RE: Sig Smith Miniplane build
 

Here are my latest “observations with my “Smith” and the ongoing experiments…..

Now it weighs 6lbs. I don’t have my notes with me. I think it was around 5lb 14oz with the other engine.

I have heard people make reference to this plane being a floater. One thing is for sure theirs and mine don’t fly the same. I about planted it yesterday because I forgot that it is not a floater. I have a 71” stick plane that floats. Lands at walking speed. The “Smith” will fall out of the sky at walking speed. I guarantee it…[:o]

Anyway, I put another 5 flights on it yesterday. With the right thrust change (reduction to 2.4°) the plane behaved better. On this note the plane was more stable in hard elevator maneuvers and recovery to flat and level was a lot more predictable.

I am inclined to believe some of the differences I am seeing in thrust all of a sudden is that with this engine I am using 12” props and with the other engine 10”.

It is flying funky while inverted. Even at half throttle it tries to climb when I go inverted. So, I will be moving the CG forward from were I have it. Back to the manufacture recommended location. I may also decrease the amount of down thrust.

Late in the afternoon the air went completely calm. Along with having some more stick time with the new configuration, I was able to pull of some nice touch and goes in both directions. Meaning, I am getting use to the new take-off and landing characteristics of the negative wing incidence I now have it set up with. I have always landed this thing with “power on” but now it is a must.

rc_wings
On the note of Props and the ST51…
I have been running a 12X4 for break in and switched to 12X5 yesterday. I am still running it pretty rich. None the less the engine was happy about the switch. Next time I will move up to the 12X6. Sister engine to this one pulled a 13X4 nicely on a 64” 6 1/2 pound-ish Decathlon.

RE: Sig Smith Miniplane build
 

This was a korky charachteristic of mine as well. I think the airplane was just plane confused. It didn't matter if it was inverted or not, when you applied power it wanted to climb.

I think the 1.5 neg on the top wing is good, but I think I would leave everything else stock.

RE: Sig Smith Miniplane build
 

Hi Supa Gloo
Can you show me how and where you fitted your perry Pump, I will be doing the same with an ASP61. I was going to mount it tottally upside down but you seem to have got it all inside.
I will start posting some photos soon.


TAC221

RE: Sig Smith Miniplane build
 

TAC221,

Do you need help with the pump in general...or specifically for installation into the SMP?

rc_wings

RE: Sig Smith Miniplane build
 

I'm in the process of building one of these planes. I have completed the top wing and just completed soldering the cabane struts without installing the plywood strips for the wing hold down bolts and when trial fitting the top wing on the struts the straight portion of the upper struts overhang the slot in the wing about 1/8" on each one. Has anyone experience this and how should I remedy this. Would decreasing the angle of the cabanes effect the flying? I would appreciate any help with this. Thanks...Pete

RE: Sig Smith Miniplane build
 

Pete,

Do you have a way to get a picture or two? That sure would help make sure we understand the question before throwing suggestions at you.

If you get things far from what the intended design was with strut angles and all you could find the need to modify the N-Struts because of it.

My suggestion at this point would be to compare and measure according to the plans side view and front view and try to find what is causing problem. It may be nothing to worry about??? It could be as simple as trimming the 1/8" off the wire and add plywood plates.

Good Luck

RE: Sig Smith Miniplane build
 

As a silent watcher while my build has been going, I finally maidened tonight. Scary scary scary!!!!:D Pitchy as anything I've ever flown, and needed all the down trim I had (as others have written) and more.

I perused the thread 'til my eyes went buggy but haven't really found if anyone has found a good CG to go with. I'm right at the LE of the bottom wing, ever so slightly nose down. Not sure if this is the problem, but it is what it acted like.

The flight was exciting, and although scary, it made me smile, because it made my heart pump. It settled right in for landing, a real floater, (after a horrible balloon on the first shot), and got zero damage. Although I wanted to try again right away (I must be a masochist), common sense prevailed, and I put her up for the night.

Any help for the extreme pitch issue from the gallery?

I'd post a pic, but the file is huge, and I don't want to resize it right now. Besides, it's boxtop, and we've all seen those. Dang it's pretty though!!;)

BTW, power is a Magnum 52 4s, and seems very well matched for the plane.

RE: Sig Smith Miniplane build
 

I built my Smith per the Sig plans and fitted her with a OS 46AX. I balanced it without any weight added right in the middle of the recommended CG. Incidence is per the plan also. No bad habits with this one and only a few clicks of down trim required.

