Thank you for posting your build thread......it's very helpful

I've also started to build my V2 version of the PURES and although the supplied manual has some good photos, the german text does complicate the build. Reading thru your posts I've come up with a few questions I would like your input on:

• My tailboom is longer than what is shown on the plan. Did you cut your tailboom to match the plan?
  
• The tow hook support blocks, RB16 & RB17 look to be best installed prior to sheeting the bottom of the fuse in order to get the best fit. Especially since my fuse bows out ever so slightly in this area and RB17 is much larger than what is shown on the plan. See photo below. What do you intend to do?
  
• No tow hook is supplied in the kit. Is it intended that we supply our own?

Thanks,

Jim

Jim:

I never compared the boom directly to the drawing, but you are entirely correct. I don't know what the deal is, but I will be in Germany in a couple of days, and I will ask directly.

Had I been cognizant to notice, my inclination would be to cut the tail end, so that the front end still fits securely in the bulkheads. But, I have a drill press, and the ability to drill new holes of the right diameter (2mm). I intend now to fly it as built. If the nose weight is excessive or the handling affected, I can still cut off the aft end and drill new holes.

As for the tow hook mount, the design in the drawing reflects Josef's original, while the parts represent a new thought. I intend to put the thick piece, RB16, directly against the balsa bottom sheeting. It is tapered, and will slide fore and aft a bit. Part RB17, the thin ply piece, should fit on top of that, bearing directly on the longerons. In my kit, it is too wide, even though tapered. I will be cutting it in half, and only using the aft, narrower end. In each and every PuRES I have built, the tow hook goes into the first hole that lines up just barely forward of the CG, and the launch is fine.

As for the tow hook, I will be obtaining either an L-hook or similar device from my local DIY store, and simply threading it in. I have never needed a nut, although I often bore out the hole from on top to match whatever hook material I am using. It seems odd to not supply a hook, but no PuRES I have ever had, has had one. The Slite always did.

I am setting out Wednesday for Germany, to see my Grandson (and also, perhaps attend a contest!). I will be gone three weeks, until 17 May. I should have access to RCGroups, so feel free to post questions while I'm gone. I have started the wing center section, but am reluctant to post photos until it is complete, which won't be until May, now. Sorry.

Yours, Greg

Well, I just had a nice e-mail chat with Josef Gergetz. The shorter length is the correct length, so I marked my boom out, and drilled new holes. It was easy, but shouldn't be necessary.

I used good ol' green frog tape, and measured everything out. I even made a mistake, but it was easy to correct. The extra hole will be plugged with a bit of epoxy, and any slop taken up when the posts are finally glued in permanently. As it is, once the 11cm are removed, no one will ever know.

I have not yet heard back from the kit manufacturer regarding the boom length.

uhhh Greg, now I see, that you already glued in the full-length tail boom.
To all others: Please cut abt 100-120 mm from the tail boom (if the boom length delivered is 800 mm).
And: As long it is not glued to the fuse, cut it on the side with the larger diameter - otherwise you get the same task as Greg !

I will talk to Ralf, that there should be a comment added to the drawing and the instructions.
Or even better: the boom should be cutted to the correct length.

Josef

Yeah, I didn't check, just glued it in before comparing it to the drawing. That was my negligence. I found the holes and slots already cut, and the big end fit properly into the bulkheads, so on I went.

Do check against the drawings.

I leave tomorrow for Germany, so no more build thread until I return, on 17 May. There is a strong chance I will get to see some flying on 6 May, and if I do, I will bring back lots of photos.

Yours, Greg

Have a good and save trip ! Looking forward to RESing together with you !

Anyone else notice that rib #14 is cut incorrectly, it's missing the notch for the spoiler framework?

Not a big deal to fix, just want to make sure I'm not missing something as everything else has been cut and fits absolutely perfect.

John:

So, back again, I hope. Did you finish your Samba?

Yours, Greg

I've been back from Germany since Thursday, and just now feeling like I'm returning to human-like consciousness. I'm sorry I didn't plan better, interupting the build thread right in the middle.

I have framed up the wing center section, up to the point where it is safe to remove from the building board and handle. The leading and trailing edges are on, the spoiler box framed up and top sheeting down. What remains is the bottom sheeting, plus inner details.

I used the handy jigs to keep everything spaced, and didn't actually build on top of the plans. The only real issue was my particular trailing edge was bowed a bit. Other wise, it went together just like the CNC-routed forebear, and turned out straight and stiff. There is a minor issue with the top sheeting, easily dealt with. Unfortunately, for some reason I lost a great deal of the pictures showing the sequence. I apologize, but hopefully I can make up for it when I put together the outer panels, which are done the same way.

I start with the two center ribs, which also hold the spoiler servo. I had to alter the one rib to match my choice of servo, but there is a Turnigy T541BBD. I had such a servo, but selected a Dymond D47, which (along with my choices for rudder/elevator and receiver) will allow me to run 2S if I so choose. Anyway, the two center ribs capture the nuts for the wing hold-down bolts, and the whole package is assembled and glued into a single unit. The accuracy of the laser cutting guarantees a straight assembly.

