Seagull boomerang 40 trainer - RC Groups
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Sep 27, 2006, 06:48 PM
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Seagull boomerang 40 trainer

Hi everyone,
I decided to learn to fly and join a club recently, went to my LHS and was suggested this model or similar.(seagull boomerang ).
And yep you guessed it I had just started reading these forums and HAD to go electric. I'd had A little experience before with free flight and then a little lps from old aeromodeller plans my grandad left me (poor results made me decide to join a club and go bigger).

Here is my dilema.
The conversion parts sugested were:
jperkins enrg 3036/1000 brushless ( ) which looks very similar to this( )
A tornado 40 amp esc ( .
A tornado 3700nimh ( ).
And APC e 11x5.5 prop.

All suggested and bought from my LHS and charger, good friendly advice and I felt confident in them.

Went to my local club field i had just joined and was greeted by some very friendly helpfull people who agreed to take her up for me to try it out.
1st try Aborted takeoff the gentleman wasn't confident it would climb.
2nd try hand launch very slow to climb and quickly brought back down.
3rd try the gentleman was looking a little worried by now the prop was changed ( a petrol one i think ) a ROG was achieved just and it seemed a little better but the gentleman had a sweat on when he landed it.
Marginal was the word used and not ideal to learn with.

My little masterpice was a failure
very helpfull people sugested i put an engine in it but seeing i was ded set on electric gave me the phone number of a fellow member and we discussed electric, lipo was sugested but not had experience with that model couldn't say for sure (nice people nice club)

So the dilema continues:
I bit the bullet and went lipo (hope to find something else to do with my 2packs of nimh and charger )
jp charger ( ).
And a 2500 3s flightpower battery (
a 3700 was reccomended but that would mean more money on battery and more on a charger (patience and money for this plane were dwindleing.)

So back for my second visit to the air field this time with the new setup and an apc e 11x7 prop A little windy but the very nice instructor agreed to try her for me.
1st try ROG take off from an observer point of view better climb rate but needed WOT to stay airbourne and kept cutting out emergency landing in carrot patch ( i think i hadn't charged the batteries properly?)
2nd try ROG better climb a little stick time for me but kept cutting out, dead stick landing by instructor phew.

Was told that if i could stop it cutting out then i might just be able to learn to fly with her but she was MARGINAL! marginal , marginal i'm begining to hate that word! she looked about 10% beter than when the other gentleman had tried her!

Here comes Question time:
can someone please help this beginner figure out what he is doing wrong. The budget is a little thin at the moment so i really need to use the same stuff . Is it just the pitch speed that i need to change or a smaller/larger prop to match the required airspeed of the model? I have a few different props APC e 12x8 12x6 11x7 and 11x5 the 12x8 gets things a little warm when stationary testing and too close to the amp max but the 11x7 pulls 36 amps WOT( short bursts) gives out 325 watts AUW is 2.3kg and just gets touch warm in the air.Iv'e tried a demo version of motorcalc but couldn't quite get it ( anyone help with this?) Just bought a tacho so when i move my black magic build will get some rpm readings.

below are a few pics of my conversion. Thanks to everyone at the club i met and my LHS.
Sorry if this should be in the begginers thread and Any help and advice will be apreciated because i'm starting to give up a little on this model which is one of the reasons i started building vintage1's version of the black magic over in the vintage thread ( ).

Please help me!
Many thanks in advance ,
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Sep 28, 2006, 02:55 AM
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Should i post this in the beginners section?
Sep 28, 2006, 04:06 AM
<- Balsa flies better ->
wolw's Avatar
Hi Mark
It's supposed to fly quite slow (trainer), why don't you try a APC-E 12x6 ?
You'll get more static thrust at the cost of pitch speed (which you don't need),
with kv 1000 you'll have enough rpm anyway. Check amps before you try it out "live"
Should be nice to float around with.

Should i post this in the beginners section?
Why ? I'm here

Sep 28, 2006, 05:22 AM
Registered User

love the pc9

Hi peter
Iv'e been looking with great interest at your pc9 thread Great!
saw the pc9 when i bought the boomerang and loved it but was rightly advised to get a trainer first (mabe my next artf ).

