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Old Jun 25, 2012, 12:12 PM
Capt. Z
falcon5's Avatar
United States, NV, Las Vegas
Joined Dec 2004
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I built an 81" long F-4 a few years ago and it had a 1.5" thick wing with a NACA 2408 airfoil. AUW was 15.5 pounds and it flew very well as a pusher prop. Here is a pic of the gear wells with a 1 1/8" thick retract unite and a 1" thick wheel for referance.
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Old Jun 25, 2012, 12:52 PM
awrightbrother's Avatar
Florida
Joined Nov 2007
2,537 Posts
Quote:
Originally Posted by rossaer View Post
Just checking in again on the length of this project. Will the jet be able to be "disassembled" for transportation? 81" in length is pushing 7 feet it won't fit in my truck at that length.
Also I like the discussion on how "scale" to keep the project. I'd vote for a slightly thicker wing and larger inlets if it helps in efficiency and performance. As long as they don't become cartoonish, better flying qualities are more desireable than scale looks on the ground....but of course that is just my opinion.

al
This where your building skills come into play. As i said before, these kits are highly modifiable. You can build it such that the nose can be disassembled at the intakes, and the wings come off, or build it as one lump. I will be shipping the fuse in at least 2 sections, otherwise the box size becomes humungous.
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Old Jun 25, 2012, 12:55 PM
I make bad look so good.
SteveC68's Avatar
League City, Texas
Joined Sep 2006
2,563 Posts
Fahim,

Just curious as to what drawings you are using for this? I looked at the exact setup that C/N is suggesting a couple years ago and ironically came up with 80" as the fuselage length for a single 90mm fan. Back when I looked at this the figures I came up with for intake area even at 80" length and a single 90mm fan looked a little on the low side for a 100% scale intake. I was planning on a small 3rd duct that would merge with the 2 main intakes just ahead of the fan. This was going to be a full duct though and not a cheater hole. As you have discovered a scale T-38 is a tough plane to tackle. Take a look at this link starting at post number 15. Some pretty nice CAD work there on the T-38. Up until these guys started this project the best drawings were from the DACO book on the T-38.

http://forum.largescaleplanes.com/in...pic=28715&st=0

Steve
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Old Jun 25, 2012, 12:56 PM
awrightbrother's Avatar
Florida
Joined Nov 2007
2,537 Posts
Quote:
Originally Posted by rossaer View Post
Just checking in again on the length of this project. Will the jet be able to be "disassembled" for transportation? 81" in length is pushing 7 feet it won't fit in my truck at that length.
Also I like the discussion on how "scale" to keep the project. I'd vote for a slightly thicker wing and larger inlets if it helps in efficiency and performance. As long as they don't become cartoonish, better flying qualities are more desireable than scale looks on the ground....but of course that is just my opinion.

al
Not to worry, I am not going to sacrifice performance for scale.
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Old Jun 25, 2012, 01:03 PM
awrightbrother's Avatar
Florida
Joined Nov 2007
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Quote:
Originally Posted by falcon5 View Post
I built an 81" long F-4 a few years ago and it had a 1.5" thick wing with a NACA 2408 airfoil. AUW was 15.5 pounds and it flew very well as a pusher prop. Here is a pic of the gear wells with a 1 1/8" thick retract unite and a 1" thick wheel for referance.
That should fit even a compact SUV or truck. But of course people can build it so it comes apart.
Fahim
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Old Jun 25, 2012, 01:09 PM
awrightbrother's Avatar
Florida
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Quote:
Originally Posted by SteveC68 View Post
Fahim,

Just curious as to what drawings you are using for this? I looked at the exact setup that C/N is suggesting a couple years ago and ironically came up with 80" as the fuselage length for a single 90mm fan. Back when I looked at this the figures I came up with for intake area even at 80" length and a single 90mm fan looked a little on the low side for a 100% scale intake. I was planning on a small 3rd duct that would merge with the 2 main intakes just ahead of the fan. This was going to be a full duct though and not a cheater hole. As you have discovered a scale T-38 is a tough plane to tackle. Take a look at this link starting at post number 15. Some pretty nice CAD work there on the T-38. Up until these guys started this project the best drawings were from the DACO book on the T-38.

http://forum.largescaleplanes.com/in...pic=28715&st=0

Steve
Steve
Yes the T38 is a tough one as I am discovering. I came up with 80.64" for a 90mm so I rounded it up to 81". We are both pretty close.

The ducts are cut at an angle in both the vertical and horiz planes, so we end up with more area than if they are looked at from the front. I was making that mistake earlier on until I realized the cut angles.

