3D Printed Glider Seagull

[Konrad]

Wow, this is the smoothest tail action I've yet seen in a 3D seagull!

With the servo installed against the servo pad the push rod clears the tail itself and the rear spar boss. Now with a free running push rod I get a little more than 60mm tail motion with the 7mm arm @ 100% radio setting.

I'm so happy I spent a bit of time thinking this through!

 

[Konrad]

I just looked over the part files for the glider and EDF seagull and the placement of the rudder servo is one of the changes between these two configurations.
This would account for the lack of input on the servo placement as I don't think too may EDF's hatched from the Aloft nest. But I still think the servo arm length findings are applicable to both versions of the seagull.

 

[Konrad]

To maintain servo resolution (100% in the radio) I'm having to go down to a 6mm long servo arm for the ailerons. This is to get 22mm up & 19mm down control surface movement. With this short a servo arm the cutout in the servo cover has to be lengthened to nearly double the as printed cutout. At 22mm motion, the hinge is offering enough resistance as to make the 0.8mm wire too flexible.

To get a better balanced feel between upright and inverted flight I'm in the habit with my plank wings to bias the control surface horn so that the pivot is ahead of the hinge line. This results in mechanical reverse elevator differential (more down than up). I will use the radio's program to get the needed aileron differential (more up than down). This is to over come the wing twist and reflex needed for upright flight.

Has anybody looked into a longer servo arm cutout. Or longer control surface control horns, to allow longer servo arms to get the push rod further away from the lower wing skin?

 

[Wayne]

The glider fuselage is very different.

 

[Konrad]

The glider fuselage is very different.

True, but are there any other changes to the mechanical geometry for the radio set up, other than the rudder servo placement? The tail surface control horn is the same and the aileron set up appear to be the same. As they all look to be the same, I assume the requirements for the servo arm length would be the same, between the glider and EDF configurations.

So the arms at 7mm for the rudder and 6mm for the aileron, is allowing me to maintain close to 100% radio input while reaching the called out spec's.

 

[Hank GB Z]

Well Konrad sent me these photos of his completed Seagull. Thought I’d post them up here. He’s currently looking for a battery that will give up the amps required for the EDf he’s installed. He also added some 320 grit sand paper to the fuse to help with grip when launching.

I think it looks awesome. But It needs a speaker that says “mine?!” Like the ones in finding Nemo.

Hank

 

[Wayne]

Came out looking great, like all of his new builds do. Like that he did the paint on the wing a little differently. Love it.

Hope he has better luck with the EDF and the new fixes, the original version was horrible under power.

 

[jure]

EDF's in general incur in a large penalty.
I changed the GWS F15 from EDF to a pusher prop with great improvement in thrust , speed, flyability , flight time , etc.

 

[Wayne]

Yep, sounds about right.. Every performance measurement takes a hit with an EDF. But a good EDF does sound good. And the small packaging can be tempting for some designs.

 

[Hank GB Z]

Yeah, we were looking at installing the 40 mm fan out of the new Horizon Hobby F-14. It is a 4 cell set up and at the very least would give more power. If anybody has that model and has any opinions on the fans and motors let us know.

Hank

 

[Mathrips]

Just some anecdotal info from my experiences with the 3d Seagull.
I live in Santa Cruz Ca. last year a friend printed and built the Seagull edf version and our view was that it did not have enough thrust to gain altitude, though it could fly level. Personally I thought I was a bit large and would not survive long in the front seat of my truck. So, I had my friend print me a seagull in 70% size. I took it to the Sunset Beach Aloft event last year (2022) and it flew great. Since then I also built a 64% seagull (that fits a 4mm spar whereas the 70% seagull requires a 4.5 mm spar which is more difficult to source. On the other hand I could not find piano wire thin enough to fit the rudder guide tube for the 64% bird so I glued another tube on). I was just at Sunset Beach last week in about 10kt winds with both of my seagulls and a friend with his full size seagull. All 3 flew beautifully. My fave so far is the 70% as it is a bit less fragile for it's size, and more sporty as well, yet still easy to see far away.
Just my thoughts.
Not sure I will make it to Sunset Beach Aloft event this year as other adventures interfere.
I do hope you all go as it is a really fun event, and so great to see everyone's gliders out flying
Kingdon

 

[Konrad]

