This is really more of a trim question, but it goes to design as well. If you have an overweight plane, it is worthwhile to increase the amount of flap throw (relative to elevator) in order to get a bit more flap deflection to help carry the additional poundage? I'm flying a plane that really goes pretty well but clearly has some issues with portliness. Most of the pattern is fine, but in areas when extra lift is needed, well, it has some minor problems. It's not grossly heavy, but heavier than I would like.

Randy, what is your flap to elevator throw ratio?

Here at our altitude, we usually wind up with 26-28 degrees of flap to 32-36 degrees of elevator. With heavier airframes, we dial out a little elevator thus getting closer to 1-1. I persoanally feel that exceeding 1-1 is not a good idea, though I tried it at one time. The quality of the turn suffered, but then the plane might have been OK had the loading been higher.

Dial out a little elevator and see what happens.  

I think I see where you are going now Randy. Simply dialing out elevator might not do the job, since you only have 17 degrees of flaps. going to 1-1 might leave you still wanting.

Is it possible for you to easily dial in more flap?

About 26 degrees on both might give you enough elevator to handle the turn if you dialed in slightly over square on the flaps.

Edit: about an hour later....

I just finished reading a classic construction artical by Jean Pailet, wherin he describes getting his best flights out of his Skylark design when he dialed in, more than a bit more flap than elevator. He also described the plane as heavy. It appears that there's room for experimentation. Randy.

 

This is really more of a trim question, but it goes to design as well. If you have an overweight plane, it is worthwhile to increase the amount of flap throw (relative to elevator) in order to get a bit more flap deflection to help carry the additional poundage?

  Yes.

    Brett

Yes, and by achieving the same lap times on longer lines, you increase line tension too.

SK

Randy,

Yes, the hingelines are sealed. This isn't a horrible problem or anything. The plane is just a bit overweight. I can fly a decent pattern with it, but I have to keep the corners a bit softer than I'd like and have to be careful in windy/turbulent conditions to get the plane to fly through certain rough spots. I was just wondering if a bit more flap would help give it a touch more lift to help in some of those spots. Perhaps help to tighten the corners somewhat. It's not a bad plane like it is.

I actually shortened the lines a bit. I have the engine running just about where I want it. But the lap times were too slow to help much in lift. I could go up in pitch to increase airspeed or shorten the lines to increase air speed. I decided to try shorter lines and that definitely helped. I may go back to the longer lines (about 2 feet) and just try another prop with a bit more pitch at some point.

Just messing around with the plane, trying to overcome some minor handicaps I managed to give it. The real cure is to build the plane again but lighter.

This is really more of a trim question, but it goes to design as well. If you have an overweight plane, it is worthwhile to increase the amount of flap throw (relative to elevator) in order to get a bit more flap deflection to help carry the additional poundage? I'm flying a plane that really goes pretty well but clearly has some issues with portliness. Most of the pattern is fine, but in areas when extra lift is needed, well, it has some minor problems. It's not grossly heavy, but heavier than I would like.

Randy,

Longer lines and more pitch are indeed good ideas. I used them successfully on a 78oz Cardinal(it was 82oz before I put it on Jenny Craig). There is one more trim suggestion:
By increasing amount of flap movement, you also increase amount of down pitch(on inside turns). This has the same effect as forward CG only it's there during turns. Move the CG back a bit more than usual. This will cause the model to become more sensitive in level flight but the upside will be smaller control surface movements. Correct sensitivity with handle spacing.

Steve

The 'Big Flap ' trick gets it feeling like a 4 w d car on gravel ,  Traction at the wing LIFTING the wing thu the corners ( squares ) .

 SO , what your feeling at the handle is the wing pulling it through and the tail being sucked along behind , as it were .

 Someone somewhere once said more flap travle relates to geting the C.G. a notch aft , and Visa Versa ,(or was it the other way round ? )
 NO ,

 With variable ratios youll definately feel the effect , like oversteer , maybe . Anyway , feel rather differant , to the usual  feedback of the

 elevator altering the angle of incedance.where sudden movements get resistance.

 Theres a continuous firm soft ( marshmellow ? ) resistance from the flaps of a higher magnitude ,than that of the elevators  which take a

 bit of detecting over the larger primary force .

