Mud Duck Aviation Forums

I've just ordered the plans for the Agri-duck and they are on there way as I type! 

I plan to modify the tail to a conventional versus the T tail.  I'm going to shape it some what similar to a Piper Pawnee style tail.  I'm also going to do a dusting hopper but with the spreader attachment instead of just a tube on the bottom of the fuse.

I'm also going to do a pull-pull setup for the rudder.  Still thinking of how I'd like to hinge the rudder.  I've thinking of making a piano style hinge made from carbon tubes if I don't use hinge points.

So far I have an O.S. .91 four stroke for power.  I hope it'll be enough.

I'm looking forward to building and flying this plane.. err.. duck!  Now if I can only decide on a yellow or a white based color scheme!

Welcome to the club of "Duck" lovers! 

As I replied to your post on RCGroups regarding the change in the tail configuration...
(http://www.rcgroups.com/forums/showthread.php?t=1072934&page=3)
I think you will be okay with that mod on the Agri-Duck, I just want to point out to (high-wing) Mud Duck owners that read this, the physics why I discourage doing it on the high-wing versions (please read my post on RCG; link above).

As for the hinging; you can choose to hinge the rudder (or any control surface for that matter) in any fashion you prefer but you will need to take additional steps depending on which surface and the type of hinge.  The rudder is made from 1/8" balsa sheet whichdoesn't leave you much extra material to sink "pin" style hinges and you run the risk of them tearing through the side of the rudder.  You would, at the least, need to add a hard-balsa or hardwood leading edge strip to the rudder to give the hinges something solid to hold onto.  As for the trailing edge of the vertical stab; it is already a hardwood dowel in its stock configuration so that doesn't require an extra step.  All the other surfaces other than the rudder do not require hard-point material on the main surface's trailing edge or the control surface's leading edge if you use the tape hinging method, but if you use any traditional style hinge in place of the tape in those locations you will need to add a cap strip to the surfaces to give a good solid anchor for the hinges.  I have seen the result of some builders just trying to sink some traditional hinges into the foamboard without using a hard point and it doesn't hold up very long.

Just a note about the tape hinges... I have not heard any complaints about them or the longevity of them from any customers.  So since they have been in service for up to 15 years on some Ducks that are still flying, I'd say builders have little to worry about with them.  They provide much more surface contact area and hinge area that traditional; they are naturally "gap-sealing", they are extremely inexpensive; and they are extremely quick to install.  Some builders can not get comfortable with the thought of a clear packing tape hinge, so here is a compromise that will keep all the benefits plus make it even stronger at the cost of appearances:  instead of using clear packing tape use 3M "Extreme" packaging tape (http://www.staples.com/Scotch-Extreme-Application-Packaging-Tape-w-Dispenser-Clear-2-x-22-yds/product_448960?cmArea=SEARCH); it is interwoven strapping tape that also has a super sticky adhesive.  It shows up where the clear tape will not, but it gives an "albino carbon-fiber" look if that sounds appealing .

Regarding your engine selection; The Agri-Duck requires more power than the Mud Duck MkII to achieve the same performance level.  The OS .19 will fly the Agri-Duck around but I think you will enjoy the plane much better with a more powerful engine.  The nose can take the weight and extra power so even if you have an old gasser laying around that may be weak in regards to power-to-weight ratio, it is right at home on a Duck's nose (or should I say "bill").  have seen Agri-Ducks flying on everything from .91 four-strokes to 40cc gas engines and everything in between without any major modifications (other than a vertical firewall for the radial mounted gassers).  At the most extreme end of what an Agri-Duck is capable of flying on is a customer named Leo's Agri-Duck that he has repetitively modified and constantly tweaking.  Leo's  Duck's weight kept creeping up more and more until it required a larger engine (originally Moki (gas-converted)  powered) he adapted a 4-stroke 80+cc gas engine to it and the all-up-weight is now over 40 pounds and still flying: htttp://www.youtube.com/user/puchmanlenny#p/u/48/bw31WOIHIMo
http://www.youtube.com/user/puchmanlenny#p/u/49/khU83OFh2GM

Greg

Thanks for the plans Greg!  I received them Saturday!  Very quick shipping!

Thanks for the comments on the hinging and engine selection.  I planned on the .91 because it is what I have on hand.  I'll check and see of I can find anything a little more powerful for a decent price. 

As for the hinging I may just end up doing the some simple CA hinges for the rudder.  I've got some foam safe CA lying around. 

The tape hinges I've never had a problem with.  I've been using them on my electric foamies for quite a while now.

Now I need to go purchase the foam board, finish the foam Fokker Dr1 triplane and clean off the building table.  Then I can start on the Duck.

I found a good deal on a 26cc gasser.  I guess I won't have to worry too much about the paint job with this.  Just got to make sure I fuel proof anywhere raw gasoline may get.  Gas really has an appetite for foam!   Maybe a little thinned epoxy resin where the fuel tank will go on the inside and some around the motor mount area.

The 26cc should be just about the perfect engine for this plane.  Not overpowered and not underpowered!

Right now I think I have decided on a yellow plane with red trim and a semi gloss black on the top of the fuse in front of the cockpit.


I can't wait to get started on this plane!
 

You're right; the 26cc gasser should work nicely on the Agri-Duck if the engine is purpose-designed as an airplane engine specifically (e.g. Zenoah G-26, SPE, MVVS, 3W, DA, Chinese knock-off, etc.). 

If you are referring to a converted McCulloch chainsaw engine or the sort, it may be marginal (based on reports from another customer).  If going the "converted" engine route I would suggest at least 30cc's.

It sounds like you are planning it out real well and I appreciate your enthusiasm for the project.

