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Northstar mods - Tell me what you think

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Northstar mods - Tell me what you think

Old 12-19-2016, 07:58 AM
  #551  
Cougar429
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Just sold my Northstar to my friend. He still had not completed the other I built for him and this would help get him airborne.

Figure if I build another, (#8) I will incorporate some of the mods to help keep the weight down. Until then guess I will just have to enjoy the two Polari.
Old 12-31-2016, 09:10 AM
  #552  
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Originally Posted by Aussieflier View Post
Hi,I have been following this thread and thought I might bring something to the table.I think that it should be said that good design in modelling also includes the ease of which the model can be built. The designer of the Northstar has taken this into account and as such many modellers over the years have comfortably started, completed and have successfully flown their Northstars. For the more experienced modeller the Northstar's simplicity encourages one to make a few modifications if for no other reason than to build a little bit of ones self into the model. In my opinion I think it a little bold to suggest that Northstar is or was lacking in it's original design. If you were to approach any designer of full sized aircraft and tell him that you intend to build his design 40 to 50% heavier the his specification he would tell you in no uncertain terms that it will not fly. It also needs to be said that since the Sea Dart ,no aircraft company ( that I am aware of )has even tried to get this formulae for an aircraft to work, I think this clearly indicates that some very expert designers have decided that a delta wing flying boat is not an easy task. The Sea Dart design required water skies to get enough airspeed and AOT to lift off, this was all about weight.A few months ago some friends of mine encouraged me to build a Northstar, my background is F3A and so I decided to upgrade the look of the model a little. I would not dare to say that I have improved the model, perhaps I can say that I have prettied it up a little. I have built the model with an electric power plant as was suggested by my friends, this turned out to be the heavy option but I think the power to weight is OK, as I have a great deal more power than a 0.46.The motor is Turnigy 600 1100 1.1KV 50mm, I am running 6S and turning an APC 10 x 7 at 19,000 rpm while drawing 105 amps.The fuselage sides and lower fin are boxed up as per the original plan, the turtle deck, canopy and nose upper are all planked in 1/8 balsa, as is the engine pod. I incorporated the 1/8 balsa fuselage bottom and then fitted a 1/8 ply keel, I then planked the Vee bottom with 1/8 balsa to form a very strong triangular box hull. i.e. All of the Vee hull is extra depth to the model. I also added hardwood strakes to give the hull more lift out of the water as well as better shock absorbing on landing. The canopy is 45mm taller than the original lines of the fuselage. I have more than doubled the height of the step in the bottom of the fuselage, I also lengthened and tapered the wing floats.The Elevator servo is in the engine pod.The fuselage, fin and engine pod are all finished in 1/2oz glass and epoxy, the bottom of the fuselage and floats have the recommended 2 layers of 2oz glass and epoxy. The wings and tail plane are covered in Solartex.The entire model is painted in Createx Auto Air and covered with 2 coats of 2 pack acrylic clear.The entire airframe (including all control surfaces) prior to glassing, covering and painting weighed 1.5 kilos this includes also the elevator servo and 150 grams of cable running from the battery compartment to the motor.After glassing, covering and painting the airframe weighed 1.9 kilos. So all of the finishing including covering and glassing the bottom added 400 grams total. I think I could get that down to less than 300 grams if I did it again.The total weight of the finished model including the 800 gram battery is 8Lb exactly. So it is comparable to a 7 1/2Lb glow model with a full tank of fuel. There is no lead in the nose.A good 0.46 develops about 850 watts at the shaft. This electric setup given an efficiency of only 85% should develop about 2000 watts at the shaft. In the end I think I am about a pound over the ideal weight but with more than double the power.I have yet to fly the model but I should have the opportunity to fly it in a few weeks.CheersLionel

Hi, I would really like to know about your experiance with your fantastic looking NS..
What happened, how did it handle, fly ??
//Rob
Old 01-30-2017, 10:18 AM
  #553  
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Default OLD Northstar finally gets airborne

I finally did the maiden flight on my Balsa USA Northstar which was given to me as a kit in 1988. Since the plane is currently located in South Lake Tahoe, the first flight was off of snow since that's the most common form of water at this time of year (the Lake is nice an smooth but far too cold to swim after a downed aircraft). Due to the pressures of work, etc, I didn't start building it until a couple of years ago and I finally finished it late last year. Since this is the first kit that I have finished in over 30 years (ARF's are a lot quicker) I pretty much stuck to the plans.

