SLITE 2-meter RES Sailplane - RC Groups
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Mar 22, 2016, 10:00 PM
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Build Log

SLITE 2-meter RES Sailplane


This is a follow-up to the Build Thread for the Pures 2-meter RES sailplane.

The Pures has been a great delight to me, and really opened my eyes to the possibilities of combining new thinking with old materials. I discovered the Pures (and the new F3B-RES class in Europe) by accident on YouTube. Designers like Josef Gergetz are getting great performance out of RES 2-meter airplanes. The kits these guys are putting together (with the help of laser cutting and CNC-routing) make anything like the venerable and honored Gentle Lady look like the stone age. Yes, I've had a Gentle Lady.

After shipping a flock of the Pures to the US, Josef told me about his new, revised design, the Slite (meaning: "Slightly" different, I'm pretty sure). We may have here in Albuquerque the first four to arrive in the States, and the slite differences have finally moved me to a new build thread.

The Slite represents many lessons from the Pures. The Slite features a different airfoil, elliptical plan form, reduced wetted area, and higher aspect ratio. To save weight over the already-light-weight Pures, construction details include thin ply trailing edges, a tapered boom and different choices of balsa.

Josef had many requests for a conventional tail, and that is now an option.

Other spiffy details include pull-spring controls, an easily adjustable tow hook, and a revised hatch cover.

We received four Slite kits from Josef. One guy wanted a conventional tail, but two other guys had seen my Pures airplanes fly and opted for the very light and efficient V-tail that Josef developed. I wanted to build the conventional tail, just to see it, so that is the version I opted for. In the end, one of the others has engaged me to build his Slite, so you get to see both versions. Forward of the boom, they are identical.

Yours, Greg
Last edited by glidermang; Mar 23, 2016 at 07:49 PM.
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Mar 22, 2016, 10:29 PM
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Slite Tail Assembly, Conventional Horizontal Tail


Finally screwed up my courage and cut the first pieces.

The conventional tail is a flat-section airfoil, assembled from "sticks" routed from balsa sheet carefully selected to be straight and soft. The result is a structure that is stiff in torsion and most likely will not warp after covering.

The first thing you will notice is that the drawings are not to scale. Never mind that, everything fits excellently. Just use a flat board. I assembled the horizontal tail with out adhesive, and could have pinned it to a board and used thin CA to finish the job. But, I didn't, not this time. Instead, because I didn't have the confidence I should have had in thin CA, I used aliphatic resin.

There is a sequence, and it begins with the center of the horizontal tail. The pictures show the bottom side up. I pinned the trailing edge next to a straight edge, and glued the three center pieces to that. I then added the leading edge, and worked outboard, inserting only the ribs that fit into recesses. Then I went back and inserted the remaining ribs.

I used the same sequence for the elevator, plus there are two tricky parts. The elevator part HR13 has an extra nub to recieve the torsion spring, and it must be on the left. The center section, HR16, has two slots for hte control horn and they must also be on the left.

The trick for me was after freeing all the pieces from the carrier (and sanding the nubs off, don't forget). I had to assemble the tail parts to get the pieces in the right place. Some almost fit where they don't belong, and there could be a problem. However, if you are NOT like me (meaning: that you are instead practical, organized, disciplined and logical) you could free up parts in sequence and know where they should go at the start.

This completes assembly of the conventional horizontal tail. What comes next for it will be lots of sanding. I will keep the upper surface straight, but slightly taper in plan form before rounding off the leading edge. The elevator will be tapered to match, leaving the upper surface to be the hinge line. Nearly a third of the material of the horizontal tail will be removed; nearly half the elevator. Sanding like that is dusty, but wear a mask. There are ways to keep it precise.

Yours, Greg
Last edited by glidermang; Mar 22, 2016 at 10:58 PM.
Mar 22, 2016, 10:52 PM
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Slite Tail Assembly, Conventiuonal Fin and Rudder


Assembly of the vertical tail is only a little bit different, and there is only one trick. The trick is to keep the holes in the lower vertical tail ribs open for the mounting tubes of 2mm carbon.

Again, like the horizontal tail, I cut the parts and sanded off the mounting nubs. I trial-assembled both fin and rudder, to make sure they worked and I had all the parts.

I started with the fin against the straight edge, but this time, I put all the ribs into the vertical post, making sure they were straight. I did NOT repeat NOT glue parts S8 to S9, S6 to S7 or S4 to S5. Instead, I only inserted the ends of each pair into its slot in the spar. I left S4 off altogether for the moment. After all the ribs were in, I attached the leading edge.

Once the glue had set, I picked up the fin and trial-inserted the 2mm mounting rods of carbon. They went in easily, and I used them to locate S4 onto the bottom of the fin. There will be excess S4 to sand off, fore and aft. Be careful inserting the carbon rods - the balsa is soft and easily deformed. When sanding is done, I will reinforce the holes with thin CA.

The rudder is designed differently, and requires a different sequence. I started with the spar against the straight edge, and glued on the bottom. I then added the bottom rib, the tip and the trailing edge. The other ribs then went up from the bottom in sequence.

Again, there will be a lot of sanding. The weather is bad tomorrow, so I will probably get to it. Unless I do the V-tails, with their spiffy jigs.

Yours, Greg
Mar 22, 2016, 11:43 PM
Flying = Falling (Slowly)
dharban's Avatar
I have been designing one of these planes, but I think I would like to build and fly one of these first. Can you furnish contact information?