RE: Sig Smith Miniplane build
 

reincarnate

Congratulations on the maiden.

We always like to see more pictures of a “Smith”. Open your picture and do the “save as” option to create a different picture to modify the size and this will leave the original untouched.

Pitchy you say? First question would be: How much throw do you have on the elevator? Ailerons can use about all you can get but the elevator is good with a small amount of travel. Somewhere not too far back I posted what I am using for throw and it is close to being too much.

You mentioned your plane is floaty on landing. How much does it weigh? Just curious.

I am still amidst experiments with mine. (have not touched anything airplane for about two weeks). But I am confident in saying the Sig suggested “CG” of about 3/16” behind the leading edge of the bottom wing is very good. Thus you would be a little nose heavy but obviously flyable.

Maybe experiment with a small amount of down thrust. Good Luck with it.

RE: Sig Smith Miniplane build
 

I just finished mine last night. Almost finished anyways; I just need to finish gluing the windshield on.

It's got a 46AX and a Bisson pitts muffler, the rest s built according to the plans with only a couple very minor changes. It balanced perfectly without adding any weight.

I'll probably bring it out to the field and get it in the air next weekend.

RE: Sig Smith Miniplane build
 

icegs,

Very nice job...looks good in yellow! Is that the test pilot in pic #2? ;)

RE: Sig Smith Miniplane build
 

The SMP is getting the pre-flight cat scan.

RE: Sig Smith Miniplane build
 

Sure is! I think he's giving it a quick airworthiness inspection before he jumps in.

RE: Sig Smith Miniplane build
 

I'll try, but you asked for it.. Like I said, its just boxtop. I'm tickled with the way it turned out, since the scheme is what what attracted me to it anyway.

I put all the elevator I could manage in, and then threw around (can't remember exactly) 50% expo on it. It was the sudden unexpected and incurable immediate nose up or immediate nose down condition I was looking to remedy. After I posted I went back through and re-checked everything. Upper and lower wing incidence good (+1% with level horizontal stab), and balance right at leading edge of lower wing. I took a shot that has helped before and reflexed both ailerons down 3 degrees (just below the plane of the wing trailing edge) This evidently was the silver bullet, as the next flight revealed a completely different airplane. A perfect little flyer that looks about as good in the air as any I own, and I own a few.

The only thing I'm not quite happy with is the roll rate. I currently have 1 Hitec 85MG running the ailerons, and I'm going to go ahead and install a second, side by side, each independently running an aileron. I can extend the throw this way with overloading the servo, and without gaining too much weight. A simple bit of programming in the radio (JR 9303 and 790 slectScan rx) and no y harness needed either. Perfect for adding aileron differential to make the rolls more axial. I'll let you know how it worked if you're interested.

You may not believe me, as I was surprised. I hadn't weighed it until just tonight. Finished RTF minus fuel is 5lb 4oz. Really happy with it. A video was taken today at the field, and I'll post a link to it when the photog puts it up.

I apologize in advance if the picture comes out huge. I tried to reduce it. Not sure what I'll get.

RE: Sig Smith Miniplane build
 

reincarnate

Box top scheme or not…..It looks nice man. You should be proud to post it. Nice job with the weight. 3/4 lb difference between yours and mine. That will make for a significant difference in flight characteristics.

I’d be interested in reading what you have to write about adding the second servo for ailerons. I think rc_wings was talking about doing the same thing as what you mentioned.

icegs

I am quite partial to the yellow myself. Turned out real nice. Did the feline approve? Good luck with the maiden?


John - - -Cat Scan - - -:D:D now that was a good one .

RE: Sig Smith Miniplane build
 

Here is the latest on my “Smith” experiments:

I left the CG alone at 3/8” behind the leading edge of the bottom wing.

I changed the down thrust from 2.5° to 1° and right thrust from 2.4° to 1.2°. For down thrust reference this is with my stab set at 0° and the wings are still at -1° bottom and -1.5° top.

This is very close to the sweet spot for my “Smith” vertical up lines are stable, my loops did not try to cork screw. Recovery from snap rolls was predictable. Take off rolls were also much improved.

Inverted required only a very slight touch to the down stick to keep it flat and level. However it would still pitch to the bottom side of the plane (climb) on an inverted 45° up line. This is one of the symptoms of being too tail heavy. It still had a slight tendency to corkscrew in outside loops however.

