New gadget- essence of a Shark

[Ken Culbertson]

Spin 66 (regular) has a "fast response" mode that the Spin 66 Pro (I think) lacks. You think right
...things like Scott Bair's bellcrank "sensor". Is this not the same thing as a pushrod sensor?
 

To some degree, getting boost at the apex of a corner is a pipe dream that may not be any closer that the 5' corner.  If the motor cannot respond with the increased RPMs in the allotted time, then do we want a boost coming out of a corner or just recovery to baseline as soon as possible.  I think reality makes it the latter, and that is where the prop makes the most difference.

Ken 

[Dave_Trible]

To some degree, getting boost at the apex of a corner is a pipe dream that may not be any closer that the 5' corner.  If the motor cannot respond with the increased RPMs in the allotted time, then do we want a boost coming out of a corner or just recovery to baseline as soon as possible.  I think reality makes it the latter, and that is where the prop makes the most difference.

Ken

And right or wrong,  to my thinking quite large IC engines don't feel much strain anyplace.   High torque, big bite  not a wimper in a corner.   If you are trying to pull too much airplane for the power loading in corners then maybe one should think about going to a smaller airplane (or lighter) or move up the food chain of engines.

Dave

[Brett Buck]

To some degree, getting boost at the apex of a corner is a pipe dream that may not be any closer that the 5' corner.  If the motor cannot respond with the increased RPMs in the allotted time, then do we want a boost coming out of a corner or just recovery to baseline as soon as possible.  I think reality makes it the latter, and that is where the prop makes the most difference.

Ken

  Yes, and doing that to excess (which *very many* of them do) will typically cause "hops" coming out of the corners.   To help cornering you need it to do something in the corner not later/

   Brett

[Matt Colan]

And right or wrong,  to my thinking quite large IC engines don't feel much strain anyplace.   High torque, big bite  not a wimper in a corner.   If you are trying to pull too much airplane for the power loading in corners then maybe one should think about going to a smaller airplane (or lighter) or move up the food chain of engines.

Dave

Problem with the large motors is you need to run a larger prop to load it properly, which runs into other corner issues. I flew the 13” 4 blade for a few years and I really liked the speed control it had. I could fly at 5.6 lap times in any condition and it was so cool and so easy! But that prop is no good in the worlds, it won’t corner like the smaller props. I finally got the eather 13” three blade Dave runs to work on the 75 (which turned out to be me sanding the back of the prop properly) and the corner became acceptable. My plane won’t turn in the same universe as a Shark, and the prop is one of those reasons. If my memory is correct, my current prop weighs 27 grams. The electric props are at least half the weight as my IC prop, and smaller diameter, that’s tough to compete with in the FAI corner world.

My next plane I’m thinking of revisiting my PA 61 (and still have provisions for the 75 to fit) because of the smaller prop it runs, and probably go the Dave route of a take apart IC fuse and electric fuse so I can gather up the materials

[Dave_Trible]

Hey Matt.   I run a 12.25" 3 blade on my RO Jett .76.-have for years.   What are you trying to load?  The engine will sit there and run all day where I want it.   I totally get about bigger props kill turn.   If I put on a 13" prop it is like adding 1 1/2 ounce of nose weight.   Granted I have a PA .75-new in the box but have not ever run one.  Maybe it's different in this respect.   Of course there is moving the CG back-OR adding about 2 1/2" or 3" to the tail moment (like a Shark) and moving the CG forward!!

Dave

[Paul Van Dort]

We saw Andrei Yatsenko at a couple of contests last year. He was using a wood prop. He preferred it to a black prop because he could tailor the flexibility.  Wow.

Christophe Holterman is using a folding 3 blade prop. Besides the fact that it facilitates the glide to landing , I have the feeling this can help in cornering. I remember a discussion here a few years back on this very subject (with relation to full size helicopters). No time to look for it now.

[frank williams]

one more try ....

If I have a pipe configuration that looks like #1,  movement from the operation point Q simply moves vertically up and down the power curve at a fixed RPM.  As you enter a corner the engine doesn't sag.

If I have a pipe configuration that has a power curve that looks #2.  Operating at point Q, as the load is increased or decreased, as in a corner, the RPM tends to changes.

An electric motor (within the limits of the ESC) driven with a passive timer I think, acts like #1.

[Brett Buck]

one more try ....

If I have a pipe configuration that looks like #1,  movement from the operation point Q simply moves vertically up and down the power curve at a fixed RPM.  As you enter a corner the engine doesn't sag.

If I have a pipe configuration that has a power curve that looks #2.  Operating at point Q, as the load is increased or decreased, as in a corner, the RPM tends to changes.

An electric motor (within the limits of the ESC) driven with a passive timer I think, acts like #1.

