soarrich

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I started this last year then got side tracked on other things. Tom Crump let me post a couple of pictures on one of his threads, but I figured it was time to make a thread on this plane.

First I'm building to teach my grandson to fly RC, it's not to make a plane for me to fly, I have plenty, so there's no rush on this one. I had him try flying my LT-40, but that didn't workout for a couple of reasons, but now he's going to be 8 and I think he's matured enough to try again.

I wanted electric because the nitro plane's noise scares him, and I wanted to do it in silk and dope because they just look so much nicer. I've used no CA, just wood glue and Ambroid, old school

I made some sanders for doing the round edges of the fin and stab from a deck of cards I bought at the dollar store, and I changed the out line of the stab/elevator and fin to make it look nicer.

soarrich

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I wanted to change the boxy look of the Sr without hurting it's flight characteristics. I started with putting the wing tips on backwards and flat on the table. I the realized there was enough scrap balsa in the kit to make some half ribs for the wing. I then added more shear-webbing and diagonal bracing. No I don't think it's needed, thousands of Srs have been built and flown without it, I just wanted to do it.

soarrich

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I glassed the center section so I had to add a solid bottom where it sits on the fuse, and added some G10 where I have the wing bolts going.

soarrich

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I started the fuse, it was a little too boxy for me so I changed it up some.

soarrich

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I made the nose a little thinner. More later my wife wants to go out now.

skylark-flier

Lookin' GOOD, Rich!!

soarrich

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Thanks, a lot of pictures to come.

I decided I didn't like the very open sticky appearance under the wing so I sheeted it over. Real windows don't seem to age well on models, they seem to be the first places age shows itself, so I got rid of them.

I didn't want rubber bands so I used 1/4" x 20 nylon screws at the trailing edge of the wing, I built a cuff that goes over the leading edge of the wing to hold it there. I've included a picture of how I made a cuff for my LT-40 ARF.

soarrich

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I didn't want the fuse to look boxy so I added stringers.

soarrich

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I started silking the wing, this is only my second silk job so I'll probably have some mistakes. These are some pictures of my wing as I silk it, the darker finish is just low light, it really looks like the pictures where it is white. This is the Nitrate coats, 2 coats brushed on so far. I fly with the great designer/builder Dick Sarpolus, so I'm going to take the wing to the field today and get his opinion if it needs more nitrate or if now I can go onto the Butyrate coats, I'm down to 4oz. of Nitrate but I've got gallons of Butyrate. It's my understanding that the Nitrate is the glue and primer, the Butyrate is the paint.

soarrich

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I'm at the fuse doping stage now. I didn't know how so I just did the bottom, then the sides, then the top, I was afraid if I tried to do it in less pieces I would have a wet cluster F on my hands.

I'm a little nervous about the stab/fuse connection, it doesn't look like there's going to be much to glue too.

Seem like enough room for the radio. I'm making it Rudder, Elevator, Throttle.

buzzard bait

I've always started with nitrate, and I used exactly what you're using, Randolph Tautening Nitrate. I used silk from Thai Silks, which is pre-shrunk, and the tautening dope barely did the job after about three or four coats. A lot of people use only butyrate dope, so I don't think it's critical at all when you make the switch, as long as you can get the shrink. Sig Litecoat and Brodak dope are plasticised to minimize shrinking, as are all the Sig colors, so make sure you've got a good tight surface before applying color. I was using dyed silk with clear dope and didn't use quite enough dope to completely seal it. I would use more coats next time. Make sure there are no pin holes before going to color.

Jim

soarrich

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Thanks for the information Jim, I also am using Thai Silks. I did the tail feathers last March and the bottom of the stab just wasn't tight enough, I thought it would tighten up, but it never did, so I just cut it off and resilked it. I've learn you just have to tug harder than you would imagine you could without ripping the silk. I'm going to be using Brodak colors waffling between Hunter Green with Ivory and Gold, Brown, Sandlewood trim over a Dianna Cream.

buzzard bait

It's a tough job, isn't it? I love the look, but I don't know if I'll do it again. The China red silk looked fabulous, but it was really hard to get it right.

I put my silk on very wet and pulled hard too, trying not to distort. Sometimes I put thinner on, took it all off, and re-did it. My biggest mistake was not putting on enough coats. After awhile oil leaked through and made the covering splotchy.

