doxilia

My Feedback: (3)

I thought this one might provide a little build-on inspiration... [8D]

...and it's baby sister, the CU-20.

David.

jmb52760

She would look even better inverted with the wheels tucked in!

I was wondering why the plan shows the cutout with a square corner there. I decided it must be for access to the throttle linkage. If I cut it as you say, then that would just improve the access. I'm sure that many people took liberties with the engine cutout to suit their individual equipment. In my case, that extra cut at the top is due to the rear needle of the OS. It will look out of place with the Rossi mounted.

I hadn't really thought about a statistical approach to alignment. My plan was just to "measure twice and cut once". I can see that this is going to be harder than usual due to the anhedral. I would think that you would want the wing mounted before attempting to align the stab so that you can sight it from in front and behind. The eyes can detect a very small error if you believe them.

AllTheGoodNamesAreTaken

My Feedback: (180)

David, that CU-20 is absolutely gorgeous!

Rhilluk

I agree, kinda retro meets modern styling!

doxilia

My Feedback: (3)

Mitch,

the statistical comment was actually a bit of a joke. But it does kind of work. Since no measurement is perfect (after all life is fractal ), other than the true and trusted measure twice, glue once (in this case), averaging out your measurements is a way of insuring consistency. But this makes some sense if you can measure to no better than 1/32 of an inch (~1 mm). I've yet to find a way of measuring things like that to < 1 mm accuracy. But that's just me.

Regarding the wing, absolutely! Can't mount the stab without having locked and stocked the wing and the fuse. You'll never see the anhedral drop and alignment wrt the wing. Of course, if the wing is not dead square, then, well... one ends up with a crow flying Curare!

David.

jmb52760

Stab/Elevator work...

Elevators come out SCARY thin. Do I need to glass these?

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doxilia

My Feedback: (3)

Mitch,

nice work. I like to back the TE of control surfaces with 1/8" HW - it protects these thin areas and also provides smoother response. You should still have some thickness there now that they have been cut down.

David.

jmb52760

That is a good idea, David, I think I'll do that. It would have been easier to do before sanding, but it won't be too hard.

Wings are now ready for sheeting.

AndyKunz

David's idea is a good one. I like to put 1/64" ply between the TE top and bottom. It makes a nice sharp edge possible, and is a lot stronger than balsa.

Andy

jetflyrf86

My Feedback: (31)

I have been following this built for a while and so decided to bite the bullet and get with the program. Just wanted to show you what 6 hours of shaving and sanding looked like. I filled two plastic shopping bags with balsa shavings. I spot glued the rudder on to do the assembly and then popped it off to shape and sand. I did not think mounting it permanently would be prudent as it would take a bit of fudging to fit the stab. It would also make it easier to set the incidences for the wing and stab. I am not decided ass to painting the fuse as I have no place to paint. I will say that the nose area was a bit of a challenge. I am going to make the canopy area removable.

I have set of Hobbico retracts coming and am going to set them up using one retract servo. Looking forward to flying this bird.

Hal Peters

P.S. Pardon my messy workshop

jmb52760

Looks good, Hal. Have you started the wing yet?

pimmnz

Hal, don't muck about trying to set up one retract servo, given the size, power and weight of modern retract servos it is much easier to use one in the wing and one in the fuselage. So much easier, and no real weight penalty.
Evan.

jmb52760

A stack of four identical wing sheets ready to go. Grain is parallel to the leading edge per Dave's suggestion. I think this is an excellent way to go because the wing rear spar is glued to the sheets at an angle so that the wood grain is being used more efficiently in holding the spar in place.

Each wing sheet is made of three sheets of 4 inch wide balsa glued on edge with white glue. Held together with masking tape while it dries. You learn so much by reading these build threads. I will NEVER go back to CA gluing the sheets again.

By cutting the sheets at the angle suggested by Dave, there is not much room left at the leading and trailing edge. They are just barely wide enough.

jmb52760

I think I'd better knock it of for the night. There's some sort of family thing going on upstairs.

