Neptune Seaplane maiden day - RC Groups
Thread Tools
Aug 02, 2008, 06:14 AM
Registered User
Tailgunner1's Avatar

Neptune Seaplane maiden day

The Neptune is a model that has been around now for 20 years or more, although with slightly different features, and made by different companies. I remember seeing pics of it in a magazine about 10 or 15 years ago and thinking, hey that looks like fun.

Well last Xmas, my wonderful wife bought me one Ė The League models Neptune 60Ē seaplane. Only problem was, I have been so busy that I have hardly had time to scratch myself let alone get it ready to go. Well finally, I got round to it, and Iíve converted it to electric, with the help of a few tips from some of you helpful guys here on RCgroups.

The kit was perfect and It was an easy build even for a 2 left hand guy like myself. The ply fuse and thick balsa wings are both very strong. The only problem at the end of the build was a large amount of pushrod slop for the elevator. Luckily, League has provided a rear hatch compartment which helps tackle such a problem pretty easily. For me, that just meant opening the hatch, spraying a bit of expandable foam down the rear of the fuse, and a couple of hours later after it dried, the pushrod slop was all gone.

I used some foam tape to waterproof that rear hatch, and I waterproofed the wing saddle by covering the wing with plastic wrap and then squeezing some bathroom silicon sealant along the saddle, putting the wing on, removing the excess sealant and letting it dry overnight. I also cut a hatch on the forward deck and used some silicon for waterproofing.

I used a Tower Pro 3520-7 brushless outrunner (with 14x7 prop) which I reckon is one of the best value .46 size electric motors on the market. I attached it, with the help of an aluminium mount I bought on line and hacked it up to a size that would fit in that cowling. I drilled some extra holes in the ply firewall and enlarged the hole in the front of the cowl. Also I cut a bit away on the bottom of the cowl near the pylon, which I will make a small air scoop to go over, and I cut a hole in the rear. All this seems to keep the motor and ESC nice and cool.

As I said, I cut a hatch in the forward deck and made a battery tray to fit the 4000mah 4s battery I am using. I ran some wires down through the pylon to the nose, with a deans plug on the end, but also put a 4mm bullet connector on the black wire just where it leaves the pylon in the fuse. This way I can plug the lipo in and screw the hatch on, then get behind the plane - plug in the aileron lead, turn the receiver battery and Lipo on and stick the wing on without worrying about loosing fingers. I also taped a Tower Pro voltage monitor to the inside of the covering so that I can easily tell what state my receiver battery is in. Stupidly I built the Lipo battery tray without even thinking about getting the CG right, but amazingly when I put it all together and hung it from the two chopsticks I use to balance models, it was spot on!! She came in at 3365 (7.4 pounds) grams from memory.

This morning I packed the missus and kid in the car and we drove about half hour to a nice little place called Redland bay. Unfortunately the geography of the spot we were at did not let me assess the wind direction too well, but I went for it anyway. She cruised very nicely on the water, as I floated out to annoy the bunch of Pelicans that had gathered to see this strange contraption that was encroaching on their territory. I throttled up and she tracked straight as an arrow as she came up on the plane ( I still had no idea which way the wind was actually going). She lifted off without incident and I flew around a few times, although she was getting buffeted a bit by the gusty conditions, so I didnít do much else but cruise. I did one perfect landing and what a joy it was to see and hear that splash down Ė Its my first seaplane but now I know what it is all the seaplane guys like about these things. Even my missus was impressed I took off again, cruised out a bit and came back to a rather dodgy landing. She came in pretty hard and bounced a few feet off the water, but everything seemed fine. I then messed about on the water for a while (almost as much fun as flying) and took off again, but she was acting pretty weird Ė I wasnít sure if it was the wind or something else. I landed again, and then had the fourth flight. She seemed a little reluctant to leave the water and I assumed that my battery was getting low so I did a circuit and landed for the 4th time. I had planned to try some simple aerobatics like a loop and roll, but even though she was flying nicely for most of the time, it just didnít feel right. I am very glad I didnít now though!!!