  It's more than that, the system reacts to parameters in addition to the load, so there's dynamics to the response, and you can't really visualize it as a partial of the torque WRT RPM.

     Brett

[Ken Culbertson]

From what I can see of pictures of the Shark it appears to be inline.  Does it have any stab incidence?  I would think not.

Ken

[Lauri Malila]

Wing-stab inline, motor thrustline ~10mm higher.
They fly best when everything is set straight  and control throws are set symmetrical. So, no stab incidence or engine thrust down. L

[Ken Culbertson]

Wing-stab inline, motor thrustline ~10mm higher.
They fly best when everything is set straight  and control throws are set symmetrical. So, no stab incidence or engine thrust down. L

Thanks, I am gluing in the stab of my first inline twin.  Zero it is!

Ken

[Brett Buck]

Thanks, I am gluing in the stab of my first inline twin.  Zero it is!

  Given the relatively high aspect ratio of the stab, alignment will have very very narrow tolerance. I am at least somewhat skeptical that 0-0 is certain to the right right answer, but the right answer might be so small that it's in the noise of the ability to measure it.

    Brett

[Lauri Malila]

I should have said that they are built as straight as possible. No intentional incidence etc. L

[Igor Burger]

It represents a standard arrangement.  For example as configured
Elevator 10 degrees the flaps are 8
Elevator  20 flaps about 16
Elevator.  30 flaps 25
Elevator   40 flaps 32
Elevator   50 flaps 39
Elevator    60 flaps 45  I think this is what we are seeing on the Shark.   Anything more that 60 degrees you lose most all power or leverage over the surface and risk cam over.

Yes, this is somehow similar to my logarithmic crank on flaps as was mentioned. But there are 2 very important differences.

1/ In whole range flaps are moving LESS than the elevator. My solution with pivot moves flaps around neutral more than elevator and it reverses when elevator reaches corner deflection. I simply did not like small flap deflection making model to loose stabilizing feedback in level flight. I even saw one of such such models not able to fly steady level flight. It is very visible especially in turbulent air. More flaps than elevator in my solution solves that problem. The other problem is that even if flaps to elevator ratio is changing properly, the function is not optimal. While I have logarithmic on flaps, this is exponential on elevator. It can work on small models, but not optimal on larger model where you can loose line (or muscle) tension in tight maneuvers. We saw many such hourglasses with round tops in Muncie some weeks ago.


2/ While this solution has constant feedback transfer from flaps, what is major source of forces back to lines and handle, my pivot solution with logarithmic flaps lowers feedback to lines (I mean ratio, not the absolute value) as deflection goes up. That will allow those snap corners where model "wants" to jump to corner and it very easily also stops its rotation after corner and all of that even at low speed. Sharks usualy need to fly fast to make tight (may be better name will be quick) corners.

[M Spencer]

" From what I can see of pictures of the Shark it appears to be inline.  Does it have any stab incidence?  I would think not. "


click here for twelve foot version : http://discovery-aeromodels.com/en/andrey-yatsenko-shark-ellipse-2-control-line-f2b-model.html  THEN click on the Drawing to get bigger .




With the Tailplane ( & elevator ) a couple of 5/8 aluminum angles ( I cut one in four , from the building supplies . $ 10 od a length .)
You cut a wede from soft 3/16 3/4 wideish , block sand . Measure with virneer if neurotic  and cut the 5 inch into quarters .
NOW if you use 1/16 pads , to protect your fancy paintwork . at the hingeline. and throw say two 1/8 matched ' scraps ' at the elevator T E
the only problem youve got is keeping the metre long alumn. there . Rubber band fig. 8 , Tape . A thoid hand  .
Actualy , if you pre rubber band one end slide over , throw a stab thickness packer there ( bands . ) you can manadge with two hands .
If you dont TRIP on the debri on the floor . 

The Point Being a metre or two is longer than six inches , so the % error is reduced . ALIGNMENT WISE .
Stab line above wing line , , you bias it UP at L E , , + incedence .
Like 3/16 ! O/A on a Strega - Patternmaster . 3/23 on the stab .

But thats extreeme . a m.m. ( 1 ) or 1/6 th on somethingbigger , For Chord Mean Line ? SEPERATION . as in Al's Mustangs & airforce . As its a good few inches up from the wing downwash .
Irrelevant for INLINE stuff .  ' O - O ' .
Sometimes you feel the stab . ' bump ' thru the lines , is it goes thru the wingwash , when theres good smooth wind , winding the loadings up . 

Marking About with Drg.s of THAT wing and a Mk 1 & 24 Spit. , as far as his flap end , the curves  pretty much mach . with a ' T ' . Bar you'd pull 1/2 inch into the Spit. Chord to meet both .