12.5 lbs too heavy for a MPX ALPINA? - RC Groups
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Apr 16, 2007, 12:56 AM
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fly2bob's Avatar

12.5 lbs too heavy for a MPX ALPINA?

It's the electric version, 4m w/s (157"). Uses an AXI 4130/20 (14.4 oz.'s!), 75 amp esc, and (2) 10 nicad packs (22 oz.'s each). Also uses a rx pack for radio. Just purchased RTF. Live is San Diego, and plan on flying at the electric field at Mission Bay. Concerned there wouldn't be much thermal activity there. Eventually might consider a lighter motor w/ pt. gear, and 6s 3300 mah lipo.
Any thoughts on this? Maybe not nessary? Guess I'll find out when I get it and try to fly w/ my knees trimbling. Thanks, Bob
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Apr 16, 2007, 04:38 AM
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Neil Stainton's Avatar
Yes I think so. I've got an Alpina Magic 4.4m which weighs 7.5lb as a glider, and I am hoping it won't weigh much more than 8lb when electrified. I'll be using a 4S LiPo battery and a geared inrunner.

Last edited by Neil Stainton; Apr 16, 2007 at 07:37 AM.
Apr 16, 2007, 06:54 AM
Tragic case
davidleitch's Avatar
There's one flying at out local club with a geared Kontronic and 10xgp3300. I believe the motor is only pulling about 80 amps. The climb is only modest and it needs a good throw to get it going. A 4S lipo pack would be much better (IMHO).

The set up with the Axi 4130 and 20 cells would certainly have great penetration in the wind. Why not give it ago, and if you don't like it switch to a lighter system? Looks great in the air, and seemed to land very steadily.
Apr 16, 2007, 07:39 AM
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Neil Stainton's Avatar
I've edited my post, I meant a 4S battery. I agree with David, why not try it as is and see how you like it? I will probably be excellent for strong conditions.

Apr 16, 2007, 09:15 PM
I'm All Thumbs
AirBornOne's Avatar

Too Heavy Bob!

I won't say it won't fly but launching could be scary.
Which Alpina version do you have?I would hope the Carbon Master Edition.
The auw for the early Alpina-e was given as 5kg/11 lbs so your not Way off.
Tangent specs a 9oz. Kontronic motor and 12 cells.
You will definitely have power though!
How did you get a 2" motor in a 1-5/8" nose?
I'm setting up with a 7oz. Hacker and 6 or 7s X 2 A-123 cells.Originally planned on 12-16 4200NiMh cells.
Show us some picts!
Apr 16, 2007, 10:28 PM
Too much is not enough
chronos333's Avatar
We are setting up electrified carbon thermik XL (4m and a good proxy to the alpina). Mine is 10.5lb ready to go with 16GP2000 with a geared inruner spinning a 17X9 at 75 amps, climb is safe at a sustained 45-60 deg.
The other guy is 11lb/5S/geared inruner/18X9 but didn't maidened yet.

Prop diameter is key when you don't have much power spare,believe me it makes a big difference in real life even if motocalc doesn't say so.

I may change the setup to spin a 18.5X10 under 5S or 6S...

About the weight, it's not too heavy if it is structurally strong enough to support it even when flying hard. Personally I always prefered to fly heavy, some says it is slower to climb, I say you get out of the sinking zone faster and have a more efficient airframe when it is windy...
2 different schools
Apr 16, 2007, 10:41 PM
around Colombia
ShredAir's Avatar
Bob, have one of the local F5B boys look over your plane, and assist you on your first flights. Regarding weight, you'll be delighted with how efficiently this plane carries this weight and how well it cruises. Don't be nose-heavy and fly mostly at the speed of best glide (rather than minimum sink), and your plane and you will be best friends very quickly.

Dieter Mahlein, ShredAir
Apr 17, 2007, 03:52 AM
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fly2bob's Avatar

thanks for the replys

Thanks for the replys guys. I'll answer them in order.

