Best Stunt Ship

[Randy Cuberly]

Is this design, Lou Wolgast's 'Pentastar,' a good performing model?

The kit is offered in two sizes.

Charles

Charles,
Since no one answered your question about the Pentastar I will.
Lou Wolgast is a close friend and flying buddy, and I've flown his Pentastar several times.  In a word yes it is a great performing airplane.  As good as anything I've flown and better than most (I've flown a lot of top stunt planes).  The wing in the Pentastar is basically a GeoXL wing designed and used by Bill Werwage in a lot of his winning stunt ships from the USA1 (World Champ)  to the Thunderbolt (Geobolt).   Lou's uses a ST60.
The airplane needs to be built reasonably light (under 60 oz) to perform best.  It's a big wing at about 720 sq in.
I currently fly a GeoXL with a Belko 56 that weighs 54oz and flys very well.  The Pentastar flies very similar (not surprising).
The Pentastar name comes from the Chrysler Logo and Lou is very much a Chrysler man!!!
The Pentastar does have a geodetic wing and builds best in a lost foam jig from Bob Hunt.

I'm not aware of the kit being offered in 2 sizes.  The only one I'm familiar with is the Big one if that's true.

Randy Cuberly

[Dave_Trible]

I do not have coordinates of real tail airfoil, but here is NACA 0007 with 40% flap deflected to 30 degrees.

You can see that flap instantly deflected to 30 degrees before corner will cause separation. Negative angle of attack 5 degrees will push it to its maximum and negative angle 10 degrees or more again looses its effectiveness because low AoA.

So while short tail very close to wing when AoA of tail is only -5 degrees because of circular flow, will make tail more effective and it will want to do tight turns, tighter than the effect before model enters circular path. While too long tails will not be able to keep entered path because of too small deflection. Both can confuse pilot.

Well ... it is simplified, because I do not count AoA of wing, flap effect on air direction and deflection is also not really instant, but the main effect is clear from that description I thing.

BTW some people asked me why I use such small movable elevator. I think picture shows it well :- ))) .. just not to allow slying over critical AoA before corner. 

Igor, thanks for an instructive read.  This caused a couple of lights to go on (in a very dark place) about issues a encountered while developing my new winged warrior over 6-7 airplanes.  I was trying to squeeze into a smaller package with a higher wing loading and finding a few new puzzles.  On one I wanted to lengthen the tail moment a little so I went from 1.97 to 2.08 ratio and found the machine started the turns well but refused to track rounds accurately.  Went back to shortened moment and the tracking returned.  Another issue I found on only one of three matching airplanes (in dimension and weight +- 2 oz.) This one ship at the same CG required more narrow handle spacing and would stall on bottom corners.  My first thought was the WING was stalling so I fixed it by adding a strip on the flap TE to add flap area-and chord.  What I now realize is the stab/elevator was stalling instead.  On this one airplane I used an elevator horn I had instead of making new.  It was just a bit shorter and gave me a little more elevator than flap deflection. I had assumed the turn was occurring faster than the flaps would deploy to full effect.  Adding to flap chord increased wing AoA sooner.  What I didn't get was the inverse-this allowed the turn with less elevator deflection,  thereby not crossing the red line on elevator stall.  Thanks again!

Dave

[Bill Little]

I can't really offer any thoughts other than to reiterate what has been mostly stated.  There is not one single model which is the "best".  There are MANY stunt models that will win the NATS or Worlds, but they must be matched to the pilot.  It is a known fact that many of the top pilots will trim the same model in different ways.  The MAIN trim issues will be the same, but the objective trim can, and often will, be different.  No one pilot is exactly like another.

ANY of the top level models will do a great job.  Finding the one right for you might be a simple matter of trim.  In the old days, trimming was no where near the level it is today so many built different models before they settled on one.  And has been stated, two "identical" models, built at the same time and everything measurable seems to be the same, they will fly slightly different.......

The pilot and his abilities, the position of the moon, Jupiter aligns with Mars, solar flares, or whatever, are the deciding factors in who "wins".

