Stall Speeds EVO vs. Sport and Parallel vs. Angle

[rpigeek]

I've been taking my time looking at different Rockets (both F1 and Harmon's). It's often hard to find one where it has the right engine, etc. I'm looking at one that has an EVO wing and an Angle Valve engine shoehorned into the cowling. I like most about it, but it has an angle valve engine which I believe has increased the stall speed beyond what I think is typical. There are a couple concerns with this, I'm hoping to stay within the expected, forthcoming MOSAIC rules, and I was attracted to the aircraft to be able to have reasonable performance at a grass / short strip (i.e. 1,800 feet) that I've operated an RV7 out of. Right now this EVO + angle valve combination and touching down with flaps at about 52 knots (actual stall speed for some reason wasn't known), but owner believed right about there.

I was hoping to have a Rocket that would stay within the expected, forthcoming MOSAIC rules with a 54 knots vs1 clean stall speed. Is this possible in typical parallel valve rockets? The performance of the angle valve is certainly amazing, but I'm leaning towards not worth the weight tradeoff if lighter, parallel engines can get below MOSAIC and land shorter.

 

[Jjackh10]

I'm no expert but I'm pretty sure the RV-7 & -8 don't meet the current proposed VS1 speed. And all rockets have heavier engines and less wing area. So I wouldn't think any of them will meet the proposed mosaic rules.

 

[rpigeek]

I'm no expert but I'm pretty sure the RV-7 & -8 don't meet the current proposed VS1 speed.

It's close on the -7 and some have squeaked under it during flight testing.

I think the point that a rocket will hit that with the wing loading intuitively makes sense. So MOSAIC is a pipe dream.

However, still interested in typical stall speeds for short field performance comparison in general.

 

[rvmills]

My Super Six is "not quite Rocket, not quite RV", so this may all be FWIW. I have also flown HR-II, F1 Sport Wing and F1 EVO Rockets, and feel the performance was fairly similar, in terms of stall and landing speeds to my plane. With the original wing on my RV-S6 (a clipped RV wing like the HR-II has), at mid-weight, clean stall was 58 and full flap stall was 52. With the new tapered wing, the speeds were (somewhat surprisingly) very close...58 clean, 53 flaps full. A testament to Steve Smith's great design. While I haven't done extensive stall testing on all of the Rockets I've flown, the stalls I have done in them were similar in performance and speed range. Low 50's for dirty, high 50's to 60 for clean. I'd think that unless you have a phenomenally light Rocket, 54 clean may not be in the cards.

In terms of landing distance, I fly off a 2500' grass strip at home, with some small trees off each end. With slight braking, on the slightly uphill runway I can turn around at just past halfway, and on the downhill runway, I just let it roll to my exit about 1800-2000' down the runway. I'd feel comfortable on an 1800' runway of decent quality, grass or pavement. In a new to me aircraft, I'd do a fair bit of work on a longer runway till I felt confident moving to the 1800' strip. And I'll go around if I don't like the set-up. ;-)

Hope this gives you some useful data.

Cheers,
Bob

 

[BobTurner]

I don’t quite understand the logic applied in the first post. Stall speed will depend on the wing, and on the gross weight. So if a parallel valve engine meets the desired goal, then so will an angled valve engine, as long as the gross weight is unchanged. Of course the heavier engine will require lighter passengers to stay with the same gross weight.

 

[rvmills]

I don’t quite understand the logic applied in the first post. Stall speed will depend on the wing, and on the gross weight. So if a parallel valve engine meets the desired goal, then so will an angled valve engine, as long as the gross weight is unchanged. Of course the heavier engine will require lighter passengers to stay with the same gross weight.

I had to think that one through too Bob, and figured all else being equal, the Angle Valve factor must mean higher weight (same pax, same fuel). Then again, if the Mosaic rules are for at MGTOW or MGLW, then a Rocket is a Rocket. Still don't think a Rocket could get that slow at MGTOW.

Cheers,
Bob

 

[uk_figs]

I was under the impression that the MOSAIC numbers were related to published numbers versus individual configurations so currently my -7 would not qualify based on Vans published numbers which is why there is an effort to expand the range a bit.
Figs

 

[vfrazier]

Is that a 6 cylinder angle valve? On an Evo wing? What prop?

Have you looked closely at the W&B yet?