Neil...That's great to hear your Alpina only wieghs 7.5 lbs! I think you'll find, from what I've been researching that electrifying it will add more than a 1/2 lbs though. From what I've found a 5s or 6s should be considered a minimum. I've seen a video of one with a AXI 4120/12 with a 4:1 pt. (planatary gear), running off of a 3200 10s, and weighs alittle over 13 lbs....it hauls butt! 6s packs wiegh about 19oz.'s. Inrunners geared are definatly lighter than my 14.4 oz. outrunner! But I don't expect to fly it in 'stong' conditions. Like I said the electric field is right by Mission Bay and only a mile, maybe two, from the ocean. Not that I've flown there yet, maybe there IS good thermal activity there on good days, don't know. Just got into electrics resently, and just renewed my AMA after not having it for 6 years, and been flying a small local slope since then.

David.....I answered some of yours above. Sounds like the one your LF could probably stand to use a few more cells and a slightly bigger prop to then drop the amps down alittle....should help the climb too. Is this correct everyone? I'm actually kinda new at this motor sys bussiness, so I don't claim to be very knowedgable about all this. Just learning as I go. It definatly can penetrate though. The current/ex owner says he's flown it twice and it haul butt between thermals. Just put the nose alittle down and you're up to 100 mph in no time. (scary...hehe, grin)

Jay...I don't plan on launching it myself. First thing I'm considering is taking the two 10 cell (20 cells total) motor (flight) packs out and relocating the rx pack (it's all velcroed in there) to get the CG correct. It'll probably have to go as far back as it will go, near the TE, and even then I might have to temporarily add alittle to the outside of the tail to get it balanced. This is all so I can take it to Torrey Pines Gliderport for a few test flights to get use to it. Then, if its a good day (lots of wind/lift), maybe I'll stick the flight pack back in, take off the tail wieght, recheck the CG, and fly it like that there too, to get use to it's speed, see what speed it likes to fly at at that weight, and get up high and to see how it stalls, etc. Then I plan making a dolly out of a plastic foldable tote box, with some modifications/add ons of course. I've seen the PVC one someone make for a dolly, but I want something that will colapse when traveling with it, and to store it. I'll use it to launch it at the electric field. They have a dirt runway. Or, maybe someone can throw it for me. The ex owner said "NO, you're not going to land it on dirt are you?!" Well what can I do, excect put alittle strip of white grip tape on the bottom? Yes, it is the Carbon Master Edition, one year old, only two (sucessful) flights on it. Won it on Ebay Sun. 4/15 for $835 equiped, setup, and fully RTF. Not sure how the very nice gentleman fit that motor in the nose unless more nose was taken off. It never really occurred to me, but now that I think of it, yes I'm sure that outrunner is larger in diameter than inrunners most use. I'll have to check that out, look that stuff up, and maybe ask him. Anyway he says it's in mint condition. What a bargain, uh? He said he invested $1320. It should definatly have enough power. Unsure how to add pics...any advise?

Chronos333....Sounds like you got the right setup, numbers and at a good weight. Should be strong enough considering the one I saw in the video was heavier and did aerobatics.

Dieter.... great advise, thanks. I've read that about this ship.

Thanks to all!!! Hopefully I'll be able to add those pics soon. Bob
Last edited by fly2bob; Apr 17, 2007 at 09:01 PM.
Apr 17, 2007, 04:12 AM
I'm All Thumbs
AirBornOne's Avatar
Definitely a good buy Bob!
To post a pict,scroll down to 'additional options'.Right under the box you reply to a post in.
Click the 'manage attachments' button in the 'Attach Files' box.Navigate to your picts and select 'em.
Apr 17, 2007, 07:33 AM
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R.M. Gellart's Avatar
Remember that the big ships fly very well and that many things you fight in a smaller ship are in your favor in a big one. I flew a ship very much like yours in XC called an Albatross, wieghed right at FAI max, ~11 some pounds, and it thermaled beutifully. A good way to try it out is go to Torrey on a good day and slope it first just to get your legs with it and be sure that things are right, then go motored. I have seen ships with less wing than you ship weigh in the 15 pound range at aerotows and fly just great. have faith!