BIG Bear
RNMM/AMM

[Trostle]

Funny how a few flying sessions later, the posts start to roll in, asking trim questions about planes that "flew perfect, right of the bench".

EricV

Eric,

I have a theory.  Just like energy where the universe has a finite amount of it (at least some think so), there is a fixed number of stunt ships that "flew perfect, right off of the bench".  And that fixed number of those kind of stunt ships were used up around 1951.

And back to the subject of this thread, the "Best Stunt Ship" has not yet been invented.

Kieth

[Randy Cuberly]

Eric,

I have a theory.  Just like energy where the universe has a finite amount of it (at least some think so), there is a fixed number of stunt ships that "flew perfect, right off of the bench".  And that fixed number of those kind of stunt ships were used up around 1951.

And back to the subject of this thread, the "Best Stunt Ship" has not yet been invented.

Kieth

And doubtfully ever will be...However one could simply consider that it's whatever's at the top of the heap at the moment...'course that keeps changing doesn't it...

Randy Cuberly

[Valentin Apostolov]

This is what I want to share with you about the Best....
All our airplanes look alike as we humans are. Each of us is differentl. If you see a good flying airplane
by someone does not meen you can fly his as he does. Try it. Some time ago I tried a first placed airplane and he flew mine. Both of us were dissatysfied. So find yours 'cause we do not alike as humans. Even blood pressure and beat of heart.

Thanks

Valentin Apostolov

[John Desrosiers]

My 03 ford lightning pick up truck . Hell yea.

[John Miller]

Is this design, Lou Wolgast's 'Pentastar,' a good performing model?

The kit is offered in two sizes.

Charles

Charles, Lou Wolgast is a very good, experenced builder, and pilot. I've had the pleasure of watching him fly his Pentastar in the past. It's a great design, that will not hold you back, so don't be afraid of building one for yourself.

I believe you live in California, so check out the Southwest Regionals contest, where you can meet Lou, and watch him fly the Pentastar in competition. The contest is held in Tucson, at the same site VSC is held atin January. It makes a nice break from winter, and there's a lt of great guys to fly with during the contest.

I'm sure some one local there will post the dates and time. I know I plan to be there spectating at the least. I'llm fly if mI can. Might see you there.

Oh, one more thing, Lou's on of the nicest guys you'll ever meet.

[Ted Fancher]

Guys, you must remember that tail volume coefficient is good parameter of flat flying airplanes, but it is not enough for stunt airplanes. The reason is, that while normal airplanes has angle of attack on tail very close to constant (the same like wing), stunt airplanes fly radiuses, so angle of attack on tail is variable and can be +/- 20 degrees on our models. This makes difference between small tail on large arm and large tail on small arm. The difference is in effectiveness of airfoil of deflected elevator.

While short tail solution tends to have stronger and stronger pitching effect during tighter and tighter turn, long tail solution loses its effectiveness as model enters tight turn. So while short models can do tight but not so well controllable turns (so they need to be little nose heavy) long tails will show good initial movement but in reality they do not do 90deg turn so well and they need little more back CG.

So it is necessary first to find proper tail length which can keep initial moment to corner and effectiveness during turn in good balance (so the pilot can do clean and tight corner) and only then to play with area of the tail.

And second thing - larger tail volume can allow back CG, but too large tail and too back CG is also not good, especially if CG goes close or back of 25% of MAC. It is because too back CG can pust tail to produce positive lift, while maneuvering needs negative lift. Theoretically in clean air and perfect airfoils does not matter, but that transition from positive to negative lift in tiny inputs from pilot in level flight cannot do anything positive, I think it simply must lead to hunting, because quaily of flow is quicly changing in such conditions and so also microscopis change of deflection leads to large effect on such large area. My last model has tail area far over 25% of wing area (close to 30%) and CG is still front of 20%. However that large tail allows anything from 15 till 25% without too much difference :- ))

Igor,

Good to see somebody else discuss the potentially counterproductive nature of a CG aft of 25% of the MAC.  That's why all my blather for the last couple of decades continuously cited 25% MAC (and a tail volume appropriate to accommodate it) as a (if not "the") desirable goal in terms of these factors.  Your example of the acceptable CG range on your 30% tail tells the story.  If you had the "classic" era 15 or 16% tail the "trailing edge" of an acceptable CG would be about where yours starts...15% MAC.

