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GWS P-40 Build Thread

Old 09-20-2007, 10:49 PM
  #76  
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What I mean to say is if you place a piece of self stick heat activated low temp covering on the foam it's going to stick out like a sore thumb when you paint over it. The covering will be above the foam <outie?> and look like a piece of tape does when applied, and painted over on foam.

How's that?

Tommy D
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Old 09-21-2007, 03:31 AM
  #77  
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Okay -- I understand now. However, I've already covered the servo wire channel with the covering (see picture, below).

If it looks terrible after painting, I can always remove it, and apply fiberglass instead...

However, I can't imagine it will really look THAT bad... :o How can it look any worse than a strip of fiberglass? Both are going to rise above the surface of the styrofoam...
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Old 09-22-2007, 09:20 PM
  #78  
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Fiberglassing is done.

Per the buyer's request, I did not fiberglass the entire aircraft -- I only fiberglassed the surfaces which will come in contact with the ground, during belly landing.

These surfaces included the belly pan, underside of the forward fuselage, underside of the rear fuselage, and the two landing gear pods.

You can see these areas, in the pictures below.
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Old 09-22-2007, 09:26 PM
  #79  
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Here's why I sand and spackle...

The first picture shows what the starboard landing gear pod looked like BEFORE sanding and spackling (but after Gorilla Glueing in place).

The second picture shows what the starboard landing gear pod looked like after sanding (but before spackling).

The last two pictures show what the starboard landing gear pod looked like AFTER sanding and spackling.
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Old 09-24-2007, 02:27 AM
  #80  
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Frankie has a new ship...
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Old 09-24-2007, 02:32 AM
  #81  
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Looks good!

Hey, did you happen to weigh those spinner? Can you tell me the size and weight. E-flite (??) is advertising them as lightweight. I'd take anything lighter than a darn Dubro!!

Thanks.
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Old 09-25-2007, 02:19 PM
  #82  
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Originally Posted by alienx View Post
Looks good!
Thank you!

Originally Posted by alienx View Post
Hey, did you happen to weigh those spinner? Can you tell me the size and weight. E-flite (??) is advertising them as lightweight. I'd take anything lighter than a darn Dubro!!
The spinner we are using is the Great Planes Spinner 3"; it is 3 inches in diameter, and weighs 53 grams.

If you are talking about a different spinner, let me know and I will see what I can do.
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Old 09-25-2007, 02:40 PM
  #83  
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Originally Posted by Lieutenant Loughead View Post
Thank you!

The spinner we are using is the Great Planes Spinner 3"; it is 3 inches in diameter, and weighs 53 grams.

If you are talking about a different spinner, let me know and I will see what I can do.
Ah, GP, I remember now. Thanks, that's what I was looking for. I think the 2" dubro's weigh almost that much. I just wanted to see if the GP's were really lightweight like the say they are.

Sometimes I think I am the only one that pays attention to weights. Just seems like a 15 ounce model shouldn't have to endure almost 2 ounces alone in the spinner. Good to see we have some options. Now, if we could get some different shapes!!!

Thanks again.
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Old 09-25-2007, 04:50 PM
  #84  
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Oh no -- you are not the only one!

I pay attention to weight! It's all part of the master equation.
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Old 09-25-2007, 07:14 PM
  #85  
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During my lunch break, I tested the same power system (Eflite Park 480, 1020 KV, MAS 10x8E prop, Tanic 3s 4440 mAh LiPo) both with, and without the 3" spinner. (See pictures, below.)

Here is what I found:
  • The power system with the spinner drew 0.05 more peak amps.
  • The power system with the spinner had 0.06 volts more voltage sag.
  • The power system with the spinner had 1 peak watt less.
  • The power system with the spinner had 51 grams less thrust.
  • The power system with the spinner had 1.8 ounces less thrust.
  • The power system with the spinner had same RPM.
  • The power system with the spinner had same prop pitch speed.
With the exception of the thrust numbers, these differences are neglegable, and could be due to the limitations of the test itself.

I also ran a test fit of the spinner to the cowl -- it's a perfect fit (see the pictures, below).

Finally, I test fit the motor, spinner, cowl, and fuselage. (See picture, below.) It looks like I will need to remove the piece of foam GWS intended for motor mount support. I will remove that with surgical precision, tonight...
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Old 09-25-2007, 07:26 PM
  #86  
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The test data, with the spinner:
  • Date of test: 9/25/2007
  • Motor: Eflite Park 480
  • Motor KV: 1020
  • Gear Ratio: 1:1
  • Prop: MAS 10x8E (With 3" Spinner)
  • Prop Pitch: 8
  • Battery: Tanic 3s 4440 mAh LiPo (Tanic #2 and Tanic #3 in parallel)
  • Peak Amp Draw: 24.69 amps
  • Minimum Volts: 10.05 volts
  • Peak Watts: 253.0 watts
  • Thrust (measured) : 1055 grams
  • Thrust (calculated) : 37.21407 ounces
  • RPM: 7560 RPM
  • Prop Pitch Speed (calculated, based on min volts, KV rating, and prop pitch) : 77.66 MPH
  • Prop Pitch Speed (calculated, based on RPM and prop pitch) : 57.27 MPH
  • Thrust Efficiency (Thrust/Amps) : 1.507252734
  • Speed Efficiency (Speed/Amps) : 2.319673037
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Old 09-25-2007, 08:27 PM
  #87  
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Good stuff LL.

