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F-8 Crusader build

Old 12-05-2006, 01:33 AM
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stiletto660
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Default F-8 Crusader build

I'm about to start scratch-building a ship based on the f-8, which I feel is one of the most attractive jets ever designed. The point is to try and mimic "jet like" characteristics through the use of a relatively high wing loading, and as a result, high speed maneuvers. If any aeronautical engineers want to chime in about these issues, feel free. Hopefully, there's enough wing area to slow it down enough for a stall into a three turn spin. I'm going to use 1/8" wing sheeting for added security against deformations or flutter at high speeds. There's also a little issue with the exhaust running over the wing, but I'm sure it will work out.

I should be able to get going on it sometime during the next few weeks. I'm going to try and get it done and trimmed before any upcoming ballistic pattern events.

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Old 12-05-2006, 05:42 AM
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Default RE: F-8 Crusader build

Looks good.

The only thing I see that you might want to change is the hinge line for the rudder. You may want to make it 90 degrees to the thrust line to avoid any roll coupling when the rudder is applied.

You also might want to increase the size of the horizontal stab by 10% to add extra stability to the design.
Old 12-05-2006, 06:33 AM
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Default RE: F-8 Crusader build

Ralph Brooke is smiling down on you! http://www.modelaircraft.org/museum/bio/brooke.pdf
Old 12-05-2006, 06:54 AM
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Default RE: F-8 Crusader build

Looks good,
Stilleto, are you goind to do a build thread? If you have time to take pics and upload them I'm sure every one here would enjoy watching it go together and then eventually seeing it.

Old 12-05-2006, 09:53 AM
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Default RE: F-8 Crusader build

Nice work. Please do a build thread so that we can follow your progress.

I encourage builders of ballistic pattern planes to consider a Jett 90. It is the same size as a 60, but it will turn a 10x10 APC at 15,500 to 16,000 rpm. For a clean, compact air frame, that engine/prop combo works very well.

8178, I remember the Ralph Brooks Crusader article in MAN back in the sixties, long before I flew RC. I wore that issue out admiring the photos.

Bob R

Old 12-05-2006, 06:34 PM
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stiletto660
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Default RE: F-8 Crusader build

I'll probably do a build thread... but I've got to hurry up and shop for other people first.

I forgot to mention that this thing really got looong.. its 78" in length with a 69" span. I'll need to look into a rear exhaust engine that's similar to a hot .60, but with a little more power. Is this Jett .90 rear exhaust? A 10x10 at 16,000 rpm is absolutely insane.

No wonder MAN did a re-issue of the Crusader article in a 1989... he passed away that year.

-Eric

Old 12-05-2006, 06:49 PM
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Default RE: F-8 Crusader build


ORIGINAL: stiletto660

I'm about to start scratch-building a ship based on the f-8, which I feel is one of the most attractive jets ever designed. The point is to try and mimic "jet like" characteristics through the use of a relatively high wing loading, and as a result, high speed maneuvers. If any aeronautical engineers want to chime in about these issues, feel free. Hopefully, there's enough wing area to slow it down enough for a stall into a three turn spin. I'm going to use 1/8" wing sheeting for added security against deformations or flutter at high speeds. There's also a little issue with the exhaust running over the wing, but I'm sure it will work out.

I should be able to get going on it sometime during the next few weeks. I'm going to try and get it done and trimmed before any upcoming ballistic pattern events.


---------------------


Real Crusaders were shoulder-winged, not low-winged. This one is not very authentic. Unless I have missed the point, which happens more and more often these days...


Ed Cregger
Old 12-05-2006, 08:39 PM
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Default RE: F-8 Crusader build

Looks cool, Eric. I'm sure there were several pattern ships with inverted sixties and pipes running over the wing, but the one that comes to mind is the Desire. I can email you the Flying Models article if you want to read how McConnville did that setup. How does 1/32" ply sheeting compare weight-wise to 1/8" balsa sheeting?
Old 12-05-2006, 09:05 PM
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stiletto660
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Default RE: F-8 Crusader build

Ed, I know, but I wanted to make this a low-winged model to allow me to trim it better for aerobatics.