Your tail length comments are well taken although, in most cases, of theoretical interest in that tails much longer than "today's usual range" become a problem to build without CGs in the too far aft range.  An understanding of the effects of too long a tail is, of course, valuable in terms of understanding how these things work.  

I love to ponder the value of off the wall "design" innovations by mentally taking them to an extreme as doing so almost immediately makes one aware that there is a limit to almost any perceived advantage when deviating from the "norm".  Think of a stunt ship with a tail moment (in the classic flawed sense) of 48 inches hinge line to hinge line on an  Impact and the impracticality of doing so becomes obvious.  You immediately recognize there is a practical limit even if you're not "schooled" in the science.

Same way with the "everyone knows you can't get too much power" in a stunt ship.  Think of mounting a Pratt and Whitney R2800 on the front of that Impact!   Ooooops!  Or just add nose weight to stabilize your stunter.  Think of putting a pound of lead right behind the spinner of your Impact and you'll quickly realize that isn't really the solution you're looking for.

etc.....

Good stuff, Igor.

Ted

[Howard Rush]

Think of putting a pound of lead right behind the spinner of your Impact and you'll quickly realize that isn't really the solution you're looking for.

Have you looked behind the spinner of my Impact lately?

[Ted Fancher]

Have you looked behind the spinner of my Impact lately?

Howie,

If we're speaking about the electro-magnetically impulsed Impact variety that would be a no.  I thought that was what the battery was for...i.e. locating the CG correctly.  Fill it up to move the CG forward and empty it to move it back.   No?

Ted

p.s.  O.K., then.  Make it three pounds.

[Ted Fancher]

This is what I want to share with you about the Best....
All our airplanes look alike as we humans are. Each of us is differentl. If you see a good flying airplane
by someone does not meen you can fly his as he does. Try it. Some time ago I tried a first placed airplane and he flew mine. Both of us were dissatysfied. So find yours 'cause we do not alike as humans. Even blood pressure and beat of heart.

Thanks

Valentin Apostolov

That's a good point, Valentin.  I wonder, however, if the major difference when you swap flights on top level airplanes with another top level pilot isn't more the difference in handle settings used by each pilot to suit his personal preferences in response and/or neutral angle.  In one series of columns from years ago I talked at length about the desirability of trimming the airplane to its maximum potential and then using our marvelous adjustable handles (and line length, etc.) to adapt our human difference/preferences to the properly trimmed airplane.  I called the two halves of the equation the "Happy Airplane" and the "Happy Pilot".

For instance, a perfectly stable airplane that flies blinding corners and tracks great in rounds but is too sensitive for the human to whom it is attached shouldn't be de-trimmed to lessen its capabilities, instead the handle should be adjusted so the pilot can take advantage of the performance available from the well trimmed airplane using control inputs with which he/she is comfortable.  The plane stays "happy" and the handle adjustment makes the pilot "happy".  Serendipity at its best!

Ted Fancher

[Doug Moon]

Biggest engine they put in was 396...

R

True, but my 68 L35 Camaro was missing the original 396.  The Muncie M21 4 speed was still there so I located a near by passenger 72 454 standard bore for $500 complete!!!!  Tweaked it a little, added some closed chamber small valve 396 heads and a solid lifter camshaft.  It was a torque beast!  I saw my very car for sale not to long ago on Craig's list.  The same guy I traded it too for his 69 vette in 1995 still has it.  If I had the cash I would buy it right back without hesitation. 

