Tigershark II modifications 10/2005

[First time Juke]

After some needed employment and backtreatment I used few hours to think what went wrong with my small R/C racer that was supposed to amaze everyone.

Firstly the specs were quite well studied, but I am not a good model builder and I made several mistakes when making the initial model...also some new aspects were found how to make it better.

I have previously flown and drawn plans for a few 1/12 scale combat models...so I tought I know enuf.

1. First mistake was that I chose a too weak model engine for the test. Only reason why I wanted the engine was..because it was lite and muffler was sorta hidden. In fact the engine caughed each time I tried to get it airborne..it over heated very rapidly too. Also the position of the cylinder on the model was wrong...instead of putting it on top it should have been hidden at underside.

2. Second...I made my model to withstand +20 G:s this too much...and caused the model to be too heavy. When painting the model the primer caused extra weight too.

3. When sanding the wings ( foil SC 6060 ) I tought it might be faster when I sand them little thinner than original ( BIG MISTAKE ). Also I tought the model might need some winglets or small washout a la Rivets and I placed the larger than intented ailerons closer to the fuse..thus loosing lift and needed power of the ailerons...

It was a pure miracle that the model did not brake after 7 attempts...longest flight being 50 meters ( 150 feet ).


Conclusion....wing was too small and foil ineffective..also the CG was little too behind...and there was no way to correct it unless the overall weight was added.

I have tried to correct those mistakes in my new modifications. Also the intented e-seat has been removed to cut weight in the intented REAL racer. Elevator is now jet like so that the drag would be reduced...in less turbulent air...ableing the pilot to bail out without braking the bones if something went wrong at altitude.

Please feel free to comment !

There is no back up group or a sponsor on this racer yet. Design has been going on about 5 years. There has been about 20 versions here so far for folks to see.

See ya later !

[First time Juke]

Re: Tigershark II modifications 10/2005

Just to get some idea of the modifications done on TS II. See the pic. That is the model TS II on the right..it is a lot longer in fuse vise...etc.

No models have been done of the pusher nor the little twin.

[First time Juke]

Re: Tigershark II modifications 10/2005

Here is a sample of my plans to get R3-A airborne.

Same foil as TS II had....but engine would have yielded 5 times the power as the small engine fitted on TS II for R/C tests.

[First time Juke]

Re: Tigershark II modifications 10/2005

My second intented racer....MISS POPEYE !

Hammerhead design is based on two Merlin engines. Intercooled by one NACA scooped radiator in the belly of the fuselage.

[First time Juke]

Re: Tigershark II modifications 10/2005

Here is an actual photo of the racer as a wooden model.

Also the first TS 2 modification with a NACA scoop.

[First time Juke]

Re: Tigershark II modifications 10/2005

Hello !

The wing are a in the latter TS II is only 12.8 m2. I honestly first tought a plane that has to go faster than Me 109 R has to have a smaller wings..little did I know back then ( I dunno much today either...but helluva lot more than in 2001 ! ).

In the last mod. the TS II wing is now 15.6 square meters and spanning ( unlike what it says in the pic ) 9.5 meters. I think that should do it.
It is marginally smaller than smallest wings on WW II fighters.

Wingtip form and foil is not decided yet...something interesting is on my mind and I have a profile program at use now too. I am working on them. Any ideas out there ?

Best regards and cheers ,

Juke T

---------------------


Almost forgot the TS II model banked at each hand launch very fast to the left ( opposite to the prop rotation ). I had to have lotsa opposite aileron applyed and all this ate the lift from the wing. This is why I think a bigger wing and bigger scale is needed to really get into the flight caracteristics of this plane. This Bronco threw me from the saddle and I did not like it.

[First time Juke]

Pony ?

I put the model pic ( TS II mods actually ) on finnish site and one dude said it looks like Mustang to him. Are you of the same opinion...it has started to look like a Mustang a bit doesn't it ?

Maybe it should be called a Pony !

[First time Juke]

Re: Tigershark II modifications 10/2005

Important notion !

The marker for CG is still in the old place after the wingtip was made wider and wing moved backwards. It should be at least width of the marker more forward.

Bear this in mind if constructing a model of the racer.

rgds,

Juke

[First time Juke]

Re: Tigershark II modifications 10/2005

Is this better or worse than the previous ?

[First time Juke]

Re: Tigershark II modifications 10/2005

Any comments on this preliminary model view ?

Here the wing is still small, but plane is much longer than a Bearcat.

Any comments regarding the new plans ( shorter version ) vs. this old one ?

http://www.aafo.com/hangartalk/attachment.php?attachmentid=3493

[First time Juke]

Re: Tigershark II modifications 10/2005

Here is a vid of the current status of the model.
I have a spare engine of more thust ( and weight ) but it needs lotsa woodcutting etc. Since there is no serious co-workers for the project I'll wait later to go further.

http://www.youtube.com/watch?v=xK1WplsYlXo

[AirDOGGe]

Re: Tigershark II modifications 10/2005

I've designed many RC planes that all flew well, but it took me some time to learn what's stable and what will barely stay in the air, if at all.

