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Author Topic: Sweepette 36D -Build-  (Read 20283 times)
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Hepcat
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« Reply #200 on: October 17, 2011, 03:42:13 PM »

There has been quite a lot of talk about Washout in this thread and discussion of whether it is better to achieve the washout by slanting the cut at the dihedral joint or by sanding it into the wing panel.  I have never seen mention on this thread, or any other, as to the significant difference between what the two methods do.  It may be so obvious that no one thinks it is worth a comment but if there are one or two like me who did not realize the difference straight away then here are my comments.

As I understand it Washout is a gradual decrease in angle of attack as the tip is approached.  On this definition the slanted cut does not produce washout as it results in a sudden  change in angle of attack at the cut and that angle then stays the same all the way to the tip.

Aerodynamically I would have thought that the angled cut was a disadvantage in two ways.  First, I think the gradual washout is often appropriate to match a gradual change in wing section as the tip is approached.  Second, a sudden change in angle of attack (and therefore lift coefficient) at a slanted cut dihedral break will inevitable give a step in the lift distribution causing vortices to add to those already at the panel junction.

I suppose it must be acknowledged that slanting the cuts does make it easier to get both tips the same – if that is what you want. Wink
 
John
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glidermaster
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« Reply #201 on: October 17, 2011, 10:25:02 PM »

A slanted cut is artificial washout in my opinion - for the reasons Hepcat gives, really. It works - no doubt about it, but there is a slight penalty doing it that way - that's what I think, anyway.
I carve actual physical washout into my solid HLG wings (as opposed to just a change in airfoil) - mostly just in the tips, but on my bigger models I carved it in root to tip. I like to apply a bit of the Ron Wittman style flare to the last couple of inches, too, but that is done by distortion. As I use lighter wood for tips, it's not a problem to do, but it is a bit prone to undoing itself, sometimes.
On a 24" (600mm) wing I wash the tips out by 1/16" or so (root to tip), then another 1/16" of 'Wittman flare'. On some of my better models I do the airfoil change thing as well. I gradually reduce camber towards the tip, and move the pos.n of max thickness forwards (as a % of chord) aswell.

I have to confess that some of these habits have little or no theoretical basis, but were adopted because doing the opposite caused problems. I have built quite a few HLG wings over the years. If I kept good records, like the Leeper, I'd know how many!

John
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« Reply #202 on: October 17, 2011, 10:45:26 PM »

...nice post Glidermaster...

John, it looks like the slanted cut washout method is for ease of construction. i.e. -one incorporates some washout into the wing without having to do a large amount of extra labor. You bring up a good point about the efficiency of the sudden angle of attack change though, as a more progressive washout would be desirable. I suspect that is why Lee also sands in extra wash on the wing tips of his gliders. Perhaps we should adopt the Mark Benns six panel wing with our slanted cuts to get a more progressive wing twist(?)(good for glide, maybe not so good for climb drag though). Just to add: the big glider Benn's flew here in the US for the nationals had a very nice glide once he got it trimmed properly for the conditions.

B, have you tried the Stanfoil on any of the new SW36 TLG's? Those are awesome looking gliders!
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BG
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« Reply #203 on: October 27, 2011, 11:53:28 PM »

Hi All,
UPDATE: So I have had SWE36 out recently for test and refinement sessions and I think I have her fully tweaked. I was out in a stiff breeze today (~15 to 20 knots) and played with declage (reducing it) until I got her to start to spin in. I backed off a bit and now have a good climb and transition with a great floating glide. I played with the cg as well and now have her at 58%.

Washout....I have more warped into the right tip (1/8) than the left (1/16) for a left glide. Benefit??...not sure but this is what we do on scale rubber ships to get a nice stable circle and it seemed to work well on my scalded cat.

B


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BG
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« Reply #204 on: November 09, 2011, 10:01:40 AM »

Hi All,
So here is my second SWE 36DII ready for final assembly (tacked together for the photos). Weight is 90g with everything including nose weight. The wing foil is flat bottomed. Also shown is the hatch for RDT etc.

b

Attached files Thumbnail(s):
Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
Re: Sweepette 36D -Build-
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« Reply #205 on: November 09, 2011, 06:38:13 PM »

Thats art BG. I like your use of colours and the blending. Thats a level to aspire to.
Happy flying with it - the man(Leeper) may make a bid for it thats too big to refuse.
John
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BG
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« Reply #206 on: November 10, 2011, 02:01:14 AM »

Thanks John, I am a lefty so this model is not gonna work for Lee....

