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Old Jun 04, 2011, 08:31 PM
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Sig EP 4*20 with 2 stroke power

Has anyone flown or seen one of these flown? I have an OS 25LA motor that I would like to find a home for. Just wondering how well the 4*20 would work with this basic 25 size 2 stroke. My motor turns a 9x5 prop well but seems to struggle with a 9x6. I love building kits and am impressed with the design and weight of this model. I would like to know where the finished weight may end up with this combo and if it balances easily with a glow motor. Most importantly, I would like to know of anyones actual experiences with this topic and the final results of their efforts. Thanks in advance for your time and efforts. Thanks, Mike
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Old Jun 04, 2011, 09:04 PM
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WAGliderGuy's Avatar
United States, WA, Seattle
Joined Feb 2010
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Yep I have at least 40 flights on my electric version, I love it! Great build too. Check out the main (electric) thread here: http://www.rcgroups.com/forums/showthread.php?t=1245819

Here is the maiden video of mine:

Sig Four-Star 20 EP Kit Maiden Flights! (2 min 2 sec)


Ignore the whole tail-heavy thing, I didn't check the elevator relative to the horizontal stab. Stupid mistake I know.

It flies great and does all the sport aerobatics I know of. Turn up the rudder throw and it knife-edges very well.

If I got another one I would probally put a nitro in it. When I built it, it looked like it would handle the vibrations of a .25 fine but I would epoxy and reinfoce where the firewall attatches to the fuse.
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Old Jun 04, 2011, 11:12 PM
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Wow that plane handles really nice (at least the pilots skills make it LOOK that way!!!!) Good video too--some of them make you dizzy. Most of all---cool kid!!! he knows what hes talking about but is also humble at the end when he says he's lucky he will get to fly it again. And I'm sure he will do well. I am really curious to see or hear about one of these where someone chose the nitro option though. But thanks for your reply--Its late right now, but I'll watch some of your other videos soon. Thanks and happy flying---great to see some young kids into some cool stuff for a change too!!!!
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Old Jun 05, 2011, 11:22 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Quote:
Originally Posted by mikeh251 View Post
Has anyone flown or seen one of these flown? I have an OS 25LA motor that I would like to find a home for. Just wondering how well the 4*20 would work with this basic 25 size 2 stroke. My motor turns a 9x5 prop well but seems to struggle with a 9x6. I love building kits and am impressed with the design and weight of this model. I would like to know where the finished weight may end up with this combo and if it balances easily with a glow motor. Most importantly, I would like to know of anyones actual experiences with this topic and the final results of their efforts. Thanks in advance for your time and efforts. Thanks, Mike
Hi Mike
Back in my oily days, what you're looking at was my favourite type of model - though that my fave engine was the OS25FP probably dates me a little...

One of my designs was, I suspect, awfully close to the 4*20 in many respects - the plan was a freebie give-away in a now-defunct English RC mag. 48" span, it flew on an OS 26 Surpass and had a pretty comprehensive aerobatic envelope. Several were built by others around the OS 20 and 25 FP two bangers also.

Given that mine flew on 'standard' sized servos where I'd use Hitec 225s now, the one above weighed, give or take a little, 48 ounces RTF, covered in the UK's favourite 'Solarfilm' which is a little lighter than Monokote. I usually used a four ounce tank and generally flew on straight fuel, as any nitro content cost severely in the UK and I'm tight

9 x 5 sounds about right - is it a new motor, or well broken in? I recall the FPs taking around a dozen runs in flight to be fully run in, though I'd fly them after a single tankful static, on a slightly rich setting.

Would suggest you look at the nose structure - do Sig make any suggestions as to re-structuring that area to take the vibes of a glow lump? The rest should be fine. Balance - your engine outweighs the outrunner for this model. Just take it easy, fit as much engine stuff - mount, tank, etc as you can to as much model as you can and keep an eye on the CG. It's much easier to deal with as you go along rather than deal with it on a finished model.

For example, if nose heaviness looks to be setting in, you could place the fuselage servos aft of the wing aperture - on the inside, please, don't ruin her looks The trick is, if you have to add weight, add some useful weight rather than just lead.

Should all work out well, never heard of anyone who didn't like their Four Star, any version.

Even more amazing - can still remember all that stuff about engines !

Good luck with your project

Dereck
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Old Jun 05, 2011, 02:33 PM
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i think you will have to reinforce the firewall area of this model for glow as the motor weight will be consideralbly higher and it will generate a lot more vibration too

personally, i think it will compromise a really nice electric design, but it should in principle be do-able

aft-ward servo location will likely be necessary
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Old Jun 05, 2011, 04:39 PM
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Joined Jan 2011
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Sig advertises it for glow or electric, so they will have good recommendations right in their instructions for using glow motors. I am assuming the instructions will be similar to a design that allows for different wheel setups ie: (taildragger and trike). They do recommend the use of mini servos. My 25 is new, it has only been run in a trainer on the ground, except (Note 1). I was just outside running it and notice that the needle setting changes as the fuel gets to 1/4 tank---I have to lean it out to get the same result as the first 3/4 of a 4oz tank. I'm looking at the placement and checking for leaks. This problem has just become apparent and may have had something to do with the bad experience with 9x6 prop. But if it only swings a 9x5 so be it. It is in a new PT- 20 that weighs in at 4lbs 1oz. I built this trainer over the winter with reduced dihedral, taildragger gear with a plastic skid on the tail and dual aileron servos. No flight yet. It turned out nice---I'm proud of the results of the variations I made from the norm. however, I'm afraid I will probably crash it and have a 25 motor to put into a nice light ep20.
(note 1) I had an old 25 3 channel trainer and recently flew 2 good flights in one calm day. Then I put the 9x6 prop on it and took it out in too much wind (IMPATIENT!!!!) It was running poorly and I couldn't keep up enough speed to handle the crosswind and put her into the tree branches. Thats when I built the pt20 and went with the "B wing Sport design" and kept it light with the taildragger setup. I didn't like the torque rod things so I went with dual servos and this may weigh a little more but the specs are 3.5-4.5 lbs and it came out at an oz over 4lbs. Anyhow, I live out in the country and have no club nearby. I crash alot but getting better. Good thing I LOVE to build. Maybe I won't crash the PT-20 and won't have the extra motor, but if I do I'd like to try it in the EP20 design. Still like to know what one might actually weigh done this way and how well it responds. Thanks for you responses and sorry for my storytelling!!!!
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Old Aug 28, 2011, 06:35 AM
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I have the same question as original post, only my motor is a 25 la. Can't believe nobody has done this?????
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Old Aug 30, 2011, 08:37 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Am idly thinking we need a 'how to do video' forum... That's pretty good stuff, WA.

Fervently hoping I don't run across a 4*20 kit in a LHS - could see it following my home. For some reason, it looks more like my dear old 4*40 looked after the clipwing mod...

The slimey mods - just alter the nose structure to match up to any handy 25 - 40-ish glow model plan or kit. It will need to be heftier to handle the vibration for sure. That business of the engine leaning out on the last tankful - any way you can lift the tank a little within the fuselage? A quarter inch could do it - may be that the fuel level in a near drained tank is too low for the engine to maintain the correct amount of suction in the tank.

D
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