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Nov 27, 2010, 11:14 AM
Derek_S's Avatar
No, I left it out. it is much easier to build wings without it

It is a funny thing, as I am very hesitant about rudder only aircraft. I was trained from the get-go with ailerons, and have never liked the idea of losing that extra control. I am what they call a bank-and-yank guy, as I have no flying finesse. If I have a rudder on a 4ch airplane, I rarely use it once I am off the ground. Bad habit I guess. Ans since ailerons work a bit better without dihedral, I left it out.

However, I recently got an Easy Star, and have been learning the merits of RET flight.

Anyways, with dihedral the wind is a bigger pain than it already is, and unfortunatly in Georgia the best time of year for me to fly is Fall. It is a bit breezy near the foothills, so I lest the dihedral out.

In retrospect, this plane would probably make a great RET plane. Had I to do it again I might have added the dihedral. Actually, i still could in the future as I am now wishing I had made the wingtips removeable for easier transport, and if I cut them off to revamp I could change all that. I guess I will decided that later, but for now I am pretty happy with how she flew, and I think with some with rudder "cheat" mixing with ailerons I will love it.
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Nov 27, 2010, 11:29 AM
Derek_S's Avatar
Forgot to mention that she weighs 40.2 oz AUW with one 2200mah battery. This means that with wing area of 510 sqin she has a loading of .078 oz/ or 11.3 oz/sq.ft. Not bad.. She could probably lift a nice payload. and, I used heavier motors than some. I may size them down some.
Nov 28, 2010, 09:31 AM
Derek_S's Avatar
Nice drawing. So that is the nose gear? I was planning on a taildragger setup more like the goose, so I have not thought through a nose gear. I would prefer it, but I think for me a free-castering tail wheel will be the easy way out.

Also, i was thinking that if you replaced the wing floats with sponsons on the fuse side, you could do a retract setup similar to the Icon A5. Somewhere someone did this (and warhead71 proposed it on his Drake seaplane) but i cannot find the thread where it was prototyped. It seems mechanically more simple, and uses conventionally available parts instead of one-off custom stuff.

the sponson could easily have a well that accomodates the concealment of the retracted gear, plus the outriggers could go away, if desired.

Here is the jist of it. More can be found on the thread.
Nov 28, 2010, 12:01 PM
Registered User
mavlo77's Avatar
Yes that is the front gear. But I like your idea about the main gear. It is simple, and that normally means that it is strong.

But I suspect the downside of these sponsons is that -if these are the only floats- the aircraft will easily flip over in crosswind conditions. So maybe it's an idea to combine them with the tip floats. But they must be quite large to hold the 60 mm (2.4") wheels. Certainly will create quite some extra drag.

Another idea is, integrating the main gear in the wing (for your taildragger not really an option). Then I should extend the motor nacelles to the trailing edge, and fold the gear like a Fokker F50. Check:

Avianca Bogota take off (2 min 11 sec)
Nov 28, 2010, 01:30 PM
Derek_S's Avatar
Its funny you post that because I had thought about the exact same thing. I sat with a pair of mechanical retracts trying to figure out if they could tuck into the nacelle but I could not figure out how to tuck all that length. the gear has to be sooooo long to get good bottom clearance.

Alternatively the wheels could just retract outward or inward (180 degrees to teh fuse direction) like WWII warbird style but again the gear has to be so long to get below the hull.
Nov 28, 2010, 02:48 PM
Registered User
mavlo77's Avatar
Originally Posted by Derek_S View Post
Its funny you post that because I had thought about the exact same thing. I sat with a pair of mechanical retracts trying to figure out if they could tuck into the nacelle but I could not figure out how to tuck all that length. the gear has to be sooooo long to get good bottom clearance.

Alternatively the wheels could just retract outward or inward (180 degrees to teh fuse direction) like WWII warbird style but again the gear has to be so long to get below the hull.
Yes, I know what you mean. Long.... About 20 cm's (or 7 to 8") yes. An aluminum tube can be good for this. And a diagonal support link is needed. But then all the forces will try to twist the wing... I think this is only an option if the wheels have spring suspension.

One option left. A combination of what you showed (rotating wheels in the fuse), but also move them in and out of the fuse using concentric tubes. That means that for extenting the wheels, one servo should first extend the wheels while in the up-position, and then activate a micro-switch to allow another servo to rotate them 180 degrees. And retracting is the other way around. But many parts, switches, not sure if this is practical.....