B
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« Reply #207 on: November 10, 2011, 01:12:32 PM »

Gentle readers,
For some reason I have not been getting 'notify' emails recently, so I apologise for not keeping up with the patter.
I will reply about canted joint washout[been doing it since my early indoor successes]and other related disiderata
when I can find time.

Ciao.
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Leeper
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« Reply #208 on: November 10, 2011, 01:27:23 PM »

Congratulations  BG on the finish of the glider. Man alive that is one great looking color scheme.
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« Reply #209 on: November 18, 2011, 04:21:10 PM »

Hi All,
Update on SWE36D ii.....first launches look pretty good but my nose construction which allows great access to the electronics etc. is too fragile for the rough and tumble of day to day flying. I will be reengineering the nose before I fly her again. Also the weather has turned here so flying is more or less off for now (snow and -20 deg.).

B
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sweepettelee
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« Reply #210 on: November 19, 2011, 02:48:48 AM »

Hello all you HLG aficionados,
I am glad you are carrying on these postings, which reminded me to reply as promised.

I am fairly sure I stumbled onto making canted dihedral joints to induce some washout even before I
had done a minute indoors.  I called it "Toe-out", as some may know.
It followed the same thought path as my use of offset & skewed wing mounting,by realizing that I, as
a human, could not build perfectly accurate & true, so I wanted to get surfaces started in what I felt
was the correct & proper flight direction.
It seemed logical that doing so would ease trimming, due to needing less tip weight, as well as reducing
some drag, since trim surfaces needed less tweaking to achieve proper flight modes.    
 
Going back to the learned 'Johns' [both 'Hepcat' & 'Glidermaster']posts of October 17, 2011:
I agree that washout is normally gradual from some arbitrary position, but beg to differ that it matters
to any noticeable degree whether it is imparted "suddenly" by dihedral joint skewing, sanding or warping.
As one might imagine, I have done all of those 'tricks', ofttimes even on the same HLG.
Keep in mind the cut angle is small[.06-.10"], & some chaps have done the math which determined
the washout angle imparted is quite small until larger cut angles are reached.
In fact, I have used .25" toe-out accidentally, with no detectable drag increase.

As the third 'John' rightly stated on Oct 17, I do sand in more washout in the last portion of each tip,
having done so since the '50s surely.  
I had learned from some great aeromodeller mentors that it was useful and "the best thing to do",
if one wanted to succeed.

Just to keep things in perspective, TLGs are still quite 'new' devices in the HLG genre, with much still
to be learned about what will make them really tick in the Future!

Thanks for listening.

Ciao,
Leeper
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« Reply #211 on: August 20, 2013, 02:17:47 AM »

 Smiley The weights that Lee provides for the wing,stab and fin ready to mount does those weights include
     the parts finished with Minwax applied?
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sweepettelee
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« Reply #212 on: August 20, 2013, 01:52:34 PM »

Roxy2 etal,
The weights I posted (years ago) on page 1
are without Minwax coats added. I typically
 add finish after attaching all surfaces.
Also, the dihedral gussets(carbon is best)&
all fiberglass bits (glued on) have been added.

Hope that helps.
Leeper
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« Reply #213 on: August 21, 2013, 01:48:03 AM »

 Cheesy Yeah that helps a lot Lee. I was struggling with the weight on the stab and fin thinking it included
 the finish coat. You guys were looking like Gods with the feather weights you are managing to get.
 Also my carbon booms are on the heavy side at 10 grams so having to carefully sand them back.
 One of them is down to 8 grams so far with room to take some more off without affecting the strength
 too much. What do u guys use to color the wings? It looks great.     
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« Reply #214 on: August 21, 2013, 11:04:45 PM »

Roxy, I would hazard a guess that Design Master floral spray paint was used; from memory you can get it in NZ.

Ployd in OZ
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« Reply #215 on: August 22, 2013, 01:53:52 AM »

 Smiley thanks Peter, one would assume that the paint colors were applied before finishing with minwax.
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sweepettelee
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« Reply #216 on: August 22, 2013, 03:36:08 AM »

Roxy2, there is no "hazard" in Ployd's guess as far as my color choice for gliders.
Primarily i use Design Masters, & AFTER two coats of Minwax.
Sometimes(often)I add bright fluorescent colors sparingly, as overcoat.
For example, Fluor red over DM yellow.
BUT, as I am quite sure, Bernie uses airbrushed colors which are mixed with thinner
or thin dope.  Maybe he will fill in the brand name.

