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
Registered User
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
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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.
Latest blog entry: First PSS Warbird effort
Mar 23, 2016, 08:27 PM
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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 !
Mar 24, 2016, 10:52 AM
Hates Palm Trees
Greg................Question: Do the Depron jigs come with the kit?
Mar 24, 2016, 12:49 PM
Registered User
Steve:

Yes, the jigs come with the kit.

Depron jigs are included for the V-tail, and each wing panel. The wing panel jigs include angle templates to ensure the end ribs of each panel properly match up for the correct dihedral.

And finally, there are balsa "combs" to ensure each wing rib is properly spaced and vertical.

Really, a complete kit. And I cannot purchase the wood or carbon tubes in this kit for less than this kit cost, shipped to my door. I'd really like to see some of the other kits available in this class of airplane (PicaRES, RES-X, Resoholic and others).

Yours, Greg
Mar 24, 2016, 01:52 PM
Hates Palm Trees
Nice.......................Josef's kit are so well thought out even a non-builder like me can build 'em.
Mar 24, 2016, 01:56 PM
Registered User
Sadly on Josef's website he states that there is a 6-month wait for a kit. Might be a great project for this next winter.

The quality of the kit and your build are outstanding Greg!
Last edited by a2zprod; Mar 24, 2016 at 01:57 PM. Reason: additional text
Mar 24, 2016, 04:41 PM
Hates Palm Trees
Quote: Sadly on Josef's website he states that there is a 6-month wait for a kit. Might be a great project for this next winter.

Yep....................It took approx. 6 months to get my PureS but Josef kept me updated throughout and delivered a great plane........Worth the wait.
Mar 24, 2016, 06:44 PM
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Slite Conventional Tail Final Shaping


The cards fell right for me today - I was able to devote some time to shaping the conventional tail surfaces. It didn't take long, but it takes PATIENCE.

It was just too easy. Normally, sanding to the extent required to round and taper flat surfaces takes quite a while, plus a dust mask plus endless patience. However, the wood quality (extremely high) and the use of brand new 3M 180 grit sandpaper made this the work of right around two hours. It feels longer, but with PATIENCE it moves right along.

I began with the horizontal stabilizer. My intent was to preserve a straight line for the hinge, and taper span-wise to save weight. Also, Josef shows a nice, egg-shaped leading edge, and I wanted to do my best to produce a sort of airfoil shape, not just a rounded leading edge.

What I did was mark off 1mm at the tips, on the bottom. I sanded the bottom surface only until there was a straight taper from center to tip. It was easy: a few strokes with a sanding block, then pull the tail over a piece of sandpaper fastened to my work bench. It was the work of less than 15 minutes to produce exactly the taper I wanted.

Rounding the leading edge, I began with marking the center of the leading edge from tip to tip. I used only my sanding block, sanding in a slope to the leading edge piece, bringing the taper chord-wise to within a millimeter of the center dots. Because of the dots, I knew it was fairly symmetrical. With about a millimeter of flat leading edge remaining, I then used the sanding block to round off what was left. Job well done.

I marked out the same taper on the tips of the elevator, and rough sanded span-wise only until close to the dots. Then I backed up the elevator to the stabilizer, and sanded gently until they matched.

To taper the elevator chord-wise, I worked only on the bottom, leaving the top flat. I started with a sanding block to remove "bulk" material, then moved to the sandpaper on the bench for final shaping. I obtained a flat bottom, tapered compared to the top to a trailing edge of about 1mm. I was happy at this point, I can tell you. Total time for the horizontal tail was right around an hour. Yes, I applied PATIENCE.

For the fin, I began by tapering it span-wise to about 2mm thick at the top. This is for aesthetics, I admit, and for weight savings. Starting with the block and finishing on the bench, the taper gave me a straight line on the starboard side, which will be the hinge side. I rounded the leading edge exactly as for the horizontal tail: mark it, taper the leading edge piece to within 1mm, then round until the marks disappear.

The rudder took the longest. I marked the same 2mm thickness at the top, then tapered one side to the mark. I turned it over, laid the fin next to it, then sanded until they matched. I marked the trialing edge, but worked only with the sand paper on the bench to achieve a straight taper to a 1mm trailing edge thickness. IT took a few swipes, but I worked slowly and it only really took about 30 minutes. It just took PATIENCE.

