Goldenduff

Hey Laddy! Not meaning to suck up but that's pretty much what I said- too heavy, needs more power. 

aa1a

My Feedback: (4)

My Northstar has a crummy Evolution 45 engine with a tuned pipe and a 3 blade. And it is a rocket! Straight up or straight down. It weighs in at around 6 lbs. Fantastic roll rate. The mods were, moving elevator and throttle servos to the back, a slightly bigger elevator, and an extension on the water rudder. It has no bad habits, on or off the water. It has some unique handling traits but it's a unique airplane. Sounds to me like you bought a dog that wasn't built right. Perhaps you should cut your losses and hang the pretty one up and build a good one.
Jim

skywagn180

I did not want to come off as slamming the model. I understand that many people have had success with this model and there are many loyal followers. I stressed that the issues I have experienced are exaggerated due to weight. I doubt I am really at nine lbs, but I do not have a scale and wanted to show readers that the plane is heavy, so I placed my estimate on the high side of the range I think it falls in. The .46 fx is actually way more than enough power to fly a plane of this wing loading. It has more power than the .60 size nitro motors in existence when this model was designed and is much lighter. Even at the weight of my model, it is capable of well over 70 mph in level flight and pushing 90 mph in a dive. It stalls traditionally at about 25 mph and flies behind the power curve at a walking pace. I refuse to call that underpowered or overweight for the engine. The design just isn't allowing the efficient use of the wing's lifting capability at takeoff and flare on land and water. My 10 points are theoretical design improvements I feel would improve the design. A theory can't be wrong until it is proven wrong. My suggested improvements are not radical changes and anyone capable of building this kit could easily accomplish them without changing the basic concept of your design. I have scoured the internet regarding this design and the are many many people experiencing the same problems I am with much lighter airframes. I am not alone. I'm sure if I had built this myself I would not be having these issues to the same extent, however this model was built with reasonable building techniques of the period and is powered within the recommended range. Thank you for your input though. I hear ya. Congratulations on your successes. I've wanted one of these since I was a kid. I will make it fly off the water.

skywagn180

I've heard many others complain of wing rock. In addition to ideas on how to improve water takeoff, has anyone experimented with stall strips or other means to cage that behavior? Mine has very minor and subtle wing rock at all speeds with any load factor over 1g. The control rods seem tight. Control surface gaps are tight. Ideas?

Cougar429

My Feedback: (3)

Yipee! My new van should be here next week, (Grand Caravan SXT with Sto'n Go) so the reason for the removable tail is now moot. I have it back on the table to see if I can build a lighter version tail assembly to therefore cut some balance weight from the nose.

That generates a question. Has anyone replaced the slab surfaces with airfoil shaped? I did that with the upper vertical fin and wondered if it would be one way to build a lighter and stronger horizontal assembly.

skywagn180

https://www.google.com/search?client...KALdr4x1ZyM%3A

Check out this link. Turns out the Polaris incorporated several of the design changes I proposed in my previous post. Somebody had many of the same ideas. I don't think my 10 points should be so easily written off. After watching video after video of NS water takeoffs, it seems that the key to getting off the ground is to use brute power to overcome hull drag and to reach a very high speed where enough air pressure is built up under the wing to pop it off the water (a type of ground effect). At that point the angle of attack can be increased enough to get the wing flying and creating lift. Again a larger step, deeper hull and v hull design would allow a more normal rotation speed, less drag and might just make the NS much more pleasant to takeoff and land. I also noticed the NSs with long water rudders tracked much better than mine. That will be my first change. I see that the lighter NSs seem to do just fine on the water takeoffs, even though the rotation speed is high. I don't see any difference in the way mine flies in the air. Honestly, I'm starting to think if I get a good water rudder on there I may be able to takeoff normally. It has no problem accelerating, it's more a directional control thing on the water takeoff runs. As soon as it starts wandering to one side on its own the tip float on that side starts slowing it down and it won't speed up. No amount of aileron and/or rudder keep a tip float off the water once it grabs, but as I said before the rudder is not touching the water on plane.

Cougar429

My Feedback: (3)

I just gave my Polaris to a friend and picked up the Ultra at Toledo last month, so am quite familiar with both. My question was aimed directly at the NS.

skywagn180, wanted to ask if this is your first full delta craft. The wing rock is a common tendency with that planform and not exclusive to the NS. A good example is shown in the films of the Avro Arrow flight tests, (my father was wiring the airport at that time). You will notice what looks to be extremely high AoA during takeoffs and landings and is normal to generate the lift requirements at low speed. Not sure if it would work, but some of the jet flyers use rate gyros for ground ops stability and it may counter the wing rock if tied to the rudder.

Another behavior you may not have experienced before is the need for a bit more throttle if bank angles start to reach 45 or above and I believe this is due to the drag increase from higher AoA during turns. Without it you may see it slow and drop a lot more than conventional designs. Again, there are exceptions to that rule. Found the same power requirement with the Ultimate Bipe. Don't know why.