FWIW, I used a duBro 3" 3-blade spinner on mine when I swtiched to the Scorpion motor. It's off the plane right now, so I should go and weigh it to see how heavy it is.
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Old 09-25-2007, 08:33 PM
  #88  
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Originally Posted by crxmanpat View Post
I should go and weigh it to see how heavy it is.
I'd like to see that!
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Old 09-25-2007, 11:27 PM
  #89  
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I'll try to remember to do that tonight.
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Old 09-26-2007, 03:08 PM
  #90  
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Question:

Why are you testing the system with that battery pack<s>?
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Old 09-26-2007, 04:28 PM
  #91  
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Originally Posted by tommytorino View Post
Question:

Why are you testing the system with that battery pack<s>?
The main reason is that these battery packs are 10C, and any amp draw over 22.2 amps would not be great for the battery.

Instead of spending big bucks on a 15C or 20C battery I don't NEED, or spending big bucks on some sort of alternative power source, I simply put two of my existing 2220 mAh LiPos in parallel so I can support a safe 44.4 amp draw.
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Old 09-26-2007, 08:06 PM
  #92  
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Okay gang -- I tackled the motor mount, today during my lunch break... I've got to say, it looks pretty darned good!

The plywood firewall will be anchored into the foam with bamboo skewers and Gorilla Glue. The owner will probably bend a prop adapter (or break a prop) before the firewall will let go...

The screws visible in pictures #4 and #5 are the landing gear screws which come with the GWS P-40 kit.

Now, I just have to figure out a way to keep everything in position while the glue is drying...
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Old 09-26-2007, 09:12 PM
  #93  
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It's looking good
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Old 09-27-2007, 12:15 AM
  #94  
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Your testing a power system on battery you don't intend to fly the model on?

Tommy D
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Old 09-27-2007, 04:56 AM
  #95  
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Tommy -- I don't intend to fly this model.
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Old 09-27-2007, 05:22 PM
  #96  
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Still I don't understand. If you test this motor/prop combo on a battery your not going to fly it on the numbers, well there worthless.

Also I thought reading back in the thread you were going to maiden/trim the model for the fellow? Seems after all this work you sure would want to fly it, no?

Tommy D
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Old 09-27-2007, 08:06 PM
  #97  
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Tommy -- batteries are funny things... No matter what battery you use for your test, someone will call your data "worthless"...

Seriously -- let's see a show of hands -- how many of you reading this thread use a 10C 3s Tanic 2220 mAh LiPo? If I had run the test using that battery alone, would that have told you anything?

What if I used a CommonSense battery? Or a Thunder Power battery? Or an Eflite battery?

What about a Danlions battery? Or a Venom battery? Or a Kokam battery? Or an Apogee battery?

How many battery brands are there out there? Nobody uses the same battery, and all batteries behave differently under different loads. The battery the owner will use is a Thunder Power Extreme -- my three-year-old 10C Tanic batteries just can't measure up to that; so I elected to put two in parallel to SIMULATE the owner's battery. (...and also to make sure my battery doesn't pop under the current draw!)

As for the maiden... I think I would prefer for the owner to maiden this airplane... I have my GWS P-40 on order (Tower Hobbies), and will get mine in the air soon enough. Actually, I will probably build mine exactly the same way (different motor); same paint scheme and everything.
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Old 09-27-2007, 08:17 PM
  #98  
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Thats exactly my point. The test is pretty much worthless if you don't use the pack thats going to be in the model.

Tommy D
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Old 09-27-2007, 09:27 PM
  #99  
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...so, by your definition, ALL power system tests are "worthless".

Honestly, Tommy, it's good information to know. If nothing else, it gives you a good idea of where to start. If you like the numbers you see, you can copy the same power system, and set up a test for yourself...

One thing I didn't mention earlier is ALTITUDE (along with other atmospheric differences) can make a difference as well.

I like testing power systems -- it's good information... I currently have 163 motor tests in my master spreadsheet (actually, I have performed other tests which were lost when I changed jobs about a year and a half ago). Tell me the weight and the wing area of your airplane; tell me the amp draw you find acceptable, and tell me how you want your airplane to behave -- I'll tell you what power system to use.
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Old 09-28-2007, 02:09 AM
  #100  
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I think by my definition, as you like to call it, the numbers you generated are not relevant.

What matters is how the plane fly’s, not how many lbs of thrust it makes with a battery pack you don’t intend to use, while stalled on a test stand. That is unless you intend to fly that test stand!

Do yourself a favor; better yet do all the poor folks who listen to your advice a favor. Build a test stand that actually measures something relevant under actual flying conditions. Then dump some dough on a regulated power supply. Might as well use that as your testing for “well known” motor suppliers. Heck they might even foot the bill for it.

Once you get all that data in a nice little packet, take the same combo, connect it to an in-flight data logger and compare the two. At that point you can take the thrust stand numbers and toss them into the garbage, where they belong.

Unsubscribed….. :p
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