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Old Aug 11, 2011, 01:39 AM
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I glued the upper trailing edge and secured it in place using my paint mixing sticks and clamps.

I applied aliphatic glue (Sigbond) to the main spar and to the ribs before I put the top LE sheeting in place. In my prior experimentation with heat activation of the glue, I got the feeling that the undiluted glue gave me the most consistent results. Also, the glue needs to be applied to both surfaces for best results. Since I cannot apply the glue to the exact spots on the sheeting, I'll carefully put the sheeting in place and transfer some of the glue already applied to the ribs, over to the sheeting.

Once the sheeting is in place and clamped between the beloved mixing sticks (again!), I pushed the top LE sheeting down on each rib to pick up some of the glue and let the assembly to dry.

Last picture shows the wing panel ready for ironing .

I noticed that the upper spar was thicker than specs only after gluing it in place . I sanded it down some trying to avoid the ribs, but apparently not enough as can be seen in the last picture. I'll sand the sheeting down in those high spots, to get to the proper profile.
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Old Aug 12, 2011, 11:38 PM
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Tonight's progress...

Laid wet paper towel on the LE sheeting and readied the covering iron at the highest setting. Some people remove the sock but I was happy with it in place.

Once the sheeting was bent due to moisture and was almost already conforming to the LE profile, I applied heat and visited each rib location and stayed there for about 10sec each. In about 5 minutes, I was done. I did first the bottom, where the curvature thus the stress is less and then the top sheeting.

Last, I glued the cap strips in place.
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Old Aug 25, 2011, 12:48 AM
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I built the left tip panel in the same manner.
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Old Aug 25, 2011, 01:31 AM
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I had already finished the right panels earlier.

I sanded the high spots down a bit, I'll do this once more when everything comes together. I also sanded the front of the D-boxes square for the installation of the leading edge strips.

At this point, I noticed that my method of sheeting the D-box (by reactivating the glue by heating) did not result in as good results as I first thought. Adhesion to some of the ribs was not very good and were failing when I tried to lightly pry them loose . As a result, I donned my chemical mask and applied a couple drops of thin CA to each rib/sheeting joint.

The LE of the outer tip panels have a slight curvature towards the wing tips. I kept those LE strip in water for a short while before gluing them in place.

After the installation of the leading edges, I sanded the end ribs flat, and glued the plywood end-cap ribs to the inner tip panels and wingtip blocks to the outer tip panels.
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Old Aug 25, 2011, 01:50 AM
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The inner and outer tip panels are joined with a plywood joiner. This piece sits between the spars. Since the profile gets thinner towards the wing tips, the plywood joiner piece has a slight taper, not quite visible in the pictures.

To be able to seat the joiner in place, I opened a slightly enlarged hole on the end-rib of the inner tip panel, which allows the insertion of the joiner. Once fully inserted, the joiner can then be shifted in position between the spars. The outer tip panel doesn't require this special treatment as the taper on that side is in the right direction.

With these, all of the wing panels are almost done . I still have to shape and sand the leading edges and the wing tips. I'm tempted to shape the leading edges after gluing the inner and outer tip panels together so that I get a good continuity between those two. I'm also not satisfied with the gap I have towards the TE of the joint, I'll have to do some more sanding there too . I was hoping to get a joint with no gaps there and use epoxy glue to join the tip panels together, and hopefully not have to use glass cloth reinforcements. Let's see if I can manage that...
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Old Sep 18, 2011, 12:39 AM
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Back to the build...

After some more tries, adjusting the sanding angles, I was able to get a satisfactory fit at the joint between the tip panels. I mixed some epoxy with microballoons and glued the tip panels and the plywood angle braces together. I added the last 4 shear webs that I had left open for access to the brace. At this step I noticed that the LE of the outer tip panel was more recessed than the one of the inner tip panel. I must have sanded the face of the D-box a bit too much .

No worries, I cut strips of hardish 1/32" balsa and glued them on the LEs of the outer tip panels. Things look more even now.

I roughly shaped the LEs of the tip panels using my razor plane. I didn't force my luck where the panels meet as the razor plane cannot work properly in the concave area. I take care of that area when sanding the LE.

I sanded the LEs to proper shape, checking frequently against the templates provided.

Finally the wing is finished ! There's some minor difficulty/binding when assembling the removable tip panels with the center panel. I have a feeling that that's due to me not being able to precisely adjust the angle of the joiner. If/when I get it right once, I may elect to tack glue it on the tip panel side.

Next is the fuse. I hope I can gain some speed and finish the model soon. I want to fly before it gets wet & cold.
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Old Sep 23, 2011, 01:18 AM
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WOW, been a while since seen the progress, the whole wing is a beaut, i want one...............errr dang i forgot i have 3 in the box now waiting for me........nice work again.
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Old Sep 24, 2011, 12:10 AM
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Thanks Balmy_breeze.

