n00bs Gonna Build a Carden

[whaturi]

Enough exit holes for air is crucial for good flow.

[gareth.ky]

I got the 6" by 6" square cutout from the canister for air out. I think that should do it. I really don't think I was getting enough air directly on the cylinder. So I chopped some more:

This may be loud but I have a good feeling about this.

[cgav8r]

Too funny

[gareth.ky]

I got a few flight in on Sunday. The new exhaust is loud, as expected. It not so bad in the air and the judges can hear when you are making judicious use of the throttle. That's actually an improvement over the canister where is sounded like you were a "switch" flyer.

The motor was still pinging and detonating so we tried a few things. 110 octane race gas made no difference over the 89 octane pump gas. Then we tried the timing. Big thanks to Greg and Jim on this. The timing is now retarded as far as it will go and that really seems to have cleared most of it up.

At this point it may have more power than it did on the canister. The C.G. moved a bit too far forward and I put 3/4 oz of lead on the tail wheel that seemed to get the balance back.

I'm switching over to the Red Line oil and 91 octane for the next 2 gallons. The motor was spitting out black gunk all day which I assume is the Red Line oil cleaning out the carbon left behind by the Lawn Boy.

Finally I think it needs a carb kit. Its dripping gunk on to the muffler from the carb. Where can you get a carb kit for these things?

[gareth.ky]

YouTube - Flying Some IMAC

[gareth.ky]

Did a few things for the contest this weekend.

• Put the red stripes on the rudder. I lacked the guts to try this fancy covering stuff when I started this job but now I'm getting much better. It's looking more and more like the full scale scheme which is cool.
• Sealed the reed block/carb stack with Yamabond 4. It was leaking and now its not. This Yamabond stuff is great! Its a 3M product that's re-branded by Yamaha and others (e.g. Ducatibond) for assembling engines.
• Move the CG even further back. I went back to the heavy tail tube so now I have added just over an oz to the tail and it could still go back some more. The airplane is very tolerant of minor CG changes. It doesn't want to rise in a level line and I haven't adjusted the elevator trim.
• Softened up the ailerons with some more expo and reduced rudder throw. Its much less twitchy and feels really locked in.
• Switched over to 92 octane gas + Red Line oil mixed 40:1.

I put 2 flights on it before the sun went down. It really felt great and sounded great. I have a Mejzlik 26x12 prop to play with on Friday. More pitch + less diameter == more vertical pull, more speed and less noise. Well that's what I want anyway. Quique and Reza both line this prop over the 27x12TH so that enough of an endorsement for me to give it a try.

I still need to totally mix out the Yaw -> Pitch coupling. It pretty disconcerting, you apply rudder for a turn and the plane pitches nose down. In rolls its does the same thing. Moving the CG back does not appear to have had any effect (good or bad) on this.

[whaturi]

Nice flying Gareth. The spacing of your roll elements looks good.

I didn't see you had posted that video until just now. Good luck for your contest, let us know how it goes.

[craig77]

Hi there bud!Ive been watching this thread with great interest!Ive just ordered the Carden 40% extra300 mid wing and the 35% extra 260

just need some info??.......how does the DA 85 pull the 260?I'll mainly be using mine for 3D and freestyle type flying

regards
Craig

[FlyguyXII]

Have you tried putting some baffeling in the cowel to help keep it kool?

[gareth.ky]

I think it will be a great freestyle airplane. I did some flying on the 26x12 and its much better. Much more like video's I have seen of the DA-85 powered airplanes out there. Good strong vertical, very responsive.

Unfortunately its been getting warm and feels like its sagging. I messed with the needles and tried to richen it up but there was no change. I don't see how I don't have enough area cut out of the front of the cowl. Like the Aeroworks airplanes have way less cut out than that and they fly fine. The motor is also making some funny rattling noise at full throttle. I sent the motor back to DA so we will see if they find anything. I think its like the bearings or something.

I have also been talking with Dennis and I'll be taking out the levels again to check some things on the airplane. Hes is a really helpful guy.So I'm hoping I can find some error in the build or the setup because my experience isn't jiving with his experience and the experience of other builders he has talked to. My mix percentage in yaw->roll is like 10% and it should be more like 1-2%. I need a Yaw->pitch mix and that should be almost 0. I'm just trying to find out why that is.

I'm going to be looking for surfaces not set to 0, stabs/wings not set to 0 and any up/down thrust that's in the motor mount.

[FlyguyXII]

gareth I would try taking a piece of 1/8in light ply and put it verticaly in the cowel slightly forward of the center of the cylinder head. I had a zdz80 cooled like this for a long time and never had any cooling problems.

[craig77]

thanx for that info bud!hope they sort out you DA!?I had a 50 do the same thing!it would be fine for abt5mins into the flight then just suddenly loose power!i tried everything with the cooling and nothing seemed to work!I eventually found out that the cylinder had warped due to excessive heat!this was quite pronounced in the really pink couloured head!it turned out that i was over reving the motor!it was installed in a EF 88" yak 54!she was running 7200 on a 23X8 mezlik on a mtw tuned pipe!way to much!!hope this is not your case!(ie damaged the motor in its early life)

looking forward to getting mine!