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Old Jul 18, 2012, 10:09 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
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Oh my gosh! I just read through Paul Naton's mod directions and realized what a lousy pilot I am. I moved the CG back to 72mm and found the plane to be a white knuckle handful. It scared me to death! Moving it to 70mm gave me a plane I was comfortable with. Paul is running 91.44mm!!!!!

Folks, that is just living with the plane for extremely long periods of time. If you're a newbie DON'T EVEN THINK of going there. If you are able to perform them, all his other mods are incredible, even for a newbie. You will have trouble flying at 70mm, although it will be possible and you'll love how the sink rate seems cut in half. You'll also love how the nose doesn't fall straight down for a 15' dive in a stall. But you won't love the lack of pitch stability in the plane and it will get a bit dicey in turns until you learn to fly. As your skills improve you can progressively move the CG back. But please HAVE FUN. Flying isn't supposed to be stark terror every second in the air. You CAN push too hard.

Obviously I need to learn to fly. There's no way I could take advantage of Paul's CG improvements at my present skill level.
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Old Jul 18, 2012, 10:15 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
3,603 Posts
Scott, the only way to do a curved fuselage decalage change would be to jig the fuse securely at the correct curve, drill and insert the carbon. Then as you release you would still end up with some relaxing to an angle you didn't intend.

Follow Dave's link to Paul's way of doing it. It's much more foolproof. Love your videos. Get back in the air!
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Old Jul 18, 2012, 10:29 AM
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Old Jul 18, 2012, 10:42 AM
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You are not a lousy pilot. Radio_Active is correct. You can not fly with a 72 mm cg unless you do the decalage mod. I think you should have gotten that if you watched the video.

Reducing the decalage angle is the equivalent of taking out a bunch of up-elevator trim. It allows the plane to assume a downward glide path and a high rate of descent. Moving the cg back restores the angle of attack on the wing to the correct value.

I have posted before that people who make this mod should do some hand-tossed power off glide tests with neutral rudder to verify the correct cg before the first powered flight.

Sorry for the excessive editing on this post but my earlier attempts were confusing, even to me.
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Old Jul 18, 2012, 11:30 AM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Try before you buy

Quote:
Originally Posted by Rockin Robbins View Post
Scott, the only way to do a curved fuselage decalage change would be to jig the fuse securely at the correct curve, drill and insert the carbon. Then as you release you would still end up with some relaxing to an angle you didn't intend.
The way I did mine didn't involve any drilling or relaxing after the pressure was released. I removed the stock spar, and made a channel to fit the carbon rod (arrow shaft). When I put the rod in the slot to test fit, the ends were sticking out because the slot was the same depth all the way along. At the time, I didn't want a major decalage change so I deepened the middle section of the slot. That meant the ends didn't stick out so much and the fuselage didn't bend as much when the ends were wrapped with tape.

This leads to the possibility that someone could make the ends of the slot deeper than the middle and the result would be a significant change. The beauty of this idea is that you can assemble it without glue and measure the angles or even fly it if you want. Then you could make adjustments to the slot before finally gluing the rod into place.
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Old Jul 18, 2012, 11:33 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
3,603 Posts
Dave, I followed your link to the article on Paul's website and didn't see the video. Thanks for setting me straight on that. And it explains why my neutral elevator setting was just slightly down--I was canceling out some of that decalage.

I hope nobody gets the idea that the Radian is a defective or poorly designed plane the way it comes stock. The decisions were made for sound reasons relating to the newbies' ability to fly the plane. The Radian, although there is magic in there, was not meant to be a contest sailplane. However, as Paul shows, it CAN BE a credible contest plane if you're willing to give up its qualities as a learner's tool. And actually, I'll bet with a more forward CG it would be perfectly acceptable for newbies with all Paul's other mods.
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Old Jul 18, 2012, 12:44 PM
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Originally Posted by Rockin Robbins View Post
Dave, I followed your link to the article on Paul's website and didn't see the video.
Sorry, the video is on a different link. I will try to find it and post.
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Old Jul 18, 2012, 02:09 PM
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Here is the video:

http://glidefast.typepad.com/glidefa...ree-video.html
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Old Jul 18, 2012, 05:01 PM
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Quote:
Originally Posted by Rockin Robbins View Post
Oh my gosh! I just read through Paul Naton's mod directions and realized what a lousy pilot I am. I moved the CG back to 72mm and found the plane to be a white knuckle handful. It scared me to death! Moving it to 70mm gave me a plane I was comfortable with. Paul is running 91.44mm!!!!!
Did you re-trim after the CG change? I moved my CG back incrementally to 3 inches over the course of about 6 flights done only on calm days. After each change in CG I re-trimmed with with power off tests before committing to a flight. Finally after each day's flying I reset the control surface mechanically to zero out the trim. So far no problems.

