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R/C's for the Sky Planes, Heli's, blimps, if it flies put it here!


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Old 07-21-2008, 02:54 PM
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Default Agri-Duck Build Big E-powered foam plane

Not to long after I started my big truck build Greg From http://www.mudduckaviation.com contacted me about build one of his new Agri-Duck Sport out of Fan Fold Foam also known as dow protective board or Blue Core. Well shortly after that a lot of things changed in my world and I have had a chance to get to them. I know this is mostly a scale 4x4 site but I thought you guys might get a kick out of this also so I decided to post it here for every one to see.

This is one of the Agri-duck Picture from his site. This is the full size version the one I will be building is a bit smaller and will be E-Powered not glow.



Specs for the one I am working on
Wing Span: 83"
Weight: 8-11 pounds
Airfoil: Under-cambered
Radio: 4 channel
Engine: .40 to .60 2-stroke

Like I said I have had the Agri Duck Sport plans for way to long and I should have started the build by now. I am going to be useing FFF and doing my best to keep things light. Most of my builds I tend to way over build. According to the Mud Duck Site the foam board version should be 8-11 pounds. I am going to try and keep the Blue Agri Duck Sport below 5 pounds. That means no hot glue and I may change out the wooden dowels with carbon fiber.

The Agri Duck Sport plan sheets fit perfectly on a sheet of FFF. I don't like to cut up plans so what I am doing is useing a pizza cuter to score the foam. I am just rolling it along the lines useing a straight edge. Works good for the ducks because they are straight. Now there are 3 plan's sheets so in order to build this all you need is 5 sheets of FFF because you will need 2 wings and fuse sides obviously.




First sheet of foam cut out.working on the repeat of this. This will get me both fuse sides and a few extra parts.





In the theme of light E-Power Blue Duck I am not useing the wood in the nose. I also decided to use 3/4" blue foam for the bulkhead's instead of FFF. On my last blue duck which was way over built I added extra bulkheads and stiffeners. I fill pretty sure that using the 3/4" for the bulkheads will do away with the need of the extra bulkheads aiding in keeping things light







Before I went to bed last night I glued the other fuse side onto the bulk heads. I am using gorilla glue and trying to not over do it. If things keep going like they are it might come out lighter then I had planed.

My experience with my other duck tells me that do to the drag they need a lot of pitch speed and a bit more power then a normal slow flying plane of the same weight. I am planing on some where in the 125watts per pound rang. I will be using emoli cells.

I also want a big freaking prop hanging off the front for no other reason then looks. I would like to have something in the 20" range and as close to square as I can get for the pitch speed. I very well may end up using a out runner in a gear box to get it to where I want. The duck want fly fast I dont care what you have powering it but I swear the more pitch speed you have the better it flys. I started out with around 35mph pitch speed on my other one and wound up with close to 80.


Mike

Ps still working on the truck guys I lost my card reader so all the photos I took with my phone I cant load to the computer. I will try and remember to bring the camera to the shop so I can get some pics of the paint job.
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Old 07-21-2008, 03:46 PM
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Wait, they still sell Mud-Ducks and Agri-Ducks? One of these scaled up a bit may be JUST what I've been looking for to house a 26cc Homelite!

I'm curious to see how the smaller one turns out.
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Old 07-21-2008, 04:01 PM
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Keith there still out there. I dont think you would need to scale one up. The Mud Duck mrkII would easily carry that Homelight Wing Span 108"
Wing Area 2182.4 sq. in.
Heck you could even put it in the agri-duck Wing Span 110"
The sport version is 75% the size of the mrkII and it still has a 83" wing span.
There supper easy to build and go together real fast. Talk about fun to fly.

Mike

Here is a video of my last duck. This one was not built with the plans I highly Highly recommend getting the plans and building one. They are a blast. This one has a bomb bay that holds right at 1000 paint balls and drops them controlled by a switch on my transmitter.

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Old 07-21-2008, 04:35 PM
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I sent Greg an email asking about a set of plans for the original full size one. If not, I bet the MK2 would handle the extra load just fine, but I'd prefer the larger one as I'd also load it up with various cameras transmitters and other electronics for FPV.
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Old 07-21-2008, 04:47 PM
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I am sure Greg will help you out. He is a supper nice guy. The way I understand it there is not any difference is size from the MK I and the MK II there has been some design changes and construction changes but they are both 108" wing spread and both could lift a couple of bolling balls. The MK II is what everyone calls the giant duck. The sport ducks are the ones that have a smaller wing span if you can call 83" small.