I cut out all the ribs from the sheet carries, and placed them in order, in pairs. The center rib pair went on the spar first, and I moved it to the marked center point of the spar. Following the drawing closely, I then threaded on each pair of ribs in turn, from inner to outer, until all were on, and sort of spaced by rough eye. I then set down the assembly on my flat board, and used the supplied comb-like jigs to properly space them all. The jigs set spacing, and ensure each rib is straight up-and-down. Tilt the jigs a bit, and the ribs will also be guaranteed square with the spar. Carefull align all the ribs, EXCEPT the two end ribs - save those for later. I then applied thin CA to each spar-rib junction, working first the left side, then the right (since the there are only enough jigs to half the job at once). I used small weights to keep all the feet flat on the board while this went on. It helps the have one of those small-diameter CA applicators for this.

All ribs down, I used the jigs and the trailing edge to establish alignment of the end ribs, and assembled the polyhedral jigs for the proper angle.

To lock everything together, it is now necessary to assemble the spoiler box. Here, I was a bit disappointed, as the two parts K4 were just about a half millimeter too short, so I have a small gap. Still, the result is structurally sound, and the gap easily filled.

The leading edge carbon tube presses in place, and like the spar is a stock piece far too long. I pressed it in place even at one end, and went along with thin CA. The excess is easily cut, as is the excess spar material, with a Dremel and cut-off wheel.

I clamped the trailing edge down on my flat board, using the board to ensure a straight, unbowed trailing edge. I clamped it down bottom-side up, and placed the rib ends in each slot with the wing upside down to make sure the top surface is smooth. A drop of thin CA at each rib locked it all together.

The top sheeting went on easily, although it was not cut to dimension. I elected to center the hole on the from portion over the bolt hole, then trimmed both edges to fit between the from spar and spoiler box. The rear section was trimmed the same, although there was much less to trim off. The width of both pieces is a very good match to the spacing of the center ribs.

There is a gap between the sheeting and the front spar. On the original from SetaTech, that gap is filled with CNC-routed pieces of thick sheet, then sanded to blend the spar and sheeting, top and bottom. With this version, the gap is unfilled, but I intend to fill it, and have a scheme to do so when we finish the center section.

That's it for now.

Now we finish the wing center section, to the point of being ready to cover.

There are parts not called out on the drawing, and not obviously useful. These little parts form a shelf in the bottom sheeting, allowing a hatch for access to the spoiler servo. Furthermore, the orientation is not obvious, and so I show them here in detail. Make two little "half-frames", and glue them to what will be the interior side of the middle sheet, of the bottom sheeting. The hatch then fits smoothly in place.

I elected to glue down the forward sheet first, then the middle. The aft sheet required trimming about 3mm off the straight edge. All three went down smoothly and square.

There is a gap between the leading edge and the sheeting. In the original, CNC-routed kits, Josef provided shaped filler pieces to give a smooth airfoil. The new, laser-cut kit does not have filler pieces, so I used scrap balsa for most of it, and some light spackle for the final shape.

The trailing edge supplied is significantly thicker than the trailing edges of the ribs. I glued it on even with the top profile of the ribs, so now is when I sanded the bottom to match the rib profile. If I build another one, I will align with the bottom, not the top. It took careful sanding, but with an aggressive grit, it went easily. I also at this time removed all the little feet. The balsa feet snapped right off; the plywood feet, I snipped off with a pair of nippers. I used a big sanding block and removed most of the bumps.

There are a series of braces and gussets, applied end-to-end between the tip ribs and the trailing edge. What I did was lay the wing down flat, and glue them in against the table top (protected with wax paper, of course). I've seen others install these small parts centered on the ribs and trailing edge, but I wanted the smooth, flat bottom. The triangles are pretty much identical, but the #1 and #8, against the tip ribs, will need minor sanding to fit against the tilted ribs.

There are plywood circles for the alignment pins. These went on without sanding or trimming - I used one of the pins to ensure they were centered on the holes.

Finally, and this is not in the plans, but a result of lessons-learned from several PuRES and Slite kits. I find it good to reinforce the joint between the tip ribs and the leading edge. I've used little triangle gussets, and also solid pieces that fill the leading edge. This time, I used 2mm scrap balsa, and fitted a straight piece between the tip rib and the next interior half rib, glues to the leading edge. This piece provides greater adhesion between the rib and the leading edge, preventing the shrinking covering from bending the rib.

The intermediate panels are next, and assemble easily.

I started with the left panel, cutting out all the left ribs and laying them on the table in order. I threaded them on the spar material provided, then used the comb jigs to space and align. Since the jigs don't extend the full span, I used one jig to set the root rib, and just left the outer rib, and the next half-rib to wait for later. A drop of thin CA on each rib/spar junction, and it was done. I shifted the jigs, and also did the last half-rib.

I put together the polyhedral angle jigs, and then set the two end ribs.