I have not done the decalage mod yet as I'm waiting to see how far back I want my CG. When I reach that point I'll make my decision based on how much mechanical trim I need to compensate for the rearward CG. If it is not too bad, I'll probably not bother to make the cut. But who knows.

Unfortunately, I have not yet been able to fly this season because of other pressing matters, so I haven't been able to pursue the business any further, but I have to say that at a 3 inch CG the Radian is beautifully behaved with very little porpoising if any.

Cliff

PS to all noobes. Don't be afraid of moving the CG back but GO SLOW AND DO A POWER OFF GLIDE TEST AFTER EACH CHANGE IN CG!!!! Re-trim as necessary.
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Old Jul 18, 2012, 05:58 PM
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Des Moines IA
Joined Dec 2005
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My Radian loves to porpoise unless I am nose heavy.
If I move my cg backto stock location I need to add up ele and then it dosent want to move forward and just drops down like being in an elevator.
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Old Jul 18, 2012, 06:26 PM
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boom stiffening

ArHi all,

I have just read the last 100 or so pages in this little thread since I want to do my first mod - stiffening the tail. Since I couldn't find a CF strip in my local hobby stofe I just bought a solid CF rod about 5 mm i diameter. I was under the impression i could just yank out the GF spar in the boom and place my new rod in its place (after creating a nicely fitting slot for it, naturally). But bending the boom and taking me into decalage altering country is something I don't want! I want my plane nice and docile.

So - can I fit a CF rod and just get more stiffness and not change anything else?
/Henrik, Sweden
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Old Jul 18, 2012, 06:56 PM
Tossing planes into the snow
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So - can I fit a CF rod and just get more stiffness and not change anything else?
Yes, definitely. The fuselage should only change shape if you apply some force while the glue is drying. If you simply make a slot and lay the rod in and glue it, there should be no change in decalage. Is there a store that sells arrows? They are very light and strong and stiff, and would be a better choice than a solid rod.
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Old Jul 18, 2012, 07:29 PM
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Gore-Tex : You do not have to remove the fiberglass stiffener that runs along the bottom of the boom. Leaving it there adds stiffness and gives you something solid to glue the CF rod to.
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Old Jul 18, 2012, 09:17 PM
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Originally Posted by Jovanx View Post
Yes, definitely. The fuselage should only change shape if you apply some force while the glue is drying. If you simply make a slot and lay the rod in and glue it, there should be no change in decalage. Is there a store that sells arrows? They are very light and strong and stiff, and would be a better choice than a solid rod.
Well, according to the salesman the rod weighed 14 grams (I made him weigh it ). You think a hollow arrow shaft is lighter AND stronger? Hm, ok...

Quote:
Originally Posted by kaptondave View Post
Gore-Tex : You do not have to remove the fiberglass stiffener that runs along the bottom of the boom. Leaving it there adds stiffness and gives you something solid to glue the CF rod to.
You mean glue the rod under the spar, on the belly of the plane, so the rod comes closest to the ground?
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Old Jul 18, 2012, 09:23 PM
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Originally Posted by kaptondave View Post
Gore-Tex : You do not have to remove the fiberglass stiffener that runs along the bottom of the boom. Leaving it there adds stiffness and gives you something solid to glue the CF rod to.
It just occurred to me that if you leave the glass strip in place as you suggest, you really don't need to use a CF tube, only a CF strip glued flat on the bottom of the fuse perpendicular to the glass strip. Together the two form a "T" beam which should reduce bending from all angles. The added CF strip is probably lighter than a tube and would also glue in place better.

Cliff
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