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Need User's Advice on Sig Mini Plane Bipe

Old 10-20-2007, 09:44 AM
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ClarkFlyer
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Default Need User's Advice on Sig Mini Plane Bipe

I have this kit coming and I've been reading various building posts and there seems to be varying opinions about various parts of the build......as always. Anyway....for those who have built and flown this plane, would you comment on:

1. I have an OS 46AX and an OS .52 FS. Which would you advise me to use? Some people think the .52 4s is too weak, but I'd really like to use it. I'm not looking for blistering performance but I don't want a dog either. What say ye?

2. Do I build the kit per the plans or do I mess with wing and stab incidence.

3. I read where one guy made his own N struts from plywood instead of making the complex struts in the kit....good idea?

4. Do I want to build in some right thrust? 2 degrees maybe? How about down thrust?

5. Apparently this plane ground loops pretty easy becomes its short coupled. Never had a plane that did this......whats the best technique for minimizing this on takeoff?

Do any of you have any other tips for this plane? As always, thanks in advance for your help!
Old 10-20-2007, 02:45 PM
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khelsea
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Built one of those 25 years ago. Stil have it. It builds tail heavy it could use extra motor weight. I used a K&B 40 pumper on mine and it took all of the power to get rolling. Gear was alittle weak and could use an upgrade. Keep adding power slowly to keep on the groundloop thing going. Flys great and very aerobatic. It can be a long build. Lanny
Old 10-20-2007, 03:52 PM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Thanks for the comments....any others?
Old 10-21-2007, 06:31 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Built mine as close to spec as possible, and it flies great! Balances perfectly with a Saito 62 up front, as well as a 1000mAh NiCd in the nose. Covered with Monokote. This kit was my finest yet, took me about 5 months of serious attention to detail.
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Old 10-21-2007, 06:33 PM
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Rv7garage
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Don't know if there's any advice I can offer, but I have a Miniplane thread out there that highlights the build. Here's the link and a couple more pics.

http://www.rcuniverse.com/forum/m_48...tm.htm#4870668
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Old 10-21-2007, 09:29 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

It comes out tail heavy with A .46 two stroke. I had an OS fs70 that I installed as the second engine and that cured that problem. If I built another one I would have ailerons on the top and bottom wing to give the roll rate the needed boost but that's just how I fly.
The ground handling problem was helped out A lot by having A switch I used for take offs. I would hit the switch and it added some right rudder, after I got used to it I just added some negative expo to the rudder, about -40% and I didn't have anymore ground handling problems. After you get used to how it handles there is no real problems but it is short coupled. Today I don't have many problems with any plane but back then it was A hand full, A great little plane in the air though. Have fun with it.
Old 10-31-2007, 09:16 PM
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slim_pkns
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Default RE: Need User's Advice on Sig Mini Plane Bipe

I flew my Smith Miniplane for about a year until I lost it to a mid-air with a profile (grumble, grumble). I had a Magnum .45 2-stroke in it and it had plenty of power. I don't have much experience with 4-strokes so I won't comment there.

Mine flew great but did balloon on exit of a turn and wanted to climb even with a little throttle. I kept it nose heavy so I don't think that was the issue. I'd suggest a bit of down thrust. Maybe others will disagree. I had several old-timers at the field suggest I add some washers to the top two engine mount screws but I just learned to fly it as is and added a liiiiiiiittle down elevator when necessary.

I loved that model and I would recommend it to anyone that loves biplanes.
Old 11-01-2007, 08:50 AM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

I appreciate the feedback. I decided to build it according to plans and live with the ballooning issues. I'm going to put an OS .50SX in it so it should have plenty of power. I build kind of heavy so it ought to be ok. I have the fuse pretty much done, tank mounted. Next step is to put a platform in for the servos and then onto the wing. Definately a builders kit. I'm getting a lot of good building experience. SIG definately assumes you've built a lot of kits when they put this one out.
Old 11-01-2007, 02:27 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Such a great little plane, but yes, Sig doesn't go into a lot of detail on the build. Still, it's a very straightforward design with nothing to really trip you up. I put dural gear on mine to avoid problems I'd read about the wire gear, so I con't comment on how the wire gear works. The dural gear is great. Take-offs and landings are a walk in the park.

Everything else I built per the plans, including the N-struts, which were quite a job. I like the 1/6" wire in the struts soldered to the mounting brackets, although I burned a little wing sheeting in the process. I'm not sure replacing the struts with plywood would look as nice.

Your plane will scream with the O.S. 50SX. Mine came out only slightly tail heavy with a SuperTiger .45. An ounce of weight on the nose balanced it out. It flies beautifully, and doesn't balloon with throttle nearly as bad as I was told, certainly not as bad as most trainers. It rolls very realistically, and flies both fast and slow with ease.
Old 11-02-2007, 11:00 AM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

To answer your questions:

1 - An OS 52 four stroke is the ideal engine in my opinion. Mine has the old 61FS (20+ years old) and it's more power than necessary
2 - Build per plan but I recommend 1-2 deg positive incidence in the horizontal tail to reduce balooning
3 - I made the "complex" struts per plan and am extremely happy. Wasn't really difficult to do
4 - No side and No down thrust. It's not required
5 - I simply installed a small, cheap, GWS gyro on the rudder, it takesoff and lands straight as an arrow. Cheating? no, it's called "using technology for your safety and enjoyment".

