operate from a grass runway during training operations in Oregon. Kind of makes me wonder if there's some more to the picture that you're painting, Mark?


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 05:51 
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Username Protected wrote:

The Sportsman flying surfaces are all conventional riveted aluminum, not composite. It's hard to have an informed conversation when the basics like this aren't understood.


I stand corrected - I was wrong - and I think I did know at one point that the Sportsman used a conventional wing, just forgot. I'm much more familiar with Van's as I've discussed. Thank you for pointing out my error.

May I ask however, what about the original oil-canning part of the discussion, aside from the wing skin deflection? Now that I'm properly shamed I would be interested in returning to that part of the conversation.


Last edited on 17 Jul 2022, 07:04, edited 4 times in total.

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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 06:04 
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Username Protected wrote:
Unfortunately I've had some involvement with RVs which were operated from non-paved strips and I got to see the labor which went into repairing the gear attachment points as a result of the non-paved field operations.


Keep in mind that Van's training RV-6A has about 20,000 hours and at least as many landings from a grass field. And again, this is their training airplane, where the technique is bound to be less than perfect. And aside from their RV-6A, all of their aircraft operate from a grass runway during training operations in Oregon. Kind of makes me wonder if there's some more to the picture that you're painting, Mark?


I did my RV-14A transition training on that strip. Having been (and continuing after) mostly a flat pavement pilot I was surprised how uneven that surface is - I had operated a few times on smoother grass strips but that one is rugged based on my admittedly limited experience.

One thing I learned was the importance of technique: even with the more sturdy nosewheel design (RV-10, 14A) and operating off pavement exclusively, he teaches the same techniqe - most importantly unloading the nosewheel early and keeping it unloaded as much of the time as possible including on landing, holding it off until it settles on its own. I spent a lot of time (waiting for weather to clear and snow to melt) talking with Mike (RV transition training pilot) about his experience with the Van's earlier nose gear design which I noted before has some reputation for being vulnerable: he was insistent that it's the pilots' technique that causes most of the problems - we discussed the very airplane (RV-6A) you're talking about in that conversation.

Last edited on 17 Jul 2022, 06:54, edited 3 times in total.

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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 06:23 
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Several local RV builders (9 & 14) have mentioned Van’s recommending a new, stronger nose wheel attachment assembly for the existing fleet.

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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 06:39 
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Username Protected wrote:
Several local RV builders (9 & 14) have mentioned Van’s recommending a new, stronger nose wheel attachment assembly for the existing fleet.


The newer design (for earlier models) is based on the RV-10 and14A which has been mostly the same since it was introduced - the 14A design hasn't changed since it was introduced AFAIK. (They've had some problems with cracks on the RV-10 assembly on airplanes with higher hours/heavy use, and I think there's been a service bulletin - the bigger engine is a lot heavier. Not aware of any issues in the 14A).

Kitplanes article on the updated design:

https://www.kitplanes.com/nosegear-job/


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 06:42 
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The Sportsman might well be a better airplane than the RV-15, just like the Glasair II was a better airplane in many ways than the RV-6. But these things start off as kits, and fiberglas is stinky, messy, and itchy.


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 10:33 
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Location: Ontario, Canada
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Username Protected wrote:
The Sportsman might well be a better airplane than the RV-15, just like the Glasair II was a better airplane in many ways than the RV-6. But these things start off as kits, and fiberglas is stinky, messy, and itchy.


There's surprisingly little glass work to do on a Sportsman. So little, in fact, that when new owner/builders take their plane at the end of the Two Weeks To Taxi program most of them don't know how to do glass work.

With respect to humps and bumps in grass, it would seem we would all do our tricycle gear airplanes a favor by treating the nose wheel in the same manner as RV transition training instructs. Imagine it to be a pogo stick rather than a wheel - keep it off the ground for as long as possible under all circumstances.

With respect to the RV10 and RV14A nose gear, if one looks at it one will find it is nearly a carbon copy of the Sportsman nose gear. The predecessor design, the Glastar, featured a nose gear which looks like a copy of the RV6A gear but in fact is a carry over from the earlier low-wing Glasair airplanes. Like the RV6A, 7A, 8A and 9A, it is a somewhat fragile setup. Interestingly the gear legs for both Vans and Glasair aircraft are made in the same shop, Langair Machining. Harmon Lange started off making this Whittman-style gear when he built a Davis DA2A some 50+ years ago. My Davis DA2A main legs were made by Harmon in 1977 and are still going strong.

Coming back to oil canning... The RVs don't have "speed wrinkles" like the BUFF although perhaps some of the younger set here might comment that their owners, and owners of most airplanes these days seem to have their fair share of personal speed wrinkles! :bugeye: :lol: If one taxis an RV taildragger over concrete with relief cuts or asphalt with cracks one quickly becomes aware of the sounds of the oil canning going on back behind one's head. This isn't a feature of the composite fuselage of the Glastar and Sportsman. Do the same thing in a Sonex and you might wonder if you really should be flying that airplane. It takes oil canning to a new level.

All that having been said, the RVs are fine airplanes indeed and the market clearly has spoken. Still, the experience of flying a Glastar or Sportsman is very different - much akin to the differences in experiences between an old Miata and a Lexus - they're both driving and both will last for years, but the Miata is a more "raw" experience (says the owner of a 1990 Miata).

None of this changes the fact that both manufacturers make excellent aircraft, both of which have withstood the test of time.


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 10:36 
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Username Protected wrote:
Several local RV builders (9 & 14) have mentioned Van’s recommending a new, stronger nose wheel attachment assembly for the existing fleet.


Turner is doing a good job holding his own wit the vans design and oilcan discussion:) Mark, I'm no expert either but I haven't heard of any main gear or tailwheel problems with vans.

