Author Topic: DO 335 ready for first flight. (Read 1489 times)

John Rist · « **on:** March 31, 2009, 05:42:01 PM »

Well the pictures tell the story. If it flys it will be fast!!!

Air Ministry . · « **Reply #1 on:** April 01, 2009, 12:12:10 AM »

Should be a rocket !
(or is that an arrow ! )

We await the flighrt report with intrest , thanks .

Mike Keville · « **Reply #2 on:** April 01, 2009, 07:42:02 AM »

If it works, bring it to Tucson, October 10-11...

John Rist · « **Reply #3 on:** April 01, 2009, 10:42:01 AM »

Quote from: Mike Keville on April 01, 2009, 07:42:02 AM

If it works, bring it to Tucson, October 10-11...

I looked on the AMA calinder for October 10-11 and did not see a Tucson listing. Whats up?

Mike Keville · « **Reply #4 on:** April 01, 2009, 09:52:26 PM »

Sanction not received yet. Look below, this section, for "3rd annual 1cc multi-engine..." yada-yada. Gives you all the info you need now.

John Rist · « **Reply #5 on:** April 06, 2009, 08:59:01 AM »

I did the engine test run Saturday. Both ran well. With two engines running I do have some vibration. Especally when I crank the back one that is driving the U-joint and shaft. I had used plastic pin henges. The vibration sheared of one of the hinges. SO I am replacing thme with sown hinges. Still hope to fly next good weather day.

PS with both engines running it pulls like crazy. It going to be fast. I made up a set of 40 ft lines to start. I also plan to use a short tank full for startest

Chris McMillin · « **Reply #6 on:** April 06, 2009, 01:45:15 PM »

John,
If you have trouble getting it to "unstick" during TO, try raising the deck angle on the ground to at least neutral. It looks like you could bend the nose wheel wire back to raise the nose.
Chris...

Paul Smith · « **Reply #7 on:** April 06, 2009, 02:01:11 PM »

Looks like a fine piece of work. I'm glad to hear you got both engines running OK.

I would like to comment that 40-foot lines are or OK for ONE healthy TeeDee .049. For two, effectively a .10, maybe 45' or 50' would be better.

John Rist · « **Reply #8 on:** April 07, 2009, 07:28:21 AM »

Quote from: Paul Smith on April 06, 2009, 02:01:11 PM

Looks like a fine piece of work. I'm glad to hear you got both engines running OK.

I would like to comment that 40-foot lines are or OK for ONE healthy TeeDee .049. For two, effectively a .10, maybe 45' or 50' would be better.

I agree. Right now I thought 40' would be a good comprise for the first flight. I will be running a short tank. If all goes well I will buy a good set of braided steel line for contest flying. Right now I plan to use spider wire for the test flight. I suspect if all goes well I will go with 50' lines. Speaking of lines, what is the advantage/disadvantave of solid verses stranded steel lines?

Paul Smith · « **Reply #9 on:** April 07, 2009, 12:04:38 PM »

Solid lines are a pain to work with because one kink ruins them. 7-strand is more flexible and user-friendly.

However, 7-strand lines are 30% air, so you would need an .012" 7-strand to safely fly your plane, or .010" solid steel. So the the solid line would have bit less drag. If your are serious about your score in speed or racing, solid is the way to go. For sport, stunt, or scale, use 7-strand.

1/2A combat used to be flown on .012" x 35" stranded, but stronger engines made the length increase to 42'. So with TWO TeeDee's, I would want something MORE than .012" x 42'. With the amount of work in your plane, don't lose it to substandard lines. I would pull 15 pounds if it were mine.

Trostle · « **Reply #10 on:** April 07, 2009, 01:11:23 PM »

As has been mentioned here before to you. 40 foot lines will screw you into the ground even if you could keep up with it. 45 foot lines would be the absolute minimum. 50 foot lines would not be too long. Maybe something between 45 and 50 feet, you might be able to keep up with it. And there is nothing that says you have to peak those engines on the ground before the release.

This is something that Paul and I agree on. Use .012 cables. The length should be at least 45 feet to approaching 50 feet. On the release, be prepared to "lead" the model by keeping the handle well in front of the wing LE. This is a bit hrd to explain, but you need to lead the model on take off by sort of walking and pulling the model forwarward in a sort of whipping action. Your push/pull engines will negate the tendency for the model to torque into the center of the circle on release, but you have the inertia of the lines wanting to make the airplane to turn in. Once it has started to roll, and if you still have it at the end of the lines, it will literally want to jumb off of the ground, particularly with the long nose gear strut on the thing. In other words, when the model is realesed, things will happen really quick. Your rmodel is not much bigger than a 1/2A proto speed ship and you have twice the power. And those things, with the right engine prop and fuel, will go over 100 mph in a 1/2 mile from a standing start. You will not have the props or fuel to go that fast, but it will be really quick. Be prepared.

Keith

John Rist · « **Reply #11 on:** April 07, 2009, 03:37:02 PM »

Quote from: Trostle on April 07, 2009, 01:11:23 PM

As has been mentioned here before to you. 40 foot lines will screw you into the ground even if you could keep up with it. 45 foot lines would be the absolute minimum. 50 foot lines would not be too long. Maybe something between 45 and 50 feet, you might be able to keep up with it. And there is nothing that says you have to peak those engines on the ground before the release.