Happy Landings,

Don
Mar 23, 2016, 08:54 AM
sleep hard
vx99's Avatar
Nice, Greg.

Thanks again for tackling the build thread. I'll go back to watching quietly, but am looking forward to the bit where you can compare flight performance vs the Pures.

Cheers.
Mar 23, 2016, 09:46 AM
Registered User
Josef's kits look like they are outstanding! Thanks for taking the time to post your build.

Rob
Mar 23, 2016, 10:24 AM
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dharban (Don):

Josef Gergetz is the designer of the Pures and the Slite. He lists his e-mail on his drawings.

josef.gergetz@gmail.com

There is a web site also: www.seta-tech.de

The Slite, the last time I communicated with Josef, is still a prototype kit. The Pures is pretty much done as a kit, and very complete. Both are listed, but the web site may not yet be responsive. So, be sure to contact Josef at his e-mail address. His English is excellent.

One last note: English instructions for the Pures are available (see the web site) and very good. The Slite does not yet have instructions as such, just construction notes on the drawings. For our local group, I settled in one evening with my wife's cousin, who is a world traveler and conversant in German. Over pizza and beer, we went through the construction notes with a German-English dictionary that included three pages of nothing but aeronautical terms. I sent those to Josef, and he pronounced them as "OK". We'll see. If our airplanes all come out straight, and there are no parts left over, we did alright, I guess.

Yours, Greg
Last edited by glidermang; Mar 23, 2016 at 03:32 PM.
Mar 23, 2016, 11:09 AM
Hates Palm Trees
Greg,

I love your intro to this build thread with the development backstory for the Slite...................This thread will get a lot of attention.

Steve
Mar 23, 2016, 07:25 PM
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Slite V-Tail, Fixed Portions


OK, gang, it was just too windy outside to go anywhere, so there I was, with nthing to do.... Ah, Springtime in the Rockies.

This was my chance to try the new, spiffy Depron foam jigs. They work great, now that you ask. It was just too easy.

I pinned down the jigs on my board, then cut out all the ribs for one tail. That helped keep everything lined up right, although it is easy to sort things out again if (like me) you sneeze and scatter all the ribs around. The tails are tapered, and the ribs re-stack in order of length.

It's an easy process: place the ribs in the jig, insert the carbon tube spar, place the trailing edge and tip rib in place, then use the CA (with the handy nozzle that Josef supplies in his kits!).

Look at the pictures.

There were two issues.

One concerned the gap between the plywood tip and trailing edge. I found that a box top from a cereal box was EXACTLY the right thickness, so I glued in a piece as filler. It will sand off.

The second concerned the plywood root ribs. I know from my experience with the Pures that the tail covering will cause the root ribs to sag as it ages, so I fabricated a piece of balsa as a sort of false spar to prevent that sag. Also, I reinforced the junction between the leading edge and root rib with a triangle brace, for the same reason. This is one of a very few mods I have made to one of Josef's kits.

The little feet that assure a straight airfoil are still there. I will not remove those until it's fit to spend a couple of hours in the garage, sanding. The same for the carbon rods that extend past the root ribs - they will be cut off with a Dremel and cutoff wheel, when their usefulness as handles goes away.

You might have noticed that the two surfaces are not identical. The spar spacing in one does not match the spar spacing in the other. That is because the mounting pins are staggered in the boom for structural reasons. Don't worry, just press on, everything will work well.

Just too easy with the jig. Maybe an hour, total.

Yours, Greg
Last edited by glidermang; Mar 25, 2016 at 05:22 PM.
Mar 23, 2016, 07:43 PM
Registered User

Slite V-Tail, Rudder-vators


And now, the moving portions of the V-tail for the Slite.

Like the conventional tail, the pieces all fit together like a puzzle. Each piece is pretty unique, making it difficult to get it in the wrong place. I cut out the pieces for one, fit them together, then pinned them to my board on waxed paper. This time, I played the part of Modern Man, and used thin CA. Much quicker than the aliphatic resin, much lighter, too, I suspect.

Yeah, I made a left and a right. They are, in fact, symmetrical, but eventually you must choose, and I did with the last piece, which is a piece of thin ply that reinforces the root.

Again, there must be a heavy-duty sanding session to finish up. We will be removing roughly a half of the total material to complete.
Mar 23, 2016, 07:44 PM
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I forgot to save all the captions! Anyone know how to edit captions?

Yours, Greg
Mar 23, 2016, 08:13 PM
Registered User
Awesome build. I'm building the XRES myself.

By the way I think the Seta-tech website is working and accepting orders now. I wish I had time to build one right now Maybe this winter.
Mar 23, 2016, 08:19 PM
Slope-a-Dope
Steve 0's Avatar
Quote:
Originally Posted by glidermang
I forgot to save all the captions! Anyone know how to edit captions?

Yours, Greg
Click Edit, Click Advanced, scroll down to your pics with the blue bars, Click the little triangle on the right, opens the text box for Captions to edit, click save. Done!

Watching the build....thinking nice, but i should buy ARF Top Model instead.
Mar 23, 2016, 08:27 PM
Registered User
Hi Greg,
Looks great! I'm going to get one so the next time you're in Tucson we can fly them. Maybe we can start a competition class like the Germans They really know how to live!
Take care and I'm enjoying the build thread!
Ray
Mar 23, 2016, 11:52 PM
Registered User
Very nice looking build. Amazing what balsa/ carbon can do !


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