There aren't a lot of pictures showing sanding. How many do you need, I wonder? They all look the same.

Total weight of the framed pieces before sanding was 12.5 grams. After sanding, total weight of all four pieces is 10g even. Not a lot, but all at the back end, and it will never fly there ever. That means there will not be a need for roughly 8g in the nose.

I should add this note: large-scale sanding like this goes best when done with PATIENCE. I really, really hate being patient.

Yours, Greg
Mar 25, 2016, 05:20 PM
Registered User

Slite V-Tail - final sanding


This turned out to be such a non-event that I'm almost ashamed to post two pictures.

For the fixed portion of the tails, I used some nippers to rough-cut remove the feet on each rib. Then, I used the sand paper fastened to the board to remove the remaining nubs. A sanding block was used to finish up and shape the tips.

The ruddervators were done almost entirely on the board. I checked progress every three or four passes, and used the sanding block if any waviness appeared in the trailing edge.

Total time, all for surfaces: 45 minutes, no fooling.

I compared the two tail sets, and the conventional tail parts weigh within two grams of the V-tail set. I'm most happy about that, for sure. The tail mount for the conventional tail will add a bit more.

Next: fuselage.

Yours, Greg
Mar 26, 2016, 02:54 PM
supreme being of leisure
ZAGNUT's Avatar
very interested to see how you tackle the wing covering. i'm thinking that the elliptical LE means you can't wrap a single covering piece from TE to TE like on the pures.....and doing an overlapped seam on that carbon LE doesn't look easy.
Mar 27, 2016, 05:33 PM
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I can not recommend to take one peace from TE to Te. Idid so and it was not so good. And to my own astonishment it is easy to iron it overlapped, as it fixed very well on the small LE.

Yours,
Hans
Mar 27, 2016, 06:24 PM
Registered User
The seams are easy. Just never use a heat gun for wrinkles, just use a iron slightly turned up over your application temperature.
Mar 27, 2016, 07:36 PM
Registered User
I can second what Hans and Bmwjoon said: that's how I did my red and yellow Pures, knowing as I did that the Slite was coming.

In addition, I applied some heat-activated adhesive to the leading edge (and all the very thin plywood edges) and that made it relatively easy to use top-and-bottom pieces. Plus, I have one other trick up my sleeve, but it will affect the final color scheme. We will see if anyone likes it.

Fuselage coming up. All the pieces are cut out, but I won't glue anything until lter tonight or possibly tomorrow. I will be doing two: one conventional tail, one V-tail.

Yours, Greg
Mar 27, 2016, 11:18 PM
Registered User

Slite Fuselage Pod


Here is how I assemble the fuselage pod. Sheeting and mounting the boom will be the next step.

The tools best used are shown here. A box cutter really works well for separating the plywood parts from the carrier sheet. Be sure to sand all the mounting nubs off - if you don't, there is a good chance parts won't fit well. Besides, think of all that weight you will be eliminating....

I cut out all the parts, and made two kits. The kits for the conventional tail and V-tail at this point are identical. Until the boom goes in, there is no difference.

I started by preparing the servo tray for the servos. I chose Hitec HS-65s, mostly out of habit. With the newer, shallower fuselage, the HS-65s are about a millimeter too tall, so I shimmed one end of the aft-most servo. Other servos that would work (and fit better, frankly) include JR285s, Futaba S3114 (which I have used on rudder/elevator duties in many DLGs. Take your pick.

Next, I tried out the plywood doubler, using the formers to make sure everything went together. In fact, I assembled the whole thing with out glue, and it all fits.

I started the main assembly by gluing the doublers to the balsa sides. There are many ways of doing this. I used thinned (with water) aliphatic glue, applied with a throw-away brush. I used the formers to make sure all was properly aligned, then weighted it down while I glued the other side. I pulled out the formers from the first side right away, and used them on the second side. I then also transferred the weights, and took the first side to a solid surface, and ran my covering iron over it. This really cooks the aliphatic and the bond is instant, and forever. You can't see it, but I set the temperature on my iron to about 2 3/4.