Here is the sport duck on the left and the MK II on the right
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Old 07-21-2008, 09:25 PM
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The plans call for a 3/8" light ply engine mount. I know that this part adds a lot of strength to the nose but I dont need near as much as a glow powered model would. I opted to instead laminate a piece of FFF with two pieces of 1/16" balsa useing gorilla glue. I first took a fork and perforated the FFF to allow the gorilla glow to expand and form a tight bond to both side's. On this piece I did wet both pieces of wood to really kick off the glue.





Not glued yet just a test fit.



Mike
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Old 07-21-2008, 10:02 PM
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I would stick to the lite ply for the firewall. Do you have or know what you'll be using to power this plane with? If you're going brushless then you'll need more strength than nitro, seriously. My electric .60 planes are faster and have more thrust than I did with my Saito .91 four stroke.
Also, since this is a kit, you could modify or add another firewall depending on which motor type you'll be using, in or outrunner.
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Old 07-21-2008, 10:15 PM
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drksyd I agree about electric planes having more speed and thrust then glow models. This is called the motor mount because on the glow model you are meant to cut a notch out to bolt the motor strieght to it. When converting it to e power and useing a out runner I don't plan to use it for that. It is more of a engine bay floor. I will be using ply to bolt the motor to. It will make more since in a moment with a new pic.

Mike
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Old 07-21-2008, 10:23 PM
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I gotcha. I thought that literally was going to be your motor mount.
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Old 07-21-2008, 10:45 PM
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My intention is to us the bulk head that goes behind where the glow motor would mount as the mount for the out runner. I will use the section of the floor so to speak the is covered by the nose for a battery mounting point. I will work that out more once I decide for sure what I am going to use for power. If I can keep the weight down to 5 pounds or less I figure 700 or so watts will be plenty. The trick part is finding a motor with low enough kv rating to let me turn a 20 or so inch prop at 700 watts on 5s with out needing a gear boxed out runner.





Mike
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Old 07-22-2008, 04:46 PM
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What do you guys think about a 3 or 4 blade prop?

I cant find a square enough prop in the 20" range. I have run the number on the apc 15.5x12 4 blade and the 15.75x13 3 blade and useing a motor and gear box I have on hand they both give me good thrust and pitch speed on 5s pulling 33-35 amps both getting right at 78% Efficiency.

Mike
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Old 07-22-2008, 05:37 PM
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Multi bladed props are good for speed and supposedly a two bladed prop should be the most efficient but that's not always the case. Since you're going with an undercambered wing I would suggest steering away from speed. For optimal efficiency and power a higher cell count would be the ticket. Unfortunately a higher cell count would mean a smaller prop. Sorry, but can't help you out much with an inrunner setup.
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Old 07-22-2008, 06:01 PM
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About the plywood firewall and electric vs. glow, I think the main killer with glow/gas engines is all the vibration. The vibration will kill weaker firewalls and glue joints long before raw power and thrust will!

After talking with Greg and getting some ideas, I'm probably 90% sure I'll go with the 'Duck, 10% still says 1/4 scale Cub. If I could find the Fome-Cor locally I'd be convinced!

The video sure was a help in pushing me that way! I love how slow it'll fly, reminds me of my little Slow Stick that I'm flying FPV now!
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Old 07-22-2008, 06:01 PM
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you would think wouldn't ya. The other duck I built was originally set up for about 35 mph prop speed wot. It flew like it was on the verge of stall all the time. I kept changing props until I had a quite high pitch speed and it flew much better. I cant explain it. Both of these props are specking out at low 50's on the pitch speed and well over 100oz of thrust. ether way the set up should have to power to rip the nose off it. I am just after looks more then anything else. So what do you think would look better?

Mike
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Old 07-22-2008, 06:03 PM
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Kieth you and I where typing at the same time. the best place to find foam core is a sign shop. I live in a town with a population of 10,000 and 3300 of them is in the state prison. There is sign shop here that has it in the right size and its pretty cheap. Might be worth a few calls.

about the slow flying. It's crazy to see something that big flying that dang slow. I swear if there is any head wind at all you can walk along beside it. In one part of the video you see me hanging in the air right over the tree and my wife says drop them. Well that's when I drop to bags of paint balls you cant see it on the video but you will notice the plan take off right after that. I was around a 15mph head wind the dang thing would have stay there tell the packs dump. I have flow a lot of plan's but I have never flow any thing like the duck. I will try and remember to post a pick of my twin boom slow stick when I get home.


Mike

Last edited by cars4fun2001 : 07-22-2008 at 06:14 PM.
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