John Hawkins

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Emily was the Allied code name for the four engine WWII Japanese flying boat Kawnishi H8K. The model spans 124" and weighs 31 pounds dry. Power comes from four OS52s four strokes. I started this project in 2004 and sometimes wondered if it would ever get to fly. It finally did on July 4th. The flight went very well with the guesstimated trims being pretty well right on except for a minor bit of down elevator being needed. Links with pictures and videos are on my web page at the upper left [link=http://rcalbum.machawk.net/]web page here[/link]

mogman

Congratulations on a great maiden. Looks fantastis, well worth the time and effort. Great videos!
Cheers, Dave.

happypappy

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Incredible airplane..........well worth the effort and flies so beautifully and looks real !

John Hawkins

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Thanks guys. During construction I sometimes wondered about the wisdom of getting into the project but I'm glad I did now that it's done. I say 'done' but a truly scale guy would be just looking at the beginning. ;-)

Newc

Great looking plane and videos!! I can only hope for the type of wind and water conditions you had when I have the maiden flights on my 104" PBN Nomad in a month or so!

I notice that the water handling is very good, including very little water spray from the hull. Did you install a spray (splash) rail, or is that due entirely to the hull design? After seeing videos of some Nomads (from the same kit supplier, G&P Sales) with spray getting to the props I have installed a 1/4" wide rail from the bow to just past the prop area in hopes that this reduces/eliminates the spray issues.

John Hawkins

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I was very surprised and happy with the spray control. At least in those water conditions none was thrown into the props at all. Although there are spray rails it doesn't appear that they come much into effect except in the very first moments of acceleration and then the hull quickly gets on plane. The minimum spray that there is, is well directed away from where it would cause problems. The hull is deep and narrow compared to other flying boats. It is built to scale. I added spray rails in front on the outside edges of the hull. The first built Emilys didn't have them but they were added later and were located somewhat inboard from the hull edge. As you can see in the slow motion shots spray is equally well controlled on landing.

I built an 89" Grumman Albatross which was basically scaled up from the G&P Sales model. While I have only the experience of the maiden flights on the Emily it's water handling is vastly superior. The Albatross pushes up a considerable nose wave and plows into the water at slow speed until it gets on step. It is relatively stubby compared with the Emily and pitching in waves can be problematic probably because of that (and its displacement). If you don't get the landings right things can get ugly. I found with the Emily that if you keep it level until the speed drops off it pretty much lands itself. There is a bounce in the video when my buddy was flying while I shot video where the approach was wrong but even so the plane was very forgiving.

The water near shore in the Emily video is calm but it is in the lee of the bar behind and there is actually a mild cross wind. We weren't able to control the weathercocking very well on takeoff but that may come with practice. The crosswind landings were no problem but the lee wing quickly settled on the wing float. Their size and angle works well too come to mention it. Looking back at an Albatross video I see that they plow. They need more displacement and should be angled up more to keep that from happening IMHO.

Good luck on the Nomad. It would be great to see videos of it when the maiden flight happens.

Oregon Craig

I'm not a scale guy, but I can certainly apprecite it. Extremely cool!
And MAN-O-MAN does it ever sound nice!

Kmot

My Feedback: (24)

That is one of the most incredible r/c models I have seen! [sm=thumbup.gif]

bigR

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John,

That is a very impressive plane. This is the first R/C Emily model I have heard of. As luck would have it, I was in the process of designing an Emily, but on a smaller scale. Now I won't be the first. []

I was going to use Ivan Pettrigrrew's Solent as a departure point. About 6 feet, span, electric powered. Already have the power system figured out. Just needed the fuselage sections to start drawing. I had no luck in obtaining a plastic model either. Thanks to your small 3 view on the website I think I can rough out some plans.

How are you steering the flying boat on the water? Do you use differential thrust or a water rudder or both? With an electric plane it is easy to mix the rudder and throttle signals into the speed controls. One would want to turn the mixing off for flight to avoid "Turning into the dead engine." Ivan used IIRC, microswitches on the rudder servo's extreme limits to shut off the outboard motor on the side he was turning into.

A great accomplishment. Now I'm inspired!

John in Kalifornia

John Hawkins

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Sorry for the preemption. I can send you the CAD drawing in the DeltaCad format as well as .dwg, .dxf or .dxb reduced in scale to six feet. I draw in metric even though I grew up with Imperial. It's easier.
Here are the formers:


Does the 'upload file' thing here actually work? If so there is something I am missing.

bigR

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That's great! Thanks. I am using Coreldraw 3 but am trying to upgrade to a later version. I would guess dxf or dwg would work. I can take fairly large files in hotmail. I'll contact you offline if you wish. I'm at [email protected]

John in Kalifornia

John Hawkins

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Reduced to six feet but those scaled down engines might be hard to come by. It's on its way.

John Hawkins

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I forgot to reply to the steering question. Differential throttle was considered but then the KISS principle kicked in and I used a water rudder. In the conditions on the day we test flew it the rudder was effective and all that was needed. Whether that holds true in wind and wave will have to be found out. A friend made an electronic PIC control but there were problems with it. Another fellow was working on a more sophisticated one but got sidelined. I could use my transmitter's programmable functions but unless there is a problem I will stick with the rudder. I don't remember the mixes contemplated but it involved mixing rudder with opposite engine controls (different engine channels on each side) and having it kick in/out on throttle position. I remember seeing this dealt with on a site for Futaba programming but maybe it was momentary switch activated. A person would want to be sure that it didn't kick in at the wrong time. To me I would like to have something activated by a momentary switch. If that were the trainer switch you wouldn't hit it accidentally. In fact maybe it could be made to work safely that way. I don't think I would ever pull that switch by accident. Hey, maybe that's a good idea - mix rudder to opposite engine and activate with the trainer switch.

bigR

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John,

I was thinking along the same lines. The newer computer radios enable you to mix any channel to another and switch the mix on and off. Since I have a number of older, reliable non computer radios, I was thinking of another way to selectively mix or not mix the throttles with the rudder. Use an elevon mixer to combine the rudder and throttle functions. The trainer switch sounds like a good idea but then you have to hold it with one hand while steering with the other. Since the trainer switch is usually on the left side, and the rudder and throttles are also this could make for awkward contortions.

