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Old Apr 15, 2012, 10:46 AM
Pursuit of Happiness
Ron101's Avatar
Brentwood, California
Joined Jul 2007
7,190 Posts
Andy your so fast it makes me sick....lol

it looks amazing man... I guess I need to check in more often you don't mess around!!

Keep up the great work! I can't wait to get paint on my F-18, it will feel like I really have something
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Old Apr 15, 2012, 11:27 AM
Retired and Lovin' it!
United States, KY, Sturgis
Joined Jul 2007
2,482 Posts
I can speak about 'rock fever'. Was stationed at Hickam from '76-'79. I didn't care for golf and the beach smells like fish. Thank God i had my private pilots license. Almost every Saturday i was down at "Hawaii Country Club of the Air' to rent a Grumman AA1 and head out for somewhere. Nothing like 70-80 miles over water in a 115 hp 2-seater to make you sit up straight and pay attention.

Tony
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Old Apr 15, 2012, 03:53 PM
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United States, NM, Hobbs
Joined Oct 2011
80 Posts
What an incredible build!

This post is jumping in after reading up to Jan. 3, 2012 and today is April 15 so this may have been contributed already. If so, my apologies. WEST epoxy had been a part of my model building and 1:1 aircraft work since the early '80s. Thankfully, I no longer do 1:1 aircraft work. It is not the hardest finish out there IMO. Aeropoxy is probably harder if that matters. What I really like about WEST is its three stages of cure.

The following is copied directly from WEST's discussion on the cure phases.

"1. Liquid-Open time
Open time (also working time or wet lay-up time) is the portion of the cure time, after mixing, that the resin/hardener mixture remains a liquid and is workable and suitable for application. All assembly and clamping should take place during the open time to assure a dependable bond.

"2.Gel-Initial cure
The mixture passes into an initial cure phase (also called the green stage) when it begins to gel or "kick-off." The epoxy is no longer workable and will progress from a tacky, gel consistency to the firmness of hard rubber, which you will be dent with your thumbnail.

"Because the mixture is only partially cured, a new application of epoxy will still chemically link with it, so the surface may still be bonded to or recoated without special preparation. However, this ability diminishes as the mixture approaches final cure.

"3.Solid-Final cure
The epoxy mixture has cured to a solid state and can be dry sanded and shaped. You should not be able to dent it with your thumbnail. At this point the epoxy has reached about 90% of its ultimate strength, so clamps can be removed. It will continue to cure over the next several days at room temperature."

End of the WEST comments.

The beauty of the end of the green stange to the early final cure is that the epoxy is very sandable. It also dents easily at this stage. As time passes it gets harder until it is fully cured. At low temperatures (50-70 F) this phase can take up to 90 days to achieve. At normal to slightly warm room temperature it takes about 30 days. At 140 degrees F it takes 3 hours to fully cure. I've set a few parts in a car on a sunny day to achieve the final hardness quickly. WEST has several choices of hardeners for the 105 resin to allow the user to match the cure time to the ambient temperature and also to the intended use. In the heat of the summer even the extra slow 209 will go pretty quickly if not spread into a thin film as soon as it's mixed. Left in a mixing cup I've had it start smoking well before its advertised pot life of 15-20 minutes. Storing it in and air conditioned environment will help extend the pot life.

An uncoated paper plate is a cheap, disposable solution to this problem. According to the WEST literature epoxy shouldn't be allowed to come into contact with wax coatings like waxed paper cups while mixing it. Plastic medical cups or uncoated paper bathroom cups work great.

If you're applying it to surfaces that are already warm to hot from the shop environment, the resin will warm up to the temperature of the substrate very quickly.

A little alcohol goes a long way in thinning WEST out. For glassing an airframe I like it thin enough that it fully wets but doesn't fill the weave of the cloth. The cloth goes transparent but the texture is still apparent. After the initial sanding a very thin second coat can be rubbed on with a paper towel to seal any frayed glass cloth. It can be filled with any one of a number of lighter primer/fillers later.

Hope this was worth the time and space.

David
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Old Apr 15, 2012, 03:57 PM
Registered User
United States, NM, Hobbs
Joined Oct 2011
80 Posts
Amazing. Shoulda looked at the last posts before going on about WEST but I like to read a book front to back. I can build pretty fast and do a good job but OMG! What a beautiful build!

David
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Old Apr 15, 2012, 11:58 PM
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Geelong, Victoria, Australia
Joined Mar 2004
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Quote:
Originally Posted by falcon5 View Post
Hmmmm... Now this gives me an idea
I was out at the March AFB museum on my trip stateside back in November, and I think this image might explain the T-38 model I could see in one of the restoration hangers, but could not get close enough to get a good look!
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Old Apr 16, 2012, 04:01 PM
Capt. Z
falcon5's Avatar
Tonopah, Nevada
Joined Dec 2004
2,542 Posts
Work continues on the electrical and fan intake duct work. Also since upgrading to all digital high torque servos on the flight controls I also upgraded the RX to the R922 to handle the extra load the servos will put on the RX power bus.

