Hi there, a friend of mine just bought himself a North Star in good shape(see pic) Before we test fly it could anyone out there give us an indication of the location of its C.G. It was presented in RCM magazine 3/1986 but that issue is no longer in my shop so thank you in advance for helping us....Cheers/Harald

about at the le of the wing tips should start you out ok-

Where is the fuel tank located at?

Check these old posts:

http://www.rcuniverse.com/forum/fb.asp?m=2586438

http://www.rcuniverse.com/forum/fb.asp?m=3210253

http://www.rcuniverse.com/forum/fb.asp?m=6138704

Behind the at

Lnewqban......thanks a lot, a metric plan was shown in post #14 of your first link above. How could I miss that in my own searches..[]...oops...and thank you - just what we need...Cheers/Harald

You are very welcome, Canardlover.

The reason I asked for the location of the fuel tank is that, if it is located aft the CG, the balance should be done with the tank being full.
As you know, a tail heavy condition is to be avoided.

Good point Lnewqban, we will check c.g. carefully. I have painful experiences since way back that "Tailheavy airplanes certainly do fly - ONCE" and that is exactly why we did not want to take a chance in this case.This plane deserves a better future than being "rekitted"......will keep you posted..Cheers/Harald

If memory serves, the CG quoted for the Northstar on the plan is for the dry aeroplane, tank empty, and is 50 mm ahead of the step, and they warn against using a bigger tank than (about) 250 ml to avoid getting tail heavy.
I used to place a pencil on the bench and balance the model on that.

That CG at 50 mm is quite safe, even sluggish after a while and it needs a push of down to hold inverted.
After a bit of flying experience you might want to move the dry CG aft a little, to 40 or even 30 mm ahead of the step

Howdy, the North Star flew last night but it sure was a SCARY flight...[X(]....The model was very "squirrely" to fly probably a result of a gusty wind combined with a very mushy elevator control. Yes, that looooooong plastic elevator control snake is far from optimal. Engine is an OS.45 FSR and a rather large 8 oz. tank is placed right behind engine in the pod. We filled her up to 2/3 with fuel and placed c.g. at 50mm ahead of the step with some weight added to the nose. Thanks alasdair for giving us that piece of info on the c.g. placement - had we gone according to the plan - just ahead of the step - I think the plane would have been lost by now...THANKS....!
Plane bounced at start and broke the nose wheel/bulkhead but will soon be repaired.
Thanks all for good info on the North Star.....Cheers/Harald

Hi, I'm glad the flight went well.
The elevator snake can be make to work fine if it is well supported.
It needs the snake outer to be supported at the servo end, and at the elevator end as near the horn as possible. Support at the tank bay floor was just not adequate so I added an extra plywood support, so that the outer was supported right at its end. There was the very minimum of innner showing, and the snake was supported at intervals all the way along. I used the Sullivan precision snake (black inner, white outer) which is supposed to expand less with heat than the other types.

On this model I also did away with the hopelessly vague throttle snake and replaced it with a micro servo behind the tank.
That meant making the tailplane removable for access.

I can recommend configuring the ailerons as elevons (as if the model were a flying wing).
They need a servo each and a transmitter mixer (or the old sliding tray mechanical mixer) so that while working as ailerons they also both come up to pitch the nose up, and both down to pitch the nose down.
Before I did this mod I would not risk an outside loop from the top with just the elevator, but now, no problem.

Alasdair, good idea with the elevon mixer configuration. Most modern transmitters we use have that function. But what do you then do with the elevator control..??..If I remeber correctly from earlier testing just hooking the elevator servo with an Y-cable to one of the elevon servos will only make it move "halfways"...?!.....please advise...Thanks...
Throttle control was OK so we will let it be for now.
BTW, do you ever fly your N.S. from water..??...this ship is not built water proof as far as we can see but that can be fixed with a larger pot of glue........!
Plan to move all servos forward to eliminate/minimise ballast in the nose while fixing the broken nose wheel.....Cheers/Harald

Harald
I flew my Northstars (3 of them over many years) ONLY from water.
I built a derivative design that I call the Lochstar (one i.c. another electric) and it is flown only from water, except for one day in January 2010 off snow which worked very well.

When I do the elevon mix I configure the model as a delta to get the elevons.
Then I put the elevator servo on a spare channel and use a free mixer to mix elevator function into it.