Key mods 1) electric power -- Hyperion 3025 motor (970 kv), 100 amp castle edge esc, 5S 4500mah 30C 525gm battery. With this setup I am able to turn a Master Airscrew 10x6 S2 prop at >15,500 rpm. I chose to go with a higher RPM setup rather than extending the pylon to get the height to turn a larger diameter prop.

2) Elevator and Rudder servos mounted in the tail. With the light motor (200 gms) and no fuel tank I was able to use the space in the Nacelle to house the servos and provide a more positive connection to the elevator. Without the cowl and without a spinner on the motor, the aircraft balances about 1" in front of the step. With the spinner and cowl installed I expect the balance point to be slightly ahead of the step. The horizontal stabilizer, elevator, and upper fin are removable for transportation purposes.

Takeoff from snow was relatively quick and no significant trim was required to get to straight and level flight. The power train has plenty of capability for flight at my altitude, 6230'. I'm hoping for an equally pleasant water flying experience when access to the lake becomes easily available 3 or 4 months from now.
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Old 02-03-2017, 08:18 AM
  #554  
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1988... wow thatīs a long time not playing... It looks nice,,

I am using a rotorstar motor 3700watt with 6s,, a 10x7 3blade is pulling about 100amps and 16000rpm..
I tried for a while to go with a higher kv and maxed 21000rpm,, crazy performance but a bit danger as well..
Old 02-03-2017, 09:50 AM
  #555  
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16K rpm with a 10x7 3 blade must lead to an insanely fast Northstar. Where is your best flying CG?

I'm still sorting mine out. I did not taper the ailerons which makes them quite sensitive. But I'm found that flying on low rates (60%% throw vs. the recommended max) gives a very comfortable flight profile. I have the CG about an inch to the rear of what is recommended for the kit (about 1 inch forward of the step) and it feels a bit nose heavy. I am wondering how far back I can push the CG without getting too tail heavy. I know on my Polaris and Polaris XL I was able to move the CG up to 1/2" behind the step.
Old 02-03-2017, 10:37 AM
  #556  
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Yes it is insane,, messured 180kmh last summer, and I actually dont go that fast all the time, but I like to fly it vertical and it seams like it can do it for ever and ever..
CG is for me a matter of preference and flying style/type, same for the throws I Always start with high and switch to low in the air..
I actually dont bother that much about CG but somewhere 1.5--2 cm ahead is what I use (3/4 of an inch)..
Old 02-20-2017, 06:50 AM
  #557  
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Gentlemen, this might "sound" insane, But I ordered a pair of pre-cut foam wing cores and canīt figure out what is up versus down,,, Does anyone know if the wing profile is symetrical, or not ????
Please HEEELP...
Old 02-20-2017, 07:06 AM
  #558  
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From what I remember the ribs are symmetrical.
Old 02-20-2017, 07:22 AM
  #559  
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What I can messure at wing center (thickest part) it seems to be symetrical, what is more difficult to see or messure is if the cord changes towards the wing tip..
Old 02-22-2017, 03:03 AM
  #560  
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Thanks for your reply,
Confirmed to be symetrical, I had a conversation with the foam core manufacturer.
So I will just add some carbon tubes, sheet with 1mm balsa and install it on the fuse.. ;-)
Old 04-17-2017, 03:24 AM
  #561  
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Default Northstar CG

I know that the topic have been discussed over and over again..
Sometimes I get confused anyway,, I started to think about CG after a question to me in this forum about "my best CG" and I realized that I had no good answer (see above)..

So consequently,, I would like to drill down into the topic a bit.

Recomended CG is 2" (5cm) ahead of the step with empty fuel tank.
So with added fuel the balance point moves about 1" (2.5cm) rearwards, meaning the model gets more "nose heavy",, Now I am woundering how sensitive the model is with regards to the all up weight ? Does the effect of burned fuel affect the characteristics more on a light model ? I have read in forums that people have Northstar model weight variations from 5--9 pounds, I am very interested in your CG experiance versus weight specially if you have a 9pound Northstar,, I am under the process of constructing a new one from scratch and the intention is to power it with a OS55/a lot of fuel on CG,, but sumarizing all the stuff I want to have onboard I am afraid the weight will be very high,, hense the thaughts about CG because I donīt want to loose all my equipment on the first flight..
On my electric I have honestly not given the CG so much focus If I recall correctly it is about 1-2cm ahead of the step. // Appresciating ypur comments// Rob
Old 04-17-2017, 05:23 AM
  #562  
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"So with added fuel the balance point moves about 1" (2.5cm) rearwards, meaning the model gets more "nose heavy",,"


