Seagull Models Harrier 3D 40 size Conversion - RC Groups
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Jun 25, 2005, 08:01 PM
Quit Chucking My Wood
rthorne's Avatar

Seagull Models Harrier 3D 40 size Conversion

A Seagull Model's 40 size Harrier 3D showed up at my LHS this week. I picked it up as it looks like an excellent plane for conversion.

I plan on running a 4120-18 with a 6s2p Irate 4400 mah pack. A 14x7e will be the prop. This combo flew a 40 size Hanger 9 Funtanna with authority. This power system is probably not enough for a die hard 3d'r but it should fly the plane just fine.

First up, I weighed all the parts on a postal scale at my office.

Fuse - 1 pound 3.1 oz
Wing - 6 oz
Wing - 6.1 oz
Stab - 3.2 oz
Rudder - 1.1 oz
Aileron - 1.8 oz
Aileron - 1.4 oz

The following parts were weighed in the bag they were packaged in just in case I decided not to do the conversion.

Cowl - 2.4 oz
Wheel Pants - 1.7 oz
Wheels - 1.2 oz
Spinner - 1.2 oz
Hardware - 3.3 oz
Gear - 2.4 oz
Wing Tubes - 4.6 oz

Total plane in the bones - 55.5 oz

5 Hitech 5475 Servos - 7.5 oz
JR Receiver - 1.2 oz
1800 mah receiver battery - 4.1 oz
Castle 60 Speed Ctrl - 2.3 oz
AXI 4120-18 - 11.3 oz
6s2p Lipo - 22 oz

Total radio gear - 48.4 oz

I should be able to come in around 103.9 ounces or right around 6.5 pounds. My Funtanna weighed nearly 7 pounds. Even though the wing on the Harrier is much thicker I'm hoping for some decent power.

Pics to follow...

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Jul 26, 2005, 02:01 AM
AKA BillyKillaWatt
Billy Haynes's Avatar

Seagull Model Harrier 3D

rthorne, I just finished mine this last weekend
I usually check the Ezone before I buy a plane, but I was in the hobby shop Saturday, saw this plane and had to have it. Hey, it comes with a battery hatch all ready made! So here's the run down on mine....
APC 14x7e, AXI 4120/18, Phoenix 60, Tanic 4900 6s2p (2-4900 3s2p in series), Hitec super slim rx, 4.8v 650mAh Hydrimax rx battery, (4) Hitec HS-325HB servos. I started on it at 3pm Saturday afternoon & finished around 3pm Sunday. Not counting breaks and mandatory sleep, I guess it took 12-13hrs to build, start to finish. I thought two std. size elevator servo's was overkill for a .40 size plane, so I made a elevator joiner out of music wire. I drilled holes in the ele's with my drill press (to make sure the holes were square to the hinge line). I epoxy the joiner in and installed both ele cont horns, centering them over the ele joiner just for a little extra security/strength. My motor mount may not be the best looking, but it works, and was what I had on hand. The standoffís, 5/8Ē hardwood dowel cut to 2 1/8Ē, with the center is drilled out. The AXI firewall is 3/16Ē aircraft ply. I used the holes in the firewall made for the glow engine mount, and glued/bolted everything together. I drilled a hole in the firewall below the fuel tank hole, then cut out the ply between the holes to make one large oval hole. I made a scoop on the bottom of the fuse just aft of the firewall. For the cowl I cut a hole in the front to get more air to the motor and made an air deflector. After the initial flights I moved the speed control in the cowl, inline with the left side cowl scoop thing. It was inside the fuse, beside the battery, but I felt it didnít have good air flow in that location. It wasnít overheating, but warmer than I was expecting. I made a battery tray out of 3/16Ē balsa, glued to the formers where the fuel tank goes, with triangle balsa on each side of the formers for added support. The two 3s2p 4900ís fit perfect in this plane! My Harrier 3D RTF weight is 6lb 2 3/4oz. I balanced it just forward of the recommended CG. First flight was a little nose heavy, the other three flights I moved the CG back a little. I think it could be moved even farther aft. It still requires some down ele when inverted. Level flight is a little under 1/2 throttle, Hover is a little over 3/4.... so the pull out of hover isnít the best, but it does pull out. Iím not sure I like the 14x7e prop. In forward flight its fine, but in hover it just sounds.... well I donít know how to describe it other than maybe stalled (?) Anyway it doesnít sound like any other plane/prop in hover Iíve had. So far Iím happy with this plane, and itís ease of transport (when you donít want to pull the trailer). This plane is easy to convert.... I give it two thumbs up
Jul 26, 2005, 08:20 AM
Quit Chucking My Wood
rthorne's Avatar
Hi Billy:

Looks Great. Mine is basically finished also. Just need to finish by securing my speed control, cutting the cowl for some air flow, remove some covering on the bottom of the fuse for air flow and then go fly it.

