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Author Topic: Sweepette 36D -Build-  (Read 21509 times)
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BG
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« Reply #150 on: April 22, 2011, 09:15:48 PM »

Hmmm... perhaps were are talking past each other?? Here is what I mean. Hope this helps.

B
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sweepettelee
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« Reply #151 on: April 22, 2011, 09:32:46 PM »

Yes, our terms used had mutually exclusive definitions...non matching info!

Another thing... the SW36D plan you are using has been updated... slightly. Roll Eyes My file copy is current & has the angles and values I quoted priorly. Grin
It is a pdf file, so I will send it to you and Tony via regular email.

If Ratz wants it on Plan Gallery it needs converting file per his allowed type. Huh

The only TLG currently so listed is SW30, which he helped me submit recently.
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BG
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« Reply #152 on: April 22, 2011, 09:39:31 PM »

Ok look forward to the updated plan...

So bottom line is I am ok with dihedral as I have 17 deg by my method.

Will update with progress on repairs soon. May also start an 2nd SWE36DII.

B
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Tmat
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« Reply #153 on: April 22, 2011, 11:51:18 PM »

Bernard,
I don't look at dihedral that way, thus the confusion.

So, no confusion now.

Tony
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BG
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« Reply #154 on: April 23, 2011, 06:46:08 PM »

Hi All,
So my repairs are near complete. Just some color touchups still to make and maybe a bit more minwax here and there. With the new slightly larger fuse and the repaired wing and new stab the AUW is 77 grams with the CG at 50%. So even after all of my fixes she is still very light for a 36D. Since I have had trouble with the turn I guess I will be adding a few grams of tip weight so that will help a little but I am also anticipating having to add some ballast.

Also, Lee will be chuffed to read the I am starting a second SWE 36DII. THe stab and fin are done and I have selected a piece of C grain for the wing. Some changes on this one will be a deeper fuse to accommodate the RDT system that I use and to get the stab even lower, and a new approach to the LE bass reinforcement. I plan to cut a slot in the LE into which I will glue a strip of bass. I think this will improve the durability of my LE. I also plan to tape the LE to improve durability. Lastly, I am thinking of trying Stan's foil but not sure if it is worth the extra effort to make the jigs.

Lastly: you guys add the dihedral numbers (center panel + tip panel) to come up with your effective dihedral number correct?

B

Bernard
« Last Edit: April 23, 2011, 07:05:27 PM by BG » Logged

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Hepcat
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« Reply #155 on: April 26, 2011, 04:16:49 PM »

Lastly: you guys add the dihedral numbers (center panel + tip panel) to come up with your effective dihedral number correct?

No, Bernard, that is not the way an Equivalent Dihedral Angle is assessed.

As is generally appreciated if a wing with dihedral is yawed then the forward wing experiences an increase in angle of attack and the rearward wing a decrease which changes the lift forces on the wings in such a way as to restore the aeroplane to an even keel. The change in angle of attack depends on the angle of yaw and the dihedral angle of the wings and so for a particular angle of yaw the change in angle of attack depends upon the dihedral angle. If one is wanting to do some calculations on the dihedral effect then one takes the lift force, acting through the centre of lift of the wing panel, and multiplies that by the distance from the centre of lift to the CG which gives the rolling moment which is trying to restore the aeroplane to level flight.

The Equivalent Dihedral Angle (called the EDA in future) is a way of comparing the restoring roll moments of different polyhedral wings by comparing each of the polyhedral wings to a plain ‘Vee’ dihedral wing. This is done by finding the roll moments of each panel of the polyhedral wing and adding them all together and then finding the dihedral angle required on a ‘Vee’ dihedral wing that will give the same rolling moment.

The calculating task is not as arduous as it might at first appear because we are only looking for proportionality between one wing and another. For example there is no need to calculate actual lift forces as the changes in angle of attack give proportionate changes in lift. Also most approaches to EDA assume an elliptical lift distribution on the wing which gives major simplifications. Some people do try to calculate from actual wing panel dimensions but these, almost inevitably, will give worse results.

I am reluctant to offer you one of my spreadsheets at the moment because since I changed to Office 2007 there have been some peculiar things happening to my spreadsheets. I think Tony Matthews may have a ‘solid’ copy he could offer you. I am working on a new version at the moment to take into account the CG position. I think all the calculators around that the moment assume that the CG is at the centre of the wing, not above or below. This is pretty close for a glider but I realised it would affect results with near vertical tip plates and long wing posts as on indoor models.

John
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BG
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« Reply #156 on: April 26, 2011, 06:05:19 PM »

Thanks for that explanation John,

I look forward to receiving a copy of the spreadsheet when you have it ready Grin.

Tony if you have one available I would love a copy of the EDA calculator.

B
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« Reply #157 on: April 26, 2011, 07:47:49 PM »

Sure Bernard,
Send me an E-mail at: [email protected]

Tony
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« Reply #158 on: April 26, 2011, 08:38:47 PM »

My spreadsheet only works one time when it's stored on my hard drive, then it freezes up. I keep Tony's email saved, and reopen the email and spreadsheet each time I want to use it. Works fine that way.
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« Reply #159 on: April 27, 2011, 11:54:45 AM »

That's wierd Paul.

