Author Topic: Tail moment and tail volume (Read 1416 times)

Ken Deboy · « **on:** February 22, 2007, 01:16:56 PM »

I'm building a modified Ringmaster (different wing) that will have a shorter tail moment than a stock RM if I don't lengthen the fuselage. Since the RM already has a short tail moment, would it be a good idea to lengthen the fuse to get back at least to original moment or possibly longer? From what I've read this helps both turning AND stability in level flight. Also does the stab/elevator area need to be changed to compensate for greater tail moment?

thanks,
Ken

Jim Pollock · « **Reply #1 on:** February 22, 2007, 05:26:46 PM »

Ken,

I would keep the proportions at least similar to the original RM. If the wing is larger than the original, then I would probably lengthen the moment to the Stab/Elevator a bit. Why the need to re-invent the venerable Ring Master anyway?

Jim Pollock

Ken Deboy · « **Reply #2 on:** February 22, 2007, 06:12:08 PM »

Not trying to reinvent, it's just that I have an S-1A fuselage without the matching wing and a Shark 402 wing kit without the matching fuse. Thought they might make a good couple since thicker wings are supposed to fly better at 5000' and a scratch built RM wing is a little beyond my current building skills.

cheers,
Ken

Jim Pollock · « **Reply #3 on:** February 24, 2007, 06:33:21 PM »

Sounds logical for a 5000 ft. Altitude.

Bob Reeves has the Twist Master, I guess yours is the Shark Master?

Jim Pollock

Bill Little · « **Reply #4 on:** February 28, 2007, 03:54:57 PM »

Hi Ken,

Pushing the tail moment back is a good thing......... how much and do you change the tail volume? How much of each I am not sure of. I have seen the equations here for figuring all that out, but don't remember them.

A classic example is the "Fancherised Twister". But how Ted came up w/the numbers, I really don't know. I steal a lot of stuff, and ain't ashamed to admit it! Those guys know more about that stuff than I do!

A *little* help here designer guys!

Bill <><

Dennis Adamisin · « **Reply #5 on:** April 08, 2007, 05:39:04 PM »

no no Bill, its not "stealing" - that gets you put in jail. Its REVERSE ENGINEERING - that gets you promoted at work.

Ken: I would lobby for the longest tail moment I could get from the existing wood pile. Sounds like you are using an S-1A fuselage and have to recut the wing opening?

* If the new wing is narrower then line up the new wing at the old leading edge position, and let the tail moment grow.

* If the new wing is wider than the old then line up the trailing edge and let the nose get shorter.

Bob Reeves · « **Reply #6 on:** April 09, 2007, 04:32:24 PM »

Quote from: Jim Pollock on February 24, 2007, 06:33:21 PM

Sounds logical for a 5000 ft. Altitude.

Bob Reeves has the Twist Master, I guess yours is the Shark Master?

Jim Pollock

After 7 years, flying that airplane is still the most fun I have ever had in CL.. Now thinking about a TwistStreak with a Saito 30

Larry Renger · « **Reply #7 on:** April 13, 2007, 07:14:12 PM »

The Streak with a much longer stabilizer span is a delight. We call it the "Doodle Streak" because Bill Netzband came up with the concept of a model with higher aspect ratio than the wing. I asked him to figure the size for the new tail, he did and it works a treat! The fuselage is left stock as is the wing.

For the Saito 30 I needed to shorten the nose 3/4" and put the tank on the inside of the nose. That worked fantastic, as the engine becomes sensitive to speed without sensitivity to fuel draw. Send it off dead lean, it richens up in level flight, but leans back out in maneuvers. My famous 8/4/8 break! Ask Proparc about this.