Seaplanes Aircraft that typically take off and land on water...radio control seaplane discussions are in here.

North Star as a Full scale aircraft?

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Old 03-24-2013, 01:25 PM
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SeaJay
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Default North Star as a Full scale aircraft?

why couldn't the Northstar be encarnated as a full scale aircraft?? I have been thinking about this for quite a few years now, and was just curious as to why it hasn't been done!! The proof of concept is flown by many of us quite regularly, and some of you have increased the size of the models, so I was just curious why it hadn't been done in all up full scale!

I know that many of you here on RCU have aviation backgrounds, and was hoping that someone could shed a little light on the subject..

I was thinking that it would be a great GA (General Aviation) airplane.. I thought that if you were to take the basic Northstar design, Modify the hull from flat bottom, to a semi-v for better water ops, it would be one awesome Plane to own..

I have talked to others about this, and was informed that the COG of a delta wing aircraft moves rearward as the speed increased, could this be countered with some canards, which would also help with take offs and landings??

Just a thought, and wanted to see what you all thought of the idea!!

Craig.
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Old 03-25-2013, 09:44 PM
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Default RE: North Star as a Full scale aircraft?

One thing you need to remember is that the desired characteristics don't always translate from smaller R/C to large full sized versions. In the early 1980s, one of the "powers that be" in the Circus Circus organization thought that a full sized Merlin powered unlimited hydroplane, based on a Stiletto four point R/C hydroplane would be a great idea and be an instant winner. It was a total flop when completed. In the 1990s, the same basic idea was tried again by Sven Ellstrom. This time, the boat was made lighter, more aerodynamic and powered by a small turbine engine. While testing, the boat took off going straight up at 125mph. When it came down, the boat landed on its transon and slammed the front back onto the water, snapping it in half at the cockpit, breaking both of the driver's legs halfway between the knee and hip joint in the process. The boat was scrapped and a conventional hydroplane was built to replace the destroyed one. Just something to think about
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Old 03-26-2013, 02:56 AM
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Default RE: North Star as a Full scale aircraft?

I think in the case of a delta wing design what you have to remember is the speed it takes to take off and land, not many places where you'd be able to drop in a plane like that even if you could design it to be fast enough to take off.
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Old 03-26-2013, 07:28 PM
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Default RE: North Star as a Full scale aircraft?

The one airplane I can think of offhand that was a model first that was adopted to full scale is the Ultimate 300.  Models get away with a lot because, although the wing mat be scaled 1/4 or 1/8th the full size, the atmosphere stays the same.  That is: air is 4x denser for a 1/4 scale model or 8x denser (relatively) for a 1/8th scale model, than it is for a full size aircraft.  That translates into more lift. 

Put another way: an ant can drop from any height and walk away.  An elephant, bear, man or dog . . . not so much.  Weight is a cubic finction - thst is to the third power - of volume.  The Northstar may be great guns with a four or five foot wingspan, but with a 40 ft wingspan it may not be able to carry enough engine to break free of the water.
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Old 03-26-2013, 08:20 PM
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Default RE: North Star as a Full scale aircraft?

The biggest issue I see is that the passenger compartment is WAY in front of the CG. Every time a passsenger got out, you would have to add sandbags to keep the CG in range.

Also, the high angle of attack flight which is so fun in the RC version would have the pilot looking at nothing but blue sky and wondering where he was going.

Scott
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Old 03-28-2013, 05:50 PM
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Default RE: North Star as a Full scale aircraft?

All good points.. I Kinda figured that with such a large wing, the wing loading would be fairly low, and would be able to easily break free of the water.. But then again, I am not an aeronauticle engineer.. I didn't really think about the air density being 8 times more for a 1/8 scale vs. a full scale. I am currently trying to wrap my head around that concept, as I am thinking that the air density per square foot wouldn't change, from an aircraft with a 4' wingspan, vs. the AD per sq/ft of a 40' wingspan. it did give me something to ponder and research tho! bt then again, thats why I posed the question here, there is a lot of knowledge to tap into!

Scott, do you think that a set of computer controlled canards be used to keep the cg in its proper place during various airspeeds and cockpit loading situations? another thought, the cockpit of the seawind is completely ahead of the wing, but I guess that the proximity is close enough that the CG won't change that drastically, compared to the distance between the northstars cog and the cockpit.
all great info, tho.. I figured that there had to be a pretty good reason that there were very few GA aircraft that has any sort of delta style of wing, and was just curious what those reasons might be.. and since I like the northstar so much, I just thought I would use that as an example.. the fact that I live on a fairly large lake didn't hurt either!
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Old 03-28-2013, 05:59 PM
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Default RE: North Star as a Full scale aircraft?

The seawind 300 is about the closest thing to a full-scale northstar as you can get.

http://www.seawind.net/
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Old 03-29-2013, 10:31 AM
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Default RE: North Star as a Full scale aircraft?

First I do think the CoG and CoP have been confused. The CoG, Centre of Gravity, do not move on an aircraft with speed. (If not on purpose by pumping fuel between different tanks or moving ballast.) The CoP, Centre of Pressure may or may not move with speed, or rather anngle of attack, less you go trans sonic or supersonic. I might remember wrong, but I did think that the CoP did not shift that much on a delta.

Next, the North Star as a full scale aircraft?
The most obvious obstacle is already mentioned, the cockpit is far from the CoG. If the airplane where to have more than one seat, ballast may have to be carried in an empty seat.

Another thing is the scaling. If the proportions should stay, with a cocpit large enough for two people, it would be a large aircraft. Wich might as well be, as a decent turboprop engine would then fit. Deltas and low aspect airplanes work best with a high power to weight ratio.

For a GA "delta" airplane search "Dyke Delta". A homebuilt that work well. Search "Convari Sea Dart" and you find the only supersonic jet seaplane ever made.
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Old 03-29-2013, 07:49 PM
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Default RE: North Star as a Full scale aircraft?

well, thanks all for the insite, it was a cool thought anyway!!  [8D]

Craig.
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Old 03-30-2013, 08:02 PM
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Default RE: North Star as a Full scale aircraft?

You may also want to Google Sea-Era. This homebuilt is a seaplane that gets half its lift from a delta and half from conventional but short wings. It's also pertinent to this discussion because its proof of concept was first flown as a 1/4 scale RC model. I learned this from a you tube video interview with the builder. Unfortunately there is also a you tube video of it crashing on its second flight, but it looks like not too seriously.

To answer your canard questionpilots regularly adjust elevator trim for different airspeeds and also for different weight and balance (GG position and passenger/baggage/fuel load). However, the weight and balance must remain within specified limits. A computer controlled elevator could allow an inherrently unstable aircraft to be flown, but is this what you want in a homebuilt? I am aware that some military fighters do just that, but they are going all out to be just a little bit superior to the other guy. I don't think it changes the answer whether the elevator is in front as a canard or in back.

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Old 03-31-2013, 07:25 PM
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Default RE: North Star as a Full scale aircraft?

Scott, after watching that video, and seeing a few others, I thought, OK, Maybe a Multi-place (seat) northstar might be out, but, Maybe a single place Northstar Might be feasable...  

thanks for pointing out the Sea Era, looks nice!!

I might have to play around with some larger scale Northstar Models to check it out...

Craig..
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