Taking that into account the cummulative area of both ducts is 10.8 sq in vs the 8.4 sq in FSA of a 90mm fan.

Fahim
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Old Jun 25, 2012, 01:31 PM
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United States, TX, Grand Prairie
Joined Nov 2005
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Quote:
Originally Posted by awrightbrother View Post
That should fit even a compact SUV or truck. But of course people can build it so it comes apart.
Fahim
Build it were the nose tip comes off and the main part could be less than 72" detached and 81 attached...that doesn't seem like it would be too hard with some wood parts and some wood or nylon screws...
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Old Jun 25, 2012, 03:22 PM
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USA, GA, Atlanta
Joined Nov 2008
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72" is manageable, but sections smaller than 65 inches make it far more manageable for those of us that transport in 4door sedans...

Although like you said, that can be left to the builder to decide
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Old Jun 25, 2012, 07:15 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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having the nose seperate inbetween the ducts is the best place ,and can be supported on each side by the inlets .spring air 602's and Tams mini retacts would work well in the 1.5" thick wing . both of these can support the weight and are high quality. also when doing inlet cacls i've been told you figure in all the way to the mid point of the radius of the lips .we may have to have a bit bigger radius then scale,as the scale lips are too sharp, but it will suck air cleanly and there will be more than enough FSA . cant wait to see some foam to be cut.
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Old Jun 25, 2012, 11:30 PM
awrightbrother's Avatar
Florida
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Quote:
Originally Posted by AIR SALLY View Post
having the nose seperate inbetween the ducts is the best place ,and can be supported on each side by the inlets .spring air 602's and Tams mini retacts would work well in the 1.5" thick wing . both of these can support the weight and are high quality. also when doing inlet cacls i've been told you figure in all the way to the mid point of the radius of the lips .we may have to have a bit bigger radius then scale,as the scale lips are too sharp, but it will suck air cleanly and there will be more than enough FSA . cant wait to see some foam to be cut.
Since I have to ship the fuse in 2 parts, I have made it separable at the ducts. The Spring Air 602 retracts are perfect. I resell then so that is what I used for the drawing.

I have an idea to make the intake walls thinner than the foam wall. Hard to explain, but will show in the build. We may not need any intake ducting because there is no obstruction in front of the fan.

This design turned out to be more complex than I had imagined. Because of the size, the parts count has gone up and so has the complexity of the cuts.

I am almost there but have one thing I can't seem to figure out. How do I make the stabilator operate. The fuse sides are not parallel, so one rod will not work. If I have 2 rods, then how do we operate each. Any ideas would be appreciated.

Fahim
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Old Jun 25, 2012, 11:49 PM
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St.Catharines, Ontario
Joined Jan 2009
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Something like pillow blocks, with a seperate servo driving each side. Or a single, bent rod operaring both sides, that runs under the thrust tube/bifurcated duct. If its split, I'm imagining a setup similar to what's in my Yellow F-18 single.
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Old Jun 26, 2012, 12:12 AM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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the easiest way for you is to make them work with two servos ....2 strong MG servos will be easier to stuff in there and no need for custom parts.
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Old Jun 26, 2012, 12:32 AM
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United States, CA, Lancaster
Joined Jan 2009
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Elevators supported by these http://www.servocity.com/html/standa...rvoblocks.html would work. HET uses two separate rods to support the elevators. See pictures. These are controlled by 2ea servos.
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Old Jun 26, 2012, 07:25 AM
Hey Guys, Watch This.......
mike2663's Avatar
USA, TX, El Paso
Joined Dec 2003
6,261 Posts
Quote:
Originally Posted by awrightbrother View Post
Since I have to ship the fuse in 2 parts, I have made it separable at the ducts. The Spring Air 602 retracts are perfect. I resell then so that is what I used for the drawing.

I have an idea to make the intake walls thinner than the foam wall. Hard to explain, but will show in the build. We may not need any intake ducting because there is no obstruction in front of the fan.

This design turned out to be more complex than I had imagined. Because of the size, the parts count has gone up and so has the complexity of the cuts.

I am almost there but have one thing I can't seem to figure out. How do I make the stabilator operate. The fuse sides are not parallel, so one rod will not work. If I have 2 rods, then how do we operate each. Any ideas would be appreciated.

Fahim

Thanks for the update. How is the target cost of $150.00 looking?

Mike
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Old Jun 26, 2012, 09:37 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
22,832 Posts
fahim, you have to do 2 seperate stab rods, as the F-5 family has anhedral in the stabs. you can still have the pivot line from stab to stab, it doesnt have to be perpendicular to the side of the fuse, just to the centerline of the fuse.
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