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More skinning. The ex-WWI pilot checks the work. Struts cut from basswood. Skid cut from Ash, soaked in hot water then put on a forming jig to set the curve. When dry it was removed and is what you see here before getting stained and drilled for mounting to fuselage.
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The fuselage was jigged in place so the wire 'L' ended cabanes could be epoxied in place. Balsa fairing were fabricated, stained then added to cabane wires. Struts were stained. Skid attachment hardware fabricated and painted. Auto hose segments were used for their shock absorption.
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'T' nuts let into bottom of skid. Brackets secured to skid to connect to those on fuselage via 'O' rings which provide shock absorption. The small 'O' is for the front skid mount. Tow release shown on nose. It is a simple pin in a hoop. Thanks to Len for helping make a better one when the first one broke at the field.
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Major construction done! Pics show things a little out of order like the cabanes not being fitted but that is okay! Strut end fittings fabricated from Proctor Enterprises items, music wire, soldered, cleaned then painted. These fitting have eyes for cable cross bracing and turnbuckles. Cabanes in place with nice tight joinery! The rear cabanes weren't glued in place just yet to allow for easier covering. It'll make sense later.
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Stub spar wing inter-connect metal fittings made from sheet steel, drilled, trued, cleaned and painted. They were assembled onto ash stub spars then glued into the root spar sockets. The alignment pin inserted into the fittings then the wings were checked for 'straightness' while the epoxy cured. Once this done then the struts got their fittings epoxied in place with the fuselage connected to the wings and everything checked for 'straightness' while epoxy cured. Gotta have 'straightness'!
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Ooops! Forgot some wingtip pics. The ply doesn't go around compound curves so this balsa block was sanded fair to LE with ply, stained then re-glued. Time for covering... my favorite thing to do! My method is to apply masking tape to the structure then brush on the adhesive. I like to use Stix-It and Koverall fabric. Lay the fabric on the structure then 'burnish' Stix-It through the fabric. Do small segments at a time and pull tight as you go. You won't even need the heating iron except to remove 'fold lines' in the cloth. Shrinking the fabric can cause major warps. This method isn't the only method but it works for me. When satisfied fabric is as you want it use a sharp X-acto blade to cut excess fabric using the masking tape as your guide. Pull the masking tape from the structure. Easy peasey! You can see now why the rear cabanes weren't epoxied until after covering. Diagonals glued in place. Toothpick pins help secure them.
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Now that all the pull-pull cables are run it's time to put on the side fabric. The fabric was attached from the rear going forward. When I got to the cable egress points the cables had to be passed through the fabric one by one. Only then could the side fuselage covering be completed. One side done. Time for the other! Tail feathers covered and allowances made for cable pass throughs. Shackles can be seen connecting horns to cables. A scrap 1/64" ply used to gaurd the pull-pull cable while the excess cut flush to the swage. The fuselage is ready for 'office' details.
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The ex-WWI pilot checks out the seat belt material. Strut mount blocks with their fittings epoxied into place. I jumped the gun on a previous post! Once the wing strut attach points secured then the struts and their fittings were set up and epoxied. The ex-WWI pilot says it's a tight squeeze to get into the cockpit but once there compfy enough! The 1/64" ply cladding for the wings was cut from sheet stock. Lots of tip, end pieces, gussets and cap strips to get glued in place. I think each aileron structure has 85 parts.
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More 1/64" ply cladding cut for application to framework. Ailerons cut free and spars added. Block were let into wing false spar so that aileron hinging can commence. Seat back formed as shown by the ex-WWI pilot sporting a new belt buckle! Aileron horns were fabricated just like the ones for the tail feathers. They are just a little larger. Close up of the cladding. Tight joints! Ailerons got hinged.
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A storage box was made from cabinet grade 1/8" ply. It will double as a coffin if the Prufling gets crashed badly enough! More covering pictures showing the 'masking tape technique'.
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A beauty shot for a homely 'bird'! Wah-wah-wooo! The start of wing covering. The aileron pull-pull cables have to be run so this covering was done in stages so the cables wouldn't be dangling about. You can see how the cable is passed through the fabric. I kept a large loop at the aileron horn end to be cut and swaged to a shckle later once the wings with ailerons get re-rigged after covering. Again, masking tape used to get adhesive application tidy. You can see the tape next to the cap strips.
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Closing the wing. Re-purposing one of my 'ship-in-bottle' tools. I had the cable on the wrong side of the pulley! Fabric work done so everything got a couple of coats of (polyurethane, here) varnish just like in the good ol' days! Dope was too expensive back then for something like this. Here is a close up of the weave. It got sealed very well with the varnish. Seat rails were fabricated for the removable seat. The spring loaded end is received by a 'pocket' block glued inside the fuselage. The 'hooked' end of the rails engages one of the strut carry through rods. The seat has to be removable because the aileron pull-pull cables connect to the tiller behind the seat.
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Here's a view inside the fuselage. Note the 'pocket' boxes glued in place. The seat in place is what the ex-WWI pilot wants to see! The wings were rigged then the aileron pull-pull cables adjusted. A turnbuckle was used to fine tune the tension of the balance cable. The turnbuckle was then safety wired. A bolt and nut is all that is needed to dis-engage the balance cable from one wing to the other. The other cable gets disconnected from the tiller inside the fuselage so that wings can be removed. Fiddly but it works! Ailerons aligned. Close up of aileron shackle in action!
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You can see the aileron cables crossed over each other. The rudder cables along the floor are loose because the rudder isn't connected. The ex-WWI pilot can shave with this shine! The whole model comes apart for easy storage. It takes almost an hour to rig so it doesn't get flown as much as it should, not that it is a great performer or anything. I like it, though, because I like 'old timey' stuff! lol I made a wing gap cover from lithoplate but it isn't shown in place in these photos.
This just about wraps up the Prufling! I hope it wasn't too boring for y'all! I'm glad I finally built a model with fully functioning cockpit controls that work without hooking up the servos. I've done cockpit controls that 'slave' off the servos before. It even has a tow release knob mounted on the panel that works! I'll have to get a picture of that posted. I don't have pics of that, yet. I'd like to thank Len B. for test flying the Prufling at my very first aerotow event, the JR Event now known as 'The Horizon Hobby Aerotow Event', now. This was my first aerotow model and I knew absolutely nothing about it. Len reached out to the community offering assistance to those with an interest and I took his offer, he was my 'first contact'. Thanks Man... I really appreciate it! This is the most fun of any segment of this RC hobby!
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