Soptwith Pup Build

Gregor77 · January 30, 2022, 07:42:01 AM

I suggest that you make the horizontal stab bolt on. Reason is that you can access the mechanism if it fails to do repairs. It happens.

octagon · January 30, 2022, 05:52:08 PM

I spent this morning working on the cabane struts. A jig is assembled and then everything is soldered while the upper end is attached to the jig and the lower ends are inserted into the fuse. Worked quite well affter an early bit of mixup with the two different sized struts on each side.
I want to be able to remove the tail feather so I can get inside if I want to. After talking with Greg Cadez I decided to use his idea, instead of something a bit more complicated I had in mind. I have created basswood hard points that will have blind nuts inserted from the bottom, and then bolts will hold the stab down on them.
Now the fight trying to get both wings parallel and lined up.
Going to watch football, enough for today.

octagon · February 01, 2022, 06:30:58 PM

A little more work on the Pup. It was suggested I make the tailfeathers removable. Greg Cadez suggested something simpler that I had planned and it seemed like a good idea. The tail is held down to the fuse with 4 bolts going into blind nuts imbedded into hardwood braces that are expoxied to the fuse stringers. I thought I had it lined up pretty well, but when I did up the forth cap screw and measured the leading edge of the stab was 1/8th of and inch closer on one side to the main spar than the other. A shim of 1/64th ply brought it square again.
The batteries will go ahead of the forward wing sadle bulkhead, just behine the front mounting block for the landing gear. I built a hatch out of 3/32nd ply and fit it in place. Have to figure out how to secure it, but I am leaning to a something simple like a cap screw or rotating latch. Supposed to be a snow day tomorrow so I will have the whole day to frustrate myself building!

Michael · February 01, 2022, 09:06:49 PM

Impressive! Nice work!

octagon · February 02, 2022, 06:31:24 PM

Today I finishing the battery hatch. I installed a sliding latch that is expoxied to the bottom of the hatch. the front end of the hatch has a lip install that hooks under the landing gear mount.
Then I turned my attention to the elevators. I constucted contol horns out of plywood as I did not want to use the nylon ones supplied with the kit, just to give the plane a bit more of a scale look. I am using a pull/pull system and I always thing it looks hinky to go to all the trouble of pull/pull on a scale model and then use nylon control horns. Saying that I may use them on the ailerons as they are on the bottom of the lower wing and not very visible and pull/pull on ailerons seems like a lot of work. Anyway, after several attempts at making the horn with the same rake and arm length for both arms, and then having to do it again, I feel they are pretty good. They system works well and all the contol wires stay the same tension through full movement of the elevators so i guess it is about right.
I also got the servo doors made and the mounting in the wing to hold the doors.

octagon · February 05, 2022, 06:33:20 PM

Only had a couple of hours to work today. I spent time making sure everything was as true as my ability allows, and I think, while not perfect, close enough. Then came the main struts. The struts are lamiated basswood that are cut to length and fit into the anchors that were previously glued into the wings. I reasoned that if they were the same length (the front struts were longer than the back by a little,) that when connected everything should line up, and it pretty much did. Needed to finesse a few things to get everything right but it is pretty close now. The main struts have wire bracing that had to be cut to length. The plans called for them to be bent and cemented into the struts but I did not like that idea much so I soldered the ends to washers that the bold holding the strut to the mount passes through. Again, I made 2 identical rods ( and again the front and back varied but they line up well. I should be getting the motor next week which will allow me to install the firewall and the cowl cheeks and cowl.

Frank v B · February 05, 2022, 10:15:05 PM

Rob,

Looking great. Keep going.

re: your "I spent time making sure everything was as true as my ability allows, and I think, while not perfect, close enough."

That's why our transmitters have trim levers.

One day closer to spring!