I started working on the fuse sides. The sides are prepared by laminating 1mm ply + 2mm balsa pieces. I decided to use the heat activated glue method again, I guess I didn't learn my lesson... I'll give it another shot, using higher temperature.

I marked the sides to be glued together ahead of time as I usually mess up in the thick of things, and I end up building two left or two right sides. I spread Sigbond on the side pieces using an old credit card as my spreader and let them to dry overnight.

I'm building the sides over the plans and I use T-pins inserted around the perimeter of the side pieces which form a simple jig that will help me build two matching sides.

The pictures show the assembly of the right side. The balsa goes outside, the ply stays inside of the fuselage. After placing the ply pieces over the balsa pieces, I passed over the assembly with my covering iron set to max temp, and with the sock removed this time for better heat transfer. This time around I could hear the glue sizzle as I passed over the ply. I could not get to every point on the fuse sides due to the pins, so I did whatever I could while the side was in the jig, then completed the ironing process after I removed the side from the jig.

I'm satisfied with the results this time around. I believe the higher temperature (no sock) did the trick. The fuse sides are nicely matched. The only complaint I have is the glue residues on the wood due to the sloppy job I did while spreading the Sigbond on the parts .
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Old Oct 02, 2011, 02:11 AM
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I need a piece of your wisdom. The original design calls for 3mm metal bolts and blind nuts for the wing mount. I'm considering to switch to 10-32 nylon bolts (2x). Do you think this is a good idea? I understand that the nylon bolts have to be closely spaced, say 1"-2" for optimal shear action (when the one of the wingtips gets caught). In my case I'll have more like 4" between the bolts. Looking forward to some guidance here. What do you use in your large ships?
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Old Oct 02, 2011, 10:49 AM
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Quote:
Originally Posted by atesus View Post
I need a piece of your wisdom. The original design calls for 3mm metal bolts and blind nuts for the wing mount. I'm considering to switch to 10-32 nylon bolts (2x). Do you think this is a good idea? I understand that the nylon bolts have to be closely spaced, say 1"-2" for optimal shear action (when the one of the wingtips gets caught). In my case I'll have more like 4" between the bolts. Looking forward to some guidance here. What do you use in your large ships?
The mechanics of resisting the torque moment dictate you need something strong close to the leading & trailing edges to resist the twist. On my MiMi DLG I have a carbon fiber peg that sticks into a bulkhead and a balsa block on the bottom of the trailing edge, and the nylon bolt is in the center of the wing which minimizes the shear load on the bolt.

If I was attaching the wing solely with two nylon bolts, I would locate the bolts as far apart as possible.

Noel
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Old Oct 05, 2011, 01:24 AM
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Thank you for your reply Noel. I'm opting to go with the nylon bolts not for saving weight but because I'm hoping that they will shear in a crash and help avoid major structural damage. Having said that, they have to be strong enough to withstand normal loads expected during launch and flying.

Here's some very useful information that I found. I'm going with these recommendations, though I'm using 10-32 bolts for a 2M and I can't mount the bolts within 1" of each other as Ollie suggests. The wing center is already built with the bolt support blocks spaced about 4" apart.

****************************
From Ollie's post on RCgroups: http://www.rcgroups.com/forums/showp...15&postcount=3

Quote:
The ideal wing mounting system should have low drag, stand up to any launch or flight loads and give, with impact and inertial loads, in a crash. Nylon wing mounting bolts can come close to meeting this ideal. Plug-in wings with rod shaped joiners do not meet the impact and inertial load objective. Rubber bands, if used in sufficient quantities to resist winch zoom launching, do not meet the impact and inertial load objective and, in any case do not meet the low drag objective. Nylon screws at the trailing edge with an indexing pin at the leading edge do not meet the impact and inertial load objectives either.

Nylon bolts which are counter sunk to be flush with the wing surface have low drag. Nylon bolts which are just big enough to take launch loads and flight loads meet the second objective. Nylon bolts which are small, close together and properly supported in the wing and fuselage will shear in a crash with minimum damage to the structure (if there isn't a bulkhead directly in the path of the wing). By placing the screws closer together the force on the wing tip to shear the bolts is reduced and the smaller the tip force, the smaller or less likely the damage.