Rainedave, I actually based this plane on the Desire when starting out with the drawings... which explains why the exhaust routing could be just as strange. I'm thinking I'll need a pumped engine since the tank location is probably going to be weird.

Old 12-06-2006, 10:02 AM
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Default RE: F-8 Crusader build

Eric,

Now that I see the dimensions of your air frame, a 10x10 prop turning 16k is probably not a good match. Maybe Bob27s on the extreme speed forum can give you his thoughts. The Jetts are not pumped, but I have run a 16 oz tettra bubbleless tank 8" behind the back plate of the Jett 90, and the motor does not sag excessively in long verticals.

Good luck with the project.

Bob R
Old 12-06-2006, 11:26 AM
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Default RE: F-8 Crusader build

Sounds like a run project !! Gotta watch this one.

90L Engine would be a heck of a match The SJ-90L and 90LX are available as both side and rear exhaust. These are physically the same size as current OS61/91 engines.

The tetra tank Bobber noted is worth considering - relieves 99% of your fuel system worries.

Worth noting, there were many, many people who flew pattern with non-pumped fuel systesm for a LOT of years. Maybe a handful of K&B LEE engines with pumps for a while. YS was the only pumped/pressure/regulated system starting in the early 80s. The OS pumper didnt show up until the late 80s.

Rossi, OS 61FSR, Webra Speed, OPS, CMB - there were no pumps needed. The tank pressure provided by a tuned pipe is substantial - beyond what most stock mufflers provide. The pump also added complexity and a point of failure. A pump is only really needed when you are trying to deliver a lot of fuel (energy, make power) at lower RPM and lower throttle settings, or you have to transport the fuel a long distance.

The idea of putting the tank aft for CG reasons didnt come around until the pattern ships grew big/fat enough and folks started sicking servos outside of the airframe so you could actually fit one that far back
Old 12-08-2006, 10:53 PM
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stiletto660
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Default RE: F-8 Crusader build

I built a preliminary 3d model to visualize how the guts of the plane are going to work out. I've got the header running up and over the wing, to a piece of long silicone tubing into a Soundmaster muffler beyond the wing saddle. There's also an option of putting the tank right behind the engine, but that would be a tight fit for the nosegear. I would also lose the "trendiness" of having the tank at the cg. I think I might do an alternative layout with the exhaust running up and into the turtledeck Magic-style. It might make it easier to put some servos over the wing.

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Old 12-09-2006, 03:47 AM
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Default RE: F-8 Crusader build

Ok, I've got a new layout with the muffler running up into the turtledeck... looks much more user friendly with regard to the radio installation.
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Old 12-09-2006, 08:07 PM
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Default RE: F-8 Crusader build


ORIGINAL: stiletto660

Ed, I know, but I wanted to make this a low-winged model to allow me to trim it better for aerobatics.

Rainedave, I actually based this plane on the Desire when starting out with the drawings... which explains why the exhaust routing could be just as strange. I'm thinking I'll need a pumped engine since the tank location is probably going to be weird.


---------------


Okey-dokey.

With a shoulder wing, you would have to run a little negative dihedral in order to get it to trim properly and eliminate some of the roll coupling. The engine installation would be a lot easier and blowing the air closer to the center line of the wing would aid in flight symmetry.

The real problem would be the landing gear and getting enough rudder area below the thrust line.

Your low wing approach is probably much better in all of those respects. Soooo, never mind. <G>

It is very pretty, by the way.


