n00bs Gonna Build a Carden

[rcplanefan]

Really like that rudder servo setup. Post some pictures when you get yours worked out, and finish that plane! I got mine to that stage last year at this time and then ran out of gas. Wound up finishing it 2 weeks before the Nats. Man, I should have finished it up much earlier than that.

Ken

[gareth.ky]

G10 is some serious stuff. You can't cut through it with a knife blade. A Dremel with a cutoff wheel has trouble but can get through it. If you want to cut out something like a control horn your best bet is Tungsten Carbide. Dremel makes a Tungsten Carbide scroll saw blade and that's what I used to cut out the horn out.

The PDF for the design is attached. The horn is 4 1/2" wide to match the SWB 4 1/2" straight double servo arm.

It took about 20 minutes to cut out. Dangerous dust goes everywhere, use a mask and dust collection.

This stuff doesn't have a memory like aluminum does. You would need more aluminum to make a part as strong because it would have to be thick enough to resist bending entirely.

I'm pretty sure I don't need two of these because its a push & pull and not a pull/pull linkage. If it was double trussed it would flex less. I don't think the linkage will let it flex all that much. I bet that I can't find a way to secure this thing to the rudder that is stronger than the material itself. The control horn and rudder will part ways before you could break it the horn.

I think I'll attach the horn to a piece of 1/8" aircraft ply. Epoxy the two together, filling up the holes so they are really locked. I'll use poly glue to secure it to the bottom of the rudder. I'll dig a channel under the skins for the poly glue to really lock into. Just like how I did the elevators. Sound good?

[TrojanMan]

Looks great Gareth! Keep it going you are almost there!

Jim

[gareth.ky]

	Quote: Originally Posted by TrojanMan
	Looks great Gareth! Keep it going you are almost there! Jim

You know it! I can see the finish line now so there is no getting side tracked.

I wish I could make the Nall but I have that wedding down in FL. I'm shooting to have it ready to maiden the weekend after Nall when I get back. Its the long weekend so I should be able to do a bunch of flying and get it good and broken in. The first contest we are looking at going to is the weekend after that.

[FlyguyXII]

Looks great!!!

[gareth.ky]

I get home Friday and a box from National Balsa is at my door. The wood is very nice, they sent what I ordered and its straight and light. Unfortunately it still warps a bit when cut, not as bad as the other stuff I have had but its noticeable. So I decided to just re-do the ailerons by hand.

I have been sitting on a little embarrassing secret. My left wing is warped along its length. It droops towards the wing tip. You can see it at the hinge line or looking down the length of the wing. I don't know how it got that way so I didn't really want to say anything about it. I might have put it in the shuck upside down when I sheeted it, I dont remember. It may have warped a bit when I put the trailing edge on it. I don't know.

I cut the hinge material off and put it back into the shuck and it sits perfectly in the shuck and its still warped. I flipped it over and put some weight on it and it straightened out. So I just glued the new hinge material on with the wing weighed down like that. Whatever works. Its straightened it out to the point that I can no longer see it by eye. Its at least as straight as the right wing. The trailing edge of the aileron still has a bit of a bow to it but I could cut that off and do the same thing to it.

Things are turning out much straighter this time:

This stuff just takes time to do right.

[gareth.ky]

You know what? This airplane building stuff is no fun on a deadline. Just watching yourself fail to meet the deadline is demoralizing. I do this to relax and forget about work. I would now like to quote one of my personal heroes, John Carmack:

"When It's Done"

No airplane will fly before its ready and no work leaves the shop until I'm satisfied with it. Make sure you have enough time when you start one of these things.

Control horns are in the elevators. I think these things are pretty easy to install but I'll give you the rundown...

First cut a hole in the surface down to the sheeting on the other side. Take some care that the hole is perpendicular to the hinge line and goes straight down. The control horn assembly fits flush up against the hinge stock. Use a screwdriver or something and scrape all the foam off the bottom:

Next you cut a ply block from a sheet the same thickness as the width of the the ball link your using. I had to laminate 3 sheets together to reach the right thickness for Hanger 9 ball links + the standoff. Then you shape and sand it until it fits flush to the surface like so:

I made this jig from some scrap hinge material and lite ply. It helps get the height of the control horns from the hinge line consistent. For a 35% airplane I had to cut some material off the horns so they would not go through the sheeting on the other side. Still keeping Jerry's measurements to the hinge line (Elevator = 1 3/4"). I don't see a reason for different linkage geometry on 35% vs. 40%. These horns are tall and I can't get 1:1 even with a 1 1/2 inch SWB arm. Not that I want that kind of geometry!

Tape up the control horn parts and sand them with 80 grit to give the glue something to bite on. Stick the control horns to the ply block with Epoxy. After it dries put some holes in the front, back and sides of the control horn. This will give the glue something to lock into when they are installed:

I used TOO MUCH poly glue to install these things. I filled all those holes and had to spend an hour with Q-Tips wiping the excess glue away as it foamed out. I prefer Poly glue for jobs like this where it can be mostly contained and it can penetrate the foam. All the tape helps keep the glue off the skins:

With the wings I'm probably not going to glue them in before covering. I think that was a mistake on the elevators. I'll cut the holes and make up the control horn parts before covering but glue them in afterwords. some Vaseline and tape should keep the glue off the covering. That's what you would do with an ARF and they are just in the way when covering.