A lovely model. Did rib stitching and a descent panel on mine, took some time, was worth it.
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Old 11-02-2007, 02:22 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

For those who may need it:
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Old 11-03-2007, 10:14 AM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Good responses all...I'm not experienced at all with gyros. How do they work? Stunning plane, by the way!
Old 11-03-2007, 12:54 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

A gyro is very easy.
Use a simple cheap one, since anything beyond that will be wasted since you are going to be using standard servos and not some super quick digital ones.

The gyro comes with instructions, it plugs into the rudder socket in the receiver and the rudder servo plugs into the gyro.
Mounting is using double sided foam tape to the fuselage side.
Set the sensitivity to about mid range, it's enough for the standard servos.
Instructions explain all that, and it's easy.

Do note however, it is a "rate gyro" and not a "heading holder".
The former simply senses yaw and gives rudder to stop it, but will not return the nose to the original heading, whereas the latter does that but you don't want it (it's used on helis)
In any case the rudder command always overides the gyro.

In practice, the correcting rudder is simply fed in earlier by the gyro, than the flyer can sense/see it is required, and the amount the gyro gives is almost the exact correct amount whereas most flyers give too much and result in an overcontrol situation.

In cross winds/gusts it's very helpful on such a small short coupled bipe, and also I can make super long takeoff runs with hardly any rudder corrections.
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Old 11-03-2007, 08:36 PM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Ok, I looked up the GWS Gyro....it was a P-something. $34.99. Here are my questions:

1. Does it come on when you turn on the receiver switch?
2. I have a 6EXA radio. Can I hook it up so that I can turn it off after takeoff?
3. How does it affect normal flight?
4. Would it have any effect while doing stunts such as snaps, rolls, loops?
5. Do you notice much faster battery discharge?
6. Any negatives at all?

Sounds like a pretty nifty deal. Squirrley planes can be a pain and this just might solver it.

In any case, thank you for your feedback.

Dave
Old 11-04-2007, 11:10 AM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

1 - yes
2 - I don't know, but why would you want to? logic says if it's on the rudder channel, it's always on. You can however fool around with the sensitivity.
3 - Makes it look a little better, it corrects uncommanded yaw moments automatically before you even notice. In gusty weather it's definitely better.
4 - Have rolled and looped it and it tracks beautifully (I "suspect" the gyro is making me look better there ) but haven't snapped it, I suspect the real Mini doesn't either
5 - Not at all, I think it takes the same current as an idling servo
6 - Yes, some people call it "cheating" but I am not exactly sure why. I call it a "partial fly-by-wire" Actually I have decided to put one in every small or short coupled taildragger in the future.
Old 11-04-2007, 11:31 AM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Well, might have to put one on order. A member of our club has a miniplane and he has a heck of a time getting it off the ground. Life's too short for that, plus you run the risk of doing damage with ground loops and such. I'd rather crash it due to my pushing the envelope!!!

Thanks a lot for the advice.

Dave
Old 11-06-2007, 04:37 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Am now flying my second Smith, lost the first one due to stupidity. Flies great and very scale like with an OS 52FS. The N struts are a pain but worthwhile taking the time to do right. I put 2 degrees of right thrust in motor and felt that it really settled down the torque roll left on take off. Haven't had any problem with the wire LG. Pretty lihtweight plane and reasonable landings help.
Check your wing incidence, I didn't and the first flight was almost a disaster!. Top wing was out 2 degrees negative and made for on hek of a wild ride. Good luck with yours.
Old 11-06-2007, 05:49 PM
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Spike
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Default RE: Need User's Advice on Sig Mini Plane Bipe

I built mine stock and it flies fine. I think I have an OS 70 4S on it. You do have to stay on the rudder and be carefull though.

http://gallery.bidinger.org/v/RC_Pla...t-Fleet/Smith/
Old 11-06-2007, 09:32 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

I flew mine in scale meets and a fullsize airshow. I used coverite/dope in the box top color scheme, and an OS 40 with a Jtec manifold. This was back in the day...'77 I think. It was a very good and forgiving flyer. I don't remember having a problem with tail heaviness. Lost it when another plane crashed straight down on top of it while parked on the flightline. Yes, a midair on the ground.[&o]

Yak
Old 11-07-2007, 08:56 AM
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ClarkFlyer
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Default RE: Need User's Advice on Sig Mini Plane Bipe

Thanks for the responses...and the pics. Spike, your cabane struts look a ton better than mine. I kind of made a mess. If I can't clean them up, I'm going to rip them apart and just start over. The final epoxy is drying as I write. We'll see.
Old 11-07-2007, 01:48 PM
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Default RE: Need User's Advice on Sig Mini Plane Bipe

ORIGINAL: ClarkFlyer

Thanks for the responses...and the pics. Spike, your cabane struts look a ton better than mine. I kind of made a mess. If I can't clean them up, I'm going to rip them apart and just start over. The final epoxy is drying as I write. We'll see.
I seem to remember that those struts were a lot of work. Glue, sand, fill, sand, fill, ...

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