I have used nylon screws for wing mounting in dozens of R/C sailplane models of various sizes over the last fifteen years and never had a screw break or pull out in th air. Over those ten years I have gradually reduced the size of screws. My flying buddies will tell you that I have a very heavy foot on the pedal. They will also tell you about some of my spectacular crashes and their surprise at how little damage resulted. Based on that experience, here are my recommendations for screw size and spacing:

MODEL // SCREW // NUMBER // SPACING (MAX)

HANDLAUNCH // 4-40 // 2 // 1/2 INCH

2-METER // 8-32 // 2 // 1 INCH

UNLIMITED // 10-24 (OR 32) // 2 // 1-1/2 INCHES

F3B or F3J // 1/4-20 // 2 // 1-1/2 INCHES

CROSSCOUNTRY 1/4-20 2 2 INCHES


The threads in the fuselage may be provided by a T-nut, plywood or, a slug of filled epoxy. The minimum number of threads which engage must be at least 6. The grain of the plywood must be perpendicular to the screw and the threads must be reinforced with CA and then chased with a tap. The filled epoxy must be the thin, slow setting kind and the filler must be high strength (such as chopped glass or flox ). The fuselage mounting must transfer the loads into the rest of the structure so that the screws shear before anything else gives.

The threads must be chased with a tap and lubricated until the screw turns freely. A dry teflon spray lubricant works well in this application. This will facilitate removal of a sheared screw. A sheared screw may be removed by pressing the point of a No. 11 blade into the end of the screw and using the blade as a screwdriver. If that doesn't provide enough torque then the No. 11 blade may be used to cut a slot in the top of the screw stub for a small screwdriver blade.

The wing must have a block to take the compression load of the tightened nylon screws. The block should be incorporated into the wing spar structure and the screws located near the thickest part of the wing. The blocks may be made of a hardwood, plywood or filled epoxy. The block in the wing must be tied into the wing structure so that the screws will shear before anything else gives. The block should be carefully countersunk so that the screw heads are flush. Any gaps may be covered with a small piece of tape.

Two piece wings work well with this system. Just locate a nylon screw near each wing root and the screws will also keep the wing halves from separating on their joiner rods.

Maintenance is simple. When the nylon begins to turn yellow, the screws should be replaced. The screws should be inspected after each flying session or hard landing. If they show signs of distortion where the wing meets the fuselage they should be replaced. If the screws start to turn brittle they can be restored by boiling them in water.
****************************
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Old Oct 05, 2011, 01:44 AM
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Following up with the previous post, I added 1/4" plywood blocks to the wing seat assembly to accept the #10-32 blind nuts. I chose the plywood a bit on the thick side to increase the gluing area between the wing seat and the fuse sides. I drilled the top half of the holes just large enough to accept the 10-32 bolts without slop and enlarged only the bottom part of the holes to receive the blind nuts. The holes on the wing itself don't have any slop either and the wing sits flush on the wing seat. This way, I'm hoping to get proper shearing when needed, without stretching of the nylon bolt.
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Old Oct 05, 2011, 02:03 AM
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I glued the 1mm ply doublers (triplers actually...) on the joint where the two plywood fuse side sections meet.

I started on adding the 3mm longerons around the periphery of the fuse sides. I weighed the 3x3 stock that came in the kit and saved the lightest ones for the aft sections of the fuse. Where the longerons go over the 1mm ply doublers, I didn't use the 3x3 stock but used 2x3 stock which I stripped from the leftover 2mm sheets.

I'm using Hitec HS65HB servos for the rudder and the elevator. These are slightly larger than the laser cut servo tray openings. So I had to do some minor sanding before they felt at home.

I glued the servo tray support rails on the fuse sides.

In parallel, I also put together some sub-assemblies used in the construction of the fuselage.
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Old Oct 08, 2011, 03:15 PM
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I started to assemble the fuselage. I first put together the wing seat box. Getting that all square first will help getting the rest of the fuse straight (fingers crossed).

The two formers at each end of the wing seat are glued at right angle to fuse sides. I first glued them on one side, then once dry, I put the two sides together making sure to keep everything properly lined up and square.

Using the previously assembled wing seat holes as template, I drilled the bolt holes on the wing and checked the fit. A flush fit between the wing seat and the bottom of the wing, both made out of hard ply, will make sure that the bolts shear -not stretch- when faced with an excessive torque (at least that's the plan ).

I glued the wing seat in place. Things look OK so far .
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Old Oct 10, 2011, 12:41 AM
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I forgot to mention that I switched to a different glue, mostly because I'm running out of Sigbond. I'm now using Elmer's Carpenter's Wood Glue Max. This is a relatively new waterproof glue, I'm trying it for the first time. I thinned it just a tad by adding about 10% purified water which allows me to use a needle cap glue bottle for application.

At some point I installed the nose former but forgot to take pictures apparently. I assembled the nose block pieces, roughly shaped the balsa sides to match the plywood spine and I glued it in place.

I assembled the stab mount. I roughened the surface of the nuts and glued in their holes using thick CA.

In order to make sure that the tail feathers are in proper alignment with the wing, I joined the fuse sides at the tail over the plans. There's a ply component inside the tail section -not exactly visible in the pictures- which is critical for the alignment of the fuselage sides. Once that piece was properly seated in the slots on the fuse sides, the assembly looked straight. After that I glued the stab mount in place.
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