Frank

octagon · February 06, 2022, 06:55:35 PM

Had a good day in the shop today. Funny I find some days are great and some you just wish you had never decided to work on the model that day. Anyway, installed the hardpoints in the ailerons and hinged them. The aileron hindges are inserted near the top of the surfaces but in and inverted V fashion, the pivot point of the hinge being at the upper wing and fuse surface. Worked well and pretty easy to get right. I built a control arm for the rudder and glued it in place. It is a piece of 3/32 ply and I used a protractor to draw it and then a band saw to cut it out. Why this did not occur to me with the elevator contol horns I haven't the foggiest. The plans call for a simple but joint where the fin meets the horizontal stab. I did not like that idea much so I cut the lower stringer of the fin after installing a sister beam and made a tongue out of laminated hard 3/32 (the fin is 3/16th thick.) I then cut a slot in the stab to accomodate the fin. after it is covered it will be held to the bottom of the stab by cheeks made of triangle stock. Should make for a strong arangement in the unlikely event I ever nose the plane over, haha.

octagon · February 08, 2022, 07:54:47 PM

Finished the landing gear and installed the wheels. I made a set of main struts but after assembling everything I felt I could do a better job than I had done. I used some of the hardwood my late brother gave me when he realized he was not going to make it, Thanks Dave. I am now waiting for the motor as the last step of assembly before covering, and of course the covering itself, which Arden says should be here this weekend. I am going to use natural colour Oracote from Germany that is like Solartex used to be, as it gives a very authentic cloth like appearance. The cowl cheeks were finished last night and after covering the fuse they have aluminum sheet applied overtop. If the thing flies well I will order graphics for it and paint the top surfaces olive drab.

octagon · February 09, 2022, 01:04:52 PM

I did a bit of research and found that the real Pup had metal landing gear legs, not wood. I used metal foil to cover them and I am pleased with the result. I was going to use collets to hold the wheels on to the axels but decided to go with a different approach, much like I did on the Neuport 11 I built 5 years ago. I cut a piece of brass tubing to the proper length. Soldered a washer to the inboard end drilled a hole in the outboard end for a cotter pin. Then I sweat soldered the brass to the shortened landing gear axel and mounted the wheel using a cotter pin. Happy with the results.

octagon · February 09, 2022, 06:28:22 PM

I spent the afternoon covering the wires for the cabane struts. The plans had them just glued, but I did not like that idea so instead I hollowed out a space for the wires in a piece of 1/8the strip balsa using Duragrit bits in a dremel. The wire fits inside and then the strut is backed with 1/64 ply. then they were stained. Happy with the way they turned out. I decided I needed to make an instrument panel. I was able to find some instrument faces I downloaded and printed. The dash is 1/64th ply with a backing of 3/32 balsa. I sandwiched a sheet of clear acetate in between to simulate the glass over the instrument.

sihinch · February 10, 2022, 09:47:37 AM

Love the dash, Rob. Nice work!

octagon · February 10, 2022, 10:09:33 AM

Thanks Simon. going to try and make bezels for the instruments today.

octagon · February 13, 2022, 05:50:35 PM

The Motor and ESC are installed. Motor is a 4250 500kv from HK and esc is 80 amp, which is probably overkill on a 4 s set up but it is what I had and I figured I could use the weight in the nose. The fuse forward section is covered with 008 aluminum. The kit only came with enought aluminum to do the cheeks but on the real plane the top of the fuse was covered in metal too, so that piece is aftermarket and lightly different in sheen. I figure that's ok as the real plane seems to have different coloured bits as well. I will use a 15.8 and as I said on 4 s this will give about 500 watts and plenty for this plane to fly scale with. I added bezels to the instruments. I had some plastic sticks left over from another build and formed them round around brass tubbing. Painted them and glued them to the dash. Happy with the effect.

octagon · March 21, 2022, 07:41:59 PM

Got back to work on the Pup after taking 3 weeks off on a holiday south. In the time I was away, the Oratex covering I ordered arrived. The stuff is very nice to work with. Sticks at low heat and shrinks well, and great on compound curves. I used all of a 5 meter roll of the stuff but am happy with the results. There is still a fair bit of work to finish up, little details mostly. The ailerons have to be connected top to bottom with pushrods, the Vickers machine gun kit installed. A spreader bar for the gear, probably should be ready to fly if I put another full days work into it. Without batteries it weighs 5 pounds 4 ounces, so I expect flying weight will be about 6 pounds. I will wait to see if and how well it flies before painting the top of the wings and fuse olive drab, and ordering graphics from Callie. The radial engine is thanks to Dave Kates who prinited it for me. It fit the cowling exactly and I think finishes the plane. I am pretty sure (because I spent hours getting it right) that the incidence is correct and everything lines up pretty well and square, so it should be a good flying plane with a low wing loading.