Lasly, I would not lose a minute of sleep trying to save a few grams on a TLG.
They are quite tolerant in that respect.
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« Reply #217 on: October 22, 2013, 05:04:19 AM »

Hello Guys

I am staring my build of the Sweeptte 36d, I already got some good C-grade wood for the wings and a nice light boom. The plans are printed and ready to go.

I saw on an earlier post a "shaping" tool and I was wondering if someone could show me how to make them??

I am also wondering about the camber?? does it dramatically effects the performance of the wing??

Finally, I would like to build a couple of more of this designs and I was wondering if the "Tapered tube .200 dia down to .100 dia about 23" long" from MRL would be a suitable boom for TLG

Thanks in advance for the help

regards

EZ Cool

DLG scratch builder  Tongue

http://static.rcgroups.net/forums/attachments/8/4/2/4/2/a5631089-24-2013-03-20%2017.09.07.jpg
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« Reply #218 on: October 22, 2013, 11:26:01 PM »

edwinzea, in regards to airfoil camber; it is best just to build the model with a flat bottomed airfoil as likely shown on the plan. Incorporate a little bit of Phillips entry(upsweep) on the bottom, sand top of wing airfoil from the High Point to the trailing edge strait line, and shape the forward top portion of the airfoil as per plan, or as per the 'Stanfoil'. It is tempting to get carried away with airfoils on HLG's(at first) utilizing undercamber, but undercamber affects the pitching moment, thus the launch and recovery. Wing loadings on HLG's are not all that high, therefore the Flat bottomed type works very well... Plus easy to build.
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« Reply #219 on: October 23, 2013, 02:31:18 AM »

Hey John

thank you for your reply, I will follow your advise on the Flatt bottom.

regards

EZ  Cool
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« Reply #220 on: February 07, 2014, 09:52:21 PM »

 :)Hello from RCbobcat55  Very interesting build and discussion. Could someone point me to the plans for the Sweepette 36 model? I built a bunch of the original sized ones many years ago when Jimmy used to fly with us at a social hall near Freeport, PA. i have a large side yard (3 1/2 acres) and was thinking of building one and installing the as3x um system out of a wrecked micro ASK-21 foamy in it. I am always building chuckies for my granddaughter who lives next door to me and would like to try out the idea. Any help at obtaining the plans would be appreciated-they don't have to be full-size as my wife runs a print shop and can print just about anything i can come up with. Thanks much-I really enjoy reading the forum on free-flight even though my primary interest is in RC Sailplanes of all types. Keep up the good work RCbobcat55 my pm is [email protected] a pdf is fine if available..
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« Reply #221 on: February 08, 2014, 05:00:44 AM »

http://www.hippocketaeronautics.com/hpa_plans/categories.php?cat_id=21&page=7
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« Reply #222 on: April 08, 2014, 10:47:24 PM »

Hi All

This is a thank you to all who provided info and build advice on the 36D DLG.

I have completed my own 36 DLG and it flies superbly. Although a little heavy 98g (due to tailboom being a sanded down arrowshaft rather than specialised boom) I get a still air time of around 70 sec.

The model flew off the board with no adjustments required thanks to all the relevant warps etc being already on the plan! Thanks Lee (and all those others involved) for a great design.

Cheers

Dave
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edwinzea
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« Reply #223 on: April 09, 2014, 02:23:33 AM »

Nice plane Dave

My Sweepette is slowly but steady comming together. The first wing panel is now sanded 18.3g the second is ready to go. I hope to have it finished with some composite twists Cheesy.

EZ 8-D
PS. pics coming soon
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sweepettelee
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« Reply #224 on: April 09, 2014, 03:55:42 AM »

Dave,

So glad you are having EZ success with your nice looking SW36D!
(Ahem, all except the clay on right tip. U thought U could get that past me, but no, caught ya!  Grin)

Some Arizona DLG RC chaps are building SW36Ds, including George Morris, who has been high in F3K WCh ranks.
I am going to Poway, CA, May 3rd, for the Torrey Pines biggie, the International RCHLG Festival.
George will be there so we might get chance to chuck some SW36Ds around!

Ciao,
Leeper
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