Seagull Yak 3U Build - Page 4 - RC Groups
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Mar 12, 2018, 05:02 PM
3 Blades is Better Than 2!
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I painted the pilot's jacket with some OD paint to get rid of the bright green. That and painted his white glove with black paint. These two changes made a big improvement IMO

As for the helmet color, I actually like the white as it gives him a bit of contrast in the sea of grey around him

Kman
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Mar 14, 2018, 12:38 PM
3 Blades is Better Than 2!
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Cockpit is finished and I glued the canopy in place with rubber cement type glue. The instructions called for gluing the tail wheel cover, but I worry about having to make adjustments to it. I optioned to attach it with small metal screws instead.

Back to working on the wings to finish those up. Not too much left to do on this one

Kman
Mar 14, 2018, 10:33 PM
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Looking good, how long till spring?
Mar 14, 2018, 11:01 PM
3 Blades is Better Than 2!
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Thanks! Spring is just a couple weeks away here

Kman
Mar 15, 2018, 05:04 PM
3 Blades is Better Than 2!
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As I am getting closer to finishing up this build, I am looking at what to set my initial CG at. I have read many conflicting reports that the CG is OK or it is too far back or too far forward. Since I want to get it right the first time, I don't want to put too much stock into what others have reported. There are too many variables that skew the measurements.

So, I have been using eCalc online for several years to calculate electric power systems for my planes and it has been an invaluable tool. I never attempt to spec out a power system without running a few options through their calculator. Another tool they offer is an online CG calculator (cgCalc), which I had never used till now. So, I decided to give it a try and see if the CG reported in the manual is good or not. I did some measurements, plugged them in, and I attached a print out of what I found.

In a nutshell, the specified CG in the manual of 160mm is good. In fact it is right in the middle of the calculated range which is about 153 to 165mm (or 6 to 6.5 inches). This gives me a bit more comfort on what the CG should be, although I will probably lean a little more forward of this range for the maiden flight just to be safe.

Kman
Mar 15, 2018, 06:54 PM
Registered User
I always error on slightly nose heavy.
Apr 01, 2018, 01:52 PM
3 Blades is Better Than 2!
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Retracts are installed, however, I have some fine tuning to do yet. The one gear door shuts flush with the bottom of the wing, but the other one hangs about a 1/4" lower than flush. I think I will just try and shim the retract mount to correct this. Overall I am not terribly impressed with the retracts. They have a bit of slop in them and they have no adjustments to try and make them any better. I will stick with them for now, but I may look at replacing them with electrics if they give me headaches down the road.

One of the wheel shafts was slightly bent on one of the oleos. I had a heck of a time trying to slide the wheel collars and wheel onto it. I had to file and polish it down a bit to get it all put together. The gear doors fit really nice, but are really heavy. I had to shim them a bit so that they wouldn't touch the wheels. I used some leftover plastic prop adapters from MAS props as shims for this.

Spring is slow getting to my neck of the woods. No Easter eggs outside today as it has been cold and snowy outside. We really need some warmer weather sometime soon.

Kman
Last edited by kman24; Apr 01, 2018 at 09:30 PM.
Apr 04, 2018, 12:35 AM
3 Blades is Better Than 2!
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I finally have the wings done! I thought I would never get them finished I got all the wires run through the wings for my lights. Of course they were all short because the light kit I used was for a smaller plane. Nothing more fun than soldering those hair thin wires end to end. But, they turned out good and I am excited to have landing lights that I can control on/off with my transmitter

The list is getting smaller for finishing this plane up. Mount the wings, install receiver, install external BEC, mount batteries, tidy things up, and then wait for old man winter to take a hike

Kman
Apr 05, 2018, 05:43 PM
3 Blades is Better Than 2!
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Here are some pics of the wings fully assembled. I need to iron out the wrinkles before I attach them tobtge fuselage.

Kman
Apr 06, 2018, 12:22 AM
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I love the scheme on this plane... I want one....
Apr 08, 2018, 10:51 PM
3 Blades is Better Than 2!
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I put the wing onto the fuselage and placed a couple 4s batteries into the battery tray. I took a CG measurement and it is a little nose heavy. It is right around 150mm. I won't be adding any nose weight, but I will be mounting my BEC and flight battery behind the CG point so that I can give my self a bit more flexibility with just the main batteries.

I plugged my receiver in and started programming my radio. I got most of the servos working in the right direction, but definitely will need to spend some time with my retract servo travel and subtrim adjustments.

Kman
Apr 10, 2018, 04:35 PM
3 Blades is Better Than 2!
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Here are a couple little details that I have been checking off the to do list. I was originally going to route the light wiring up to the battery bay, but I decided it would be much tidier to keep it below the battery bay and just route the single control/power lead up to the receiver. I just used some double sided tape to stick it onto the wing.

Also, I needed to drill out the hood scoop on the cowl. This will be the only air inlet for air to cool off the ESC and motor. There are two holes in the back of the fuselage for the air to exit. I used my trusty Dremel tool with a routing bit to carve the hole opening. When I started to cut it open, the bit grabbed a little faster than I was anticipating and it broke a big chunk out :eek" I got really lucky and the chunk was only in that area that I was taking out. After that had happened, I really took my time and didn't get too detailed as trying to make it absolutely perfect. I figured the less I had that tool spinning around in there the better as I would hate to have to do fiberglass repair at this stage of the build

Kman
Apr 10, 2018, 08:23 PM
3 Blades is Better Than 2!
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Here's a little video of my retracts and lights

Retract Setup for Yak 3U (2 min 38 sec)


Kman
Apr 14, 2018, 04:11 PM
3 Blades is Better Than 2!
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Got a couple more pics to share on the battery compartment. I ended up installing the BEC underneath the cockpit since there was a lot of empty space for it to fit. I then placed the 3s 2200mah battery that would power it next to the tail servos. The two 4s 5000mah batteries then have all the space between the firewall and the tail servos. There is a good 2-3 inches that I can move them fore/aft to help adjust the CG. The receiver is then mounted on the opposite side of the receiver battery. Overall, I am pleased with the placement of everything

Kman
Apr 17, 2018, 10:03 PM
3 Blades is Better Than 2!
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Finished


Well, I am calling this one complete! Did a taxi test and everything looked good. Overall, I am really happy with this one and I really like how it turned out. Only thing that I really would like to change is the retracts. I think they look a bit goofy sticky out giving it the bow legged effect. It would be nice if they were 85 degree instead of 90 degree. I may look at swapping them out down the road, but for now I am going to maiden it and see how it goes. I am officially going to start cleaning up my work table and start putting the building things away for the spring/summer, because from this point till the fall it is going to be all about flying (no building)

Cheers - Kman


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