Also, there have been several incidents of tipovers/prop strikes/nose gear failure on the -A block variants.

However, I can confidently say the ones I have seen have all been pilot error. As Turner mentioned the nose gear is solely for taxiing and steering, and is not designed for loading (there is a weight limit on the nose, sometimes ignored). Anyway, it's acknowledged that the nose gear is fragile but designed intentionally to save weight, therefore requiring some pilot technique.

Recently vans changed the design to help alleviate some of those concerns https://www.vansaircraft.com/2019/06/ne ... nish-kits/

But vans doesn't recommend a retrofit for the existing fleet, again because with proper technique it's adequate. The factory designed a more robust mount/gear to engineer better controls instead of relying on humans to apply correct technique. As an aside, there is an aftermarket company that sells a retrofit nose gear brace. But it just appears to transfer the load to an upper attachment point, and making failures even worse.

So long story short don't try to land on the nosewheel (good advice for any aircraft except carrier landings) and it's not a problem:)


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 12:38 
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Username Protected wrote:
Recently vans changed the design to help alleviate some of those concerns https://www.vansaircraft.com/2019/06/ne ... nish-kits/

But vans doesn't recommend a retrofit for the existing fleet...


This is a topic of some debate. Let's just say that some consider Vans position regarding retrofit to be based more on legal advice than engineering principles. I have no horse in the race so cannot comment further.

The retrofit also requires replacement of the complete engine mount; the new engine mount may not be a direct bolt-on replacement on older aircraft (firewall bolt holes may not match up perfectly). This is likely the largest deterrent to retrofit.

A close friend had his 9A go over on its back, despite witness-verified excellent pilot technique with the elevator held full nose-up. A small depression in the grass was all it took. Truly unfortunate as the resulting damage was quite expensive to repair. The aircraft was taxiing behind another RV (sorry, can't remember if it was a 7A or 9A)... the first airplane missed the little divot by about six inches, the second one.. didn't.

I've also helped replace an RV6 engine mount which cracked at the main gear mounts. This aircraft operated from grass.

These are two aircraft with which I have direct hands-on experience, hence the small degree of conviction with which I make my statements.


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 12:53 
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Yeah Mark I built and flew an RV-9A so have some horse in the fight. I didn't fly in grass after I got my wheelpants, but without them I don't have any qualms. I think you need to have the stick in your belly while taxiing and landing a nose gear RV.

And the new engine mount/nosewheel is not really meant as a retrofit, that's for planes under construction. 100% agree it's a PITA to retrofit. Bummer about your friends RV, I could offer my own anecdotal evidence (nose gear RVs operated solely from grass nearly thousands of hours with no issues) but whatever, I read ya and agree, if you want to off-road get the tailwheel! A lot of factors such as tire pressure and w&b could have affected your friend who flipped. But if it had enough energy to flip, pretty much means there was too much weight in the nose.

With all that said there's a pretty large vans RV community in DFW and I know some of the "professional builders" and mechanics pretty well. First I've heard of the main gear cracks, but have heard of engine mount cracks in general.

But the RV15 prototype looks like it has a tailwheel with a shock absorber.


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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 14:04 
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I love the Sportsman. I think they are beautiful and fairly fast, and they are a nice tradeoff between a plane meant for off airport flying, vs one meant for hard surface plane. A gentleman's backcountry plane, if you will.
That being said, I have seen a Sportsman try to follow a SuperCub into some fun places. Its simply not going to happen. Cubs are meant to go into sub 300' sandbars, and I believe the RV15 will probably be capable of this also, judging from what I see on the videos.
Put simply, it is silly to compare the Sportsman to the RV15. Just not in the same class.
The 15 does go toe to toe with the S-21 on most metrics, especially if the S-21 has cub style Caban gear.

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 Post subject: Re: RV-15
PostPosted: 17 Jul 2022, 17:08 
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Username Protected wrote:
That being said, I have seen a Sportsman try to follow a SuperCub into some fun places. Its simply not going to happen. Cubs are meant to go into sub 300' sandbars...


THIS is absolutely true. A Sportsman is not a SuperCub. There is at least one Sportsman that is, but it has been built by one of the founders of the company and it's pretty special. The flip side of the coin is there aren't many SuperCubs that will fly very fast.

Once again, it comes down to design tradeoffs, a consideration of which corner of the performance envelope the designer tried to nudge the design. I fully expect the RV15 will be doing its best to do the usual Vans "total performance" thing. BUT there's no SuperCub-like performance into a 300' sandbar AND 140+KTAS in the same airplane on the same mission. If builders/owners can keep this in mind, remembering their choices of equipment will constrain the performance of their aircraft closer to one corner or the other of the envelope then a positive outcome is possible. Nothing hurts worse than seeing somebody trying to make an airplane do something that it can't do. We "canna' defy the laws of physics" (in the famous words of Star Trek's Scotty. Try to bend those laws and we end up bending airplanes and, worst case, bending or breaking human bodies.

I wanted cruise speed so I opted for trike gear and wheel pants... I operate from grass and gravel but no true backwoods strips. It's a tradeoff I accept in order to get 134KTAS on 180hp (which turn out to be "book" numbers for this airplane).


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 Post subject: Re: RV-15
PostPosted: 25 Jul 2022, 13:03 
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Aircraft: C-182RG, C-172, PA28
First public reveal happened this morning at OSH

Sounds like they're shooting for an empty weight of 900 lbs, with enough useful load for 2 adults, full fuel, and 250 lbs of cargo.

Designed as a 2 seater, goal speed of 140 knots with full fairings and standard tires.

[youtube]https://youtu.be/l8xkK0GeuZY[/youtube]


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