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Old Mar 21, 2006, 12:50 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
Build Log
Sig Somethin' Extra EP conversion

OK so i'm about to recieve like the title says a sig somethin' extra kit not the arf and im planning on converting it to ep. This will be the spot for my build thread once i start.

I should start by saying that while i am not new to electric planes i am new to glow to EP conversions and electric planes this size. So please bare with my ingorance. i have checked out grramps SE conversion which was loaded with great info.

So for the build i am planning on lightening the plane up as much as i can, replacing most the ply with balsa excpet firewall area. I am hoping to get the plane's AUW 55oz area.

So now I have a few questions to start off with. I found grramps SE conversion which was loaded with great info., i didn't find the exact info i was looking for. I currently have a pjs 3d1900 that is rated for planes up to well 1900 grams which is just over 4 pounds. Im not looking for screaming 3d prop hanging performance so what is your all's opinion will this motor be enough to fly the plane while performing realitivly easy acrobatics(rols, loops, KE). this motor i believe is rated for a 3s pack.

I also have 2 apogee 3s HD1500 mah packs and two electric power 12c 3s 2200mah packs that i could wire either in series or parallel.

I would like to use as much of my current electrics that i have, however if either my motor or batts wont work i am willing to buy up, but only as a last resort. I was looking at a axi 2826/10 motor which i know will fly the plane based on grramps post, but like i said i would like to try and stick with what i have if at all possible.

So Thanks for taking a look at my thread, And for taking the time to help with my conversion.

-Derek
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Old Mar 21, 2006, 03:50 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
Anyone have any comments or suggestions?
-Derek
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Old Mar 21, 2006, 04:50 PM
RC, cheaper than therapy
zonkm's Avatar
Spokane, WA
Joined Mar 2006
51 Posts
Larger Conversions

I'm pretty new to this site and don't know a lot about the type of conversion you're talking about but I'm doing research for one of my own sometime in the near future (By that I mean hopefully sometime this decade...lol).

I have a 1/6 scale Sig Piper Cub I'd like to convert to electric. It is supposed to have a .35 - .46 glow in it with what I believe to be in the 7lb AUW range. -Sigh- someday.

I look forward to anything I will learn off of your thread.. good luck to you!

Scott
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Old Mar 21, 2006, 05:54 PM
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United Kingdom, Dorset
Joined May 2002
3,075 Posts
I don't know the motor you have but if it's designed for models up to 4lbs I'd say its not up to the job. The Sig SE will be at least this weight and the motor will then be pushed to the limit most of the flight. That said, the SE has a lot of wing area and will fly on quite low power. But you want it to fly loops, rolls and KE, so you want a motor that will do more than just 'fly' it.
Also, batteries need to match the type of flying you intend doing. I'd want about 500W minimum (about 100W/lb) which means I'd want to be pulling about 50A WOT from a 3s lipo. This would dictate about 5000mAh if you wanted to discharge at 10C. Paralleling your electric power 2200's would get you in the ball park.
Finally, one of the advantages of electric power is the ease with which you can move stuff around from model to model. So build it for what you've got and see how it goes. If it works and you like it - leave it in. If it doesn't work well you can take the motor out and fit a new one. The same with the batteries. Just make sure that when you build you plan to allow stuff to be swapped about. My guess is that it will fly with what you've got but you'll want 'more power' and the pjs will find its way into a smaller model in the future.

Mike
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Old Mar 21, 2006, 10:04 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
Quote:
Originally Posted by Mike Seale
My guess is that it will fly with what you've got but you'll want 'more power' and the pjs will find its way into a smaller model in the future.

Mike
Thanks for all the advice mike. I know your right on the motor thing. Im sure it will fly but i dont think it will have the over all power i want. I have been looking into a geared setup now instead of the DD units. I was looking at a medusa 3400 geared 5:1 swinging a 13X8 prop. It pulled around 40 amps with 80 or so oz static thurst. I just purchased motocalc and will be running some more numbers to see exactly what motor and gear box combo will work best with my batteries i currently have.


Scott I hope that this thread will be somewhat helpful for you and your build, Also if you find out anything better in your quest drop me a line here.

Thanks everyone, This will be quite the experience for me, and im looking forward to the conversion.

I'll post my motocalc findings tomorrrow.
-Derek
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Old Mar 22, 2006, 01:21 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
As promised here are my motocalc findings. I was actually quite suprised at what i found, and after running tests i have decided to go the gearbox route in favor of a DD unit. To get optimum performance with a DD unit i would have had to not only buy a new motor but also more batteries, which doing both was not a option.
Here are the results, i compared a Medusa 28,32,3400 and 4200 and the Neu 1107. Im not sure which motor i will ultimately end up going with because they all perform about the same. According to motocal all three have around a 1.3-4:1 thrust ratio and will get steep climbs and excellent acceleration.

Now the real tast will be to see if i can keep the AUW under 60oz, which judging by the few other conversions shouldn't be too hard.

