Limited B: Not so limited

This is the thread to aid in development of new ideas and classes. Post working rules and gather feedback!

Moderator: hbartel

S3HD
Posts: 370
Joined: Thu Mar 15, 2001 9:20 pm
Location: USA
Contact:

Limited B: Not so limited

Post by S3HD »

After having flown my first Limited B contest, I have to weigh in with my humble opinion that it didn't seem as tame as I thought it was going to be.
We tached everybody, the wind was hellacious, the temp was around 42 degrees. I think the highest tach was 14,300 on my OS 25FX turning a MAS 10 x 4. I was flying a TufFlight Panther.
The other planes flown were another Panther with an OS 25FX, a Chris Quinn "Battle Axe"-type design, OS 25FX, and a Piranha, with a OS 25LA.
All flew and performed very slightly less than regular Open B planes, (if you don't consider certain super high performance types like the kind Mike Fuller used to fly with Jett 30's on them).

We had one bad mid-air that broke the wing on the Battle Axe, though probably repairable, and the broke the fuse on the Piranha, and that seemed repairable too, but I didn't examine it closely. Perhaps Jay and Danny will comment on their mid-air on this topic.

I had a mid-air with the other Panther that I was able to fly out of, but Dick's Panther crashed with some damage to the center of the wing/engine area.

I don't think I'm convinced that Limited Open B is where it needs to be yet, but this was only one, very small contest with only 4 rounds, and terrible weather conditions.

The speed of the planes, and the performance in turns seemed about like regular Open B.

Flame Away!
~John
jfromm
Posts: 268
Joined: Sat Nov 16, 2002 1:53 pm
Location: USA

Post by jfromm »

John,

We no longer endorse flaming on these forums and you are correct that Limited-B is about the same as Open-B. In fact, I would need to get a more powerful Webra 25 to be competitive in that class or I would have to do some modifications on my OS 25s. I wouldn’t be surprised if they ban the lower power and lower cost Magnum 28s next. This is the same problem I’m seeing with Scale 2548. By the time you reduce your weights and increase your power to reach the restrictions, you have a very fast and tight turning destruction machine. We are on a different airplane with the same destination as last year.
User avatar
Ed Kettler
Posts: 3437
Joined: Sat Dec 15, 2001 6:05 pm
Location: USA
Contact:

Post by Ed Kettler »

Jay,

I'm still waitng for a formal change request from you to change the engine specs for 2548.[:D] We now have a Rules Committee (Lee, Kirk, Dr. Evil) to evaluate the rules change proposals and make recommendations to the Board. We are evaluating lowering the RPM in 2548 and Limited B at mid-year (the next allowed change point) to address the speeds. There is no movement in Limited B to eliminate Magnum 28s.

Regards,
Ed
Wingman
Posts: 285
Joined: Mon Mar 24, 2003 3:27 pm
Location: USA

Post by Wingman »

I don't have any Limited B experience so no comments there. But I do have to disagree that you need more engine than an OS .25 FX in Open B to be competitive. I fly a completely stock OS .25 FX with an Ultrathrust/mousse can and have been very competitive - even against the higher powered Webras, Jetts and Foras. It's more the pilot, airframe preparation and an understanding of the model's capabilities than anything else.

Also, if Limited B and Open B are not that different in the view of the pilots flying both classes, maybe its time to merge them back together under the current Open B/AMA rules so that we can increase the total number of pilots in the Open B class.
jfromm
Posts: 268
Joined: Sat Nov 16, 2002 1:53 pm
Location: USA

Post by jfromm »

Ed,

I'm still doing testing.[?] Just adding a Magnum .28 to the list would not fix the problem. I also think that if there is an engine requiring throttle position to limit RPM they should be penalized an additional 500 RPM, and that would apply to SSC as well. I feel that there is currently no control, no penalty, and no way to police over taching. I don’t think it is far when people are having problems taching under 17.5K and they are using 30% nitro fuel. The current engine rule of not being able to use a Magnum .28 is not the biggest problem it is just a personal annoyance to me[:(].

I'm finding at 500 AGL with a 3.9 lb airplane I need 13K RPM to launch, and with that, it flies great!
headshot
Posts: 55
Joined: Mon Feb 10, 2003 10:19 pm
Location: USA

Post by headshot »

John, and Jay

I have to respectfully disagree. In my experience, I have noticed that the straight line speeds are similar to what we had in the old Open B days, while the speed bleeds off in the corners and the loops/turns of combat, so there is noticeably less in the way of furballing. Also, I noticed that even with the difference in the various airframes, the speed and performance of the planes was all within the same range, making this a true "pilots" competition.

I have also noticed similar performance in my 3 1/2 lb 2548 planes.

Just my opinion of course, but I have flown practice Limited B with a total of four of us flying, a couple of time now, and these observations have rung true each time.

Jay L.
jfromm
Posts: 268
Joined: Sat Nov 16, 2002 1:53 pm
Location: USA

Post by jfromm »

Jay,

Flying for fun and flying for NPS tend to look different. Two years ago I would have agreed with you. If you are not turning 15.5K RPM, then you are not flying to competitive NPS flying standards. I'm still trying to figure out how to get to 15.5K RPM myself, but I am hitting 15K. This could be some of the differences we are seeing.
Hat Trick
Posts: 1540
Joined: Thu Mar 15, 2001 6:58 pm
Location: USA
Contact:

Post by Hat Trick »

Limited B planes are no slouches but if you've seen the latest generation of OPen B planes you can't miss that it is a lot slower. If you remember seeing the 1/2 A plane that Lee flew at the Nats last year that's the kind of speed and performance I'm talking about. You really have to see it to believe it. A 2.?# plane with a control line engine doing tremendous RPM's make a limited B plane look like a trainer.

