Tigermoth

Can anyone help with the best CG Location for the Northstar. I bought one with no plans or instructions. I'm going to recover it with Ultracote and have already pulled the old covering off. I'm moving the fuel tank over the CG and also want to move the engine forward to eliminate extra weight in the nose. Maybe 4"
forward and 1" raised. Does anybody have more mods I should be looking at before I start recovering. Someone added 2.5" to the rudder for better rudder response. Is this a good idea? Any tips would be welcome. Thanks.

PeterC

Hi Tiger, I've been flying a Northstar for a number of years now. As to the CG location Mine balances forward on the step when the tank is empty and it rocks back on the step when the tank is full. With the tank on the CG I would keep it resting on the forward part of the hull. Your mods sound interesting but I don't think adding to the rudder will do much. It flys much like a jet (looks like one too) and the rudder is pretty useless except on the water. Make sure you have enough of a water rudder to do some good. Mine is pretty much like the plans and it does not respond well on the water. A hot 46 and a 9X7 Graupner three blade prop works great for me.
Peter

Gill

I am building a plane with a similar engine mounting to the Northstar. My set of Northstar plans shows about a 2 degree downthrust. Have any of you Northstar pilots found the engine offsets critical?

Thanks for your experienced comments.

PeterC

The downthrust is an interesting feature on the Northstar. Personally my next Northstar will have the downthrust removed as I don't see any need for it with the high thrust line. Traditionally, pylon mounted engines have upthrust to counter the nose down tendency of the high thrust line. The arrangement of the tail-engine assembly on the Northstar is unique and when all things are considered I can't see any use for downthrust; or upthrust for that matter! When I build my next one I will be able to add downthrust if necessary but I would like to swing a larger prop and downthrust negates that ability.
Maybe Laddie could shed some light on this design feature?
Peter

Johng

My Feedback: (4)

CG location is indeed crucial on this plane, and takes a bunch of lead. If you can work out a solid way to get the engine forward, go for it.

I test flew one for a friend, and it had "pitch-up". That is, you would get the nose up past a certain angle, and it would just keep going up no matter what you try - until the plane was in a full stall 3-d style tight loop. If you weren't pulling up, the plane was really well behaved for high speed flight. The pitch-up flip was actually kind of fun, as long as you had altitude.

THe end of the flight was a little different. I brought it around and had it in a nice approach, crossed a dock about 20' high and was getting ready to flare, when it did it's pitch-up thing. It didn't have the energy to flip over, so it just hung there vertical for a sec, then pitched down and went straight into the water. Good thing the water was deep there, because it just went about halfway in, until it's own bouyancy stopped it and popped it back up to the surface, where it settled on its belly, unhurt. - Sort of like when you are canoeing and throw a paddle down into the water - it pops back up. If I could do that predictably, I'd land it that way every time.....

Unfortunately, it's not my plane, and I can't help you with the actual location of the CG

tpstorey

The "pitch up" tendency is a characteristic of a tail heavy delta wing. The aerodynamic center of a delta will actually move back as speed increases. So, if you take off at a decent speed the AC can actually be behind the CG where it belongs, but as the delta slows down the AC begins to creep forward till suddenly it is ahead of the CG and the delta pitches up or down suddenly. My North Star did the same thing, and luckily I knew what it was, added a bit more nose weight, and she flew like she was suppose to.

Johng

My Feedback: (4)

I'm sure it also has to do with the fact that the stabilizer is close-in and above the wing, so the as the main wing stalls, the stab gets blanketed with bad air - aerodynamically "disappearing". We could hear the prop stalling in the bad air as well when this was happening.

Same thing happened on FS F-104s and other t-tail planes. The Boeing 717 ( son of MD-8x) has small elevator-like devices on the engine pylons to pitch the plane down should the plane get to the angle of attack where the stab is blanketed.

This would be a much better behaved plane if the horizontal stab was 6" further back and away from the wing.

PeterC

I have noticed the same "deep stall" characteristic on my Nothstar. Laddie M advertised this as a vertical landing feature of this design; I never liked it. I think this is something we have to live with though. If you add enough lead so it will never stall you will also probably never get it off the water,(nose heavy like crazy). Once you learn of this trait just land like you take off,i.e. fast.
The Northstar is NOT a slow speed aircraft, live with it and enjoy it for what it is. More power the better. I have a
Rossi "Q" with pipe for my next one.