Goldenduff

 

Has anyone replaced the slab surfaces with airfoil shaped? I did that with the upper vertical fin and wondered if it would be one way to build a lighter and stronger horizontal assembly.

Hello Cougar (sadly the first time I've used that greeting in my life!!), I hope all is well. Call me autistic but an airfoil shape is not necessarily lighter. Do you mean provide lift and therefore make the craft appear lighter or do you mean make it open structure and lighter than solid slab?

Do you think an airfoil horizontal slab would significanly increase lift, if so do you think it would cause a nose down effect that could actually counteract increased lift when accelerating?

Like I said mine is still in the box (am playing with a VERY tatty 2nd hand one) so can still easily change the new build.

Skywagon- I think your complaints should be directed at the builder not the designer because the NS has a huge and loyal following (and has been made several sizes and is still in production) which would be inconsistent with a poor design? I think you should commit to recovering and try to replace the nose weight with further forward servos and battery etc. Also before recovering sharpen up (and increase) the step, also sharpen the fuse and tip float edges .

Here to help and discuss not cuss!

toolmaker7341

The wiggle is caused by the thick airfoil section. It was first noticed in the 60's with the thick winged pattern planes ie. Tauras,Kwik fli.Kaos. I never heard of a cure.

Goldenduff

A thinner wing lol!

Cougar429

My Feedback: (3)

I was never a big fan of heavy slab stabs, (there's a mouthful) with their tendency to flex and warp with changes in humidity. Now THAT'S something you will see in amphibs.

A well designed and built open structure should be significantly lighter and stiffer than any slab. However, strength can be an issue as they can also be relatively fragile. I was intending to add C/F. Just wondered if I should build flat or if the added complexity is worth the effort.

alasdair

B.T.W. skywagn180, isn't Vancouver in BC Canada? not WA, USA? Or has someone in Wa state copied the name for a place there?

In previous posts on this thread I have listed my ownmods for the Northstar, virtually all different from yours. In fact I used so many mods I gave my model a new name (Lochstar). But that's not relevant to your posting.
I had three Northstars, all built by other people, and they are the best fun model waterplane available as a kit!
Build a 6 lb Northstar (or up to 7 lb MAX), fly itand come back to us.

Your #4
I have wondered about a step on the floats, but never tried. Anyone tried it?

Your #5
I fitted plywood edges, spray strips, sticking down 6 mm (1/4") below the hull side on later models. it's an extreme form of sharp edge and I'm convinced it helps TO on smooth water. Your model is basically too heavy.

Your #6
Most builders add a bit of extra water rudder (it's probably on the plan, which I don't have).

Your #10
Most model deltas that I've seen suffer a little wing rock. I don't know a cure but I've learned to live with it.

skywagn180

It is not my first deltaish plane, and I am aware that the wing shape tends to have these behaviors. However I'm not convinced that they cannot be tamed. This is not really a true delta though as it has a horizontal stab and elevator. The tail's short coupling and high sweep wing obviously makes it act very similar to a delta wing craft though. I don't notice the need for increased power in high bank angles because I hardly ever leave full power with my NS because I'm having too much fun screaming around the patch with a smile on my face. I do notice wing rock being aggrevated at high bank angles though. Thank you for your positive input and thoughts on Aoa.

skywagn180

Thank you for your input. You bring up good points and you are being heard. I may eventually recover and lighten the NS, but not until I figure out if I can get it off the water as is. Again, I am happy with the flight performance in every respect but water takeoffs. My complaints are not directed at all at the designer, but at the group. I posted this in the modification forum to solicit ideas on how to improve my plane. I intentionally did not post on a fan site or forum because I want to tap the knowledge of those that are interested in improving the design. Although I appreciate the designers input and that of the loyal followers of the design, I was trying to avoid the inherent bias that exists with those people. Even the best designs in the world can be better. We are all here to learn and improve our models right? If not you may be in the wrong forum.

skywagn180

Interesting thought! Although I think the high wing sweep may be the bigger culprit in this design, airflow separation due to the airfoil design itself may be something to look at. Maybe I will make up strips of VGs mounted to a thin plastic sheet I can tape in various locations to see what happens. Vortilons is another option I am considering. Also my leading edges are very sharp across the entire wingspan. Is this common? i wonder if this is also causing seperation issues at higher AoAs. Thanks!

skywagn180

The builder of my NS built the horizontal stab with sticks. It is not solid, but the elevator is. I had to heat up and warp the stab back to shape as it was deformed. I'm not sure the weight savings was worth it. An airfoiled tail is almost always better than a slab, but the way this model is meant to be flown I personally wouldn't think it would be worth the time and effort. Just my 2 cents.

skywagn180

Actually Vancouver, Wa came first! We are across the Columbia River from Portland, Oregon and it is one of the biggest cities in Washington State, USA. We get this a lot. Thanks for your input on the NS. I will look at your post.