On taking off the wing, I found there was a hell of a lot of water in there. Being an ex navy guy, Iím well aware that boats always end up with some water in the bilge no matter what you do, but this seemed like a hell of a lot considering I was sure she was pretty well waterproofed. The electronics did not get wet except for a few drops on the lipo and a few drops on the receiver. The motor and ESC in the pod were bone dry. I wanted to Corrosion X those components anyway, but unfortunately they donít seem to sell that stuff in Australia. As I hadnít waterproofed the wood of the fuse, I decided it might be a good idea to tip that salt water out and tip some fresh water in and swill it around a bit to get rid of some of that salt. I did that and found my problem, There was a tear in the covering a bit forward of the step which had been the cause of her taking on heaps of water. When I say heaps, I mean, that holding the fuse pointing nose down, the water filled up heaps of the nose, When I tipped the water out, I think, it would have been around 500 to 750mls, thatís half to three quarters of a kilo of water!!! I donít know if the tear in the covering was already there, but realistically I think it must have happened on the super dodgy second landing, which means I then had two more flights with heaps of water on board. I donít know how the hell it flew with that water sloshing around in there. I guess the fact that I was very gentle on climb, cruise and landing and didnít do anything radical, probably kept most of the water forward of the step, but if I had done that loop or roll, sheíd probably be history.

Got some great video, but accidentally deleted the best of it, so will try and get some more in the coming weeks and make a video to post on Youtube. Anyway, this was meant to be a quick post, and I really seem to be dribbling on hereÖ Basically, Iím very happy with my first seaplane experience, and after day one of flying, even with my small problem, Iíd highly recommend this Seaplane.

Sign up now
to remove ads between posts
Aug 05, 2008, 06:46 AM
Registered User
Dynarace's Avatar
Nice job, T! I was waiting for someone to review an electric conversion, but since I had the kit and a spare.46 (and none of my lipo's/ESC's would fit so the $ needed was intimidating!) I went ahead with the glow build. Not finished yet, but nearly there and quite excited.

Not my first float plane, but I'm hoping this one will be better for sport patterns. As I was reading your tale I was thinking you had to have significant water on board as you described the heavy unstable handling. I'm sure it's impossible to completely keep dry, but that was a heck of a lot of water...

Again, great job. Keep us posted on your experience with more aggressive flying!

Aug 05, 2008, 07:12 AM
Registered User
Tailgunner1's Avatar
Hi Linc,

Havenít had time for more flying, but have fixed the tear. I believe now that the covering kind of peeled away in that area and this weakened it causing it to tear a little. I actually had the plane just drifting off shore for about 3 minutes while my missus was fiddling with the camera, and it was no doubt taking on water all that time.

I have ironed it back down and put another layer of covering over the bottom and part of the sides of the forward section, and have ironed everywhere else where the covering joins. I also tried to make the rudder pushrod exit hole a little more waterproof with a bit of scrap covering. Hopefully she should be pretty waterproof now.

Make sure all your covering is firmly in place on the bottom of the plane before you maiden

Yeah, looking at the little piece of video I have of the last short flight, the plane seems to be kind of rocking back and forward as it takes off and flys the circuit LOL. I can just imagine that water sloshing back and forward in there. I'm still amazed it flew!

Anyway, hopefully things will be a bit better on the next run and I'll get to see a bit more of what she is capable of.

Also, when I was messing around with it today I noticed that one of the floats was starting to come away from the tape on one end. I'm not so sure this double sided tape is such a good idea. I wouldnt want a float to come loose in flight and have to try and land and get back to shore on one! I think I may ditch the tape and cut away a bit of covering at the end of each float and epoxy them in place.

Will keep ya posted,

Last edited by Tailgunner1; Aug 05, 2008 at 07:19 AM.
Aug 06, 2008, 10:02 AM
Registered User
Dynarace's Avatar
Thanks Paul. I've read that others simply silicone the wing tip floats down because those foam square stickers peel, and I was planning on doing the same.

Covering complaints seem to be the sole issue w/ this bird. I may just put a second layer on the bottom after your experience. Watch your leading edges as well - several people have lost wing/stabilizer coverings mid-flight...
Aug 06, 2008, 03:44 PM
Registered User
Tailgunner1's Avatar
I splashed a bit of paint on her here and there yesterday for better orientation, and was going to cut away some covering today to epoxy the floats down. I'm glad I decided to look in on this thread here at 5:40am! Silicone! Well that sounds like a better simpler option Thanks for that tip!