The jp site says a maximum of 11x7 prop and the overlander site says 12x8.
12x8 static is too many amps for my setup but mabe it will unload under flight?
Thanks for the suggestion of the 12x6 i'll hopefully try it today and give amps volts and rpm.
Glad your here peter doesn't seem to be many others around

hopefully some motorcalc wizard out there could help?
any offers chaps?
Many thanks
Sep 28, 2006, 11:35 AM
Registered User

testing testing 123

Hi all again

Did some prop testing today, not sure how accurate things were but at least i got some .

Well here are the results any thoughts peter ?
any coments anyone else, i'd hate to have to go back to the glow guys and admit they were right.

APC-E 11x5.5 /33.3 amps /8730 rpm /334watts.
APC-E 11x7 /36.6 amps /8070 rpm /350watts.
APC-E 12x6 /36.9 amps /7680 rpm /353watts. last notch not availiable.
APC-E 12x8 /39.9 amps /7170 rpm /370watts. last two notches not availiable.

Mabe things will unload in flight?
Can i calculate thrust with these?
Any help is apreciated.
Last edited by markcanon; Sep 28, 2006 at 11:48 AM.
Sep 28, 2006, 11:42 AM
Registered User
A bit more info.

It's a sports trainer with a symetrical wing i think weigh's 2.3kg a span of 155 cm and a wing area of 3950 sq cm and recommended 0.40 - 0.46 cu ins 2 stroke.

If the weather is good tomorrow i'm going to take her to test fly with the range of props, if it does ok i'll buy another 2500 batery and a spare plane if the LHS still has it in only 45 ( a spare wing alone is about 36 lol).

Many thanks,
Sep 28, 2006, 03:09 PM
<- Balsa flies better ->
wolw's Avatar
Your voltage under load is very low (3.19V/Cell 12x6, 3.09V/cell 12x8).

You should get that other LiPo and run them in parallel, it will give you 5000mAh,
your plane is big enough and the LiPos light (418gr 5000mAh). It will give you quite a lot extra power (keeping voltage under load) and your LiPos will last longer. Higher voltage under load > happy Lipos > happy motor > happy Mark

The PC-9 is a perfect second plane, I really miss it (might but another one)

Sep 28, 2006, 03:49 PM
Registered User
thanks peter

I think the motor and controller are maxed out with the 12x6 and 12x8 not sure if a 5000mAh would make that much difference but i'll take your word for it.
When budget allows I might get a better charger and a 3700mAh, at present i use nose weight but the 3700mAh will balance it without.

If i manage to get some flight time in and crash it, will do what you suggest with the next one. or change to a bigger motor and use this setup in a 30 size plane.
Mabe someone could suggest a 30 size trainer here in the uk? might be a cheaper option?

Thanks for your help peter, going to go read through your pc9 thread again
Almost happy
Sep 28, 2006, 04:22 PM
<- Balsa flies better ->
wolw's Avatar
Here you go, from Sussex Model Centre (where I bought the PC-9), Looks just same as the Protech Colibri I have, great for winter flying with skis ( might not be useful for you )

Sep 28, 2006, 05:32 PM
Registered User
thanks pete
looks better than the boomerang, is that an artf for that price?

Yep we gave up on real snow many years ago now lol.

Why is there such a power difference needed between the two, only 10cm span smaller? does the boomerang have lead in it? .

i've heared only good things about SMS.

thankyou again
Sep 28, 2006, 06:19 PM
Registered User
lake flyer's Avatar
I don't know if this will help or not .

I have a Sig 1/6 scale Cub on floats , it weighs 5.5 lbs , just a little more than your plane , I am using a 400 watt motor and it will rise off water at 1/2 throttle and cruise arround at 1/3 throttle.

Good luck , don't get discouraged.
Sep 28, 2006, 09:05 PM
Registered User


Thanks for the encouragement lake flyer

I think in useful terms mine is more like a 300watt motor .

I was hoping to transfer it one day into my 72" flair cub kit when it has been finished but i think it will be heavier than your sig ( lots of ply).

Which makes me come to the conclusion that it will just manage to take off and need almost 2/3 throttle to cruse round, hope i'm wrong .

Anyone else out there built a flair kit and electrified it?

I'll try not to get discouraged, thanks again lake flyer

Sep 30, 2006, 05:11 AM
Registered User
Was gonna try flight testing yesterday, rain lightening and thunder lol.
Bloomin english weather.
Oct 03, 2006, 09:51 PM
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lake flyer's Avatar
Move to Canada , we never have weather problems , ha ha, I wish!
Oct 04, 2006, 12:18 AM
Registered User

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