More to come as soon as i get the kit later this week.
-Derek
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Old Mar 22, 2006, 02:03 PM
Buildbuildbuild, Flyflyfly...
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Copenhagen, Denmark
Joined May 2004
164 Posts
Ooh yeah... Another Somethin Extra "E". I just started to build mine yesterday. Ill build mine more or less stock, except for stick-built tailfeathers to keep the tail light, and counterweights on rudder and elevator for more control authority. It will probably end up in the mid 80s oz AUW. Im going to put a Hyperion Z4020/14 in the nose, with a 5 cell lipo right behind it. Should give me about 900W, so Im not too worried about the weight Ill still be somewhere north of 160W/lb. Should be fun...
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Old Mar 22, 2006, 02:39 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
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Quote:
Originally Posted by lownslow
Ooh yeah... Another Somethin Extra "E". I just started to build mine yesterday. Ill build mine more or less stock, except for stick-built tailfeathers to keep the tail light, and counterweights on rudder and elevator for more control authority. It will probably end up in the mid 80s oz AUW. Im going to put a Hyperion Z4020/14 in the nose, with a 5 cell lipo right behind it. Should give me about 900W, so Im not too worried about the weight Ill still be somewhere north of 160W/lb. Should be fun...

WOW. That should be enough power. Mine will be pulling about 350-400watts. I am going to try and cut out as much wieght as possible to get it down around 60oz or less(hoping for the low 50's). Should be do-able based on the two other conversions i have seen here. I too will be building the tail feathers, and aleraons stick like. It would be a fun comparison to see how your extra E performs on 5s compaired to my lighter and 3s version. Yours most definetly will have more power but would be interesting none the less.

Start a bulid thread for your extra so we can both take tips from one another.
good luck with yours

-Derek
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Old Mar 22, 2006, 05:06 PM
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Belfast / Dublin
Joined May 2004
1,554 Posts
if you are building from kit an AUW of less 55oz is easily within reach - then you can use a Mega 16/25/4 or 16/25/3 and gear it

likewise your axi 2826 xx will be plenty of power - more than enough - you will prop hang with it, but not have wild climb out ... with the geared mega, you will prop hang 'til the doctor arrives.

use micro gear like hitec 85 servos and solite covering and do a stick build on the tail, - stab, ele. rudder and ailerons.... put lightening holes where you can

see Daking's conversion flying at i think 53oz... awesome performance on mega 16/25/4

beware the comments that 400 watts aren't enough - this s only true for a converted 5 lb dog of a SSE ...where standard practice is to put in some monster of an axi 41xxxx motor ... 'nuff said, you don't want to go there.

build light and 400 watts will be overkill for your purposes - especially if they are a geared 400 watts -

the SSE needs almost no pitch speed to fly - even in 4.75lb glow configuration... at 3 odd lbs electric it will float like a balloon

big bird

big bird
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Last edited by big bird; Mar 28, 2006 at 01:13 PM.
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Old Mar 22, 2006, 05:45 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
big bird Thanks for the great info. I am building from a kit and not trying to run an ARF through jenny creig so yah mid 50oz shouldn't be asking too much. I was thinking of running a geared mega, but ii am liking the stats of the neu's better efficent motor, plus a buddy of mine has one and has nothing but good remarks for them.

All in all i think it will be a sweet conversion, and im really looking forward to starting in on the build.

So to recap by final setup will most likely be
Motor: geared 4.4:1 Nue 1107/2y
ESC: CC pheonix 45
Battery: 2x3s2200mah wired paralel to make a 3s4400mah pack
servos: hs-85
Covering: solite
AUW <=55oz
Mods: alerons, elevator and tail fin will be stick construction along with replacing as much ply as i can with balsa, as well as a few other tricks to loose those ounces.

If someone terribly disagrees with my motor choice, speak up. I wont be ordering the motor for a few weeks so i can still be convinced if there is something out there that will run better on my 3s packs

-Derek
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Old Mar 22, 2006, 07:27 PM
Straight up is all I ask
Fairfield Ct USA
Joined Apr 2002
2,323 Posts
A heavy hitter

I'm just finnishing up my Somthin Extra conversion. Hacker c50 10 L 6.7 running on 6s3p thunderpower . I got 1200 whatts at 60 amps on a 16x10 prop. I dont know the weight but I'll let you know how it flies when the wind dies down
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Old Mar 22, 2006, 07:46 PM
Brunswick, Ohio
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Joined Aug 2003
5,736 Posts
FWIW, it's a lot to ask of solite to cover such a big model. I built a glow Somethin' Extra from the kit and I built a Four Star 40 for E power from the kit. With the Four Star I was going to go with Solite for weight savings but the difference in strength is so dramatic that in the end I went with econocoat and it's still in one piece today.

Jim
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Old Mar 22, 2006, 09:46 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
Thanks for all the info, Im not too worried about solite standing up to the task of holding the plane together. The plane is actually pretty strong to begin with, and im not going to be throwing it around hard so honestly not too worried about the solite. Good info though

-Derek
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Old Mar 22, 2006, 10:08 PM
Brunswick, Ohio
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Joined Aug 2003
5,736 Posts
wing twist is more along the lines of what I'm talking about. You may see what I'm takling about when you get it together. Sig makes great kits, the Somethin's extra is a snap to build.

Jim
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Old Mar 22, 2006, 11:36 PM
Dumb Thumbs
Kirkland WA
Joined Jul 2005
446 Posts
ahh forgot about wing twist. you may be right there. I guess i'll find out once its covered. Although the extra's wing construction is pretty strong, it may still flex. And if it does well i'll just remove it and use a stronger cover for the wings, no biggy.

-Thanks for the heads up
Derek
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