Starduster 40, building in Norway

[Roy Heitmann]

Hi there.
After approx 20 years absence, I'm back in the control line business. Made me a couple of planes last winter (Legacy 40 and Accentor, both from Brodak). The Legacy is no longer with us, as the bellcrank came rushing out trough the wing during a flight! Suspended bellcranks for me in the future! The Accentor works fine as a trainer.
I've now a Starduster from RSM on the building board, and have with great interest followed Fred Cesquim's building of the same, and got some tips on the building process. Thanks to Fred.
One topic however I've been working on, is to get the hinges as frictionless as possible. Having your plane on a slack line in a poor wingover, friction in the hinges is not what you want to fight against while recovering. All the hinges on the marked to day, have some amount of friction between the two parts. Not much, but when you add up the number of hinges in a stunter, it begins to count. So, after some thinking and trying, I came up with a solution I would like to shear (or maybe it's already invented, making me the goof of the year!). But anyhow, here is what I did:
* Starting with a Robart hinge, I drilled out the the rivet the hinge is pivoting round. Took care not to drill into the plastic part.
* With the two parts separated, I trimmed the edges, to make a flush design.
* I then cut an approx 1" long piece out of a 1.5mm (approx 1/16") carbon fiber rod. This rod fits exactly into the holes on the Robart hinge, and the hinge pivoted with no friction, and with no slack. (Take care to cut the number of rods you need to the same length). I don't know if a rod of 1/16" will fit in as well as the 1.5mm rod. But as we use the metric system here in Norway, 1.5 mm is what we get, and it worked fine.
* Next thing is to make grooves in the flap and elevator to fit in the rod and space for the pivot point of the Robart hinge.
* Epoxy in place the rod, taking good care not to get any glue into the places it shouldn't be. I tried to pull off the hinge after the glue had dried, but I wrecked the bals wood around it. So, it sticks well enough. But as an extra precaution you can glue som silkspan over the rods when covering.
* Mounting the flap/elevator to the wing and stab is standard procedure drilling a hole the Robart hinge can be glued into.

Take a look at the pictures attached, they show the procedure.

Happy landings to you all!
Roy

[John Park]

Yes, I like this - it reminds me of a different but related system worked out many years ago by the Englishman Dave Day (see here: http://www.windyurtnowski.com/DaveDay/hinges.htm).  Dave's system worked well on the two models on which I tried it, but it was rather too laborious to be persevered with.  Yours looks much more practical.  ("Marked"? Du er jo norsk!)

[Roy Heitmann]

Yes, I like this - it reminds me of a different but related system worked out many years ago by the Englishman Dave Day (see here: http://www.windyurtnowski.com/DaveDay/hinges.htm).  Dave's system worked well on the two models on which I tried it, but it was rather too laborious to be persevered with.  Yours looks much more practical.  ("Marked"? Du er jo norsk!)

Oops! Sometimes the language slips. Getting a bit rusty with my English.

[John Park]

You're doing fine! Our two languages have many little traps for the unwary - I say things like: "det er for sent i aaret" all the time!  Anyway, I do like your hinges, and look forward to hearing how they work in practice.  Ha det bra!

[Steve Helmick]

Should we be concerned with wear on the CF rod, or abrasion by the CF rod on the plastic Robart hinges? Has the CF rod been used like this before? Is it able to withstand ~2k flights? Build for 2k, even if it only lasts for 200!

I like the idea, but I'd also prefer to use a single hinge pin per flap and per elevator so they can be removed, modified, replaced, or salvaged. Maybe brass tubing sleeves at the hinge locations could be fixed to a smaller CF rod with CA, simulating the fairly typical piano wire hinge pin? My "Eagle" has Robart hinges, and I like them, but there is a lot of appeal to removable wiggly parts for me.  Steve 

[Roy Heitmann]

I like your philosophy, build for 2K, aiming for 200!
I'm no expert on CF, so how sensitive it to abrasion in this concept, I do not know. Time and use will show. My idea was to come up with a hinge with as little friction as possible, and on the test bench it worked fine. And of the two materials in question, the CF rod and the plastic Robart hinge, I would put my money on that the CF rod will outlive the plastic. But I'm afraid a confirmation on this will take some time. I want be airborne with my Starduster before spring 2017.
Would be happy if someone else would try the idea out and shear the experience with us.

[Michael Palm]

I will try this on my next build and smear som vaseline on the rod. Maybe the plane will live for 200+ flights, time will show 

[Roy Heitmann]

Ooops. I don't think smearing vaseline on the rod is any good idea. Over time I belive the vaseline will turn rancid and increase friction. But, on the other hand, it's all theory, and not verified by testing. So maybe your plane will live for 200+ flights. To me, I belive the question how many flights my plane will survive will not depend on the hinges, but if I'm able to keep my plane above ground level long enough!!!!