Thanks again,
Greg

Yes it is a purpose built plane engine.  It's an RCGF 26 cc.  So it's not too heavy and underpowered such as a converted engine.  Of course I sort of regret not buying that converted 35cc engine that was going for $40.00 at the swapmeet this past weekend.  OK I don't regret it all that much considering I would have still needed to buy the ignition.

That should be a nice fit.  You will just need to make a vertical firewall for radial mounting.  Simply cut off the "chin" that the stock mount is installed on and add a 3/8" (or lighter if the engine recommends) light ply firwall.


Yeah I've had one or two of them sitting around... with a universal ignition running over $150 typically (back then anyway) it doesn't make sense when for almost the same money you can have a new purpose built engine.

Just received the 26cc engine the other day.  it looks great and is lighter than I thought it would be. Now to finish up the current project on the table, buy some foam board, and start cutting.

Great!  I'm looking forward to progress reports once the build gets underway!

Greg

I'm plannin on buying a Weed Eater engine at my Wal-Mart sometime this summer.  So far they seem to be the best bang for your buck.  Buy a Weed Eater and junk everything but the engine.  $80 bucks can get me atleast a 26cc engine brand new.

Matt,

  A word of caution here, Unless you have converted a weedwacker engine before or have the help of friends with a lathe ect, there is a fair amount of legwork to be done, it's not just a "scrap the wacker" and bolt it onto the plane kind of thing.  I only point this out because you mentioned previously you were having trouble bending the landing gear wire because you didn't have a vise; you will need a vise at the very least to convert this engine.  It is pretty easy for a seasoned machinist or someone who works a lot on fabricating stuff, but for the uninitiated it is a daunting task that may give up on and $80 is a lot to invest without following through, which brings me to the next point.  The conversion will also require you to purchase a few aftermarket parts (flywheel hub, etc.) unless you have a friend with a lathe and the correct materials to make the parts for you. Most people also remove the magneto system and install an electronic ignition system (another $80-$120) because it is cleaner, lighter, and more power.  If you keep the magneto system for the ignition you will need to cut new "keyways" into the flywheel (as well as have the "fins" machined down) so that way you can change the timing of the ignition to provide you with the right timing to give you the power to swing the prop at the right rpms.

  When all is said and done, you will still be spending over $100+ to get that engine "flyable".  There are plenty of small (15cc-26cc) Chinese gas engines brand new out there for very cheap and it won't take you weeks/months and tons of aggravation to get in the air.  I have converted engines but I have a garage full of tools and equipment to do it with and except for the satisfaction to say I did it and experience the challenge of it, it is not worth the hassle and I only buy engines now.  I would keep an eye on the classifieds on RCU, RCG, and Flying Giants... I bet you can get your hands on a low-time used 26cc engine for nearly what it will cost you to convert, and whats better is that it is a sure thing.

Good Luck,
Greg

Matthew, if you haven't gotten around to the hinging yet here's another type to consider.
It's how I did the rudder on my War-Duck. Used a line similar to how it's done on some real birds.

After running a 1/8" CF tube down the hinge line, between the outer sheets, mark the hinge line then make the staggered cuts. This gives you approx 1/2" of foam for the hinge to work against, along with the outer sheets on the sides. After you make the cut, do a second one to the outer edges on each part, maybe 1/16". This allows the rudder to pivot without rubbing the V stabilizer.

I sharpen the end of the CF rod and using a hand drill,just guide it by eye to run it through the foam.
If for some reason you need to pull the rudder, all you have to do is slip out the rod. I use a dab of glue on each end just as a safety factor, but I really doubt the rod will come out as the foam swells up against it after it's installed.

I would have used the same on the elevator if I had thought of it earlier, as is I went with the tape. It's held up for going on 3 years now on my first Duck.

Oh two other things. One is definitely the Duck way of doing things. Greg will get a kick out of this.

I went with flying wires on the tail to add strength instead of the "normal" rod set up. Knew the foam itself wouldn't be strong enough for the wires to pull against. Looking around the shop I spied the knock outs for the hubs on the wheels.  I'm a bit on the anal side and tend to save all those little scraps for use "someday".

Well I still had the four from the first Duck too. Picked out 6 of them, drilled a hole for the wire retaining bolt to go through, and epoxied them in place.  Perfect and done the Duck way!!!!


Second one, and you are only the second person to know of this, as one it's a surprise to my flying buddies, and two as it kinda relates to dusting.


You know how when those WWII birds would first fire up there would be that big cloud of smoke from the rich setting used to start em?    Well since I had built a Fighter version of the Duck, one thing led to another and I thought "How cool would it be to have this bird replicate this on start up?"

I had a big old empty chin intake I had added to the nose, and I left the rear open to exhaust any air pushed in the front.   Next I had to come up with something to use for the cloud of smoke. Since it was to be exhaust flow it had to be dirty, so anything white was out. While racking my brains, the wife tells me she wants to cook on the grill so would I PLEASE clean it out.

BINGO!!!!! there it was! The remains of the last charcoal fire. Dirty sooty charcoal dust.

After fulfilling my grill duties, it was off to the shop with a container of dust..........er smoke.

Dabbed about a teaspoon of the magic smoke in the rear of the intake. Hooked up the pack, and fired up the motor.


IT WORKED LIKE A CHARM!!!!!!! Little puff of smoke, and then as the prop wound up, I got a nice billowing cloud of dirty gray smoke exiting the exhaust and blowing back under the plane. 

I was giggling like a little girl seeing it in action. And then the thought of surprising the guys at the field with it hit me.    Going to blow their minds when it fires up to a cloud of smoke and then just like the real ones, cleans up and powers off into the air.

That start up trick sounds great!  You will have to get that on video as well one day!  First retracts, now "rich" smoke on an electric, whats next? Functioning wing mounted paintball machine guns? 

Uh Oh, did I just plant a seed?