Tigermoth

PeterC

Thanks for the reply. I'll play around with that cg location and see how far I need to move the engine forward.

What does yours weigh with all equipment installed?

My plane, bare bones (no covering is at 4.5 Lbs) Seems heavy to me.

PeterC

I think 4.5lbs is quite light. Do you have it balanced yet? Don't be shy with the lead. Better heavy than tail heavy. I have never weighed mine, I figure it weighs what it has to weigh and once it's finished I can't do much about it. I bet mine weighs close to 6.5lbs ready to fly.
Moving the motor forward is interesting; it definitely will save you nose weight but you may get some vibrations and structural problems from the motor being hung out so far. Personally I have no complaints with the original design although mounting the fuel tank mid-ships is a good idea. I've seen that done before and it works quite well as long as your plumbing is in good order.
If you think one Northstar is fun try two, you and a buddy each with one and then do some formation flying.
Peter

Tigermoth

PeterC

I'll post some pics and let you know how it flies when the jobs done. Thanks again.

staggerwing

My Feedback: (5)

From the instruction manual and plans the recommended CG is 16 inches forward from the back of the wing. DO NOT include the alerons in this measurment. I balanced mine there and it flys great.

ayarpee

My Feedback: (15)

Just flew my new Northstar for the first time. Flew fabulously -- what a thrill! Built it just like the manual says, no changes. And no regrets. Weighs 6.5 pounds on my home scale, with about a pound of lead in front. CG about 17 inches forward, just to be safe because you guys gave me a scare. Appreciate it tho. Surprisngly the rear 10 ounce gas tank barely moved the CG when full. Fast, but easy to fly --- tho not for beginners at all. (Reminds me very much of my Great Planes Patriot, rolls on a rail.) Just skims the water on landing, gorgeous. Used OS 46 with standard muffler. Other mufflers could increase the speed, tho mine was fast enough for me. Beautiful

Strykaas

Hello,

I've noticed you've moved the fuel tank to the cg ; do u use a perry pump then ?

aston70

My Feedback: (1)

I think I saw plans for this plane once a long time ago in RCM? Does anyone know where I could get a copy of those plans or what RCM issue it was in?

Thanks

Siskiyouline

My Feedback: (1)

The plans are available from R/C modeler for $20.00 + shipping. The plan number is PL-960 and the issue date is 03-86.

Balsa USA who kits the plane has their plans available for $17.00 + shipping.
I have an older set of the Balsa USA plans and they do not include the wing rib patterns.

Bud

PeterC

Aston70--- The Balsa USA kit is really reasonably priced. Why not buy the kit, it's probably a lot cheaper than scratch building and a lot les agrivating.
Just my two bits worth,
Peter

aston70

My Feedback: (1)

"Why not buy the kit, it's probably a lot cheaper than scratch building and a lot les agrivating. "

Thanks Peter,

This is true from a builder's standpoint, but I have ideas in my head for a different project and I just wanted to see the plans even if it was just a copy from the magazine. I don't want to actually build a Northstar. Besides, I am one of those who don't see any aggravation in scratch building and designing. For me, it's a challenge that I enjoy and kits get old sometimes. It would make sense to just buy one though. I guess I should have made my intentions more clear.

Thanks Bud for the info. I know I had that 03-86 issue once. I'll look and see if I can find it.

Strykaas

What about this ?

aston70

My Feedback: (1)

Yes, thanks Strykaas. That's what I wanted to see.

Strykaas

You're welcome !

I wonder whether my previous post will get nuked ?

PeterC

Here's my vote; I vote the Northstar as the BEST sea/float plane ever.
(I know there's no vote going on but I had to vote anyway.)
Anyone care to challenge?
Peter

Strykaas

I think this aircraft is one of the most original and uncommon R/C seaplane. Not scale though.

Another one is the piaggio Pegna PC-7 : http://www.rcuniverse.com/forum/m_11...tm.htm#1117872

Last, you have the sea dart :