[John Park]

Petroleum jelly should be all right - I've always used it on bearing points in the control system, and it doesn't dry out like ordinary automotive grease does.  However: the silicone grease I use for lubricating rubber motors in my free-flight models might be an even better bet.  I get it from radio component shops - it's used for lubricating switches etc.

[Roy Heitmann]

OK. Building board is on the table, ready to start building the Starduster.
I use a wooden board, made up by a number of 1"x3" pine spars laminated to a 5'x1' board that easily accepts pins and screws. Since it's laminated, it won't curl or bend, as long as it's kept dry.
The plane will be electric converted, as noise regulations in the county where I live, forbids use of noisy, smelly objects as a combustion engine. But it's OK for me. Electric power has many other advantages, as no need for fuelproofing area round the engine , no sore fingers flipping the prop, little need for cleaning up the plane after each flight.

I started the building beginning with the easy parts, stab and elevator, fin and flaps. Easy forward building.

When I came to the wing, I had to do some thinking how to make me a jig. Fred Cesquim gave me the answer, by using L-shaped aluminum plate as support for leading- and trailing edge. But with some modifications:
- I drilled oval holes in the plate, so I could screw it to my building board. The oval shape gave me the possibility  to adjust the distance so it gave a firm hold to the wing spars.
- When pegging the leading edge to the aluminum plate, I noticed a gap between leading edge and plate on the lower side. This would lead to poor gluing, so I made me some "bridges" that clamped on the upper and lower part of the leading edge, giving an even pressure on the leading edge and closing the gap.
It's extremely important that the leading- and trailing edge are fastened to the aluminum plate at the same height in it's full lengt. I used a calipers to ensure no deviation greater than 0.5 mm.

I also decided to swap the bellcrank system that came with the set with a fully adjustable control set from Tom Morris. Tom made an excellent job with this, highly recommended.
The bellcrank mouning system from RSM is as close to a suspended mounting system as you can get, but I decided to make the support plates a little bigger. Gave me 6 grams extra weight, but on the other hand, Tom's system was 23 grams lighter.

As for now, I'm preparing for sheeting the wing, mount the weight box and LG-supports. Will be back later

[fred cesquim]

nice to see the progress! going fast now Roy!

[Roy Heitmann]

nice to see the progress! going fast now Roy!

Finally back to the building board. A bit behind schedule  after a short vacation and an even shorter surgery in the hospital, but mainly because of the famous three TTT's: Things Take Time!:
On the road I decided to swap the nuts and bolts in the kit with mm-sized bolts, as I can purchase these bolts at any hardware shop here in Norway. Well, nearly then. Not blindnuts. So, optimistic I ordered needed blindnuts from my "local" hobby shop (lies approx. 100 miles from where I live) and got a backorder of 8-10 weeks delivery time!!!
Well, I got some time to do some planning instead of building. And one one thing I had to plan, was how to secure access to motor, battery and ESC. The lay out from RMS was a little "left handed" if I may say. I was not able to dismount the motor with the cowling solution on the drawings. So I redesigned the cowling, simply by gluing the nose ring to the lower cowling, and bolt it to the upper cowling using a blind nut. That gave me access to the motor mounting, so I can swap the motor with a new in case it gets damaged. Which happens.
I also had to modify the battery floor, making a bigger hole in the floor so I could get hold of the ESC. Reinforced the floor a bit afterwards.
Last challenge was the fuse covering. In spite of heavy use of ammonia soaking the 3/32 balsa sheet that came with the set, cracked when bending it over the top of the fuse wall. So I made a laminating covering with 2 1.5 mm thick balsa sheets, which came out very nice and maybe even stronger.
The wing has been finished. Sheeting, gutting and sanding (what a mess) ended. Applied 2 layers of thinned dope with talc, sanded down after each layer, and 2 new layers of clear dope. Ready to be covered. Planning to use polyester tissue on the wing, silkspan on the wing tips and the rest of the plane. Getting the wing, tail and elevator finished and ready for covering was a milestone.
Big question is: to paint or not to paint!! Paint adds weight, improves appearance, but not performance. Is there anyone out there happening to read this who have a good idea what to do? Ready for all suggestions.

Well, that's as far as I have come. Will be back when more progress has been done.

[Roy Heitmann]

nice to see the progress! going fast now Roy!

Hi Fred. Could you give me a coaching in how to make a new post on my tread? Only way I have found out to give some news, is to click on "quote" and write new message that way. But that can't be right. Give me clue, will you?
Thanks in advance.
Roy

[Gordon Van Tighem]

Click on 'reply', bottom right?

[Roy Heitmann]

Click on 'reply', bottom right?
Got it! Thanks.