 

[rpigeek]

Is that a 6 cylinder angle valve? On an Evo wing? What prop?
Have you looked closely at the W&B yet?

Yes, 6 cylinder angle valve. EVO Wing. MTV-9.

No W&B yet, seen useful load numbers of 891 which doesn't seem horrible (i.e. 1,109 empty) for the weight of the engine.

Going to see it in person this weekend.

 

[rpigeek]

So if a parallel valve engine meets the desired goal, then so will an angled valve engine, as long as the gross weight is unchanged.

Right, the angle valve engines are usually significantly heavier, particularly on a 6 cylinder. I thought I heard 50 lbs heavier for a 6 cylinder and it's all on the nose of course which kills stall speed.

 

[F1 Rocket]

Yes, 6 cylinder angle valve. EVO Wing. MTV-9.

No W&B yet, seen useful load numbers of 891 which doesn't seem horrible (i.e. 1,109 empty) for the weight of the engine.

Going to see it in person this weekend.

1109 empty is very light for a F1 Evo. Especially with an angle valve 540 in it. I’d want to see it on a set of calibrated scales.

 

[rpigeek]

1109 empty is very light for a F1 Evo. Especially with an angle valve 540 in it. I’d want to see it on a set of calibrated scales.

That was what I thought after seeing the useful load and assuming a standard 2,000 lb gross weight. I'll find out more this weekend. I hadn't even thought about the EVO wing weight as well.

 

[Little Al]

Yes, 6 cylinder angle valve. EVO Wing. MTV-9.

No W&B yet, seen useful load numbers of 891 which doesn't seem horrible (i.e. 1,109 empty) for the weight of the engine.

Going to see it in person this weekend.

Bring your own scales and do your own weight and balance on that one before you put and money down. I would be surprised if it even had 691 lbs useful load on that one. Really neat article in kit planes of a Harmon Rocket that was built with long wings or unclipped wings. Added vgs and had very impressive stall numbers in the low 40s

 

[penguin]

Quoting stall speeds from individual experimental aircraft is always fraught with difficulty for two reasons, did the pilot understand how to stall the aircraft to achieve a minimum stall speed number and what is the slow speed pressure error correction for that aircraft? Carrying out a stall is not as simple as your flight instructor made out if the aim is to determine the minimum possible speed, technique is critical to ensure the aircraft is at 1g only, many do not know how. Many owners have no idea what the PEC for their aircraft is, using the GPS 3 leg method it is not difficult to find out but many don't bother. With an accurate pitot-static system and a skilled pilot comparisons are valid, but ...

 

[clam]

My Super Six is "not quite Rocket, not quite RV", so this may all be FWIW. I have also flown HR-II, F1 Sport Wing and F1 EVO Rockets, and feel the performance was fairly similar, in terms of stall and landing speeds to my plane. With the original wing on my RV-S6 (a clipped RV wing like the HR-II has), at mid-weight, clean stall was 58 and full flap stall was 52. With the new tapered wing, the speeds were (somewhat surprisingly) very close...58 clean, 53 flaps full. A testament to Steve Smith's great design. While I haven't done extensive stall testing on all of the Rockets I've flown, the stalls I have done in them were similar in performance and speed range. Low 50's for dirty, high 50's to 60 for clean. I'd think that unless you have a phenomenally light Rocket, 54 clean may not be in the cards.

In terms of landing distance, I fly off a 2500' grass strip at home, with some small trees off each end. With slight braking, on the slightly uphill runway I can turn around at just past halfway, and on the downhill runway, I just let it roll to my exit about 1800-2000' down the runway. I'd feel comfortable on an 1800' runway of decent quality, grass or pavement. In a new to me aircraft, I'd do a fair bit of work on a longer runway till I felt confident moving to the 1800' strip. And I'll go around if I don't like the set-up. ;-)

Hope this gives you some useful data.

Cheers,
Bob

Rocket and Super-RV drivers, what speed do you fly on approach, short final, in the flare, and at touch down? Use a mid-weight, or whatever weight numbers are easy to quote. 1.3Vso in the range above would be about 68 knots. The ask isn't scientific or gnats-a$$, just the numbers in your head in the pattern. Part of the exercise is to see how closely my personal RV-8 speeds are to the Rockets. Looking at this particular quote above, Rocket speeds are slower than I would have thought.