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Sep 13, 2018, 08:14 PM
Registered User
thumbs1's Avatar
Ya know, I went back to the plans and for the life of me can not find anything concerning where the cg should be. Is there a definite place listed on the plans somewhere for it?

goldguy. I read a post from years ago where you said the balance point of your 26" dart was 5.5" back from the leading edge at the cord. Obviously mine is not there. Actually I don't know where the balance point should be on mine. Anyway will that change depending on how it was built, to much glue in the tail for example and the weight of the motor? I would think not but I don't know.
Last edited by thumbs1; Sep 13, 2018 at 08:32 PM.
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Sep 13, 2018, 09:26 PM
Registered User
I R Irv, That's a sweet little dart there... What is that like an 8" wing span ?
Sep 13, 2018, 09:27 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
25% CG is mentioned in post #1 of this thread

Quote:
Originally Posted by goldguy
Here's a great little flying machine for indoor or outdoor flying. It's just a MAAC Cub, a Midwest Delta Dart, BMFA Dart or AMA Dart scaled up and how simple is that? Simple maybe, but a fantastic performer for a rudder and elevator design. Here's where Brian Cooper started the first RC version .............. http://www.modelflying.co.uk/news/ar...-dart-mk9/6759

I have built two versions of this design so far, a 24 and 26 inch wing span, both with a wing loading of approximately 3 ounces per square foot. LIGHT is MIGHT. Any one ounce outrunner that turns a big prop at low amps and a smaller lipo is a perfect match.

And perform they do. Depending on how it's set up, you can fly within an eight foot circle, stall turns, loops and rolls both ways, harrier, hoover, tail touches, wall landings, rolling circles, etc. and yes, all this without ailerons. Yet, with a few click of the trims here and there, you have the perfect free flight. This design is now becoming the favorite at our local indoor meets and is a perfect trainer for learning to fly in a confined space.

It's an easy simple quick build and here's a few guide lines...................

Mount the stab at 2 degrees negative, the wing at 0 and 6 degrees down thrust on the motor, with a few for side thrust. Extensive testing ( by 'A Useless Geek') shows 15 degrees of dihedral is optimum for aerobatics. Balance at 25 percent for starters and move it back to suit your flying style. Note, I overlapped the LE of the stab and the TE of the wing two inches......just because it looked cool and adds strength.

The solid blue one in the pictures is a 28 inch span balsa built-up version, powered by a PJS300SF at 8 ounces, built by Paul Cook of Bristol, England. His design was featured by John Stennard's Q&EFI indoor column. The rest are all foam versions.



Dart flyers make a 'point' of having fun..........
Sep 14, 2018, 02:34 AM
flyin' fool
goldguy's Avatar
T1:

Use the online calc. It will show you the CG at the cord line. Project a spot parallel to the cord on both panels at the same distance and place a blob of hot glue that comes to a point as you pull the gun away. Or, cut off plastic headed pins and glue at the locations

Put your fingers on these points to check. Never use the ends of your fingers without, that's not accurate enough.

Before I mark a permanent CG location I start off on the bench using two length of dowel that have a blunt point and hold them in my vise spread apart so both points are the same height. I go out and fly, adjusting and fiddling until I'm completely satisfied and the model is flying exactly the way I want. Personally, most of my models are flown a tad tail heavy because I like extreme aerobatics.

Fussy Frank
Last edited by goldguy; Sep 14, 2018 at 02:55 AM.
Sep 14, 2018, 02:49 AM
flyin' fool
goldguy's Avatar
Not sure. Tell me the full span, the length of the cord and the length of the tips.

I'll do the math and let you know.
Sep 14, 2018, 08:44 AM
Registered User
thumbs1's Avatar
Thanks I appreciate that. I really like the plastic pin idea.

The way I have been doing it is taking a 2x4 as a base and drilling two holes far enough the get the fuselage between them. The I put two pencils in the holes with the erasers up. Then place the plane on the erasers and balance from there.