Apr 17, 2007, 08:56 PM
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fly2bob's Avatar


Thanks Jay and Marc. Jay I've added pics in the past a long time ago, but forgot, thanks for the reminder. Marc, that's what I was planning on doing, it's just that flying at Torrey has gotten so anal, and I hate flying with the paragliders that don't follow the rules. I had a bad experience there 6 years ago, and that's why I stopped flying there. I was 200 feet up at the north face heading south towards me with a loaded up Renegade. I put in reflex, and yell north to south through the bowl to do a nice big wingover in front of me, when all of the sudden a paraglider launched without blowing his whisle or yelling 'launching'. And he didn't launch straight out then go north, he launched in a northern direction right as I was pulling up through my wingover. I shot past him doing at least 70 mph. Another 5 feet north of where he was and he would have been history. I yelled 'god dam it', and went to land. I left and have never been back since. Also, besides rebecoming an AMA member, which I have because I'm going to fly at the electric field, to fly at Torrey, you also HAVE to become a gulls member. I love the gulls and the site, I grew up there, just don't like all the traffic on the weekends, and $40 for a few test flights, since I don't plan on flying there regularly, just doesn't make too much sence. Maybe I'll do it, I don't know. I'd be alittle freaked out enough the way it is flyinig this big heavy ship for the first time. I'd definatly keep it out there with major blue sky between me and anyone else. Then again, there's always Poway slope. The first pic is my version off of the Tangent site, second is what my plane looks like except the pic is of the glider version, third and forth are my actual plane, arriving in a week or so.
Pretty plane. Best regards, Bob
Last edited by fly2bob; Apr 17, 2007 at 09:08 PM.
Apr 17, 2007, 10:24 PM
Bob, you should be fine at that weight. I've got an Alpina 4001 flying with a Kontronik 600-18 with 4.3:1 gear reduction on 14 GP3300 cells with an 18x10 prop. All up weight on mine is 11.5 lbs and it flys and thermals very well at that weight. In fact, I like it better at the higher weight than when I had it as a pure sailplane at 9 lbs. I had no problems doing an hour with it this last weekend.

Apr 17, 2007, 11:01 PM
I care about rising air !
MTT's Avatar
12.5 lbs, that's 5.7 kgs....
It is a bit on the heavy side for an Alpina, but not excessively so, and it will still fly and thermal OK. As cmallen said, these large sailplanes often perform better with a little bit more weight on them.

What size prop are you using, and what type of cells ?
And why 2 10 cell packs ?

My very first e-sailplane was an old Alpina, with a Kontronik FUN500-27, 5.2:1 gearbox, 14x8.5 prop, on 14 1700 mAh NiCd cells. That setup was marginal...
Weight was 4.8 kgs = 10.6 lbs.
I could handlaunch it, but it really needed a good shove, and some headwind, with no wind, it was really tricky.

I later changed the setup to a 17x11 prop, on 12 RC2400 cells, and that worked much better, weight was a little more, just under 5 kgs ( 11 lbs ), but it still flew and thermaled very well.

All in all, I think you will enjoy your Alpina, even if it is slightly overweight.
BTW, on their HP, Tangent list the weight of the elektro-alpina at 5.1 kgs for the thermal version, and 5.6 kgs for the master carbon edition, so you're not so far off.

Enjoy your Alpina !
Apr 18, 2007, 12:17 AM
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fly2bob's Avatar
MTT.....18x10 prop, nicads, don't know mah's. Thats just the way the previous owner did it. Instead of (1) 20 cell pk.....(2) 10 cell pk.'s (connected I'm sure). Do you have the CTE or the CME? Bob
Apr 19, 2007, 10:40 AM
Registered User
I'm building one too (if you call buying parts and putting them on the shelf "building").

I'll run 12 3300 cells and a Aveox F-12 (mainly because it is what I have), a 17x9 or 11 for 80-90 amps draw, 800 watts in, 50 mph pitch speed, and 7 pounds thrust. I calculate about 11-12 pounds all up.

The local guys here tell me they can take weight.

Let us know how it goes!


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