Sig Somethin' Extra advice
 

Greetings all!

I'm currently buildind a Sig Somethin' Extra and I'd like some advice from anyone who's built one or who can give me an engineer's point of view...

1. The plug in wings are quite sturdy (sheeted D-box) but with the double ply sandwich root rib they seem a little heavy. Is this doubling of heavy ply in the root overkill, and would it hurt if I made some (strategic) lightening holes in one or both? The only reason I can think of that these root ribs should be solid (no holes) is for good adhesion in the (max. surface area) in the build...Am I missing something here?

2. Should the firewall (bulkhead) be set back a little to accomodate a longer saito 56 4-stroke?

3. Can two servos be put down the tail for rudder & elevator if the plane is building nose heavy? (I'm doing built-up tail feathers and ailerons instead of the stock slabs of balsa, so it should build out a little nose heavy)

Any advice on these questions will be greatly appreciated...thanks in advance

inverted flyer [sm=drowning.gif]

RE: Sig Somethin' Extra advice
 

inverted, have a couple of questions for you,

2. the Saito 56 is a light engine, why do you think you would need to move it back?

3. the tail feathers and ailerons are built of balsa sticks with the kit, why do you think you would use slabs of balsa?

using a Siato 56 for power and putting the servos in the rear should create a balance problem, very tail heavy.

Ed M.

RE: Sig Somethin' Extra advice
 

Mine is on the board now and I'm sticking with the plans. I have seen several of the ARF versions fly, and everyone knows that kits always fly better than ARF's, so I'm looking forward to finishing it. The model Airplane News article said not to skimp on the engine so I'm using a .52 two stroke. The two ARF's I've seen fly had a .70 four stroke and a hot BB .46 two stroke.

RE: Sig Somethin' Extra advice
 

The SE will take a lot of aerial abuse if you leave the root ribs alone. Most people fly the plane too fast anyway. Making the root ribs lighter may cause you some real problems in high speed, high "G" load situations.

The plane flys great the way it was designed. Save yourself the time and trouble and build it the way it comes.

RE: Sig Somethin' Extra advice
 

Thanks very much for the feedback, but I'm still in the dark on a number of points:

1. In response to Bentgear, I'm using stick built ailerons & tail instead of the kit slabs...the kit tail/aileron is slab-built (just 1/4" slabs with some holes cut in), not stick built, so I'm hoping to save weight/increase strength ....I'm also hoping to use carbon for the tail-braces, instead of the supplied steel, and with both of the above weight advantages, I hope to have the opportunity of mounting a servo or two down the tail....any comments?

2. Also, agreed, the saito 56 is light, but it's considerably longer than an equivalent 2 stroke, so I thought that for both esthetic as well as CG reasons, I might move it back some, to place it's mass where it ought to be... and so that it looks right

I agree also with Paul Carnes that a 56 maybe a little under-powered, but it's a start and since the mounting holes are identical to a saito 72...I can always upgrade to the monster... when the monster calls

Silversurfer makes an interesting point about high G/ high load situations, (so maybe I'll leave well enough alone)... but most of those forces are acting on the aluminium wing tube, that is to say, transferred from the wing surfaces via the spars through the first couple of ribs onto the cardboard phenolic impregnated female tube and onto the aluminium tube....If this is correct (and I'm not sure that it is), I don't see why the root ribs can't have holes fore and aft, at a respectable distance from the main wing-tube assembly. Any comments?

All comments welcome and many thanks for those already offered:D

RE: Sig Somethin' Extra advice
 

Inverted, sorry I got the tail feather construction mixed up with another plane someone asked me about. Yes, it is balsa slab with holes, but the two I have built sure were light already.

You can also use one long piece of grass trimmer string for the tail bracing. Thread it thru the hard points in the vert and horz stabs and then drill two holes in the fuse close to the bottom. Run it thru the holes in bottom and then CA where it comes out the other side. Great strength is not needed, just something to keep the flex out.