Ed Cregger
Old 12-11-2006, 10:36 AM
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Default RE: F-8 Crusader build


ORIGINAL: stiletto660

Ok, I've got a new layout with the muffler running up into the turtledeck... looks much more user friendly with regard to the radio installation.
Just a word of caution - using a long, small ID diameter exhaust tube like that may (will?) result in unacceptable engine performance. All manner of pressure distributions will occur (experience with this) which ma result in undesired back pressure issues, and there are some temperature/heat transfer issues to consider as well.
Old 12-12-2006, 09:55 PM
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Default RE: F-8 Crusader build

I think I'm going to run with this layout. It's very similar to the Desire, but I couldn't fit the fuel tank up into the canopy like he did. This location would probably allow me to run a non-pumped engine as well. I'll probably make the plots this week.

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Old 12-14-2006, 11:22 AM
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Default RE: F-8 Crusader build

I was "talking" with Rainedave not long ago about the Crusader. It truly is a beautiful design.

Having said you patterned your plane after the Desire, I was wondering how much you consulted and borrowed from Brooks original Crusader in M.A.N? If you've studied the plans for that plane, could you tell me what you specifically wanted to change about it and why. For example, was the wing loading on Brook's Crusader too low, too much wing area etc etc. I know Brook's Crusader had a "slab" stabilizer.

Just wanted to get a feeling for what you didn't like, and what you wanted to change. I'll be watching this build with great interest.

(Nice graphics)

Duane
Old 12-14-2006, 02:06 PM
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Default RE: F-8 Crusader build

I was just a young kid in the 80's (I'm only 32 now), so the only MAN article I actually saw firsthand was the re-issue in 89. I guess basically, I was looking at it from the angle that ballistic pattern planes could be a "new" form of pattern competition, and contemporary designs could be brought up for it from the ground up - like this one has been. I also wanted it to be insanely long like the real jet looks... which might hamper the snap ability, but I'm probably going to mostly fly it "blue angels" style with big smooth maneuvers.
Old 12-14-2006, 02:38 PM
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Default RE: F-8 Crusader build

Big, smooth, graceful maneuvers are what it's all about for me. You do it like the Blue Angels, and you'll win every event. I fly an SPA-legal King Altair, (vintage 1967), which is essentially a 2-meter plane way ahead of its time. The long tail moment concept goes all the way back to the Taurus in 1962. I'll include a picture of both. The King Altair designer, Vic Husak was a friend of Taurus designer Ed Kazmirski.

The long tail moment help the plane tract very smoothly, and do very pretty, elegant maneuvers

Good luck--I'll be watching your thread.

Duane
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Old 12-28-2006, 09:20 PM
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Default RE: F-8 Crusader build

Eric, how're the plans coming along?

On a side note and continuing from Brooke's Crusader, was his Gladiator published as a construction article? Do plans exist?
Old 12-28-2006, 09:49 PM
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Default RE: F-8 Crusader build

Ralph’s Gladiator was Kitted by Fliteglass, located at the time near Ralph’s home in South Seattle. I do not recall ever seeing any Gladiators other than the Fliteglass kits that were pretty popular around the Northwest.
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Old 12-28-2006, 10:16 PM
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Default RE: F-8 Crusader build

Thanks, 8178. Was it a good flier?
Old 12-30-2006, 01:09 PM
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Default RE: F-8 Crusader build


ORIGINAL: rainedave

Thanks, 8178. Was it a good flier?
The ones I saw flew very well but were a little heavy and had a pretty big frontal area. I believe other than the fuselage it shared the Crusader parts. Of course it had a foam wing but looked like the Crusader wing. The one you see in the picture above was before the one he built and flew for the Masters.
Old 12-30-2006, 08:58 PM
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Default RE: F-8 Crusader build

I managed to get the wings framed up. I'm currently sheeting the bottom this evening. I hope the swept wings don't do any weird saberdancing in flight.

A big thanks to Joe Bridi for the "lost jig" idea for building straight wing panels.
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Old 12-30-2006, 09:04 PM
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Default RE: F-8 Crusader build

Very nice work. The only tricky part with swept wings are the retract gear mounts and fitting the wing to the fuselage.

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