Maybe your machine?


Tony
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sweepettelee
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« Reply #160 on: April 27, 2011, 02:54:53 PM »

Just a thought... PLove suggested I add new 1 gig RAM [or ROM?...whatever] board when I had similar PC troubles. Did wonders. It cost less than 90 bucks including diagnostic/burnin testing. At Staples.
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Leeper
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« Reply #161 on: April 27, 2011, 03:27:17 PM »

That's wierd Paul. Maybe your machine? Tony

I would assume so.
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Tmat
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« Reply #162 on: April 27, 2011, 04:35:56 PM »

RAM Leeper. RAM is amazingly cheap these days. It's always good to have as much as you can squeeze into your machine.

Tony
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sweepettelee
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« Reply #163 on: April 27, 2011, 10:48:23 PM »

THX for info on RAMming, Tmat. Grin
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« Reply #164 on: April 27, 2011, 11:53:53 PM »

 Shocked Shocked Shocked Shocked


Tmat
-that Leeper, he's a card. And should be dealt with! Grin
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« Reply #165 on: April 28, 2011, 09:43:35 PM »

Right! Back on topic me hearties... Grin

So here is a vid of the RDT mechanism in action: http://www.youtube.com/watch?v=_2uS5yvYnec

Also I provide photos of the repaired model and some close ups of the RDT installations etc. The new stab is ready and the model is balanced at 50%. It now weighs 80 grams ready to throw. She is also a lot cleaner than before; fewer bits out in the breeze. I will use a bit of tape to close the RDT hatch.

Now for some better weather eh?

B
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Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
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Re: Sweepette 36D -Build-
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sweepettelee
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« Reply #166 on: April 28, 2011, 10:39:50 PM »

Excellent Bernie! A.N. Other beauty from your glider creating shop!

I hope you can get a break with the weatherman soon, to fling it about.
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« Reply #167 on: April 29, 2011, 10:49:30 AM »

Really nice job!
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« Reply #168 on: April 29, 2011, 10:24:50 PM »

Here is another EDA spreadsheet and a graphical method from Blaine Beron-Rawdon a modelling Aero Engineer, who worked on the Gosamor Condor.
They are slightly different in approach but as Hepcat noted they are for comparative uses only and this should be taken into consideration when comparing models.

I like your colour scheme on the SW36 and copied it on my small 12" CLG. The repaired model looks great.
John

Download - Calculation of Equivalent Dihedral Angle.doc
Download - Guide Calculator eda1.xls
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« Reply #169 on: May 21, 2011, 07:06:15 PM »

Thanks for the calculator...will try to put her to good use.

Went out to play with the SWE36 today...still having trouble getting a nice turn (even with a gob of clay on the wingtip). She just loves to float off on a very broad arc. Perhaps I will carve a bit of the washin tab off??

B
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« Reply #170 on: May 21, 2011, 07:53:19 PM »

Don't think that is correct thing to do. You want a bit more glide drag turn, not less.
I would try more right rudder tab.
Most SW30s or 36Ds, also Tim's, Stan B's, etal, normally don't need much weight, if any, on glideside tip to fly properly.
As example, my rudder tabs are mostly about .06 to right at fin top. My washin wedges are stock size, ala Stan kits.
[2.0 >2.5 long, as I recall]
How is the launch/recovery going?
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BG
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« Reply #171 on: May 22, 2011, 11:47:01 PM »

Hi All,
Took her out again today and had some success....I added a rudder wedge (1 inch long 1/8th thick) and got a decent turn. Did some launches and got ok results (trying to get the vids uploaded now). At the end of the session i threw the stab off. So my question....when I glue the stab back on do I add more skew (I think I had less than the 1/16th required) and or a bit of tilt (like my butterfly...which I frisby tip launch due to it being set to turn right). I figure one or both of these additions will allow me to ditch the rudder wedges.

B
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« Reply #172 on: May 23, 2011, 01:05:59 PM »

Yes.  More skew to meet 1/16 requirement and just a hint of tilt should not hurt.
My feeling is, tilt on TLGs is not as powerful as on a plane with bigger stab percentage.
That should allow you to delete fin wedges.
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« Reply #173 on: May 24, 2011, 08:39:05 PM »

Hi All,
So I had sopme time with the bird today....the corrected stab skew seems to have solved the right turn issue so that is good news. My launches seem ok and I am getting used to the spin (? think? I will get some video next time so that my techniques can be evaluated). Now my last issue is getting the recovery tuned....I was getting a fairly consistent stall at the top which required a dive to half launch height before she recovered. I added some declage and this improved with some stalls and some good recoveries. I am guessing that a tad more declage and I will have a consistent recovery. This may result in a stalling glide however so I figure a forward CG shift might be required.

thoughts?

B
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« Reply #174 on: May 24, 2011, 09:12:46 PM »

Again...Yes.  If your CG is per plan [2.25" or 57mm]as are mine, then you should be fine.
But a bit more forward is sometimes better, as the recovery will tend to swing and sweep
[pun intended] smoothly into glide.
Good to hear the skew fix seems to be rewarding you with better flights!

Practice, experiment, "wax on, wax off, Grasshopper!"  Cheesy
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