The retract switch could be used to switch the mix on and off. Gear down, mix on, in the air no mix. If I get the time I will breadboard a circuit to do the on/off mixing function. Would take a couple of IC's and a few resistors, caps, etc. I design electronic stuff also. Too many hobbies....

OTOH, maybe I could save this for later in the year and just buy a new radio. Really want to get to building that Emily. Should I start a new thread? This one is for YOUR plane, which is really a great accomplishment.

Already went to the local 99 cent discount store and bought a jar of mayo for the plastic container. I compared the diameter with that of the cowls on the plans John sent me. Both were about 2.8 inches. The 7-inch 3-bladed prop looks good with enough blade area outside the cowl to be effective. This dimension is close to the plans also. Don't know about the mayo, some off brand. Hope it doesn't clog the plumbing.

John in Kalifornia

John Hawkins

My Feedback: (2)

I would definitely look for low fat mayo to keep the weight build up to a minimum.
Now that I think of it the mixer that was given to me used the retract switch to activate it. There is a commercial one available but I forget who makes it.

Did the plan translate ok to dxf? I forgot that there was a bmp picture in there on a layer assuming the dxf conversion saved it. This was a scan from the datafile book on the Emily.

bigR

My Feedback: (2)

If you could find the name of that mixer it would save me some time building my own. Not that I don't enjoy designing circuits but why reinvent the wheel?

The plans came through fine after I unzipped the file, downloaded the demo CAD program, installed it and imported the dxf file. I then saved it as a DeltaCad file.

It's going to take me a while to learn this program, but it must be easier than AutoCad, which I never was able to get very good at. I'm an old DOS guy but the mouse-directed drawing programs are so much easier to use than that command line stuff. I notice that there are some cheaper shareware versions of DeltaCad on the 'net but I would just as soon pay for the latest "professional" version to make sure it is all up to date.

Think I've talked my wife into buying a new computer. She is frustrated that she can't watch videos on the Internet. The combination of Windows 98, Firefox Mozilla and an old slow computer with a short memory isn't the best for video streaming.

John Hawkins

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Eight flights in now. A few pictures:








There is a [link=http://rcalbum.machawk.net/]video and slide show [/link]of the day's flying on my web page. The links are at the upper right hand side

Kmot

My Feedback: (24)

That is such a magnificent plane. [sm=thumbup.gif]

I bet there are some wealthy Japanese gentlemen who would pay to see that fly in Japan.

r_kopka

[link=http://www.rc-wasserflug.de/Forum.php?OTMP=/topic%3D101277469291]in German[/link]

RK

dutch Jan Hermkens

Hello John,

congratulations with your succesfull maidenflight!
As it looks on the videofilm, the 4x 0.52 Osmax four-stroke, as I calculated for you, did not have any problem with the model.

cheers,

Jan from the Netherlands.

John Hawkins

My Feedback: (2)

Jan, yes, lots of power form the 52s. When I bought my first one some years ago to replace a Magnum 45 I found the power less than what I had hoped for but then as it broke in things improved. Another factor in its performance has been fuel choice. I was skeptical if changing from 10% to 15% nitro would make any difference, not having seen any of significance in two strokes, but it sure did although I don't have objective observations to prove it.

It would be interesting to start only two engines and see if the thing would fly.

g_boxwood

John, your model is wonderful!

Not only she looks and flies great but you built her in a record-setting time! Marvelous job!

I'm interested in the water steering/rudder issue as well, as I'm about to decide wheter or not I will install one in my 86" Canadair.

What's the best place for the water-rudder? Any size reccomendation? How did you waterpoof the bushing? What kind of linkage did you use?

Thanks in advance for the replies, and keep up the very good work!

John Hawkins

My Feedback: (2)

Thanks for the thumbs up.

Initially I considered differential throttle for water steering but then decided to go with the simpler route of a water rudder. The full scalel had an extension at the second step to help water handling and it looked like a good place to fit in a rudder instead so that decision was easy. Any farther back and it would be out of the water when you needed it although the farther back the more effective it would be.

I'll include some pictures of the mechanical part of it. Basically it consists of a brass tube with another brass tube inside it to both form a bushing and a water seal. The inner tube then has a steel rod inside of it which is the shaft. A steel rod inside a brass tube would soon rust and seize so hence the two brass tubes.

Missing in the drawing is another coller on the inner shaft to keep it from dropping. In the picture the inner brass tube as shown has to be cut off.

Newc

For what it's worth, for my 104" PBN Nomad I'm using a similar water rudder set up as for the Emily with a couple of changes. My shaft is brass and the tube through which it goes is aluminum, with the boottom of the tube flaired. Then I have 'O' rings above and below the tube (the bottom one fits well inside the flair of the tube), on the shaft. Along with a small amount of grease on the shaft, I don't expect any problems.

g_boxwood

Very good point! I attached a picture in my thread (2nd page, last message): could you answer there? I don't want to contaminate your thread...

http://www.rcuniverse.com/forum/m_44..._2/key_/tm.htm

Thank you,