I removed the weights from the second side, and also heated it. There will be curvature, but don't worry, the longerons will take care of that. I glued down the longerons to each side with medium CA.

From my Pures experience, I know that there can be a misalignment of the balsa sides. The formers will align with the plywood, but the balsa is pretty soft and may shift. Don't worry - the plywood is key, and you may add balsa to top or bottom as required, and sand the excess off and be just fine.

Once the longerons were down, I assembled the formers to the servo tray, and glued that to one side. I then glued down all the formers, using a small square to make sure the forward and aft formers were vertical. Be sure to insert the blocks with the hold-down nuts at this time, but don't glue them in!I applied glue to the servo tray, and all the formers except the first and last, and laid down the other side, amking sure there was good contact on both sides of the servo tray. When that set, I glued the side to the first and last formers. And there it is, all done and pretty darn straight. The hold-down nuts slide back in forth - they will be fixed in place later, when the wing is mounted.

It may seem strange, but the tapered boom is inserted backwards, from the rear. It may take some fiddling, but the forward end WILL repeat WILL go into the last former. There will be some small slop, but the fuselage jigs (part of the kit, naturally) will hold everything in place when we mount the boom.

When the nose block is glued on, and the first sheet of 2mm cross-grained skin applied to the bottom, we can use the fuselage jigs to align the boom and fix it in place. When I do that, I will do both a boom for a conventional tail, and a boom for a V-tail.

Yours, Greg
Mar 27, 2016, 11:57 PM
Onward and Upward
CatManDu's Avatar
Nice! Greg, did you have to wait 6 months for a kit? Will there be any dealers in the States? Thanks,

Randy
Mar 29, 2016, 01:25 PM
Registered User
Randy:

No, we didn't have to wait. I had a working relationship with Josef from working several Pures buys, and he let me know what was coming. When he finished up what I understand are his prototype kits, we got the last four here in Albuquerque.

There is a whole slew of kits coming out, if you don't wish to wait. Check out zeller-modellbau.com, isthmusmodels.com, holleinshop.com and ar-flugmodelle.at

Yours, Greg
Mar 29, 2016, 02:03 PM
Registered User

Slite Fuselage - mounting the Boom for the Conventional Tail


Start by making up the boom itself. Now is the time to insert all the carbon rods that mount the tail surfaces. The pictures show the way. All the tail pylon pieces stack up just fine. I inserted the short carbon rods and then just stacked the pieces on one by one. A bead of medium CA between the bottom one and the boom, and between each piece, made up a nice, solid tail mount.

Oh, yeah: round the ends of the carbon rods that will be inserted into the tail surfaces. They will go in a lot easier.

I assembled the jigs for the boom and laid everything out. Measure once, measure twice and measure again, and I usually get a straight airplane. The pictures show the layout. I got to use the flattest, levelest piece of anything in our house: the granite counter top (with suitable protection against dripping glue). I found that if I weighted the tail boom down, that it fit in the jigs and was perfectly centered int he aft-most former. Everything in place, and then use CA to tack it together. I followed up with 30-minute epoxy, mixed with glass fibers. The aft fairing, applied with medium CA sandwich-fashion, locks the boom and fuselage together for all time. I'm going to stop here, and next will be the boom/fuselage for the V-tail.

I made some mods to suit my own particular fancies.

The horizontal tail is removable, but uses the carbon mounting rods as locators. I dislike locators bearing against soft balsa, so I drilled out the locating holes and inserted carbon tubes, left over from the V-tail spars. They fit exactly on the carbon rods, and now I have carbon-to-carbon.

I desired a removable vertical tail as well, so covered the root rib of the \vertical with some hard, 1mm plywood, suitably drilled. I reinforced one of the interior ribs with another piece of plywood. The vertical tail rods now bear on the plywood for alignment, and I feel better. I don't think Josef intended the vertical to be removable, but I needed it if I could get it.

If I could do this one over, I'd install the horizontal tail with the locating recess up, and put the plywood piece P3 into the recess to locate the rods. It would also bear the pressure of the mounting bolt.

Yours, Greg
Last edited by glidermang; Mar 29, 2016 at 02:08 PM.


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