I was going to post some pictures along the way but I still have not figured out how to reduce the size of the picture so I can post them here.

Your, right it was a very easy conversion. Most of the time, which wasn't much, was spent building another fire wall that could be bolted on to the already mounted blind nuts. We had the same idea but I did mine a little differently, with the same result.

I'll figure out the camera thing and get them posted.

I'm glad your's came out the way it did weight wise. I don't expect my setup to be great at hovering but it should handle every thing else just fine.
Jul 26, 2005, 09:31 AM
AKA BillyKillaWatt
Billy Haynes's Avatar
I also added some white stripes on the bottom of the wing to help orientation. The landing gear also seems to be a little weak. On a rough field, I'm not sure how long the gear will last. I flex's a lot just taxing round. My landings weren't bad at all, but still had to bend them back to shape once. O yeah, I forgot. The posted weight is with out wheel pants.
Jul 26, 2005, 05:23 PM
Quit Chucking My Wood
rthorne's Avatar

How much current are you pulling on that setup at full throttle?

Jul 26, 2005, 11:49 PM
AKA BillyKillaWatt
Billy Haynes's Avatar
If I remember correct it's 50A w/batteries fully charged
Jul 27, 2005, 04:09 AM
Registered User

I finished my harrier 40 conversion a month ago - gone a slightly different route to you guys and went for an AXI 2826-12 running on 16 3300 Nimh cells running on an APC 12x6 prop. Mine comes out at 7lb dead.

The stock U/C is pants - far to light weight for a model that weighs 6lb - I retrofitted a Carbon one after the first session. This does have an advantage in that the standard U/C does sit the model in a fairly flat attitude - the carbon U/C is a little longer and it will give better prop clearance and makes takeoffs and landings much easier. In fact this plane is one of the easiest I have for making almost perfect landings everytime.

While my power setup is tame compared to yours - the plane does fly very nicely - more a sports aerobat rather than a 3d'er (suits my style of flying). However the one thing it does very well is the Harrier! I guess all that ply in the fuz makes the basic airframe heavy - all we need to do is get them to build for electric - I'm sure 1-2lbs could be shaved off the weight.

Next model is a Pilot Seduction FreeStyle - which is already on the board !
Jul 29, 2005, 10:15 PM
Quit Chucking My Wood
rthorne's Avatar
Just curious where the CG ended up on each of your planes? The way I have it setup now I'm at about 125mm but the manual calls for 140 to 150 mm.

Jul 30, 2005, 04:32 PM
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rthorne's Avatar
Well no guts no glory, I went anhd put a test flight on the plane this morning. The CG is forward at 125mm but I'd rather be nose heavy than tail heavy.

I need about 3 clicks of up and 2 clicks of right and the plane was nice and level.

I didn't get very far though. I was having some terrible glitching with the aileron. Its the same exact problem I had with this radio/motor/speed control setup when it was in my Funtanna. The motor and reciever are not the problem as they were swapped out previosly.

So I'm down to maybe a bad servo or noise getting into the receiver from the speed control. I just went to the hobby shop and met a buddy of mine there. He brought me a set of regular non-digital servos to try, Hitec 615's and I bought a couple of JR RF Rings (AKA ferrites). I'll wrap my speed control cable around it a couple of times and try that. If that doesn't work then I'll swap out the servo's. But I have a funny feeling, for what every reason, that I'm getting some noise or RFI into the receiver. When I had this setup in my Funtanna it affected more than one servo. So we'll see.

Anyways back to the plane. Other than the servo glitches the plane flew around pretty well. I didn't try any rolls or loops, but half throttle seemed to be plenty.