This is something that Paul and I agree on. Use .012 cables. The length should be at least 45 feet to approaching 50 feet. On the release, be prepared to "lead" the model by keeping the handle well in front of the wing LE. This is a bit hrd to explain, but you need to lead the model on take off by sort of walking and pulling the model forwarward in a sort of whipping action. Your push/pull engines will negate the tendency for the model to torque into the center of the circle on release, but you have the inertia of the lines wanting to make the airplane to turn in. Once it has started to roll, and if you still have it at the end of the lines, it will literally want to jumb off of the ground, particularly with the long nose gear strut on the thing. In other words, when the model is realesed, things will happen really quick. Your rmodel is not much bigger than a 1/2A proto speed ship and you have twice the power. And those things, with the right engine prop and fuel, will go over 100 mph in a 1/2 mile from a standing start. You will not have the props or fuel to go that fast, but it will be really quick. Be prepared.

Keith

Keith,

Thanks (I think)! I do understand the leading and whipping the lines to get them moving. Had not thought about it before but I do understand. If my math is correct 60 mph gives 3 sec lap time on 40 ft lines. I may be wrong but I would be surprised if she will do 60. It has lots of drag and I am running 10% nitro. So far all of engine test have been on the rich side. Of course they will lean out in the air. Some have suggested to put the rear prop on backwards to kill some of its pull. Not sure of this but it is a thought. For sure - first run will be a very short fill of the tank.

wwwarbird · « **Reply #12 on:** April 10, 2009, 06:28:02 PM »

John,

Looks pretty cool but I'll strongly second Keith's comments, it's gonna be REAL fast so be ready. What you have built here is basically a small motor holder for TWO Tee Dee's. With the size of the model you have it would be pretty fast even with one engine. I said somewhere in a earlier post on this model that it would be almost as fast as a bottle rocket, not quite, but close! I'm sticking with that opinion. Have fun with it and keeps us posted!

John Rist · « **Reply #13 on:** April 11, 2009, 12:54:50 PM »

Well the last of the mods/fixes are done on the DO 335. I did the final engine test run today and all is ready for a less windy day test flight next week. wwwarbird they may look like Tee Dees but in truth they are just Tee Dees in drag. Both have Sure Start position and cylinders installed. The rear one has a LH Medallion crank installed. I am swinging 5Dx3P 3 bladed props. I am using a 10% caster/synthetic blend. I put the tack on them today. They are turnind 17,000 to 19,000 rpm not the 25,000 to 50,000 rpm a TD should turn. Besides she is a lead sled with landing gears hanging out all over the place. My best guess is 60 MPH at 3 second laps. If its more than that Heaven help me because I am old and slow. Any way, Happy Easter to all - I will report first flight.

wwwarbird · « **Reply #14 on:** April 11, 2009, 05:05:48 PM »

Okee-Dokee.

Allen Goff · « **Reply #15 on:** April 12, 2009, 06:56:37 AM »

Good looken ship John.

Happy Easter.
Allen

john e. holliday · « **Reply #16 on:** May 05, 2009, 05:37:43 PM »

That looks like quite an under taking. Has the test flights been made yet? First flights could be done with one engine just to see if it flies. Thats where the shorter lines come into effect. Hope it flies as well as it looks. DOC Holliday

jim gilmore · « **Reply #17 on:** May 06, 2009, 12:04:38 AM »

Personally i'd use a 5.5/2 for the props.

John Rist · « **Reply #18 on:** May 06, 2009, 08:50:12 AM »

Well we had a brief break in the weather yesterday. No rain and no wind. (Today we are back to flood watches). So I finally put the first flight on the DO335. I have a paved parking lot behind work to fly off from. I went through the normal dum tricks to get the engines started. The procedure I use is to start the front engine ans set its NVA to the rich side of lean. Ithen stop it by pinching the fuel line. I then start the rear engine and set it's NVA. A bump with the starter on the front and she is ready to go. Well I did all this but the front engine would not restart. I was running low on fuel so I shut down the rear engine. Well as always it was my error. The electric starter has a reversing switch. When I went from rear start to front start I forgot to flip the switch and I was cranking the front engine backwards. Refueled the tank and this time both started right away. My helper set the DO335 on the runway and let her go. She has a rather small rather thin wing so it takes some speed to get airborne. Acceleration is quite good and she lifted, very smoothly, after a 1/2 lap of taxeying. Flight was smooth, level, and very controlable. Nothing twitchey. Speed was good. I didn't time it but lap times seemed to around 3 second or so on the 40' lines. I lost count but at 15 to 18 laps the rear engine quit. At this point in time it took a noise up angle of attack to keep her airborne. I did a couple of touch and goes trying to check out the single engine flight performance. I finally bumped the prop on one of the touches and the flight was over. By the way line pull was good throughout the flight.
What I learned: 1) She flies great. 2) Speed is about right but I will go to 45' lines. 3) I need to set the front NVA a little leaner to improve single engine performance. 4) I plan one more test flight and I will put her up until contest time.

Mike Keville · « **Reply #19 on:** May 06, 2009, 05:30:37 PM »

Planning to bring it to Tucson in October for our 3rd annual 1/2A multi-engine profile scale gathering?

john e. holliday · « **Reply #20 on:** May 07, 2009, 05:56:33 PM »

That is great news. If you take it to Arizona beware as you may not want to come home. Everytime I go out there the mountains just facinate me. DOC Holliday

John Rist · « **Reply #21 on:** May 08, 2009, 08:23:55 PM »

Quote from: Mike Keville on May 06, 2009, 05:30:37 PM

Planning to bring it to Tucson in October for our 3rd annual 1/2A multi-engine profile scale gathering?

I'am thinking about it. Only one small problem. $$$$ Driving distance to Tucson, AZ from Huntsville AL
1,686 mi – Driving time one way 24 howers. This makes it a 6 to 8 day trip for a one day contest. But I am thinking about it

Air Ministry . · « **Reply #22 on:** May 19, 2009, 02:59:27 AM »

20$% nitro and more pitch on the back prop ! ( just kidding ) but wouldnt slow it down .