While not a full blown 3D machine, it sure is a lot of fun to fly. Keeping it light just makes it fly that much better.

Ed M.

RE: Sig Somethin' Extra advice
 

Apart from, possibly, increasing the rudder area, and using sheeting on the turtle neck to stop it looking like an emaciated horse, and replacing the tail wheel so it doesn't stress the rudder so much, I see no reason to modify anything on the SE.

I have built two; used 1/64th ply on one and sanded 3/16 balsa on the other behind the canopy, over the existing stringers. They both fly great, doing exactly what I ask of them.

-David C.

RE: Sig Somethin' Extra advice
 

mine is by the prints, with FS OS 70 up front,my only change was to use golden rods for controls,sig is to soft,had to move the battery to the rear of fuse for balance.

RE: Sig Somethin' Extra advice
 

David C.

Where did you find 1/64 ply?? The best I could find at the LHS was 1/32 balsa.... that looked like paper almost and you used 1/64??? Help.

RJM

RE: Sig Somethin' Extra advice
 

The tail- wheel mod sounds good, as does the rudder - thanks for that D.Cutler....I'm bent on gittin' this thing down as close to 4 lbs as I can....
thanks for all the input and keep it coming
;)

RE: Sig Somethin' Extra advice
 

RJMcNaughton,
Balsa USA
http://www.balsausa.com/wood/itemlis...=29&shopperid=
1/64" X 6" X 48" Birch ply $5.58

RE: Sig Somethin' Extra advice
 

Yes, you can move the firewall back so the engine's mass ends up in the same place as it would with a two-stroke. In, fact you probably won't be able to get theCG back far enough unless you do move the firewall or resort to putting servos and/or the battery in the tail.

Personally, I'd keep the servos inside. It looks better, and the servos don't get coated in oil. If you feel the nylon pushrods are not good enough, you can use the yellow Sullivan rods, or get some carbon fibre pushrods from Central Hobbies. Run the CH rods through the standard nylon outer tubes.

Converting to pull-pull is also an option, but quite a bit more work than just using carbon rods.

RE: Sig Somethin' Extra advice
 

If there's anything that can improve an already great flier it's making it lighter. With your Saito 56 it should fly great.

It already floats as slow as you like on landing, and is the only aerobatic plane I have ever had that shows absolutely no sign of snapping at higher elevator deflections.

As you've probably read, it's worthwhile restricting the aileron movement to only about 40% rate, at least on the first few flights as it rolls in the blinking of an eye!

-David C.

RE: Sig Somethin' Extra advice
 

David, what size engine do you reccomend for the somethin extra. (2-stroke)

RE: Sig Somethin' Extra advice
 

I put a 2 stroke thunder tiger .46 on mine and have not had any issues whatsoever. as mentioned before, most fly this plane way too fast. I have 2 planes with the tt .46 and don't think I have owned or seen a more responsive engine. I feel it's a perfect match for the SE.

HL

RE: Sig Somethin' Extra advice
 

Mine has a TT .46 on it as well. Good match.
John

RE: Sig Somethin' Extra advice
 

Ditto with the TT46 Pro. My kit built SSE flies great with this
motor swinging an APC 11.5 X 4 prop.

A 12 X 4 would probably give a bit better verticle but there is
no quite enough ground clearance using the stock landing gear.
So the 11.5 X 4 is the best bet.

Mike Hammer

RE: Sig Somethin' Extra advice
 

Here's what I did to my SE.

