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Can I Produce Washout with Ailerons

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Can I Produce Washout with Ailerons

Old 01-31-2011, 01:41 PM
  #26  
Merlin Man
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Default RE: Can I Produce Washout with Ailerons


There are some great ideas coming through oh this thread. The wing slats idea would help alot I would imagine( butis way out of scale

Incidently, the wing loading on calculation with an 11lb. model is 32 not 35oz./sq.ft (. I've been taking the word of others without actually doind the maths myself.! )

I have flown quite a few models with this or higher loadings ( ESM Spitfire 72" 15lbs., Platt P51 82" span 23lbs are two of the "worst" ) .Both these models were quite manageable if deadsticked, though the Spitty more so than the P51. They both had flaps and generous washout.

So I am thinking that it is the lack of washout that is being the main problem here. . I have not finished the model yet but only a few more things to do before I readdress the wings again.

Lnewqban, I cannot seem to get your second link to work. I would like to see this as I may go onto the Flaps after the washout.

Cheers
Merlin Man..............................................f rom the Rolls Royce / Packard variety.
Old 01-31-2011, 01:50 PM
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Default RE: Can I Produce Washout with Ailerons

Lnewqban, split flaps may be easier to add but their primary addition is drag more than lift due to the split style.  Hence my suggestion to cut away part of the wing and add plain flaps.  Plain flaps at smaller angles provide camber more effectively and doesn't slow the model with larger amounts of added drag.

But either way flaps or not this is not going to be a fun airplane to fly with the wing loading being so heavy.  Certainly it will fly.  But the requirement to keep the speed allways on the boil will take some of the flight style options away.  Adding the fixes we've discussed here may aid a little but it won't address the root of the trouble which is the wing loading.

The optimum solution to the wing loading problem would have been to buy a different model.  By avoiding the ones that have known issues with high wing loading and hence poor flying charactaristics we'd force the makers to build and sell better products.

Old 01-31-2011, 07:53 PM
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Default RE: Can I Produce Washout with Ailerons

Hi,

Yes, I agree that another model choice would be the solution. But, I amsorta stuck with this one and I would like to improve it.

As we know,, this is a high wing loading but not extreme or even higher than I have flown before..( I havean ESM 72" Spitfire with a 16lb weight and higher wing load as was a 22lb. 82" P51. both of these, with flaps and generous were easily manageable if they went deadstick which occasionally happened. ) They have about 2* washout.

I have just used a borrowed Laser wing incidence meter and asI suspected there isWASH IN inthe wing tips.!! How could a manufacturer get away with that !! I think this is amajor contributor to these stalls ?

Using this meter for the first time (and without instructions) I am not sure how the "scale" graduations relate to DEGREES but it does show the relative incidences. The root has a reading of '3 " and the tip of "2.5" and the other is "2 " These would be roughly degrees so the wash in is not much BUT the fact it is there explains alot in my opinion. What do you guys think ?

( BTW this meter is absolutely great ! It's a Great Planes one.)

Cheers,
M.M. ..........................the Rolls Royce/ Packard one .
Old 02-01-2011, 03:08 AM
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Default RE: Can I Produce Washout with Ailerons

M.M.,

I don't know why the links I posted above don't work for you.
I just rechecked each, and they work for me.

Is this the meter that you are using?

http://manuals.hobbico.com/gpm/gpmr4020-manual.pdf

If you find it to be symmetrical, may be the wash-in is intentional, as a way to promote snap rolls.

It almost seems that one option would be to flip the wing and have wash-out instead, but then, there is the inverted dihedral, servos and landing gear.[]
Old 02-01-2011, 04:53 AM
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Default RE: Can I Produce Washout with Ailerons

Set the meter aside
draw a straight line from TE to LE at the tip
along exact center of each
do this for both tips
IF the wing is straight - the wing can be balanced on four pins along two exactly parallel blocks of wood
THEN- the center of the wing should also be level (coincident) with the tips
Frankly I have no use for these incidence meters- any of em
A difference in sanding LE/TE radius throws everything in a cocked hat.
BTW No one deliberately sets up the tips to promote a snap roll -
Old 02-01-2011, 10:27 AM
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Default RE: Can I Produce Washout with Ailerons

Even if the shaping is consistent from center to tip for the leading edge stock diffences in the % of radius in the stock can make a difference in how the guage seats the wing's LE into the V shape.  I've never bothered with a gauge either for this reason and it's interesting to see so many confirm this suspicion.  To more correctly confrim the issue I'd suggest blocking up the wing or sitting he model on it's gear on a table and measure from the table to the center of the LE and TE at root and tip.  Any washin or washout would be a lot easier to determine with certainty.
Old 03-25-2011, 02:57 PM
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Default RE: Can I Produce Washout with Ailerons

Hi All,
Well, after some thought I decided to run with the "up" aileron mod. Each aileron "s trailing edgeis4mm above the top of the trailing edge.

I have had 3 flights with the PC9. It flies beautifully. It is fast and smooth , rolls are very axial ( if that is a correct expression ? ) . I have not conducted anystall tests yet. The motor is new and running rich and I am not keen to slow it down too much for a stall test at this stage.

The landings have , so far been hot. I ran out of runway on my first but with better touch down placemant the last two have been better.. I have been very conscious of the speed during the approach and final and have probably erred on the side of being too fast , but appart from a long run out , OK.

I am looking forward to further flights and becoming more comfortable with the speed thing.

Cheers,
Merlin Man.
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Old 03-25-2011, 04:02 PM
  #33  
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Default RE: Can I Produce Washout with Ailerons

I don't think this has been mentioned yet, but an easy to do, and try, fix is a stall strip. A small triangle stock strip, about 1/8th to 1/4 span tacked to the leading edge inboard part of the wing will cause the inboard portion to stall first and not change the cruise flight noticably.
Old 03-25-2011, 04:52 PM
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Default RE: Can I Produce Washout with Ailerons

The other way to reduce wing loading is to cut down on the wet weight. Is this possible?
Old 03-28-2011, 02:57 PM
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Default RE: Can I Produce Washout with Ailerons

Hi,

Cutting the wet weight will of course work but, it will also cut your engine run time and with a thirsty 120 2 stroke, I only have about 12 minutes to start with.I could reengine with something more economical , but think I will stick with what I've got .

Thanks for the suggestion however.
Cheers,
M.M.
Old 03-28-2011, 04:51 PM
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Default RE: Can I Produce Washout with Ailerons

Use of small batteries would also work.

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