[MarcusCordeiro]

True, but my 68 L35 Camaro was missing the original 396.  The Muncie M21 4 speed was still there so I located a near by passenger 72 454 standard bore for $500 complete!!!!  Tweaked it a little, added some closed chamber small valve 396 heads and a solid lifter camshaft.  It was a torque beast!  I saw my very car for sale not to long ago on Craig's list.  The same guy I traded it too for his 69 vette in 1995 still has it.  If I had the cash I would buy it right back without hesitation. 

That sure sounds like a nice ride, and the 4 speed muncie!!
Add a laughing-gas plate and run 10s...
$500 on a 454?!?
Why does that never happen to me??

Marcus

[Dennis Moritz]

Dan Banjok's Vista has a thicker blunter wing than the custom. Nearly a straight leading edge. He flew it to seventh at the NATs. A few extra appearance points would have put it very near to top 5. A plane way outside the conventional specs. I forget the name of the Big Jim Greenaway design (Patternmaster) and it's derivatives. Definitely not an Impact. Windy used those numbers to finish in top 5. Al Rabe's planes differ hugely from the norm. (Any of the current norms.) Heavier with a smaller wing and big flaps. The Sharks certainly do not look like a Bob Hunt or Paul Walker or a Ted Fancher or Randy Smith (and so forth) plane. I bet their numbers have evolved a separate tree. Can we remember way back (a few years) to Berringer.

[Dennis Moritz]

Top 5 this years showed off different flying styles as well.

[Brett Buck]

Dan Banjok's Vista has a thicker blunter wing than the custom. Nearly a straight leading edge. He flew it to seventh at the NATs. A few extra appearance points would have put it very near to top 5. A plane way outside the conventional specs. I forget the name of the Big Jim Greenaway design (Patternmaster) and it's derivatives. Definitely not an Impact. Windy used those numbers to finish in top 5. Al Rabe's planes differ hugely from the norm. (Any of the current norms.) Heavier with a smaller wing and big flaps. The Sharks certainly do not look like a Bob Hunt or Paul Walker or a Ted Fancher or Randy Smith (and so forth) plane. I bet their numbers have evolved a separate tree. Can we remember way back (a few years) to Berringer.

   These are all *very close* in their basic dimensions. I got the impression that the question was about the gross characteristics like aspect ratio, tail moments, etc, in which case they are essentially the same. All within a few percent. The only notable deviation was the B-17.

    If we want to start a different "which design is best" discussion (which will immediately turn into a pissing contest) then that's a bit of a different story. We can already find any number of those threads. I think the correct answer is pretty clear from the results, but that certainly won't stop anybody from arguing about it.

     Brett

[Bill Little]

   These are all *very close* in their basic dimensions. I got the impression that the question was about the gross characteristics like aspect ratio, tail moments, etc, in which case they are essentially the same. All within a few percent. The only notable deviation was the B-17.

    If we want to start a different "which design is best" discussion (which will immediately turn into a pissing contest) then that's a bit of a different story. We can already find any number of those threads. I think the correct answer is pretty clear from the results, but that certainly won't stop anybody from arguing about it.

     Brett

Hi Brett,

I think the two of us agree that you are telling a great truth.  The problem with a discussion like that is that the ones winning Nats and World Championships would not jump in and say THEIR model is the greatest stunt ship around.  If it were so, Ted, Paul, Billy, you, etc., would not go on developing their "designs" trying to find something that suits them better!

Years ago I thought the Nobler was the greatest, then I flew a Thunderbird II, and I liked it a "little" better, then a nice well powered light Ares, etc., etc..  I ave been flying my Geo Juno for almost 16 years in PAMPA class. (ya think I need a replacement? LOL!!)  I have had several Classic ships in that period, all flew well.  But if I fly the Geo Juno well, it is trimmed out, and I am comfortable with it why am I building three new PAMPA class stunters?  One will be very similar to the G.J., the other two wander a bit off that design.  I am looking to see just what does work for me.  You guys don't have to worry about me knocking y'all out of the top five (I might not even be physically able to return), but I will be doing it to have as much fun as I can and do the best "I" can.

Bill