Center of lift should be 1/3 of the distance from the leading edge for best results, with some changes if wings are swept. On conventional aircraft with qa lifting wing and standard stabilizer, the center of gravity should be on or slightly behind the C/L so that when balancing in your had at the center of lift, the nose will want to drop down slightly, with the wind blowing over the rear stabilizer providing the downforce to keep the nose up. This makes for good stability. The rear "wings should not be providing and upward force or lift. A center of gravity set too far forward of the center of lift will make it hard to get the nose up. Too far back and you may stall and spin in.

Canards Like Rutan's EZ series have different CG requirements, so we won't go into those right now.

One trick I do is place the fuel tank as close to the center of lift over the wing, so that fuel usage doesn't affect the center of gravity so much. My radio, batteries and as many servos as possible sit forward of it when possible.

The airfoil type shouldn't affect it too much, as you can make a flat wing model fly if desired. Heck, you can make almost anything fly if it's a light model.

Weight is critical. The heavier you are, the more power you need and the faster the speed to achieve sufficent lift.

Use as little epoxy as possible if possible, except for critical areas like engine and gear mounts. Many wood superglues at hobbyshops are both light AND strong.

Wait until you achieve good flights with the TS before attacking pushers and twins. Learn the basics of aircraft design and it's requirements/limitations first.


I recommend starting with a smaller model ( 40-50 inch span) for experiments until you get a design right, then build it in a larger scales. It's cheaper and easier to do. I did most of my early experiments with 35-40" wings and a hearty O.S. .10 FSR.


Some real specs on your drawings concerning weight, model engine size and proportions would be very helpful, as I'm sure your tigershark doesn't really have a 1000+hp motor.


If the plane veers off to one side at launch, ajust the rudder in the opposite direction, NOT THE ALIERONS.

I once lost a new pre-fab biplane that I had mounted a larger motor upon to get airborne off a rough field. I installed a K&B .40 c.i. engine with an 11" prop instead of the recommended O.S..25 c.i. with 9.5" prop. The plane rolled left at take-off from the extra torque, I mistakenly applied right alieron to try to straighten it out instead of right rudder, and ended up cart-wheeling the plane into pieces. I was young and it was my first bipe (christian Eagle) and I didn't know any better back then.



You can also offset the engine's thrust to point the opposite direction of unintended flight to help control prop torque and unwanted roll.

Note that wing shape and angle of incidence is more critical than airfoil shape, and both sides of the wing must be as identical as possible to prevent unwanted roll action. I bought a used Bob Martin SR-7 slope soarer hanging from the ceiling of a local hobby shop once that had a slightly asymentrical wing, and the dang thing would always go into an unwanted roll at the top of loops.


More later. The TS II design looks like it will fly quite well when set-up properly. Right now I'm on a laptop as I'm rebuilding my desktop. when I get the latter going I'll load photoshop and see if I can provide more visual details.

Meanwhile, this page shows some basic rules concerning C/G and C/L. See if there's anything helpful there:

http://adamone.rchomepage.com/index5.htm

NOTE: What they call AC (aerodynamic center) is the same as center-of-lift.

[split-s]

Re: Tigershark II modifications 10/2005

These are some pretty cool looking designs, kind of remind me of "Crimson Skies".

Is the object, though, in positioning the wings far forward to obstruct the pilot's forward-and-down view as thoroughly as possible?

$

[First time Juke]

Re: Tigershark II modifications 10/2005

These are some pretty cool looking designs, kind of remind me of "Crimson Skies".

Is the object, though, in positioning the wings far forward to obstruct the pilot's forward-and-down view as thoroughly as possible?

$

No the object was to scale down the Merlin powered racer and keep the vital parts of the airframe in very flyable and yet fast form. The wing has lotsa sweep so there is a good visibility. Definitely not the best possible while taxiing. Needs a check at least.

[First time Juke]

Re: Tigershark II modifications 10/2005

Wait until you achieve good flights with the TS before attacking pushers and twins. Learn the basics of aircraft design and it's requirements/limitations first.


I recommend starting with a smaller model ( 40-50 inch span) for experiments until you get a design right, then build it in a larger scales. It's cheaper and easier to do. I did most of my early experiments with 35-40" wings and a hearty O.S. .10 FSR.

You can also offset the engine's thrust to point the opposite direction of unintended flight to help control prop torque and unwanted roll.

Note that wing shape and angle of incidence is more critical than airfoil shape, and both sides of the wing must be as identical as possible to prevent unwanted roll action. I bought a used Bob Martin SR-7 slope soarer hanging from the ceiling of a local hobby shop once that had a slightly asymentrical wing, and the dang thing would always go into an unwanted roll at the top of loops.


More later. The TS II design looks like it will fly quite well when set-up properly. Right now I'm on a laptop as I'm rebuilding my desktop. when I get the latter going I'll load photoshop and see if I can provide more visual details.

Meanwhile, this page shows some basic rules concerning C/G and C/L. See if there's anything helpful there:

http://adamone.rchomepage.com/index5.htm

NOTE: What they call AC (aerodynamic center) is the same as center-of-lift.

Lotsa helpful data. I think I am gonna go for my 2-seater pusher soon. Do you think it'll veer just like a tractor ?

I have planned 1/5 scale and a .30 size engine.