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Author Topic: Washin  (Read 807 times)
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RobinB
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« on: April 10, 2013, 07:38:29 AM »

I got hold of a copy of an old M.A.N. article recently about a model for which I already had the plan.
I was interested to see if there was any extra info. in the write-up.

In the article the designer says that he builds the inner panels flat and then adds a piece of trailing edge stock to the right panel's TE
rather than build in any twist.

To my mind it looks a bit 'clunky' but, on the other hand, building the panel 'flat' has it's attractions.

Has anyone here used this approach?
Did it work any differently to building the twist in?

Robin

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Indoorflyer
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« Reply #1 on: April 10, 2013, 07:57:13 AM »

Wash-in=increased angle of attack
Wash-out=reduced angle of attack

I can't visualize how a piece on the trailing edge increases the angle of attack at that wing cross section.
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RobinB
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« Reply #2 on: April 10, 2013, 08:17:35 AM »

I was perhaps a little lazy with the details.

A piece of reversed triangular-section strip is glued to the TE of the right inner panel, just inboard of the dihedral break.
The idea is that its' length is adjusted to obtain the desired mount of roll.

Robin
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Tmat
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« Reply #3 on: April 10, 2013, 09:21:33 AM »

Built a Dixielander like that many years ago. It worked just fine. In fact, I could cut away some of the wash-in wedge to tune the amount of roll to match the rudder wedge (also a piece of trailing edge) to get the spiral climb I was after.


Tony
-that was many moons ago..... Wink
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DaddyO
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« Reply #4 on: April 10, 2013, 10:40:21 AM »

Hiya Robin

As you know I've been using 'Gurney' strips (or planks) Wink for a few years now, but I'm moving over to the 'wedge' because I think they are a little 'smoother'. They are also easier to attach better and less likely to get damaged. All my DLG's use them and seemed effective enough, hence my gradual changing over . . .

Obviously they are easier to fix and stay put whereas washin does vary slightly and is a little more difficult to fine tune.

Cheers
Paul

ps
Sorry, but I will be conspicious y my absence on Sunday I trust you'll have a good un. Smiley
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flydean1
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« Reply #5 on: April 10, 2013, 12:44:19 PM »

I have tried both, and both seem to work well.  The advantage of the washin wedge TE stock and Gurney flap is the ease with which they can be changed.  On my B/C Nos Gas T-Bird, they seemed to be less effective, however, High Thrust gassies are  sometimes resistant to roll inputs.  This was gleaned from reading Fast Richard's various discourses on his designs.
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binbag
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« Reply #6 on: April 13, 2013, 05:57:03 AM »

A little sketch here would be a real help as I am a little confused, but very interested.
Thanks
Ralph
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flydean1
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« Reply #7 on: April 13, 2013, 12:20:13 PM »

I tried to attach a drawing.  It wouldn't go, so you are on your own.  You can contact me via email at the following:

flydean at att dot net

I can send it to you as an email attachment which is MUCH easier than this forum.
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Tmat
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« Reply #8 on: April 13, 2013, 03:52:49 PM »

Ok here is a quick sketch.
Turn the TE stock backwards (thick end towards TE) and glue on the bottom of the wing. Length determines the amount of effective washin.

Tmat
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Re: Washin
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binbag
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« Reply #9 on: April 13, 2013, 04:37:24 PM »

Excellent that makes it really clear

Cheers
Ralph
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Sandgroper
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« Reply #10 on: May 11, 2013, 10:16:50 PM »

G`day Robin,

I built my 60"span Slow 525 with only 2.5mm wash in and despite lots of left rudder packing and 1.5 deg left thrust the model was turning right and going flat after a couple of seconds climb.
I glued a piece of 25 x6mm TE stock 96mm long under the TE next to the tip dihedral break-much better keeps going up but still a little flat.
 Next time out I added a further 25 mmTE section to the 96mm - too much the model ended up left and upwind,cut off 12mm and it climbs just right,so 12mm + or - of perfect can make a difference.

Cheers
Phil
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danberry
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« Reply #11 on: May 15, 2013, 09:30:16 AM »

You are over-elevated. Too much decalage and the plane is chasing it's tail.
If you want to climb steeper, lower the stab, remove some wash-in tab and remove some left tab. And add tail weight. The plane will go up steeper.
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Sandgroper
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« Reply #12 on: May 17, 2013, 09:51:10 PM »

Yes I agree Dan dropping the tail will let me get rid of the ugly rudder packing,I may try that later but at the moment its the best flying model I have had for years and I will leave it alone Wink Slop models normally use both tips washed out and the RH inner panel washed in which extends building times so for this wing I built the tips flat and used 2.5mm of wash in instead of the 6-8mm I would normally use and then the exercise was to see how much TE material I needed to correct any lack of wash in shown during the trimming phase.
I reduced the decalage to 1.5 deg during construction dropping the wing LE 2mm and the tail TE 0.5mm so it was possibly already under elevated as it needed 7g of tail weight to glide.
 The climb is nearly one turn in 8 sec, perfect pull out and glide is open and bouncy.

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