Just sand the carbon tube down

Yeah--chuck it up in a drillpress or lathe and just use a strip of sandpaper like a bath towel and sand! Takes 2 times--have to dechuck and switch ends.

That 2nd takeoff was perfect except for the dolly. 🙂

Wet sand carbon fiber to control dust, also ventilation and mask.

Michael

Congratulations for the really great maiden flight(s).....bravo!!!

Maybe you can try a CF Aeronaut folding propeller??

ettore

Nice flight Smoothie. Looks like you are getting it sorted out. And thanks for posting all the info and results for the dolly as it will help
others that attempt it, namely me.

J

I'll mic the aluminum and CF tubes later and see how far I'd have to go for the CF to fit -- I'd have to do the entire length (68cm) as it passes through the same tube in the fuselage.

While I have a minilathe, the pass-through diameter is less than 20mm as I recall -- it'd be a little tricky to set that up, although it's probably doable. The wall thickness of the CF is supposed to be 1mm -- need to check that too, to see what I'd end up with after reducing the diameter.

Edit: With the spar being 68 cm long, that makes it too long for my minilathe or drill press -- so it would have to be done entirely by hand.

And thanks for posting all the info and results for the dolly as it will help
others that attempt it, namely me.

Thanks John! I'll be starting on the new dolly soon, and I think this will be the ticket. Or so I hope. I'll definitely post photos and share results.

Maybe you can try a CF Aeronaut folding propeller??

It's early in the game for me to say, but I'm not sure a folding prop is necessary or would even make much of a difference. In the first flight video, one of the passes I make is entirely power-off -- the prop just freewheeled and barely lost altitude. I do like to fly with a lot of throttle management with Komets, from wide-open to glide. In reading first-hand pilot accounts of the real Komet, when demonstrating the 163, they did the same thing!

The CF tube is 20.15mm (it's the "roll wrapped" type and shiny):

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The aluminum tube is 19.93mm. So only 0.22mm difference.

Is it OK to wet sand that type (rolled) CF tube, or do you end up going through layers and make a mess?

Did I buy the wrong type of tube? I don't have much experience with spars like this.

Edit: With the spar being 68 cm long, that makes it too long for my minilathe or drill press -- so it would have to be done entirely by hand.

Sand away

The functional priorities, now that the Komet has flown, are:

1) make a new dolly that works better and drops every time

2) replace the flimsy tail gear

Other tasks are cosmetic -- making the earlier functional repairs disappear if possible.

I started on a new dolly -- it'll be plywood again, but dispense with the aluminum kit gear, which bends one way or the other with little provocation. The bolt axles are too flimsy as well. I'm going with a 5/32" (4mm) music wire axle this time which I think will be sturdier, absorb small shocks better, and stay aligned better. I'm awaiting some hardware (should arrive tomorrow, thanks Amazon Prime) that I'll need to continue.

I also started on the tail gear. The kit gear is a single wire from the wheel to the rudder, with a control horn in-between, and limited access through the removable side plate. Cutting the wire at mid-point was a real pain, using a variety of grinding attachments on a dremel -- the angle made it impossible to use a carbide wheel which would have made quick work of it. I made up a new tail gear from heavier 1/8" music wire. To connect the two wires, I've ordered some 2m to 3m couplers (also Amazon) -- I'll drill out each side to the correct wire diameter, then install with the previous control horn. Tedious, given the tight access, but should be doable. The couplers will be here tomorrow as well.

Meantime, I got to work making my functional fiberglass repairs look good. First the fuselage bottom -- the fiberglass was sanded and edges feathered, then those areas repainted with BEHR and sprayed with satin polycrylic. One of the great things about this paint is how nicely it blends. I also replaced some of the nomenclature graphics (I'd printed extra) and repainted the simulated skid dark gray.

On the top, there were areas where the gel coat had popped off. As before, the area edges (especially if the edges were "loose") were hit with thin Bob Smith CA to seal them down, then Bondo two-part glazing used to fill. I used yellow Frog tape to isolate the areas, so the work areas didn't "grow" unnecessarily. After sanding, I first brushed on a coat of 76 blue gray, then airbrushed the same, feathering out. Finally the 81 and 82 mottling was added and things blended together very well.

After the second flight Wednesday, I noticed the Talon 90 ESC was warm -- it has a big heat sink and I suppose it's supposed to be warm. Nonetheless, I don't have a whole lot of ventilation going through there. I decided to improve two aspects of the venting. There's an open hole just above the skid -- this is where the towing hard point was located. I thought it might be fun to design and 3D print a duct (18mm dia.) going from that opening to the ESC. It took less than an hour to design and about 2.5 hours to print. I sanded and painted flat black after the photos were taken. I got lucky -- it fit and was the right size and angles on my first attempt. It's very thin-walled, and weighs next to nothing.

The real Komet had a scoop on the bottom of the "cowl" -- While I had a small vacuformed one there from the start, it was damaged in one of the takeoff mishaps. I made a new one, but 3D printed, and enlarged the hole under the scoop. Then I drilled 4 more holes in the firewall in hopes to get a bit more air moving through the cowl. The dummy rocket nozzle on the tail is open, which will help.

All in all, one of those rare days where things went very smoothly and much accomplished! Nothing but high winds this weekend (otherwise beautiful), so there's a good chance I'll get the dolly and tail wheel completed -- I'm looking forward to flying this bird again, if you can't tell!

I might even try wet sanding the CF spar tube tomorrow as suggested.

As you might recall, I bent the aluminum wing spar a bit on both sides, on the first takeoff attempt cartwheel. I was able to straighten it a little but not perfect. I doubt it affected anything and I couldn't really see it when the model was assembled. As far as I know, I can't buy a replacement from CY, so I thought it might be interesting to replace it with a carbon fiber tube spar -- seems to me if this were a new kit, that's how they'd do it.

Unfortunately, the 20mm tube (18mm ID) was about 0.25mm larger diameter than the aluminum tube. On the advice of several of you, I proceeded with sanding the CF tube this morning, starting with 100 grit and working down to 320 wet/dry. More than an hour and at least one blister later, I have it down to the right diameter and cut to 27" length.

The aluminum spar weighs in at 105gm. The CF spar is 60gm.

I'm new to large CF spars -- this has a 1mm wall thickness, same as the aluminum. That should be fine, right??

A common complaint running through the old CY Models Komet threads concerned the too-light tail gear wire -- 2.5mm, and probably not the best quality music wire. I found this to be true as well -- every episode required pulling the gear away from the fuselage and straightening directionally. I knew it was only a matter of time before it snapped.

The wire goes from wheel to rudder and getting the rudder off is problematic -- not to mention, even once you do, getting the wire out (bent at top and bottom) is easier said than done.

After cutting the wire in-between rudder and wheel, I sourced a nice little coupler with multiple set screws, designed to go from 2mm to 3mm shafts. I drilled out both sides to accommodate the old rudder wire (2.5mm) and the newly bent tail gear wire (0.125), and installed with the original control horn.

Looks like it'll work fine. and with the hatch, at least it's accessible (if tight), should I need to re-tighten or align anything.

Nick, you're making me recall just how easy the sloper version Komet of mine was to build and fly.........

Nick, you're making me recall just how easy the sloper version Komet of mine was to build and fly.........

Ken, funny you say that -- I was thinking how fun it'd be to buy another, stick a 4s motor/esc and 3 servos it and fly it completely stock (knowing what I know now on the setup). Wouldn't look like much on the ground, but in the sky?

The new-and-improved, latest-greatest dolly should be finished today. I'm looking Tuesday morning to try it out.