Landing was great, the plane was very stable and with a little elevator I was able to flare it for a very smooooth landing. So maybe the CG at 125mm isn't so bad. I'll determine that when I start doing some manuvers like a knife edge and inverted flight.

I'm very pleased with the plane so far.

Last edited by rthorne; Jul 30, 2005 at 07:36 PM.
Jul 31, 2005, 08:19 AM
Registered User
Its not bad is it !

As I said in my previous post - this model is just great at landings - it has so far made all my attempts look absolutely perfect

I measured my CoG this morning - its 140mm, so I guess you can safely bring it back quite a bit.

I made a tray that fits behind the canopy (you need to cut the film covering) and fitted my Multiplex IPX RX back there. I'm using a 3amp Medusa super BEC to power the radio. Single elevator servo down at the back end (cheap futaba digitals all round) - elevator halves joined by a carbon rod.

I'm saving up for some lipo batteries - I can save at least a lb of weight by ditching the 16 cell nimh packs - so the lower voltage of a 4s pack should be offset by the lighter weight!

Anyway - have fun with your Harrier ... I know I am!
Jul 31, 2005, 01:49 PM
Quit Chucking My Wood
rthorne's Avatar
I had a good day this morning. The JR Ferrite solved my glitching problem. I'm glad that problem has been solved.

This plane is fun to fly. I didn't do any major manuevers today, just basic flying with some loops and rolls. And not one bad landing, it just floats right in and does not tip stall.

I need to work on moving the cg back. The plan is to move my receiver pack further back in the fuse. I need to open the bottom of the fuse for cooling anyways so I'll figure out where the battery needs to go and work from there.

Seagull has a winner with this plane.

Aug 02, 2005, 11:46 AM
AKA BillyKillaWatt
Billy Haynes's Avatar
I flew mine a lot yesterday (so much now I'm sunburned.. guess I shouldíve reapplied sunscreen later in the day.... ouch) I now have my CG at 140mm. This made the landing much slower and a little bit easier to hover. I'm going to move it farther back, to 150mm. This should also help improve the ability to harrier, which I'm having trouble with (strange given the name of the plane is Harrier). A new set of landing gear is defiantly in order. I find the gear to flex too much. Also with the gear being two pieces, the holes in the gear somewhat larger than the screws, the gear tends to pivot on the landing gear plate letting the wheels move farther aft (helping me to nose over easier). I'll just get some aluminum from the hobby shop and make a one piece gear out of heavier gauge metal. The spins werenít very flat, but when I move the CG back hopefully that will improve also.
Aug 06, 2005, 10:49 PM
Quit Chucking My Wood
rthorne's Avatar
4 more good flights on the plane. The cg is still at 125mm and flying great. I'll eventually get the cg back 15 to 25 mm. In the mean time I'll just keep having fun with it.

The 4120 pulls the plane straight up without stopping. According to my watt meter I'm pulling 850 watts and my tach says 8500 rpm on the 14x7e prop.
At 6.5 pounds thats 130 watts per pound which is turning out to be plenty of power for my type of flying.

Aug 07, 2005, 12:40 AM
AKA BillyKillaWatt
Billy Haynes's Avatar

prop test

I tested several props (checking current draw). 14x7e, 15x10e, 14x4W. I knew the 15x10e would draw a lot of amps. What supprised me is how much less the 14x4W (non-electric) prop drew. I have the 14x4W on it right now, should be able to see how it performs tomarrow(err..... today). I had a 13x4W prop on my Saito powered TWIST & it worked great.... we'll see how a APC wide prop does on an electric motor
Aug 07, 2005, 10:21 AM
Quit Chucking My Wood
rthorne's Avatar
Hi Billy:

Our current numbers are different on the 14x7e prop. I'm only drawing 44 amps or so at full throttle. We're running different batteries 4400mah vs 4900 mah but I don't think that would be the cause.

On my 1st 4120-18 I was drawing about 52 amps with this setup. I started noticeing a problem with the motor, seemed like something was sticking when I turned the motor by hand.

I took the motor back to the hobby shop who in turn sent it back to Hobby Lobby. There reply was that it seemed have gotten hot as the magnets were discolored.

Hobby Lobby sent me a brand new motor and now my current draw is quite a bit less (now 44 amps) but I'm getting the same end results with the 14x7e prop.


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