Next, I glued on the trailing edge. This edge stock was very straight, so there was no need to clamp. Learning a lesson from the center section, I made sure the BOTTOM of each rib was even with the bottom of the trailing edge stock, and made sure also that each rib was fully inserted into the appropriate slot.

Now, the leading edge stock was inserted into the notches at the nose of each rib, and secured with thin CA. I used a Dremel and cut-off wheel to remove the excess leading edge and spar material (and yes, there is more than enough for the right panel).

I quickly knocked off or cut all the feet on each rib, and made sure the panel would lay flat on the table. The gussets V1L through V4L, and rib braces S1L and S2L went in, flat on the board. Only Gusset V1L needed any sanding to fit. The panel is now ready for finish sanding. And, indeed, have the excess material on top of the trailing edge wade trimming to final shape much easier. In fact, I was able to make three or four passes with a razor plane, which really saved a lot of sanding.

I do the wing tips last.

I start with the tip rib, and glue on the plywood tip (with the tiny, little triangle ribs). Then I use the tip rib and root rib to mark the trailing edge.

By the way: all wood-to-wood joints are Titebond; all wood-to-carbon joints are thin CA.

The trailing edge is not tapered like the trailing edge stock on the other three panels. It has to be tapered. Once the point where each rib ends is marked on the trailing edge, I lay some masking tape to protect the portion that will NOT be tapered. I prefer green Frog Tape, but whatever. I started with a razor plane, and made three passes down the length of the trailing edge, being sure to neither cut the entire thickness of the stock, nor cut the tape itself. I then used a very aggressive sanding block and sanded until the gouge marks from the plane disappeared. It only took about a minute of sanding, and I let the sandpaper impinge directly on the tape. The tape kept the protected portion from being cut. I finished with fine sandpaper, for a polished finish. The final trailing edge is 1mm thick, tapered from exactly the trailing edge of each, individual rib. Maybe ten minutes, tops.

The spar material for the tips is a single carbon tube, and I threaded the ribs onto the tube in order. The tip rib fits right on the end of the tube. I used the jigs to line everything up, and once all was square with the jigs, I hit each rib/spar junction EXCEPT the root rib with a drop of thin CA (while holding my breath). I then used the 8 degree polyhedral jig to lean the root rib, and hit that one with thin CA, too.

The leading edge goes on next, while the tip can still rest on the bench on the little feet.

Remove all the feet (I used a sharp razor blade) and glue the trailing edge on each rib. I clamped it down, upside down, to avoid damaging the ribs themselves. Now, you can cut the tube and leading edge. You can finish the tips by sanding the root ribs to make the spar and leading edge perfectly flat with the balsa.

The G10 polyhedral braces were a little too big to go into the spars, and required some sanding. Once I got a firm fit, though, the tips went on the intermediate panels almost perfectly. Not only that, but the tip angle was exactly the same, left-versus-right. When I marry up all five panels, I won't glue the joiners, but only glue the ribs together.

Greg,
I am finding your posts extremely helpful with the assembly of my PURES. A couple of questions/comments:

• The head of the supplied nylon M5 wing mounting screw is larger than the hole in FV2. I have some M5 nylon screws with a smaller head that are a perfect fit. Opening the hole in FV2 after it is installed would be a bit of a pain, but you would have to be careful making the hole bigger prior to installation as there is not a lot of material left next to the ribs. Of course, one could always grind the head of the screw down until it fits as well.
• There are two 2.5mm x 1000mm carbon rods supplied for the leading edges. Measuring the leading edge from the plans, I come up with a total of 2008mm required, not counting cutting kerf. It looks to be a bit too short. Am I correct? How did you deal with this?

Thanks,
Jim

Jim:

Like you, I found that the wing bolts supplied had heads that were too big. Like you, I consigned them to my box of homeless things, where I found two M5 bolts with suitable heads. In fact, they were salvaged from my last PuRES.

The two tubes of 2.5 diameter carbon are for the leading edges of the center panel and two intermediate panels only. You get a lot extra, while Hollein is spared the labor of cutting. For the tip panels, there is a shorter carbon tube for the spar, plus a rod of 2mm carbon of the same length for the tip leading edges. I didn't cut either spar or leading edge until after one tip was complete.

Good luck.

Greg

I finished the wing structure by fixing the wing joiner rods into the intermediate panels. This is one of the (minor) ways the new, laser-cut kit differs fromt he original: there are no aluminum tubes in the intermediate panels.

I did a trial fit, and the height of each wing tip above my bench was almost exactly the same, no more than one millimeter difference. So, I fitted everything together, then spread some 15-minute epoxy with milled glass around the wing joiner tubes where they fit into the ribs of the intermediate panels.

The bare-bones airplane sure looks pretty. I think of the PuRES, all square, sort of as line a Mustang P-51, and the Slite, with its elliptical wing, as sort of like a Spitfire.

The last thing I did at this point, was install the blocks for the tow hook. I glued the two ply blocks together, then sanded the edges of the wider block until it fit centered at the design CG location. It fits down against the bottom of the fuselage, so that the wider portion bears against the longerons. Very secure. I haven't decided yet on a tow hook.

It is time to cover.