Thanks again Alasdair and others. Second flight the day before yesterday after repair and servos had been moved forward was very satisfying. We could now reduce nose ballast from 280g to 185g. With 2/3 of fuel in the tank we moved c.g back to 30mm ahead of the step - see pic with chalk mark at 50mm ahead of step. Flight was straightforward so next time we will try c.g. just ahead of the step as indicated on the plan......Cheers/Harald

Howdy all North Star lovers. Happened to see an interesting thread with a guy adding some five degrees of down thrust to the engine on an Arrow:
http://www.rcuniverse.com/forum/m_10559476/tm.htm
Anyone who has tried this on the North Star...???...Cheers/Harald

PS...Alasdair...do I see a canard foreplane on your Loch Star..??!!!..I sure like that..more info please and a close up pic...THANKS..!../canardlover

Hi,
I posted this on a "Northstar Mods" thread under Seaplanes. I'll stick them in again on this one.
I based my model on the Northstar (of which I've had 3 over the years, all built by other people and fantastic fun). I made up my own structure, changed the wing section, the span, the fuselage section, made the tail removable, I lengthened the nose, added a cockpit with pilot and all flying canards (and gave it the name Lochstar as it is a bit different). This first Lochstar had an Irvine 53 with standard silencer.

The canards are pivoted at about 20-22% of their MAC and have their own servo. They go about 7 degrees each way for pitch control (mixed as slave to elevator) and about 50 degrees LE up for airbrake (see photos). Airbrake is not strickly needed, but handy in calm weather for steepening the approach and reducing float in the flare.

The canards add a little to the pitch control, but I did it mainly for the looks and the airbrake experiment. Using the ailerons as elevons makes a bigger difference to the pitch response and I definately recommend that. The airbrake experiment was for a future jet powered project in which airbrakes will be very necessary, and the usual options are unsuitable for a delta wing flying boat.

On my latest model, I started with a foam wing core, sheeted it only back to max thickness, and added cap strips on the foam from there to the TE . Then I cut away the uncovered foam leaving what looks like a built up wing, but with the solid leading edge that stands up to rough handling.
This one is electric, powered by a brushless outrunner and 5S lipo (about 750 watts). photos at the Loch Tay Splash-in near Kenmore, which this year is on June18/19.

BTW, a chap had an "Arrow" yesterday at Ullswater in the Lake district, powered by an Irvine 53.
He never did get it airborne.

Alasdair, thanks a lot for sharing your experience with us on the North/Loch Stars..! I am pleasantly surprised to see you brake with the canard but a bit puzzled that the nose does not pitch up violently during braking..?!?..is much compensation needed with the elevator/elevons when braking like that..?? Borrowed one of your pics from the N.S. mods thread where both elevator and elevons appear to be close to neutral..?!
As a swede I cannot help but comparing with our JAS 39 Gripen which also brakes with the foreplane but "the other way around" and on the ground.
Very little - if anything - on engine downthrust in the "N.S. mods thread" - what do you use on the Loch Star..?
OK, I will try to persuade my friend to convert his N.S. to use elevons....Cheers/Harald

The Eurofighter ("Typhoon") uses its canards LE down like the Gripen on the landing roll.
The additional downforce helps to keep the wheels down, increasing the wheelbraking available (as on racing cars).

I turned mine LE up so that they would give additional lift that will reduce landing speed as I want to use them on the landing approach.
But, more importantly, the transient force (as they go through max lift, from normal position to braking position and back) is UP. That means that if I do a go-around (overshoot) from a landing approach the canards move from a high drag position with a bit of lift, down through maximum lift into their normal position. That gives a transient nose up effect which is just what you want in a go-around. A transient nose down might have unfortunate consequences.

I started by using about 60 degrees of LE up for braking, and there is a slight nose up pitch change which needs no compensation on the elevons.

Now I use 30 or 35 degrees of LE up which gives almost as much drag, still plenty of drag, but also a significant amount of lift which needs a little "down" elevon mixed in for trim compensation. That has a side effect of increasing wing camber and so increasing wing lift. It is not much but will knock another knot or two off the stalling speed.
The way I have it configured, up trim affects only the elevons, not the elevator.

I was flying it again on Sunday and noticed in particular that on an already stable approach, when I flicked the airbrake switch, the nose came up slightly but the flightpath angled down noticeably.

On my Lochstars I mounted the engine at zero degrees, no up or downthrust and I am quite happy with that.

Some time ago a Swedish chap called Alexander Thunberg told me (by email) that on the Swedish jet fighter JAS 39 Gripen the foreplanes are at +25 degrees on approach, and on touchdown, with the airbrakes activated, the canard turns down to -54 degrees depending on speed.

Also a friend found photos on the web that seem to show the Gripen foreplanes at a high angle on approach.
I also came across a photo of a Rafale on the approach (to a carrier?) and its foreplanes look as though they are at about 25 degrees.

I have been told that the Eurofighter does NOT use its foreplanes in the air to provide lift or drag in this manner as the structure is not stressed for it, and it was decided that making the whole airframe stronger would add too much weight.

Alasdair, thanks a lot for your input here but it appears we are now starting to digress from the North Star subject quite a bit (all my fault...[]) For this reason I started another thread and hope you will follow.....Cheers/Harald
http://www.rcuniverse.com/forum/m_10...m.htm#10588958