If the CG moves back, the model has become more tail heavy.
Old 04-17-2017, 06:19 AM
  #563  
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This is what I mean,, its easy to get confused,,.. if you burn 8oz fuel the tail gets 8oz lighter... the balace point (whatever you have balanced it on) moves back (towards rear) about one inch when you refuel with full 8oz fuel tank. Check again where the balance is with full versus empy tank..//Rob
Old 04-17-2017, 02:14 PM
  #564  
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WIth the tank aft of the CG, shouldn't the model be balanced with the tank full? Then, as fuel burns off, the model becomes more nose heavy. If you balance with the tank empty, and then add fuel for a flight, it will become even more tail heavy, a bad situation.

Just askin'

Bob
Old 04-17-2017, 02:24 PM
  #565  
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Just forget about the tank being empty or full. It doesn't matter. You balance these planes with an empty tank. This holds true for every model I've ever built, and the Northstar is no exception. The center of gravity will change as the amount of fuel in the tank changes. Not a big deal.
Old 04-17-2017, 03:21 PM
  #566  
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Yes, that is right,,, it should be balanced empty at 2 inches ahead of the step...so when you fill the tank the balance moves one inch closer to the step... anyway I am very interested in your experiences regarding total weight and CG... //Rob
Old 04-18-2017, 04:37 AM
  #567  
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Sorry to disagree Senrak and RobKit, but everything that I've ever read contradicts this. A look at the instructions should clear this up. If Laddie wanted this balanced with an empty tank then I agree that he moved the CG forward to compensate for the empty tank. But everything I've read for the past 55+ years says to balance on an empty tank when the tank is in the front, and balance with the cg when the tank is aft, so that as the fuel burns off the CG will move forward, not aft.

Should we check our mutual instruction booklets to see what Laddie says? He'd be the the best judge. He's forgotten more than the 3 of us would ever know, combined.

Just my $.02

Bob
Old 04-18-2017, 02:32 PM
  #568  
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Well, I can see the logic in your approach with regards to models in general, however,, your asumption is correct. The Northstar drawing/instructions say clearly 2 inches ahead of the step with empty fuel tank (btw recommended fuel tank is 8oz).. so that is that, Subsequently if the tank is moved from the pod to the CG point the model should be fine balancing somewhere 1--2" ahead of the step, As I understand it people do this in order to save total weight and/or to locate servos in the pod for better elevator & engine response.....

//Rob

Ps...
Hope I am not confusing you now,, English is not my first languge so please read with that in mind.. //

Last edited by RobKit; 04-18-2017 at 02:42 PM. Reason: Forgot to say..
Old 04-28-2017, 07:29 PM
  #569  
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Rob,

I am flying an electric Northstar and I located my rudder and elevator servos in the pylon. Both are 25 gram servos and even with that weight in the tail it balances at about 1.5" in front of the step (the motor weighs 200 grams). I will gradually add weight to the tail; first will be a spinner and eventually I will add the plastic cover for the motor. The first few flights with the 1.5" CG have been OK but I want to gradually move the CG back to the step to make it more responsive.

I chose to put the elevator servo in the tail in order to be certain that I had maximum response from the elevator. I put the rudder servo there because it was convenient to locate it there. As long as your engine is not too heavy I would certainly put the throttle servo in the tail as it can be very light. Some of the new digital servos are very light and you can probably put all three servos in the pylon for a total weight of less than 50 grams. By locating your aileron servos as far forward as possible you can probably minimize the amount of nose weight you need to get a proper CG. Since I am using a 500 gram batter for my power source I don't need to add nose weight.