Replaced main gear with Dubro fiber gear which is taller so I also beefed up the landing gear plate. Replaced the tail gear with a Sullivan gear. Sliced off the top half of the tail fin and fixed it to the leading edge of the rudder as a counter balance. This improved knife edge performance big time! I have a friend that just added material to the trailing edge of the rudder and his doesn't come close to mine in knife edge and he has more power on the nose than I do. Moved the elevator servo to an aft mount just under the horizontal stab. Added pull pull cables for the rudder. Slapped an OS50SX on the nose and she's one happy bird! I've had a stock SE before this one and I was very happy with these mods. Don't over look beefing up the landing gear plate... especially if you fly on a grass field... :D. I've got pics in my gallery if you want to take a peak.

btw... to those of you who state that this plane needs no mods and flies great per plans. I agree. I like the SE as a stock per plans plane too... so please don't take offense to my mod suggestions. But I also like to put my own stamp on what I fly to see if I can improve performance, looks or whatever. That being said bashing and mods can be fun too [8D].

RE: Sig Somethin' Extra advice
 

I have the Evolution .46NT on mine. I'm using an APC 12.25x3.75. The .46NT seems to have more power than the TT .46 or OS .46FX. I later put the Tower muffler on it and gained around 1000 RPM.

To have ground clearance I put a 1/2" block under the main gear. I sanded a leading edge, covered it, and it looks good. You may want to consider doing something like this because it doesn't look bad at all if you shape it well, and they work.

RE: Sig Somethin' Extra advice
 

Hey all, I'm building #2....the trees took the "initial" life of #1. Build goes much faster the 2nd time! I have a Magnum 52 for this one, stayed mostly stock except the tail wheel.

I have a funky warp in the fuse side of the left wing, there is about a 1/8" gap at the TE, does anyone think this is a big deal? I dont know how I would even fix it..... I thought it was a little off when building but not that much, kicking myself for not asking for a new part from Sig.

Mac

RE: Sig Somethin' Extra advice
 

The easiest solution is to cut a "wing rib" from soft 1/8" foam and sandwich that between the wing and fuselage. Works a treat, weighs about nothing and takes 2 minutes to do.

/Red B.

RE: Sig Somethin' Extra advice
 

Miine has the same gap on both wings at the ailerons.

RE: Sig Somethin' Extra advice
 

I am having a blast flying the kit I finished 2 or 3 months ago. Slow, fast, sane or insane. Saito 56 with APC 12 x 6 does great for anything but very extended vertical. Used the 2 - 56 metal pushrods from my old ultra stik 40 for elevator & rudder. Ran them in the som-xtra outer plastic tubes with Dubro ez links on servos and Dubro safety lock kwik link at the surface. Added Dubro HD servo arms and control horns. Drilled landing gear holes so 8-32 nylon screws with matching blind nuts in the fuselage could be used. Just say no to wheelpants/wingpunchers. Tailwheel is the type that mounts in a slot in the rear of the fuselage with the steering arm going into the rudder. With a flat receiver pack you can move it from the firewall to the servos for balance changes. I did not need any added weight.

RE: Sig Somethin' Extra advice
 

Did you use a mini servo like the Hitech HS-55 for the throttle? I flew mine today with the new servo and it is a bit lighter.

Another way to save weight is to use wood dowels for the pushrods thru the fuselage. Glad to hear that you are using the Saito .56. I have that on my Sig Kavalier and it flies great. You can cut weight some more by going down to an 8 oz fuel tank if yours is larger. Mine runs about 15 minutes, or more on that. I use the APC 12x6 prop too.

Featherlite Dubro wheels saves a lot weight.

RE: Sig Somethin' Extra advice
 

Inverted flyer, To save weight you can probably drill lightening holes in the wing ribs and, as you suggested, stick build the tail feathers. The slab stock feathers work just fine and were most likely very economical for Sig to make. That said, as a professional woodworker, that slab construction is a POS. I put a Sullivan tail wheel on mine (great) and enlarged the rudder by 1 1/2" (38mm). I chucked the stock landing gear in favor of a polished aluminum gear with taller and wider stance. Photos in "my models". As a suggestion, if you wanted to make an engine cowl, having a longer engine like that Saito .56 would make a better looking transition from cowl to fuselage. Good luck!