Okay, i didnt pay much attention to the wing covering only the fuse, but will run the iron over that too,

Jan 20, 2012, 02:41 PM
Registered User
Mike Sloan's Avatar
Very old thread....however I just built a V1 Neptune (League Models) and have a question regarding CG. Alot of people on the forums are stating the CG to be at 4 inches back from LE. In my instructions it states that the CG is 79mm (3.11) inches back. Which is it? Is the 4 inch recommendation based on flt testing?

I am powering it with an Eflight Power 46. I have on order a couple of GenAce 4Cell/4000mAh batteries. Being impatient I took it out and tried flying it with a 3 Cell/2000mAh battery (14 X 7 prop)....It got up on plane nicely...but I ran out of pond befor it would get airborne...Hope the 4 Cell will do the trick. Does the Neptune take along time to get airborne?

Jan 21, 2012, 03:42 PM
I think you didn't have a enough power on 3 cell. Your neptune should not need a lot of runway to take off.
Jan 24, 2012, 10:14 PM
Fuzzy Member
lupy's Avatar
The 4 cell should be fine. The 14" prop is pretty big, I am using a 12 X 6 on mine with a power 32. Plenty of power on a cheap 4 cell 5000. At full throttle it can take off in around 50ft. I rarely do it like that as I like more scale runs.
Jan 25, 2012, 05:31 AM
Registered User
Mike Sloan's Avatar
Is that a power 32 from Value Hobby... or Efligt power 32? I think the Value Hobby motor is 900 kv...
I think the kv on my P46 is lower... Around 670kv. It took the 14X7 prop to get me up around 1090w at 52A.
Last edited by Mike Sloan; Jan 29, 2012 at 07:18 PM.
Jan 29, 2012, 11:30 AM
Fuzzy Member
lupy's Avatar
Mine is the eflight version. I am drawing about 42A with a $23 HK 4X5000 battery for a measured 650 watts. Assuming your gear is resonably efficent, that should be plenty unless you want to prop hang. What weight is yours coming in at?
Jan 29, 2012, 07:17 PM
Registered User
Mike Sloan's Avatar
Hi Lupy-

My Setup:
I installed the Power 46 on my Neptune. It's a 670kv motor and weighs about 10.3 oz. Mounted a 100A opto speed control inside the body (no overheat yet) with 15" /14ga. extensions to the motor. ZIPPY Flightmax 2500mAh 6.6V 5C LiFePo4 Receiver Pack mounted behind the servos to power the receiver. Overkill, but helped with getting my CG back towards 4". Mounted the battery in the forward hatch. Removed a vertical section of a bulkhead so I could push battery as far back toward the pylon as possible.

My instructions (League Models V1) state the CG to be 79mm (3.11") back from the leading edge. Most on this forum have indicated that their instructions stated 4"? I am about 3.2" with a Zippy 5Cell/5000mAh battery.....and 3.75" with the GenAce 4Cell/4000mAh. Plane flies very similar with both batteries.

14 X 7 APC prop my numbers are:

5Cell/5000mAh 30C
1154 Watts
19.18V (under load)

4Cell/4000mAh 25C
709.1 Watts
15.82V(under load)

That being said.....I think I went with too much power (which added to my weight up front). Like you said...600-700 Watts is plenty for this plane. Once airborne I am at about a 1/4 throttle. Still trying to get use to the pitch down with throttle increase....and pitch up when I chop the throttle. Tried trimming the motor up 3 deg. which helped but still am getting pitch changes with power...still tweaking. Once the power is off....really wants to float, making for some long approaches! Just ordered the Value Hobby GForce G36 (920KV) which should get me 800W with a 4Cell running a 12 X 6 prop. That will trim 2+ ounces off the nose and perhaps, be more efficient than the Power46. I have a couple of GenAce 4Cell/4000mAh batteries and I think this setup should be optimal. That Zippy 5 Cell is so big and heavy...have visions of that thing blowing through the hull with a hard landing

Plane weighs 7.5 lbs with the 4Cell....and 8 lbs with the 5cell. When I get some time I will put some pictures up. Any recommendations and "sage" advise appreciated!!!

