RE: Sig Smith Miniplane build
 

These are sweet. I used them on my last project. There was no play at all! I would make sure to use locktite though.

RE: Sig Smith Miniplane build
 

Now have the two fuse sides framed up and completed. Only deviation was that the book called for building the second side over the first. This did not appeal to me as was having trouble lining it up accurately, so just built the second one over the plan. End result was two identical sides, and that was the goal anyways.

Really like the "Super Phatic" glue. No bad odor, stinging eyes and choking [:@], but does stick to fingers. :eek: Dry time is workable. Allowed me to get a couple backyard E-flights in between allowing the frames to dry. :D

Supper call gotta run. Hopefully get back at it later tonight.

RE: Sig Smith Miniplane build
 

Any concerns with the landing gear blocks pulling out on this plane without any additional support added inside the fuse? It just seems a little weak with the small amount of surface area holding them. Has anyone pulled the gear out while flying off a grass strip? Real HARD smack down landings don't count!!! Was thinking of adding at minimum some balsa triangle stock as support, but might make something a little better out of light ply just to give a little more strength????? [sm=confused.gif] Not sure if required.

RE: Sig Smith Miniplane build
 

I went with tri-stock on the gear. It adds almost no weight and, well, what the heck...one less thing to worry about.

Don

RE: Sig Smith Miniplane build
 

When I augered my mini into the ground ([sm=cry_smile.gif]), the landing block, as built per mfg, ripped parts of the fuse sides with it. It is fine stock. However, piece of mind never hurts. Brace it if you'd rather. It sure won't hurt it any.

RE: Sig Smith Miniplane build
 

Lord knows I have tried to knock the landing gear off this thing a time or two[:o]. I have never succeded;). I'll look tonight and see if I added triangle stock.

Rather than making a new post I'll just write here that I built my landing gear blocks with out adding any triangle stock. But you can be sure I used 30 minute epoxy. As Don mentioned, a couple peices of triangle stock are next to no weight.

RE: Sig Smith Miniplane build
 

I just run across this on the internet while surfing a link provided courtesy Model Aviation magazine article


http://richard.ferriere.free.fr/3vues/miniplane.jpg

RE: Sig Smith Miniplane build
 

Thanks guys....I think I will beef it up a little just to be sure.

RE: Sig Smith Miniplane build
 

I'm not going to say anything else about the airfoil either! :D

RE: Sig Smith Miniplane build
 

Looks purdy flat pardner.

RE: Sig Smith Miniplane build
 

My computer went weird and I commented on something that doesn't exist anymore. So edited it out.

I'm pretty sure no one will ever know what I'm talking about, so I'll just say I like the Smith Mini Plane to fill an edited post!

RE: Sig Smith Miniplane build
 

Well, I have made some progress at modifying the (Ugly Duckling)

Here is a picture of what I did for a servo horn to create more differential on the ailerons. I am now getting about 7/8” up travel and around 9/16” down travel. I’ll post exacts later.

The other pictures show where I cut some 1/32” balsa into 5/16” wide strips and then cut four different lengths to glue into the wing saddle for the lower wing. Gluing and pinning them down in a progressive sequence in order to change the incidence of the lower wing. Lastly I did the same thing for the upper wing just wider pieces.

With a little sanding I now have -1° on the lower wing, - 1.5° on the upper wing, while the horizontal stab is at 0°.

I use to have the battery located under the fuel tank and the receiver behind the servos directly underneath the pilot. I have swapped the location of both of those in preparation for the heavier engine and I’ll be moving the “C/G” back maybe an 1/8” or so for more extreme aerobatics.

Next up will be some minor covering mods and patching the holes I cut in the wing to work on the bellcranks.

RE: Sig Smith Miniplane build
 

RICKSTUBBZ,

Looking forward to the flight report. You just gave me an idea... rather than moving the servos into the wing for dual servo setup, what about using two smaller (powerful) servos side by side instead of one in the lower wing center? Connect each to a control rod. Little to no modification required and will get the differential control required via radio programming.

As for my build...coming along slowly. Starting the stringers on the fuse. They are proving to be a little more work than first anticipated as need to get a slight twist in them for proper alignment. Hope to have the fuse completed this week and sitting on wheels.

rc_wings

Had to get out my trusty CA, as the new glue I was using did not cut it for stringers.......Ready for sheeting.

RE: Sig Smith Miniplane build
 

Rick-

How's it coming along?

RE: Sig Smith Miniplane build
 

Ahh..........SLOOOOOOW:).

Not going to see the air this weekend that is for sure[&o]. But I have managed an hour or two here and there to keep it headed in the right direction.


absolutely, there is no reason you could not do that.

RE: Sig Smith Miniplane build
 

I flew my Smith yesterday. Mixed reviews from the modifications I made.

With out a doubt the increased differential on the ailerons made an improvement. The thing will almost roll on an axis now. However the roll rate is still a little slower than I would like.

It is now balanced at 3/8” behind the leading edge of bottom wing. This does not seam to cause any specific handling problems. It is back to being able to snap fast enough to make your head spin.