I keep thinking while finishing the front wheel first... Will take a while, so I have some time . BTW I don't forget about the pictures and video's... Will be posted, for sure. But I just want to finish it a bit more so I can better show the complete construction.
Nov 28, 2010, 05:52 PM
Derek_S's Avatar
Seemingly good news: I was afraid that the plywood that I did the mockup with would not work in use, so I was seeking alternative means. After banging my head trying to figure out a suitable and easy way out.

So I decided to put the ply to the test. I soaked it in water for about 2 hours and pulled it out. It seemed very solid! I am very happy. It did swell just a little, but operated just fine. I may have not said before, but it is a pretty solid feeling setup, to start with.

I am going to soak it overnight. I also thought about putting a coat of .75oz glass over it. Anyways, if the ply works, it will be easy to make with ordinary tools, although just a tad bulky. maybe the glass will also reduce soaking of water in the wood, to keep it light.
Dec 07, 2010, 11:36 AM
Registered User
mavlo77's Avatar
Good news here too....

After considering many options for the actuator of my retractable front gear, I found a solution. A normal servo, modified for continuous rotation was turning too slow (2 seconds for one rotation). With the pitch of M2 thread, it would take 2 minutes or so to retract the gear... Then I considered a DVD motor, but mechanically difficult to find a neat solution....

Then I opened up a standard servo, and found that it is quite easy to remove the potmeter, and replace it with a M2 shaft.

I used the 3th gear after the motor. Normally 2 more gears connect the output shaft. So I reduced the reduction with about 4 x 4 times maybe...

So now a full retract takes about 6 seconds or so.

See movie below. I also made a close-up picture.

Puddle Twin II XL front gear worm (0 min 20 sec)

Potmeter in the servo is replaced by 2 1K resistors. Now I need to build it inside the fuse, and see if it works as a system . BTW, I will add stoppers (wheel collars or something), so the force will not be on the gear internally.
Last edited by mavlo77; Dec 07, 2010 at 11:47 AM.
Dec 09, 2010, 02:01 PM
Registered User
mavlo77's Avatar
New update.....

Puddle Twin II XL front gear retract demo (0 min 52 sec)

Now the rest...
Dec 09, 2010, 02:15 PM
Registered User
dniweerf's Avatar
Netjes...Heeeel netjes..

gr Gert
Dec 09, 2010, 02:51 PM
Registered User
mavlo77's Avatar
Thanks Gert!

Some challenges on my list though...

- Connect steering servo, will use light one as it is connected with double control, and with springs (needed because retracting the wheel increases the distance a bit).
- Switch for automatically disabling steering servo when retracted
- Wheel doors, can only close when fully retracte and can always open
- Main landing gear.....
- Switch on the outside (watertight) to disable the retract system. This is to prevent accidental activating retract system when on the ground.
Dec 09, 2010, 07:13 PM
Derek_S's Avatar
Very cool progress. I should be able to get to working on mine again next week or so after finals.
Dec 11, 2010, 06:44 AM
Registered User
mavlo77's Avatar
Thanks, looking forward to your creative work .

For my main gear I think the only realistic way is the Goose style, you demonstrated... There is simply not enough space for other styles, I'm afraid. It needs to be after the COG, so well after the step where the fuse gets narrower.

Also the wheels should extend wide enough to make it stable, especially as my front wheel is is positioned quite forward.
Dec 24, 2010, 01:18 PM
Registered User
mavlo77's Avatar
Derek, Any progress in your work?

Front gear is nearly finished now. Bottom is finished too. It now steers, retracts and is suspended.... Only need the make the doors to open and close through a mechanlcal tink to the push/pull retract mechanism.... I will upload a video when finished.

For the main gear I am still thinking about your demonstrated Goose style.

But I am looking for a way to make it light.... Maybe you have a creative idea how to use one servo to activate both legs? And preferably through a fixed non pivotting feed through (watertight). And even more preferable is a horizontal feed through, so I can use a rotating thread to activate both sides in the same way as I do with my front gear (video).....

Modification of a servo to a continuous rotating M2 thread, like in my video above is quite simple. It is really a strong and light construction, high torque. Only sensitive parts are the end position micro switches... So I prefer to use the same activator in my main gear.
Dec 24, 2010, 05:25 PM
Derek_S's Avatar
Not really, I atually have just maidened it recently, and am actually enjoying it a bit just for flying. I am going to have to build another fuse for the gear since I have decided not to cut up my good one!

I have decided to make it out of aluminum... Thanks for the reminded, need to get on it!

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