Last edited by Mike Sloan; Jan 30, 2012 at 05:38 AM.
Feb 01, 2012, 06:48 PM
Fuzzy Member
lupy's Avatar
I had exactly that happen with my first seamaster, didn't tie the battery down, bounced off a wave on take off, reduced elevator and smacked the next wave. The battery went right through and sank to the bottom
I built a platform that holds the battery off the hull on stronger cross rails. Now it puts the load on the frame members instead of the light ply floor. I stuck velcro on it to keep the battery from sliding around. I plowed my neptune II in pretty hard the other day, and the battery was still in it's place.

As far as what you should do, A lot depends on where and how you fly, 128oz is pretty heavy in my book, but a number of people fly with that weight all the time. I built mine (version II) really light, 88 oz rtf, but it was so light that aerobatics didn't look smooth, also it jumped around a lot with any gusts. I put in a heavier battery and some other stuff, now it's 96oz or so, and is more stable. If I flew on a bigger lake with more wind, I would bump it up some more to 106 or so.

Dropping the prop dia will help with the pitching up and down, you can drop the motor too. My 12" prop just has clearance, I would never mount one that close with glow.
Feb 02, 2012, 12:26 PM
Registered User
Mike Sloan's Avatar

I was able to get my "flying weight" down to 7lbs by going to a smaller motor with higher kv (900). This allowed me to go down to a 12 X 6 prop (much lighter than a 14 X 7 due to the hub size). Now my CG is a perfect 4" back and the flying characteristics are more stable with less "porpoising" with power changes. I had to shorten the nose pod down about 3/4" which also helped with my CG. Don't know the quality or longevity of this new motor (Value Hobby GForce G36-920KV)....but has plenty of power and really nice bench numbers:

12 X 6 APC prop
GenAce 4 cell/4000mAh 25C
52.47 Amps
817.4 Watts
15.52 Volts under load)

Got 12 minutes of flying, light aerobatics, a few landings and takeoffs...still had 3.9v/cell.

So pretty much a complete success.....except on last flight I did not judge where the shoreline was and landed about 10 feet short and rode up into some rocks:

Will try to see how close I can match the blue "china coat" monocoat is a little dark.

Feb 05, 2012, 07:18 AM
Registered User
Mike Sloan's Avatar
It appears that the "Ultra Coat" line of coverings most closely match the colors on the Neptune V1. Cub Yellow and Midnight blue....I think Ultra red (not sure on that one).

I have had more time flying with the new motor (Value Hobby GForce G36-920KV)...and it seems to do the job perfectly. Has plenty of power getting the Neptune off the lake with a 12 X 6 prop. I took out the upward thrust I had and returned to neutral. With the CG at 4 inches the power on "downward" pitch has been reduced, however, she still balloons when you reduce power. I was able to mix some down elevator into my Tx (DX6i) that helped with this. I get consistent 15 min flights (aerobatics with a few T and Go's) and still have 3.9v/cell on the GenAce 4 cell/4000mAh batteries.

Regarding the placement of the ESC. Many have mounted the ESC in the pod and extended the battery wires. Not wanting to mess with adding Caps to do this safely....I oversized the ESC (100 Amp Opto) and mounted it in the body. Even after 15 min. of flying, the ESC was just warm to the touch. I think this might be the way to go. I still soaked everything in corrosionX (except servos)....that stuff is amazing!

Thinking about getting a second Neptune. Does the Maxford V2 have enough improvements to justify the higher price?

Last edited by Mike Sloan; Feb 05, 2012 at 07:24 AM.
Feb 05, 2012, 07:41 PM
Fuzzy Member
lupy's Avatar
I have the Version II, I ended up re-doing the ailerons because I felt they were too small and a little soft. They have inboard servos, which is a nice feature, most people have flown them just fine as is. The covering on mine was fine, some have reported problems, but esp if you are not going with glow you should be fine.

It is suppost to be lighter than the v1 by 6 oz or so. It also has a carbon center spar in the wing and a carbon motor pylon which are stronger than the version one parts. No Idea if that makes it worth that much more.

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Neptune seaplane??? gouda Waterplanes 37 Mar 15, 2009 11:55 PM
Discussion Neptune Seaplane ARF ryan_m Waterplanes 2 Jul 28, 2006 06:15 AM
Aquila grande maiden day ferincr Thermal 19 Jul 17, 2005 09:37 AM
Info on Neptune Seaplane gouda Sport Planes 2 Mar 11, 2005 03:08 PM
Help! Dandy Carnage on Maiden Day maxalentix Parkflyers 24 Oct 06, 2004 07:27 AM