I'll get the measurements to you I am on the way out the door.

thanks
Sep 14, 2018, 10:30 AM
Registered User
thumbs1's Avatar
Ok have the measurements

The wing span is............................ 251/2"

The cord is .......................................15 1/2"

The wing tips are ...........................3 1/8"

Where is this calculator. It would be great if I could do these things myself.
Last edited by thumbs1; Sep 14, 2018 at 10:38 AM.
Sep 14, 2018, 11:27 AM
flyin' fool
goldguy's Avatar
I posted it on the previous page.
Last edited by goldguy; Sep 14, 2018 at 11:34 AM.
Sep 14, 2018, 11:34 AM
flyin' fool
goldguy's Avatar
Your CG should be 5" back at the cord according to the calc.
Sep 14, 2018, 01:47 PM
Registered User
thumbs1's Avatar
Quote:
Originally Posted by goldguy
Your CG should be 5" back at the cord according to the calc.
oops thats right you did sorry

ok that was where it was on the first flight. So the cg should be close. Which begs the question whats wrong? You mentioned
to much control. Should I cut back on the throws and add expo? I think i am at 50% throws now. Could be this is a real touchy(performance ) flyer for me. Like I said before it had its moments of good flight. Could be I'm giving to much input. Ok next time out less input setup the way it was.
Sep 14, 2018, 02:40 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by thumbs1
oops thats right you did sorry

ok that was where it was on the first flight. So the cg should be close. Which begs the question whats wrong? You mentioned
to much control. Should I cut back on the throws and add expo? I think i am at 50% throws now. Could be this is a real touchy(performance ) flyer for me. Like I said before it had its moments of good flight. Could be I'm giving to much input. Ok next time out less input setup the way it was.
An RET plane with a dihedral wing should fly "hands off" when everything has been done correctly .

With the recommended CG and the rudder & elevator centered : on the next flight , try to observe it's tendencies ( at about half throttle ) so you can make corrections ( tuning the plane ) .

All correction adjustments should be made in small increments .

If it constantly wants to nose down , move the battery rearward a little . If it wants to nose up , move the battery forward a little ..... or add a little more down thrust to the motor .

If it constantly pulls to the left , trim a little right rudder ..... or add more right thrust to the motor . If it constantly pulls to the right , trim a little left rudder .... or take out some of the right thrust on the motor .

Make those adjustments until it flies "hands off" at about half throttle . It is normal for increased or full-throttle to cause a plane to climb a little and/or torque roll to the left a little . In this video , the plane has been tuned to fly hands off at half throttle ..... but with full throttle it climbs and makes a big lazy left turn all by itself :


SnowBall Autopilot (0 min 55 sec)
Sep 14, 2018, 05:49 PM
Registered User
thumbs1's Avatar
Ha well the my dart is not quite at that point yet. LOL Now that I know the cg at least I have a starting point that I can work with. That eliminates at least one major factor. Ill get that right tonight. I bought some small round head pins. This very well come down to pilot error. I have no problem with the possibilities the is in fact me. If so I can work on that as long as I can get her behave long enough to get a bit of exp flying her. Its all good it will get worked out. I may start another fuselage for when I get her right. Actually it isn't that bad but I'm not done yet. LOL
Sep 14, 2018, 05:59 PM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
As we recall (?) wasn’t there a Dart on FMS simulator ( I used that last week at my friends office flying the old Trainer One ) … That would be an easy way to get more stick time without crashing … not a real replacement for flying , just practice …
Latest blog entry: Lost plans
Sep 14, 2018, 06:37 PM
Registered User
thumbs1's Avatar
The only simulator I have is a free one on line Absolute RC. I haven't found one other than that for a mac. I'll look into it and see if it is mac comparable. Actually I learned to fly on that simulator. Your right they are a great help.

Do you have a link to the sim. my secretary blocks the one i tried
Last edited by thumbs1; Sep 14, 2018 at 06:50 PM.
Sep 14, 2018, 09:39 PM
flyin' fool
goldguy's Avatar
Forget expo, that doesn't help you in learning to give small inputs, the basis for flying smoothly. Just decrease the throws, you don't need much just to get it trimmed.

Like B or C sez …………… any good R/E design should be able to fly without help from the pilot. I've flown my NutBalls and Darts around the gym in free flight mode just see how many laps I could get it. My best was 13 before I picked the TX off the floor. I've even posted a vid way back when of a NB take off and fly without input at all.


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