From the JR web site:

"The R922 receiver is designed for models using multiple high-torque servos, such as giant-scale airplanes and jet models. It features a robust power bus designed to manage high-current loads, as well as dual 16AWG battery input leads with EC3 connectors for use with larger battery packs. This makes it possible to support high-current systems straight through the R922 without the need for a separate power system."


Thanks to Ron101 and his thread on ripple currents and CAPS I also decide to beef up the system in that area as well.
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Old Apr 16, 2012, 05:49 PM
Capt. Z
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Tonopah, Nevada
Joined Dec 2004
2,542 Posts
Doodling around with how to do the open ducting stuff around the fans.. well here is what I have so far..

The shape of this thing fits right in the fuselage and will pretty much seal off 99% of the air from passing around the fans. So all the air must pass through the fans. I guess it's a start and will get me in the air anyway. After a few test flights maybe I can fine tune it with somthing else.
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Old Apr 16, 2012, 06:02 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
20,529 Posts
shoot now put a "V" shaped divider wall in there and you pretty much have ducts ,that should work well enough. maybe some fod screen and your on your way to safe flight.
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Old Apr 16, 2012, 08:25 PM
Capt. Z
falcon5's Avatar
Tonopah, Nevada
Joined Dec 2004
2,542 Posts
Sounds good Rodger, I have the V shape planed out and your right I think it should make for a pretty reasonable duct. Thanks

Made the thrust tubes today and instead of a gradual taper all the way down the pipe I made them constant diameter for 90% of the duct then the last 10% starts the taper to 85% FSA
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Old Apr 16, 2012, 08:57 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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those are long ducts,im guessing close to 3 ft? ...so that was a great idea to stave off the losses that go with super long tail pipes.i would be good to know what these fan do as far as thrust with and with out the tail pipes on the bench. it's going to effect it some .
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Old Apr 16, 2012, 09:20 PM
Capt. Z
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Tonopah, Nevada
Joined Dec 2004
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Quote:
Originally Posted by AIR SALLY View Post
those are long ducts,im guessing close to 3 ft? ....
Good eye, they are 3.1 feet long as you them in the pics. I made them a tad long and an inch or two will be trimed off on instalation. I won't be bench testing these out of the plane so first run will be mounted in the plane and ready to go. Stu bench tested the fans so I have complete faith in those..the rest of the system, ESC and such...well if it blows I will have a halon extinguisher at the ready. : ) With only 10S and a ton of caps I hope to be good to go. : )

I will do a basic pull test once installed in the plane with this digital scale to see what it does. It won't be super acurate as the weight of the plane will be on the wheels but maybe I can extrapolate the numbers a little and say if the plane on the ground pulls the fish scale 20 pounds maybe i am actualy getting 22+ or whatever.
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Last edited by falcon5; Apr 16, 2012 at 09:30 PM.
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Old Apr 16, 2012, 09:47 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
20,529 Posts
yeah you could pull the plane and see what it take for it to break away (start rolling )
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Old Apr 16, 2012, 10:43 PM
Official Boat Bum
Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
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What are you using for thrust tube material (both the tapered aft nozzles and the constant volume exhaust tubes)?

I learned something new today; I assumed it would have been more efficient to have a gradual restriction applied to the whole length of the tube, not just the last bit. (of course your aft nozzles are gradual enough, just not as gradual as a 3 foot long tube!)
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Old Apr 16, 2012, 11:32 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,022 Posts
Quote:
Originally Posted by Eddie P View Post
What are you using for thrust tube material (both the tapered aft nozzles and the constant volume exhaust tubes)?

I learned something new today; I assumed it would have been more efficient to have a gradual restriction applied to the whole length of the tube, not just the last bit. (of course your aft nozzles are gradual enough, just not as gradual as a 3 foot long tube!)
Do you have more details about it?
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Old Apr 16, 2012, 11:38 PM
Official Boat Bum
Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
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Quote:
Originally Posted by AIR SALLY View Post
those are long ducts,im guessing close to 3 ft? ...so that was a great idea to stave off the losses that go with super long tail pipes.i would be good to know what these fan do as far as thrust with and with out the tail pipes on the bench. it's going to effect it some .
Only this, via Sally's comment above. He's pretty up on ducting though. I'd like to know more about it too, but I always assumed it would have been better to have a gradual taper through the full length of the tube. I suppose not?
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