Cougar429

My Feedback: (3)

I am tending towards your water problems originating from the higher weight, lower power to weight ratio. The higher weight will push the fuse and floats lower into the water, increasing drag and perhaps exacerbating the tendency for one float to dig in. It will also require more power to force through and up into plane before you can accelerate enough to lift off.

That brings up another question: When it digs in, does it do so to the point the leading edge of the wing tip becomes submerged? If so you may need to provide additional tip floatation. Something as simple as adding some foam to the outboard of the float/wingtip or along the bottom surface of the float may keep that from occuring. Normally, drag from the tip float should not affect your performance or tracking that much.

Does the tip problem occur once up on plane or while still in displacement, (or in transition)?

I think a sharp leading edge is not helping. That is more towards high speed flight and unless it is drooped will hurt low speed lift. Unless you can reshape the LE perhaps some form of spanwise dam, (similar to those used on the BAE Hawk or the dogleg on the Arrow or F-4) can help keep the flow adhered.

Since on the Northstar you are prevented during water ops of honking high AoA while early in the takeoff, you need to build up a cushion of air below the wing to help it get off the water. This is done between the fuse and tip floats.

alasdair

[quote]ORIGINAL: skywagn180

Actually Vancouver, Wa came first! We are across the Columbia River from Portland, Oregon and it is one of the biggest cities in Washington State, USA. We get this a lot. Thanks for your input on the NS. I will look at your post.
[quote]ORIGINAL: alasdair

Well, I learned a little geography today. Thank you

skywagn180

Cougar, it accelerates well and easily planes on the main hull. As I get close to rotation speed the main hull rises and a wing will tend to drop until the tip float contacts the water again. The drag of the tip float pulls the NS to its side. At that point the rudder is not effective enough to correct the drift, the speed bleeds off and the entire plane settles back to the surface. If I tried to use elevons to correct, the low side touches the water and also slows the hull preventing reaching rotation. It is so close to taking off it is ridiculous. Any light chop on the water allows for a normal takeoff. The leading edge does not dig. When it does plane, it planes clean with good acceleration. I just need to be able to correct the drift somehow. I am adding a water rudder tonight and I will head to the lake. I will bring lots of tape and .020 aluminum sheet for experimenting with some step mods. I don't think people are realizing this thing is very close to being flyable on glassy water. I wouldn't be waistline my time if I wasn't confident I can make it work as is.

hairy46

My Feedback: (1)

I was going with the os55 but may put on a evolution 60

skywagn180

Unfortunately you will probably need to go with a four blade on a modern .60 to take advantage of the extra power. If you can find a really high pitched three blade it might work. Either way you will probably be looking for a specialty prop or modifying the plane. I looked into more power long ago. In my experience multi-blade props tend to rob performance at the the high rpms and smaller diameters required for these two strokes to turn them. There is no substitute for a high performance, long and mid-pitched two blade on most sport planes. The NS just won't allow the use of these more efficient props. A 10" is all I can safely get on mine and I had to go three blade to keep the rpms within an acceptable range. If you give up the downthrust you might get by with an 11", but at what cost to handling? I don't know. You could always get a racing two stroke and rip a small diameter extremely high pitched prop if you can find one. Sport nitro motors just aren't designed for the kind of rpms you would get with a .60 on a 10 inch sport prop. Just my opinion.

Cougar429

My Feedback: (3)

I suspect your problem is that a normal weight NS would be off the water by that point. The water rudder extension sounds like your only option at this point. Not normally required.

I have been getting good performance when shortening larger diameter 2-blade props. Have done that with both Graupner and M/A.

Again, if anyone can get a 3-blade to work on a 2-stroke you've beaten my years of trying.

flybyjohn

My Feedback: (2)

skywagn180, I have the Polaris, actually 2 of them, I made a 100% and a 90% version, and the outlines of it and the NS are almost identical. They are however different planes. The polaris has a wing loading of 8.4 oz/ sqft. and the NS's wing loading is 20-22 oz / sqft. My 90% polaris was built light and I got the wing loading down to 7 oz/ sqft. and the handling was so much better that I don't even take my 100% out any more. Now I don't have a NS (yet) and so I don't know what kind of flying characteristics it has but I would say that with a heavier wing loading, it is going to behave like a different plane than one with a light wing loading. My tip floats on my Polarii do get caught on the water quite a bit and pulls me for a big ground loop sometimes, so that characteristis is still common between the two.

I guess what I am saying is that the little bit of difference between the wing loading on my two polarii makes a big difference in the handling and flying and so I would imagine that the NS is no different.

Both my polarii fly great in the air at fast speeds, however it is the lower speed flying that really makes the lighter wing loaded plane shine. The handling is so light that I can hardly make it stall and when it does it is alway recoverable in a few feet of elevation.

skywagn180

That might be something to try as well. I could cut down a bigger two blade for a higher load, wider chord prop. It might give me more thrust. Only one way to find out. Thanks for the idea. There is no doubt in my mind a plastic covered NS would go lift off at the planing speeds I am reaching.