The wing incidence mod will take some getting use to as far as landing and take off. Use to be that once she started rolling on the takeoff run I would let completely off the elevator (or darn close) and the plane would lift off in a nice shallow accent. Not any more. It wants to stay stuck to the ground and elevator is needed to break ground. Landing is different but ok. Needs a little more throttle at flair. There is now noticeably less down trim in the elevator. But still is not flat with the stab. The airplane seams to track more stable at flat and level flight as well as through shallow corners. Meaning less bouncing around and less corrective input with the ailerons in particular.

One problem I have with this plane is it tries to roll out of a loop. Or any elevator input for that matter. The problem was mild before. Now it is worse. Lateral balance seems to be good. Can’t find any significant flexing. I figure I need to pull the engine off, and the radio out, and hang the thing from the ceiling since it is close to 25 years old.

RE: Sig Smith Miniplane build
 

Neat.


Without the plans in front of me, I don't know if your CG is in fore or aft. If it is aft, it might be similar to increasing throw in the elevator causing the stall you mentioned. Decrease throw.

It actually sounds like the incidence in the top wing fixed the roll-out. I know you liked it when it would lift off the runway on its own, but the straight and level you explained sounds like you got it right.

This would be par for the course. When you change one thing, it always effects the airplane somewhere else. It still sounded manageble though. With time you might get used to it.

Thinking about making a "fresh" Miniplane?

Brian

RE: Sig Smith Miniplane build
 

Sig calls the Smith Miniplane's airfoil "semi-symmetrical" and in general that's probably an accurate description. I think of semi-symmetrical as having an undersurface that's smoothly curved the entire chord but not as deeply curved as the top surface. This airfoil is flat behind the spar so you can build the wing pinned to the board, but with a curve up from the spar to the leading edge. This type of airfoil is commonly described as "flat bottomed with Phillips entry". It's a good practical compromise. Sig's Smith flies so well I never thought it should have symmetrical wings. It's probably also similar to the full-scale Miniplane's airfoil. It's important to realize that the flat portion of the lower surface isn't parallel with the airfoil's center line and that an incidence meter should be used to set the incidence of the wing relative to the fuselage.

RE: Sig Smith Miniplane build
 

The Horizontal is glued flat to the fuse box. This is the centerline of the airplane. Bring the hoizontal level and adjust incidence to wing with the meter. When the bubble on the level is centered on the horizontal, this is zero degrees.

Set the incidence relative to the horizontal. To the fuse would be correct here because there is no incidence to the horizontal, and it is glued to the centerline of the fuse- providing the fuse is square, not warped or twisted.. If you set the incidence to the horizontal, you will run less risk of having adjustments being wrong. It can correct for "slight" alignment issues should any builder have any. ;)

RE: Sig Smith Miniplane build
 

Build is going slowwww. Did not have much time last couple weeks to devote to the SMP as had to do some mods to a couple other birds, and fortunately been flying a little too. :D Hope to have some time this weekend to get some building done.

Rick - Any new mods done to try and improve the SMP? Or you going to retire it and start "fresh"? Curious if you still recommend the changes you made after flying a little more - or stick to the plans????

RE: Sig Smith Miniplane build
 

I recommend putting micro servos at each aileron rather than one centered with long linkages. Mine mounted on plywood hatch covers, servos completely inside the wings.

RE: Sig Smith Miniplane build
 

Wazz Up,

I just finished prepping the Smith for another go at it tomorrow.

I found the solder joint on right rear strut at the top wing had broke lose. Fixed that. (I had redone them all for the incidence change.)

I also rechecked engine thrust. Last weekend I was thrashing so much to get it done I never rechecked them after mounting the new engine. Anyway, I found the down thrust was now 2.5° and right thrust was about 3.6. I am cool with the reduction in down thrust. But the right thrust had increased some. Based on the way the plane was flying last week I decided to take some out. It is now at 2.4°. We will see how it acts tomorrow.

rc_wings

I'd like to see other current "Smith" pilots chime in on what their elevator trim looks like with everything set at 0 incidences. I still say if I were to build a new one I would add at least 1° maybe 2° positive (up in front) on the horizontal stab. I say this because mine when built and balanced according to the book needed significant down trim. I need to play with it some more to know how I feel about the "toe in" on the wings. (Having the top wing negative 1/2° compared to the bottom.) I'll report back after tomorrows flying to see if the thrust helps or fixes my other problem.

RE: Sig Smith Miniplane build
 

After a not so successfull first flight I made the following modifications:

Top wing incidence : -1.5 deg (approx. 2.5 mm ply between the wing and wing support and between the wing and the N strut.)
engine thrust angle: -2 deg (wedge between engine support and firewall)
elevator: trimmed down 5 mm for level flight

RE: Sig Smith Miniplane build
 

I sure had my hands full with my Smith on its test flight, after balancing at the front of the c.g. range and carefully building and checking wings and surfaces for warps etc. it needed lots of down trim, maybe all I had available, and still seemed tail heavy. It was a hairy flight with several near-impacts although a somewhat hot landing went alright. After adding nose ballast and tuning the control throws the plane was a joy. So I have to wonder about the design and suspect the wing incidence needs looking at.

RE: Sig Smith Miniplane build
 

Honestly, I don't remember having all the trouble. Mine were built stock with a little down on the engine.