Gordie M

Hi All,

Finished my Sig 1/5 scale cub which I have bashed to a L4 with the greenhouse.

Specs:
Kit: Sig 1/5 cub kit.

Engine: OS72a 4 stroke with in cowl muffler adapter fitting. made my own brace for the muffler to stop it coming loose in flight - see pics.

Landing gear: Robort 1/5 scaleCub gear.

Finishing: Solartex Olive Drab + 21st century film Dove Grey. Major decals stars/bars. Coverite stick on numbers. Dulon car paint custom tinted into a spray can for the OD colour, grey car lacquer primer for the dove grey paint.

Weight: 8lb 7oz finished, BUT, she's tail heavy so 8oz lead in nose = about 9lbs flying weight.

Mods:
Basically all on the fuse. Spruce stringers to top half of fuse + hardwood sticks, etc... in the cabin area. Wing mounting as per kit but cut out the roof ribs (part C2 - I think) from behind the back spar section and made my own part rib on the fuse centreline back to the next former (F5 - I think). Cut out most of former F4 and added a new angled former for the back of the cabin. Carbontape on both sides of allcabin formers and vertical sticks. Door and windowstock except I added a window latch to the door latch as per pics. Cabin roof is lift off as per kit, but enlarged back to rear spar - so it's a bit bigger than scale - made from .030" lexan and retained with 4-40 nylon bolts and washers. Extra hardwood blocks in fuse bottom to suit the Robart gear. Non-stock windows are 030" lexan on roof and 020" on sides (this stuff is heavy so I think 020 everywhere would be better) exposed window frames are 1/16 x 1/4 spruce glued with thin CA (very carefully!!) to the lexan - these look too big and I would consider smaller if I ever do it again, but on the other hand you need the width to cover the stick frame structure underneath. 3/16 and 1/4 dowels inside the cabin to mock up the scale bracing tubes. Boot cowl is litho plate alum with rivits using RC56 glue over the stock balsa sheeting.

Documentation:
None. She's a total fabrication of what I liked from looking at other models on RCU plus what I could build (my skills) or source with the tools and equipment I have. It's a flying model, hence the side mount engine. No doubt the "rivet counters" will be horrified........

Still to do:
- Lateral balance .
- Set the elev / rudder throws and loc-tite everything.
- Make some landing gear bungee covers.


Qs:
Anyone who's flown this kit can you comment on the CG location- as per above at the recommended 3 1/2 inches back I'm up for 8oz of lead - will the plane tolerate the CG further back?
Radio setup: I've got 2 to 1 differential in ailerons (1/2" down, 1" up) whats the expo settings you use on all controls? Do people slave the rudder to aileron to counter the adverse yaw?

Pics:

Gordie M

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Gordie M

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Gordie M

Last pics

ggraham500

My Feedback: (4)

Gorgeous

SunDevilPilot

Stunning job!

I have approximately 75 flights on my Sig 1/5th Cub and it is my favorite plane I own. Mine is electric powered. Here is the amount of Expo I use:

(Keep in mind I have a Futaba radio so my expo is "-". A JR would be positive.

Ailerons: Only have high rate programmed and -35% Expo.
Elevator: Low Rate Expo -25
High Rate Expo -50
Rudder: Only have high rate programmed -35

I like to fly the plane with no aileron to rudder mix. The plane does fine but you really need to take advantage of the Cub and learn to fly the rudder.

CG - My CG is right where they said it should be and I think my model flys slightly tail heavy. It doesn't get squirly but I can see I have some down elevator.

Video from my plane. I made a camera mount that replaces the stock wing hatch. I have both hatches so I didn't have to modify the plane keeping it scale.

http://www.youtube.com/watch?v=A0WJelqyLJA

You may consider backing up the o-rings on the gear with a set of rubber bands. I found the O-Rings dry rot fairly quickly and you really don't want to have them fail allowing the gear to collapse.

SunDevilPilot

SunDevilPilot

Something to add.....

I took no effort to lighten up the motor mount and even added a scratch built motor to the nose. With all this weight, and the 5 cell 5000 Mah flight battery at the firewall, I needed no lead. Your weight sounds like it would fly fine. I would venture to say my plane is probably heavier in it's electric configuration. The plane flys light so don't fear the weight.

Here is my motor before paint.

FYI: I enjoy flying my 1/5th Scale Cub so much I decided to tackle the 1/4 Sig Kit. This model is built in the stick truss fashion unlike the laser cutting in the 1/5th scale. Really an enjoyable, if not labor intensive, process. I'll attach a photo of my 1/4 scale as it is today.

SunDevilPilot

Gordie M

Thanks for the info SDP.

My radio is Futaba, so I'll copy your expo settings to start with.

I read your thread whilst building mine and must say your workmanship is the very best I've seen.

I added the nose weight yesterday - bolting to the underside of the engine mount - and will recheck final balance once the bungee covers, etc...are on to get CG exactly as per plans. 9lbs all up should be OK based on your comments.

Just noticed I haven't painted the oil cooler on the cowl LOL....

cheers,

Gordie.

brenthampton79

Gordie that airplane is awsome, you did a great job, one of these days I would like to do an L-4 model of a full scale one I have flown with my orthodontist 5 or 6 years ago. I am having my lhs order me a sig citabria to do a replica of my brothers and I full size citabria we bought this year. Again awsome awsome awsome job!

RCVFR

My Feedback: (7)

Beautiful work on your Cub. I built one with a magnum .70 4 stroke, good for weight and for turning a scale 14" prop, but way too much engine. Maiden flight take off jumped off the ground in about 10 ft, very uncublike, and I had to work through a learning curve to fly it somewhat scale, ultimately dropping down to a 13X6 prop for more suitable power. The only thing I would do differently on a "next" build of this plane would be to replace the upper cabin wing mount area with stronger aircraft ply rather than the light ply provided. Landing stresses can tend to "separate" the wing halves and must be very gentle on touchdown. In all other respects, this is an excellent kit. You did a very nice job.

Gordie M

Jim,

I swaped out all the balsa spars and stringers in the top of the cabin with spruce + added a few gussets and the cabon strip to the the fuse side vertical members. Also the bracing dowels in the roof area between the spars help as well. After the mods the cabin was much stiffer than the original frame up with kit parts, hopefully it's enough. Time will tell....

Balanced her today and set up the radio, just need to run in and tune the engine then its maiden time. I'm picking I'll be way overpowered with the OS72a as you were, but I bought this engine with an eye for future use so will have to learn throttle control as you did.

cheers.

Gordie.

ARUP

Nice job!

bkyrdflyer

My Feedback: (1)

That is one of the best looking cubs I have seen. Good job!

Gordie M

Guys, been a while.

A few pics of the cub flying last weekend. Shes a great thing, I love it.

cheers,

Gordie

ARUP

Very nice! I can see the pilot and radio man were ducking the enemy fire at the time the photos were made! (just kidding around) I'm going to build a 1/4 Navy version sometime.

SkyPilot101

Gordie, Awsome L4, just picked up a Sig 1/5 Cub , you got me thinking!