[gareth.ky]

First a tip for using Forstner bits on aircraft ply. I always get tearout on the back of that part when I use them. I tried lots of stuff to eliminate it but nothing worked 100% all the time. Turns out the best thing is to drill the part from both sides. That always works and gives zero tearout. The trick is how to get the thing to drill in the exact same spot from the other side?

Well just bore down until the point of the bit just pierces through the material and stop.

Then flip the part over. See the little pinholes? Lower the running bit into the tiny hole and just hold the part very loosely. Let the drill move the part around and bit locate itself as you slowly drill down. As the outside cutter is about to make contact hold the part firmly.

Its a long description but it takes no time at all to do and works like magic:

The first tank tray I made was a copy of one of Walt's designs. It turned out to be too long and had the strap holes in the wrong place to really get a good hold of the tank. I wasted 1/2 a day on this:

The second design is simpler to make, fewer of those pesky holes (PDF plan is attached: tank tray-2.pdf). Also its got a big slot down the side to get the Velcro in the sweet spot on the tank. It could even fit something like the Tank Tourniquet. There is room to move the tank just a little to match the CG. There isn't much vertical clearance between the tank and the hatch so I opted to use the wing tube as the back support. Front supports are some square aircraft ply blocks. An I-Beam cross member is also glued in to add stiffness and keep the tray from flexing.

Few other small jobs got cleared up. Everything got a coat of polyurethane. The can tunnel floor is in. I'm going to have a section that runs up to the top of the motor box to contain any carb spray. It will also funnel more air down into the back section of the canister tunnel. I like things to be accessible to inspect and work on so for me it has to be removable.

The throttle servo is mounted in a box on the side of the motor box. Its got a straight shot linkage to the throttle. It is also on the 'wet' side of the carb spray divider, just how things worked out. I'm not sure what to use for a throttle linkage. People have suggested using threaded rod, and nyrod with ball links. I kinda favor using carbon tube (Hey, it works on foamies, why scrimp here?) but I can't find fittings to make it work. Who makes stuff like that? The throttle arm is tapped for 2-56.

Holes got cut in the fuse for servo wires and for the switches, two Fromeko Kodiak's. One thing I now appreciate about these switches; the switch is oriented vertically. I'll have one switch on either side of the airplane and this means that "Up" will always be "On". Smart, less to remember. Switches are located up front where I expect the batteries to be. The other option was way in the back but that would have been aft of the CG and required 2x the wire to make it work.

[gareth.ky]

Found one place that sells carbon fiber pushrod ends, Central Hobbies.

[why_fly_high]

	Quote: Originally Posted by gareth.ky
	Found one place that sells carbon fiber pushrod ends, Central Hobbies.

I have always used 4-40 threaded rod and gotten the carbon rod that has the right ID. Then I JB weld it in. If short leave the all thread full length. If longer I put about 3 inches in the rod. Works fine on my 40% Extra. I used them on the rudder. used ti prolinks on the other surfaces.

Dan

[gareth.ky]

	Quote: Originally Posted by why_fly_high
	I have always used 4-40 threaded rod and gotten the carbon rod that has the right ID. Then I JB weld it in. If short leave the all thread full length. If longer I put about 3 inches in the rod. Works fine on my 40% Extra. I used them on the rudder. used ti prolinks on the other surfaces. Dan

Well that sounds like that would work just fine. Who has the carbon tube around heres? Also do you bore out the throttle arm for 4-40? (The throttle arm on the DA-85 comes tapped for 2-56).

[SunDevilPilot1]

	Quote: Originally Posted by gareth.ky
	Well that sounds like that would work just fine. Who has the carbon tube around heres? Also do you bore out the throttle arm for 4-40? (The throttle arm on the DA-85 comes tapped for 2-56).

Don't bore out the throttle. Just buy the Dubro Ball Link for 4-40 Rod and a 2-56 Ball. I got mine from Tower but your LHS may have them. I also used the Central Hobbies titanium Ends with Carbon Rod for the throttle linkage on my DA50. Good Stuff.

Dubro Part # 2139 Tower # LXD916

SunDevilPilot

[gareth.ky]

Thanks SunDevil!

Dubro Swivel Ball Links 2-56 w/4-40 Hardware That's what I was looking for, the missing link. I think I got the rest figured out:

The closest carbon tube to 4-40 (.109") in inner diameter that Tower sells is 0.188" OD, 0.116" ID which is just a hair larger than 4-40 which is just fine, you need to get some JB Weld in there.

4-40 Stainless All thread, which will probably give you just as good adhesion as the titanium ends and much cheaper. Certainly wont rust.

So you can put the parts together from tower for about 11 bones including ball links. Much cheaper that the Central Hobbies option.

[why_fly_high]

Update?

Dan

[gareth.ky]

I just stepped off the airplane from a 4 day Florida vacation. So is no news good news?