I modified my 4 Star also, going for a little classier look, at least that's what I thought. Yours has a good 1930s looks to it. I'd go with Golden Age wheels instead of WWI type. It's looking really nice. The diagonals in the wing are an excellent idea. I hate it when wings warp after a few years, and that should prevent it. Sig does that on the 4 Star 60. Here's mine, silked...

soarrich

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I think they're 30's looking.

http://www3.towerhobbies.com/cgi-bin...&I=LXWAB2&P=ML

Did you silk it in Yellow then put swatches of Red silk to make the trim? Looks great!

TomCrump

Your progress looks great, Rich !

buzzard bait

Thanks Rich; I silked with red on the fuse and yellow on wings and tail feathers. Then I used Sig Red (Tennessee?) dope to paint on trim, cowl and the sheeted fuse area behind the cowl. The cowl is carved balsa block covered in silk. One of the great things about silk is the way it goes around compound curves like the cowl. Once it is well doped you can feather the seams with sandpaper.

Jim

Pork Chop

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subscribed

soarrich

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I took my fuse the other day to have my friend look it over, he said it was coming along well. He pointed out that at the bottom front of the windshield there was a bridge forming, very small, but he said it would just continue growing as the dope aged. You would not believe how hard I had put that silk down, I was afraid of that area so I had cut a small strip about 1" wide and really pulled it down tight and still it started bridging across the angle. My friend said the thing to do was cut the bridge out then put some epoxy in it's place, so I did. I forgot to take pictures of the little bridging spots but I got some pictures of the repair. The first picture is showing how much I cut out, I wanted to get all the bridging out, no matter how small it was. The second picture shows the epoxy with fairing compound. The third picture shows it with one coat of dope, I'll sand it and recoat several times to get it right

I got a real big scare, because my friend said everything else looked good I brushed on my first Butyrate coat. I will never use a brush on dope again other than to attach and stretch the silk. I had so many wrinkles on the wing, top and bottom I almost cut the silk off and reapplied it. I think it is because when you brush it on you get all different thicknesses of the dope applied. I thought that the spay gun would apply a even coat and it would all shrink tight, it did.

countilaw

Subscribed... can't wait to see more. Great job.

Pork Chop

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I finally caught up on the thread Rich. I love the changes you made it definitely looks like it is from the 30's and all the changes you made goes well together. I love how the Kadet can be changed to look different yet they fly the same which is awesome of course. Well done!

TomCrump

Rich, It's been 40+ years since I've doped a model, but I seem to remember that the silk gets sloppy, but tightens up as the nitrate dries.

soarrich

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As Buzzer Bait has said the Thai silk that we are using is pre-shrunk, you really have to get it tight. I think the Sig silk is not pre-shrunk, but it comes in smaller pieces and slightly more expensive than gold by weight. The dope I use, both the Nitrate and Butyrate is tautening so it does tighten up, but I don't think as much as with the old silks.

countilaw

This is the best place to get silk. I've used this company for years and the prices can't be beat.

Dharma Trading Company

http://www.dharmatrading.com/fabric/silk/silk-habotai-8mm.html?lnav=fabric_silk.html


Frank

pd1

i love the changes you made to the Kadet.

The loosening you had while doping is not from brushing, it's from the brand of silk you are using.
Thai silks seem to be pre shrunk and don't have much shrink left in them, I only use that brand silk on solid or sheeted areas now.
As countilaw said Dharma silk is better for your open framework because it will shrink more than Thai silk.
I started with silk from Thai silks and switched to Dharma Trading and I've been happy ever since.

Bridging is caused by the dope shrinking and pulling away from the two surfaces. that is a good place for non tautening dope.
I keep a small bottle of clear butyrate that has a couple drops of castor oil added to reduce shrinking on the bench just for those areas, it helps.
Looking forward to more pictures and updates.

buzzard bait, your plane looks great, nice job.
Paul

soarrich

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countilaw & pd1

Thanks for the info. I bought from Dharma once before, but when I went to buy this time I remember Thai Silks and they had some silk that was printed so I bought from them not knowing there is a difference.

I bought a couple Sr wing kits, I'm going to build a plane something like a "Proctor Antic" with them, I'll get some Dharma silk for that.