I also agree the RPM limit is to high in limited B. I don't think you want to have any modifications at all required on a stock engine to hit the RPM limit easily. I would rather see 30% of the guys having to do something to get under the limit than 90% of the guys having to perform some engine modification to get up to the limit. If your not at the max RPM limit you will be at a disadvantage. It should be simple, not hard to hit the limit. We want the event to be slower anyway!
jfromm
Posts: 268
Joined: Sat Nov 16, 2002 1:53 pm
Location: USA

Post by jfromm »

Mike,

I agree with you and I think the limit should have been set at 14K RPM. My lower cost engines only go 13K on a standard setup. At 15K I think it is pretty much Open-B of last years standard which I don’t think was the intentions of the class.
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

Jay, there is no restriction on the Magnum 28 for Limited B and none is envisioned. The engine rules were specifically written to be pretty open for anything .29 and under.

If you think Limited B is the same as Open B then the Open B folks in your area are flying stones. We flew some limited B a couple of weekends back informally at our club. One of the combat crazies commented after a heat that he didn't think it was much slower than Open B. Brian took off for a demo flight with his Webra-powered Avenger, and I think THAT pretty much disproved the notion that Limited B is ANYWHERE near the current crop of open B ships. If you think there's no difference, you'll just have to trust me, there IS a difference. HUGE difference.

I agree that the rpm limits of LimB are probably too high, we drafted the rules at 15.5k to be consistent with 2548, but I feel that is too high. I am pushing for a reduction to 14.5, but the rules were voted on at 15.5 and no way to change, I am told, until midyear. All I can say is don't plan on 15.5k staying the LimB limit as I will be pushing 14.5 and I think many other folks will be too.

However, physics is physics and I challenge you to demonstrate to me, either theoretically or in the air, how an engine turning a 4 pitch prop at 15.5k rpm can pull a plane as fast as another engine turning a 4 pitch prop at 20k rpm on the same plane. I'm missing something here. Prove it to me by math, or by bringing your LimitedB-plane-that's-as-fast-as-an-OpenB-plane to our May 22 meet. I think I (or more specifically, Brian) have a plane that will give you an in-air demo that might be convincing.....
boilermaker
Posts: 100
Joined: Thu Sep 02, 2004 9:10 pm
Contact:

Post by boilermaker »

The rules that were posted for Limited-B call state a maximum RPM of 15K.
jfromm
Posts: 268
Joined: Sat Nov 16, 2002 1:53 pm
Location: USA

Post by jfromm »

Scott G,

I said 9X4 at 19K verses and 10X4 and 15.5 and I feel the 10X4 is better. Don’t compare it to a 9X4 at 20K on me. It is funny that if you read back on my post, I said I should consider a Webra and that is what you were doing to get the 20K! I have a Master Degree in engineering and I can explain to you what is going on. It is funny how we are saying the same thing! Thanks for your hard work on the rules, and I support you if you want to slow it down.

Scott M,

I knew you were smart!!!!
boilermaker
Posts: 100
Joined: Thu Sep 02, 2004 9:10 pm
Contact:

Post by boilermaker »

I'm more of a smart ass really.
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

Jay, put that Master's to work, baby, and 'splain away! I hope you have a Master's in Education too (maybe Long Haul Loescher can help you) cuz it's gonna take some 'splainin to convince me an airscrew travelling forward 4 inches per revolution will move the same speed at 19k (20k, pick your poison) as 15.5k. Then there's the little problem of the physical evidence I've seen with my own eyes. I ain't so old yet that I can't tell the difference in speed.... Bring that hot-rot Limited B plane to our meet and after I kick your butt we'll have a little race between our Open B plane and your hot rod LimB. After I prove the laws of physics to you in a straight line, I'll give you a Masters in LimB vs. OpenB by showing you how this thing does sustained vertical or horizontal turns without slowing down. I could probably do loops higher than you can count (without your slide rule) before I slowed down, try THAT with your LimB, buckwheat! Hope you're bringing your Emperor butt up to our meet so I have yet another person I can put a whuppin on, this meet is going to be MINE. As usual.

p.s. Brian hasn't even gragitated from High School yet but when I told him (while he was actually BUILDING his OWN combat planes!!!) the Emperor says LimB planes are as fast as Open B's he got a good chuckle. He's flown 'em too so I think he needs one of your lessons!!!
boilermaker
Posts: 100
Joined: Thu Sep 02, 2004 9:10 pm
Contact:

Post by boilermaker »

Unless you're boring that prop through magic air pulling a massless airplane, neither of them are traveling forward 4" per revolution. In thin air, say at 11 inches of Mercury (I said thin, didn't I) The 10x4 MAS at 15.5K will have more static thrust than a 9x4 apc at 19K. In that case, equal planes in a vertical climb, the 10x4 at 15.5K will win the race.

I'll leave the demonstration of this to you!
Post Reply

Return to “Proposed Provisional Classes”