Bob

Bob
Old 04-29-2017, 02:12 AM
  #570  
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Thanks for sharing information of your setup.. I agree that it would be interesting to balance it as close as possible to the step..
Can you tell us what motor/wires/esc you are using ? I suppose the esc is in the front !?
It would also be interesting to know the total weight... //Rob
Old 04-29-2017, 01:57 PM
  #571  
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Rob,

The motor is a Hyperion Zs3026 with a 970 KV rating. Weight is about 200 grams and it has about a 70 amp limit. (Hyperion motors were manufactured in the same facility as Scorpion Motors but were sold with higher wattage limits; which is probably why they are no longer available). The ESC is a Castle Creations 100 amp edge located in the forward compartment. I plan to use a small, 40 mm computer fan for cooling. The esc to motor wires are 12 gauge high stand count (very flexible) about 800mm long. The battery is a Hobby People 5S (18.5v) 4500 mah that weighs about 510 grams. Total weight, with battery installed and ready to fly, is about 6.25 lbs. The first few flights used a master airscrew 10x6 scimitar prop which gave about a 950 watt motor draw. These flights were off of snow. The next set of flights, off water, will be with a MA 10x7 scimitar prop. If I don't have sufficient power to get off the water cleanly, then the next step will be to use a MA 10x7 three blade prop.
Depending how the CG works out, I am still considering modifying the aircraft so that the ESC is mounted just behind the hatch and sticking through the top deck for cooling. This mod would also allow me to shorten the esc-motor wires.

Bob
Old 04-30-2017, 03:16 PM
  #572  
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Thanks,, that is great info... I am suprsed that you are using that small amount of power, but on the other hand you seem to have managed to keep the Northstar very light,,
If you are to move the ESC to the pod,,I would suggest to consider the possibility of it getting damaged, there is threads about this and the best precaution is to add some extra condensators when having long bat--esc wires.. My next Northstar will be as light as it is possible to build it and I hope to be able to use a smaller motor ..
But first I have to understand & learn how to make it light. :-)
Regarding increased load on your motor you might want to be careful since it is already close to its max load (according to eCalc) check out eCalc for guidence,,
It looks to me like you might want to go to 4S lipo if you want more thrust with a 10x7 3blade.. Or.. your motor is maybe "under specified" so you might be fine..
I am shure you have thaught about thiese things already,,
//Rob
Old 04-30-2017, 09:04 PM
  #573  
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No, I am not thinking about moving the ESC into the pod, I will just move it back a few cm to the compartment that is just to the rear of the forward hatch. It will still require motor leads of at least 70 cm.

I built my Northstar using a Balsa USA kit. If you don't use too much glue or paint (I covered it with film) it should come out at about the weight I quoted. If I install the plastic motor cowl and spinner, the weight will approach 6.5 lbs.. If you really want a light NS there is thread on RCG? where someone built the model substituting a lot of foam for balsa and it came out well under 6 lbs.

Most motors will allow a burst of power of 15 sec that is about 50% more than the max power that eCalc provides. This is what is needed to get off the water quickly. Cruise power for the NS is reasonably low, under 500 watts. My setup is good for a few high speed passes and some aerobatics but won't hold up for a full throttle for 100% of the battery capacity. One can design a higher power setup but the weight will go up and the flight times get short.
Old 05-02-2017, 02:50 PM
  #574  
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Aha ok..Yes I agree it is better to keep the esc close to the battery,, Think I read about that model with balsa and foam, yes maybe that is the way forward..
I have experimented a lot with high pwr setups and the most insane I used is a 3700Watt motor 800kV on 6S,, (I even tried 8S once), But as far as I knowt there is no lipos available
that can give me reasonable time in the air, and it is off course a heavy setup, I like to test and have fun with crazy much power..
Right now I am considering to use my last foam-core wing for my next NS, but not so shure it will be lighter than the original wing design..

Thank you for your input.
//Rob
Old 05-03-2017, 08:28 AM
  #575  
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Rob,

I forgot to mention that I am flying my Northstar from a lake at an altitude of 1900 meters. It makes a big difference when you use eCalc.

If you are looking to build a "go fast" Northstar and you have an extra foam core wing, you might consider the following. The NS has a reasonably light wing loading. I have flown a plane with the same wing area, a Great Planes Seawind, that weighs 4 lbs more and it flys relatively well even with a wing loading in excess of 30 oz/ft2. Adding even 50% of that weight difference as batteries would allow you to get to 10,000 mah as a 6s which will give you a few minutes of flying time. If you don't want to worry too much about balance, go to the site www.modelaero.com and look at the Polaris EX. It is a variant of the Polaris which in turn is a scaled down foam version of the NS. The Polaris EX mounts the motor pretty much on the step which would allow you to add batteries pretty much around the CG

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