Talking  20 - 30 deg flap ea way here .

AND longer lines'l give you more airspace AND lift @ the same sec. per Lap . More inertia to , so thatll keep you on the balls of your feet .
and help your appreciation of timing. Effects are less obvious in rounds , probly improve steerability in overhead 8 s .Watch the wind up .

Brett's line of thought is what I have been thinking. I have plenty of power and drive on the engine. Certainly enough to pull it through maneuvers even with more flap travel ... easily. What I wanted was just to get a touch more lift out of the wing.

However, there's a new problem. I looked at the elevator adjustment (it's a slider horn) and I already have it out at the end of the horn. No more room. Hmmm... Maybe I'll just need to live with it. It's not a bad flying plane at all. In good conditions, it's a lot of fun to fly. But in heavy turbulence or dead air, it just doesn't have quite enough lift in the corners and in areas of the pattern where you really need it.

 

Hi Randy

As I had stated earlier up this thread, you can add on a little to the TE of the flaps to increase area, That was one of the suggestions along with moving toward 1 to 1.
I agree with Brett that adding flap movement is the first thing I would try, and putting out more thrust from the power plant does wonders. however the adding of a foot or maybe 2 will give you actual real lift, and if you are only adding a foot It will not make major feel changes or kill off performance.
I had a plane several years back I trimmed for a flyer who added a little extra paint and it was too heavy by just a tad. I added a 1\2 ounce nose weight to put the plane just a slight bit toward a more foward CG. then added 1 foot to the lines after that, Those 2 things were enough to make a substantial differance in flight and took the plane from one you eased thru the corners to now one that you could hit harder.
I have seen many many times back in the late 70s and early 80s when many went to the ST 60 the planes would drop in the corners if hit too hard, They added about a 1\4 inch pice to the flaps or made new ones to eleminate the loss of lift, Frank McMillan did much the same to a couple of his planes with excellent results.

Regards
Randy

I'll give the additional flap a try. If it works, I'll just build new flaps for it.

Randy

Another thing I have done is take a dremel tool and made the slider slot longer, If your elevator slider has enough material you can maybe add to the slot by grinding a litle out

Randy

And, I was about to hack the P-38 to bits. flew it on 016 solids.

Year and a half since its flown- On .018 7 strand steel, which it

hit squares with acceptably. or predictably at least . Just as well

I recalled it, or didnt hack it up to soon.was going to pull in Stab

4 in and redisign stab.May do it , but not till ive tried it again on

non elastic lines . (next onel have to loose 12 or more ounces)

A/ If shes heavy it should punch through gusts . If say above 20 ft Alt its being deflected from path , three guesses .

B/ If shes stalling out in tight turns, which gets scarey in the bottom ones , Al Rabes bring the CG Fwd and increase Flap travel , to get

MORE LIFT.may be it.

Might pay to see if it stalls / wags / drops (looses lift) in the bottom corners.OBVIOUSLY  use a reserve of hight .IE pull out a bit high and hard.
(this is a TEST) preferably over  dropped of  ground. *
If its NOT stalling it may just be theres not enough ridjidity / resiliance in the control wires. The feeling like a Octopus out there .

Does it point / track ,STRAIGHT thru gusts @ height .Or are they steering it to a degree ? despite handle posn. One should
FEEL the air load on controls.Elev. easy.      BIG flap load not really the same feel  . at all .   


* not everyones cup of tea , but considerd a catapult launched plane to fly of a conical hill. Arrestor wires to stop runaway 'alighting'
   so would get Vert-8s 1/2 above , 1/2 below horizontal . See what I mean about a bit of 'drop of' , to avoid impacts. !
 the other drawback hitting over hard Sq bottoms is LEAPING aft if youve lost airspeed (stalled out) to maintain steering  .

* not sure if this will catch on ! Ifitll screw around like a combat wing , go anywhere you want ,its a good air test.Before trying pattern manouvres.

  a perspective seperate from the 'prescribed flight path'. your trying for pointability and responce .If its O.K. there , It can clarify a few issues    elsewhere.                               

 Like the odd vehical , some take more time for assimilation , learning there form rather than bending them to yours.                                      Matt.