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Old Nov 09, 2012, 12:15 PM
I don't like your altitude
Stupot46's Avatar
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http://www.rcgroups.com/forums/attac...mentid=4143628

I came across this whilst reading the "Wabbit" thread.
Stuart
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Old Nov 10, 2012, 11:52 AM
Herk
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So far my polyplank is a turkey. Sort of flys - but not very well - bad idea for a thermal model.
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Old Nov 10, 2012, 01:03 PM
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Knoll53's Avatar
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Looks like it should float well..... What was the complaint??? Control issues?
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Old Nov 10, 2012, 01:32 PM
Herk
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Quote:
Originally Posted by Knoll53 View Post
Looks like it should float well..... What was the complaint??? Control issues?
It took quite a bit more nose weight than it should have needed in order to be pitch stable. Then - it has to fly quite fast in order to fly at all. With the current balance setup, it's hard to hold the nose up in order to fly slowly. I'll keep playing with it, but the wing doesn't seem to be very suitable for a tail-less model.
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Old Nov 10, 2012, 05:10 PM
Herk
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Finally got it to fly - was able to take some nose weight out.

It took abut twice as much reflex in the outer panels as I originally set in there. When flying the excessive polyhedral caused really terrible dutch roll - almost uncontrollable.

So it demonstrates that if it does not look "TLAR" - it probably isn't.

Fun experiment - now ended.
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Old Nov 10, 2012, 07:53 PM
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You survived another experiment...I'm going to have to start calling you Mr. Lucky.

The Monokote was in shreads after a couple of hard landings last week in Big Sur so I tore it off and covered it with Koverall....done.

Today saw some great ridge lift at the coast. Maybe 20mph from the right direction. Even with 17oz. of ballast, it was no speed demon. I'm going to have to get serious about ballast on the next one. I can see why the DS guys like 60" ships. Any bigger and they'd be too heavy to carry out of the car. 17oz. was hardly enough today. Also, the ballast moved the CG forward so the elevator was stupid slow. Very smooth flying though. Had a nice high speed cartwheel landing and snapped off the external lead weight thanks to a break-away nylon bolts. Worked nice. No damage. Continued to fly "light".

When this plane is inverted, it can hyperstall....kinda fun. Still toying with CG and elevator throws. It's too much fun flying to be monkeying around with the Tx. I get closer every time out.

I'll post a couple of videos this evening.

Plank 101 in 20mph flying light. (0 min 0 sec)


Kent
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Old Nov 10, 2012, 09:33 PM
Herk
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Man that sub-fin would have helped with those landings ---- unless you wanted to do those touch and go's
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Old Nov 10, 2012, 09:50 PM
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I think that I could have avoided the cartwheel if I had more up elevator AND if I was 20 years younger. All in all, another fun, no damage day.

Plank 101 - 20 mph with ballast (8 min 19 sec)


Plank 101 - cartwheel landing (4 min 39 sec)


Plank 101 - Playing chicken with the cliff (0 min 0 sec)
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Old Nov 10, 2012, 09:58 PM
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Quote:
Originally Posted by HerkS View Post
Man that sub-fin would have helped with those landings ---- unless you wanted to do those touch and go's
The touch and goes are a blast. They are indeed the reason I removed the sub-fin. The wing sits so low to the ground, it's amazing that it can get flying again once down on the ground skidding. It gives a whole new meaning to ground effect.

It's a very hands-on plane. There is no stability. You are always flying. Cross winds really throw it around. A substantial sub fin would, no doubt, improve stability in cross winds. Oh well ..... design is a study in compromise.

Kent
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Old Nov 11, 2012, 07:11 PM
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Nice weather in Big Sur today so just had to take hike and try the plank out with the new forward CG. Much more controllable now. Just to make things interesting, I tried to thermal with 16oz. of ballast.

Plank 101 - Thermalling Garrapata with ballast - 17 oz./s.f. (5 min 17 sec)


I'll spare you the 1/2 hour video of thermalling light.

Kent
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Old Nov 12, 2012, 12:57 PM
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I'll limit the next version to 2m in hopes of being able to ballast it up to a good flying speed for the big winds. Currently planning on 4 lbs. of ballast just to achieve 25oz./s.f.

A few variations. I big flap might be fun to maximize drag for crow landings which will be needed at 25 oz/s.f.

Kent
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Old Nov 14, 2012, 01:25 PM
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current version
fuse enlarged for 4 lbs. of lead and tail lengthened

The side area of the fuse and fin behind the TE of the wing is about 20% of the wing area. This may be more than needed. Total fin height is 15". Looks OK in the model but a mock up is needed to decide.

Kent
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Old Nov 16, 2012, 04:25 PM
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Re-thinking the need for high wing loading for the "big winds" which only occur for maybe one month per year, I'm back to 2.5m. With 4 lbs. of ballast that will be a respectable wing loading of 19.7 oz/ s.f.....Should be a good all rounder sport plane. Big enough to see when thermalling with a 12" chord and heavy enough to be fun on the slopes.

The fin has been reduced in size and moment arm. Similar to Plank 101.

Kent
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Old Nov 26, 2012, 11:22 PM
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A little slope relaxation...

Conditions looked too light today after work but the little plank was able to soar even with the ballast. Brian, the paraglider pilot was entertained enough to land and come over to learn more about the Plank 101.

The elevator rates are turned down so much now that every turn required full back stick. Flies much smoother with this set up. No problem with stalling a loop with this set up.

light winds with ballast (0 min 0 sec)


Kent
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Last edited by Knoll53; Nov 27, 2012 at 01:30 AM.
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Old Nov 27, 2012, 09:56 AM
Herk
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Kent - this has been a great forum. Thanks again for getting it started.

It's good to see you enjoying your fin so much

I sure hope that you build the 2.5 M version.

I guess that'll be Plank 201 - the sophomore version.
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