I need to thank Hank for posting the photos of my finished Sea Gull. Mine as printed by Aloft came out about 200 grams over weight (770 grams )as defined by PrintPlane. But I think this weight was done to add a lot of durability on the slope. I have about 3 flights on mine, all on the slope. I find that I like to use a lot of rudder making my turns. I find that an aft CG works well, with very little reflexed ailerons. I'm using a 3 cell HV (4.35) Hyperion battery (2400 mAh?) both for power and for balance, coupled to the stock 40mm fan. With this power system I get a little more than a sustainer power system. Like I said I've only flown the Sea Gull as a slope ship. As such I allow the bird to drop a long way gaining speed when I launch. This results in a no drama launch. Still working on fine tuning the radio set up. After I learn to do a straight out launch on the slope, then I’ll risk a flat land launch and flying session. But as I said the EDF at my flying weight I don't expect much of a climb rate.

A note about finishing. I found that the print lines allow the paint to move a lot by capillary action! To control this I fill in the print lines around the eye and beak with white paint then add the color. This helps maintain a crisp paint line.

FYI: I get very little pitch up with the new thrust tube. I think the earlier non-thrust tube pitch up may have gotten folks into trouble, stalling at launch. I think the glider only version as printed by Aloft makes a fine sport/gag slope bird. With the 40mm EDF unit, I don't think the EDF Sea Gull really makes a practical flat land flying model. Yes it can be done! But everything has to align perfectly ( launch, wind and climb out). Again just not practical with a 40mm EDF at the printed weight. (When I get more comfortable with the bird I will try some flat land flying).

 

[Wayne]

I'm not sure the EDF makes sense even if it was super light.

Yes, we print the structures heavier then the designer would like, but they are now able to handle a tiny bit of mis handling on the way to the slope. LOL We did some LIGHT weight prints early on and they would have been a pile of plastic after the first landing. They fly well at the current weights.

Agree - Rudder makes her turn like a real bird. I barely use the ailerons at all. They are handy when landing with some rough surface air.

Looking forward to the flight of birds this year at Sunset.

 

[jure]

... Agree - Rudder makes her turn like a real bird. I barely use the ailerons at all. They are handy when landing with some rough surface air.

@Wayne, I am getting ready for my 3D Printed Seagull build.
In preparation, I read from some of the comments in the YouTube videos that some people have flown the Seagull with elevons only ( i.e. 2 servos ) ,
saving the weight and "complication " of the tail movement and servo.
Any opinion on this ?

 

[Konrad]

I wouldn't leave off the rudder. There are times I like/need the control response of the rudder. The Seagull at times doesn't have enough control to fly in a skid. The use of rudder really really helps with overall flying characteristics of the model. Do make sure the tail movement is free. See some of my notes mentioning this earlier.

Saving 10 grams from the elimination of the rudder servo isn't worth the loss of control.

 

[Red]

I wouldn't leave off the rudder. There are times I like/need the control response of the rudder. The Seagull at times doesn't have enough control to fly in a skid. The use of rudder really really helps with overall flying characteristics of the model. Do make sure the tail movement is free. See some of my notes mentioning this earlier.

Saving 10 grams from the elimination of the rudder servo isn't worth the loss of control.

And you need nose weight anyway, might as well add the servo. I'll echo the comments, the Seagull really, REALLY likes rudder. I have it on a mix and leave it on all the time.

 

[thenated0g]

I flew the seagull for about 5 minutes before I realized it even had a rudder and I thought it flew really well, but I'm not really a guy with much experience using rudder while flying. So take that with the grain of salt.

 

[jure]

OK , thanks to all for the feedback, will keep the rudder servo at the beginning.
I think that the model is meant to be flown gently anyway , no need for aggressive aerobatic maneuvers.

Nathan confirms that the rudder is not an absolute requirement.

 

[Konrad]

Not absolute, but highly desired!!!

With the glider having the servo ahead of the CG I can’t see any advantage in the flight profile to omit it.

The fact that you won't have the speed/inertia for most of the flight profile is all the more reason to have a rudder.

P.S.
Do you have a link to U-Tube that started this thought process?

 

[Hank GB Z]

@thenated0g

Were you flying Red’s seagull? I only ask because if it had the mix going you may not realize how much the ship needs with out the mix.

Now I have not flown the seagul but I’m of the camp that aside from certain Rudder Elevator models more control is always better.

If saving 5-10 grams really does improve the flying that much a design review of the structure is probably in order.

Hank