With my particular set-up I do believe I could go back to 0° down thrust with the engine. But keep in mind that is with my wings set-up with -1° and -1.5°.

I can tell you for sure that changing the angle of attack of the wings created a trickle down effect with everything else. If you have never had the chance to experiment with this stuff it is quite interesting when you get to do it first hand in comparison to reading about it. I also believe that the bigger props that I am now running due to the engine change have adversely effected how the plane flies as well.

RE: Sig Smith Miniplane build
 

rc_wings or anyone thinking of using the Super Tigre .51…..

I started off with the 12X6 yesterday. Up from the 12X4 and 12X5 previously. I’m still running the engine a little rich. Also I am using FAI (no nitro) fuel. Anyway, the 12X6 is a pretty good prop for this engine in this aircraft weight range. However at full throttle it pulls the “Smith” along pretty darn quick. Of coarse there is the throttle stick. It doesn’t have to be all the way up.

I put up one flight with a 13X4 prop. There are pro’s and con’s with this prop on my plane (at my planes weight). I liked the speed and pulling power with this prop. Take off run was stable (no excess torque to the left) But it would help cause some thing to be very cautious of when going vertical. One example being on a stall turn. As I cut back throttle to around 1/4 to bleed off speed (while going vertical) I waited too long to pull the throttle back to idle and kick the rudder and the thing went right into a quick torque snap. Also I was hanging it on the prop once with a lot of rudder and elevator stuck in it to hold it in place and found the plane did not like it. It went into a violent unexpected snap roll/spin. This prop pulls some crazy static thrust and the torque to go with it. All I am saying here is be careful if you try this prop. Until you get use to it unexpected things might happen. It also might be me and/or my plane since it is a little heavy.

RE: Sig Smith Miniplane build
 

Thanks for the info Rick, will take this all into consideration. I have been stalled for a few weeks on the SMP build as the weather has been really nice so have been putting some time in at the flying field and doing some periodic maint on the planes to keep them going. The SMP fuse is almost completed, and as the weather begins to turn, will be able to give it more attention...that is if work does not get in the way!!! Will try to post some pics as soon as there is something substantial to view!

Marko

RE: Sig Smith Miniplane build
 

I've added the second servo (HS85MG) for the ailerons. It fit with only some Exacto work to the bay, as I had already made the ply rails long enough to accomodate. Weight gain was negligible, not even enough to change the reading (...probably started at the bottom of the oz, and ended up on top...) and it definitely gave me a little oomph and throw. Biggest change was that it moved the CG abck about 1/4-3/8", right about where Rick is seeing his. Added a little offset and was ready to test.

Only problem was that when I flew Sunday, the wind was strong and unpredictable due to oncoming front, and my trim was off a little. One exciting flight. Spent about three laps trying to line up to land, and never got a chance to see what it would do, as the wind only got stronger. Not a fun little airplane to fly in 12-15 mph winds, especially coming at 45 deg across either runway. Ok...thats a lie, as it was pretty fun getting it back in. When they're off, and you absolutely have to fly it all the way in, that is a good time...after you're down.

I plan to try again tonight after work if the weather holds.

RE: Sig Smith Miniplane build
 

He! just find this. Here is a version of the SM. Built per plan Power OS SF 40. Really a CRAFTMAN KIT. This little plane will test you and you have to be patient. Raymond

RE: Sig Smith Miniplane build
 

Good Job!
Congradulations!

RE: Sig Smith Miniplane build
 

Warbird2, I like that rubber suspended landing gear arrangement!

RE: Sig Smith Miniplane build
 

I finally managed to get mine in the air. It's been sitting ready to go for a month now. I had it up three times, and it flew great.

I have a 46AX with a 11x6 prop, and it's more power than this plane ever really needs. Vertical performance isn't really a problem. It will climb straight up at about 2/3 throttle as far as I could ever want. Ground handling is not bad at all. It definitely has a good pull to the left when you open the throttle, but it's very predictable. Landing is a breeze. It's been the easiest first flight of any of my planes. The only trim was about five clicks down on the elevator. I started having fun with this one right away. Aerobatics are smooth, and the snap rolls are impressive.

It was built almost exactly according to the plans. The only changes were a little bracing for the landing gear, and a little strengthening in the spar joints. It came out to 5.3lbs fueled and ready to go.

RE: Sig Smith Miniplane build
 

Nice work icegs. Congrats on the successful maiden!

RE: Sig Smith Miniplane build
 

Real quick...What size pilot are you guys putting in the Mini??