Happy Holidays to all, and to all a good night!

jetflyrf86

My Feedback: (31)

Hi all,
I had asked Mich for a cutting plan for the skins as he was a bit behind in shipping. I did the skins and found I am about a 1/16" short at the root. I don"t know why Eureka did not suggest 3/8" stock for the foam wing leading edges, as his materials list was for the built up wing. Same for the stab. Not a big deal, but would have made it a bit simpler.

I will be using Pacer finishing resin for skinning the foam. My method is one developed by Bob Violet. I then apply it to the skins with an old credit card to remove all of the excess until there is a dull sheen all over the wood. With the removed resin(which is put back in the cup), I place a light coat on leading and trailing edges. The whole mess get stacked up and taped together and put between 2 pieces of 3/8" tempered glass and weighted down with every heavy thing I can find. Looking for about close to 100 lbs. Then let it cure overnight. So that is what works for me. I'll try to post some pics of the method.

Hal Peters

jmb52760

Hal,

Are you sheeting with the leading edge attached? I am not. I attached and shaped 3/8 inch stock to the trailing edge prior to sheeting, but left the leading edge off. As stated above, I have just barely enough width on a 12 inch wide sheet to line the leading edge up with one side.

I will glue and shape the leading edge after sheeting, I'll just use my own stock and bring the wing shape out to what the plan calls for.

I'm not sure if this is what Don had in mind, but it's working for me.

One minor problem is that because I was so marginal on width, I tried to just hit the edge of the trailing edge with the edge of the sheet. I was using a guide, but still missed it by just a hair. Since I'm using the contact cement, once it touches it's locked in place. I may have to cut the trailing edge back and re-install a 1/16 inch cap on it to bring it out to the shape on the plan. This won't be difficult at all, and will not effect the strength (in my humble opinion).

(And yes, I am building on Christmas day. I'm also cooking two ducks, which gives me plenty of time to run down to the basement and do the next step or two. Santa must not have read my list, because there was no NIB Rossi under the tree.)

Mitch

hook57

My Feedback: (21)

Dox, is that atrue"vintage" nylon prop on it? Looks like a TF, not sure,but it looks about 35 years ago familiar. It is really averysweet arss C-20.
hook

jetflyrf86

My Feedback: (31)

Are you sheeting with the leading edge attached? I am not. I attached and shaped 3/8 inch stock to the trailing edge prior to sheeting, but left the leading edge off. As stated above, I have just barely enough width on a 12 inch wide sheet to line the leading edge up with one side.

I will glue and shape the leading edge after sheeting, I'll just use my own stock and bring the wing shape out to what the plan calls for.

I'm not sure if this is what Don had in mind, but it's working for me. No attached leading edge, just trailing edge. Sorry for not clarifying the method. Just came back from a Christmas dinner at a friends house and decided to put the stabs to bed. I put my sheeting together with CA. I have used both methods (Titebond Glue). Too much taping and if you don"t keep the sheets flat it is open to have some uneven seams. I glue the one side with CA. When dry turn it over and sand the other side with a mouse type sander using 220 paper. I lay the sheets out with 2 bottoms and 2 tops so the sanded side is up. Saves a bunch of time for the final finishing. If the weather cooperates tomorrow it will be stick time. If not skinning the wings will be on the agenda.

jmb52760

Wheel well and servo cutout progress:

jmb52760

Leading edge installation. I used 3/8 inch stock for this. I'll cut this back as necessary to stay within the plan.

peterteunissen

So, forgive my ignorance, but... I'm starting work on my Eureka Curare kit, and I'm thinking about the finishing process already (like to think ahead). I'm pretty handy with Monocote and a sealing iron, but have never glassed a fuse. Thinking about it gives me visions of a big mess with epoxy (or equivalent) all over the building board, my hands, my clothes and a not-so smooth finish, which will then require lots of sanding, more spackling etc. My question is why glass a fuse at all? What's the idea behind it? Make it more durable? More stiff? Suggestions and thoughts more then welcome!

-Peter

jmb52760

An excellent question, I'd like to hear from the group on this one as well.

For sure, it adds strength, but the fuselage is surely strong enough without it. The question would be is the increase in weight justified from a performance or durability standpoint.

Aside from aesthetics, I'm hoping that glassing the fuselage will prevent much of the hangar rash that comes with transporting the aircraft.