Re: V-tail myths (was RE: [RCSE] I'm afraid of my sailplane)

[DUWorm]

Every design contains a series of compromises.  The 727 had a t-tail.  Was it for performance or because the exhaust of the Fuse mounted engines was in the way of a standard tail?  What part does structure play in the decision making compromise.

Most commercial aircraft have the horizontal stabilizer mounted to the fuse, not the vertical fin.  So why do most model sailplanes have the stabilizer mounted in the fin instead of the fuse?  For one, many models use a fairly standard, long arm bellcrank.  In other words, for the bellcrank to fit the stabilizer must be at least two inches above the bottom of the fuse.  How about to reduce ground strikes on the stabilizer when landing in tall grass? 

How do you trim a commercial jet?  Typically, not by moving the elevator, but by moving the stabilizer.  Remember that Alaskan crash of the califorina coast?  It was the result of the worm screw mechinisim that was used for trimming the aircraft.  In my head, I can visualize the trimming mechanism for trimming both stabilizers at one time.  Would this be more difficult with a monster v-tail? 

I am not an engineer in this area, just read a-lot.  I seem to remember that as an aircraft approaches supersonic flight,  a vertical tail, or one approaching vertical becomes more and more important. 

V-tails were the rage for a while in handlaunch.  I loved the way the v-tail flew for that particular task.  I doubt a structure could be built light enough to be competitive with the new discus launch handlaunch.  The centrifical force moments on the v-tail would just twist the tail off if build light enough to be competitive. 

The Super V's I have flown, flew great, really great.  For their specific task.

So why is the full flying stablizer on a contest ship so popular?  Because it is so stupid simple.  It is easy to trim and nearly impossible to screw up.  Although I have seen some that are screwed up.

Call me a tweeker.  I am always changing something to see it will fly, handle or perform better.  V-tails let me tweak thing that I cannot tweak on a standard tail.  By modifying differentail in the v-tail I can change the way the plane pitches when rolled left or right. 

So, what is that hot acrobatic sailplane out there that has a v-tail?  The FOX or something similar? 

Just because someone else said it is so, doesn't make it so.  My above comments are based upon my personal experiences.  My personal experience wishes there were more v-tail models available.

Finally, there is the issue of the buyer.  Decisions are made everyday based upon on what it is perceived the buyer will buy.  This series of posts confirms the reality that some are just afraid of a v-tail, even thought they cannot really state why.  Even thought they cannot state why, they just know it can't be right. If your going to spend a ton of money building something, you had better make sure that someone will buy it.

enough ranting

Sherman Knight
425-576-4028 wk pacific std time