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Old May 27, 2012, 07:20 AM
Now in TN!
J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
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It won't be taking your breath away on vertical but it will fly Andy. Remember that forward swept wing that Laine flew formation with you and the Cutlass at SEFF? It weighed 22.5 lbs.
The 38 will fly and you might be be surprised at how well.

J
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Old May 27, 2012, 09:38 AM
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Oshkosh, WI
Joined Nov 2002
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Has anyone made a test panel weight comparison of the surface filler (can't remember brand) vs say 0.75oz/sq-yd glass/epoxy? I hav sneaking suspicion the former weighs more than the latter at equal strength; especially with attention to wt when applying the epoxy.

Phil
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Old May 27, 2012, 09:55 AM
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United States, CO, Hotchkiss
Joined Oct 2006
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Andy, it looks sweet. The heavier the wing loading, the better it will ride. Your pilots will thank you in that rough Tonopah air! It will fly just fine.
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Old May 27, 2012, 10:04 AM
killickb
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The Villages. Florida
Joined Jan 2005
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jofro, you say you would not fly any EDF at higher than 145gm/dm2 First am I right in saying this is approx 47oz/sg ft ? Even if wrong does this really apply to any EDF e.g. 30mm to 120mm powered models? Wouldn't there be other factors such as wing cube loading, scale factors, wing augmentation devices, thrust etc. Just trying to get an idea of what wing loading ranges are deemed "flyable" for what "size/complexity" of model -- this would be a good comparison chart if possible to create? Not forgetting that your and F-5's skill levels with heavy EDF's are much higher than most.
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Old May 27, 2012, 10:23 AM
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USA, OH, Beavercreek
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Phil: Using the data in this thread

http://www.rcuniverse.com/forum/m_10..._1/key_/tm.htm

where the thread starter compared the two Styro sprays on the market to finish balsa... The gentleman found on testing the weight that the unthinned Styrospray weighed approximately 10gms (.35ozs) per square foot. When he thinned it 1/3rd with denatured alcohol it came in at 7gms (.25ozs) per square foot. This was on balsa wood... SOOOO I don't think the weight gain can be blamed much on the Styrospray but than is just my humble opinion
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Old May 27, 2012, 10:49 AM
Capt. Z
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Tonopah, Nevada
Joined Dec 2004
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Yeah I think an airframe this size should be ok at 40 lbs, I have seen smaller and heavier fly preaty nice..I will re visit what it uses for a power plant after she flys.
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Old May 27, 2012, 11:59 AM
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United States, IL, Edwardsville
Joined Dec 2011
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Man the real 38 has a terrible thrust to weight ratio. Plan 10000 feet and 500 knots entry at 10000 feet for a loop! Fly it like the real one and it will fly fine. Remember - speed is life! Rotate fast, fly fast and land fast. It will track like an arrow! Don't pull power in the flare until the sink rate has been arrested! Good luck!

Fitz
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Old May 27, 2012, 05:51 PM
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Quote:
Originally Posted by killickb View Post
jofro, you say you would not fly any EDF at higher than 145gm/dm2 First am I right in saying this is approx 47oz/sg ft ? Even if wrong does this really apply to any EDF e.g. 30mm to 120mm powered models? Wouldn't there be other factors such as wing cube loading, scale factors, wing augmentation devices, thrust etc. Just trying to get an idea of what wing loading ranges are deemed "flyable" for what "size/complexity" of model -- this would be a good comparison chart if possible to create? Not forgetting that your and F-5's skill levels with heavy EDF's are much higher than most.
Hi, I was only trying to find out what is apx. w/loading of his model. That is always the first thing I like to know about any new model and is a good guide how it will fly. Sure, there are number of factors as you have mentioned but we all know that heavy loaded models are not very good gliders and have a good reputation for very short life span, Joe.
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Old May 27, 2012, 06:34 PM
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Originally Posted by falcon5 View Post
Yeah I think an airframe this size should be ok at 40 lbs, I have seen smaller and heavier fly preaty nice..I will re visit what it uses for a power plant after she flys.
Hi, put on some hard rubber tyres, loaded up to full flying weight, hook it up on the string and see what it pulls on the ground at full stick. If you know your apx. wing loading that should give you good picture how it will fly. ( subj. to your GofG), Joe.
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Old May 27, 2012, 07:46 PM
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IIRC, there is a ()^2/3 rule for comparing wing loading for planes of large difference in wing area. Thus a for a 40-lb 1/4 scale T-38 with an area of 11.6 sq-ft (55 oz/sq-ft), can be expected to behave as a 31 oz/sqft model with a 5sq-ft wing area. Any comments?

Phil
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Old May 27, 2012, 07:48 PM
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Oshkosh, WI
Joined Nov 2002
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Originally Posted by RAMFlyer View Post
Phil: Using the data in this thread

http://www.rcuniverse.com/forum/m_10..._1/key_/tm.htm

where the thread starter compared the two Styro sprays on the market to finish balsa... The gentleman found on testing the weight that the unthinned Styrospray weighed approximately 10gms (.35ozs) per square foot. When he thinned it 1/3rd with denatured alcohol it came in at 7gms (.25ozs) per square foot. This was on balsa wood... SOOOO I don't think the weight gain can be blamed much on the Styrospray but than is just my humble opinion
You're probably correct, Ramflyer. Only problem I had with that reference is the error in weight units & not taking a tare weight b4 application.

Phil
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Old May 27, 2012, 08:56 PM
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Originally Posted by PhilLin View Post
IIRC, there is a ()^2/3 rule for comparing wing loading for planes of large difference in wing area. Thus a for a 40-lb 1/4 scale T-38 with an area of 11.6 sq-ft (55 oz/sq-ft), can be expected to behave as a 31 oz/sqft model with a 5sq-ft wing area. Any comments?

Phil
I wouldn't quite relay on that rule, it may work with an ave. prop trainer, EDF is another story, being a pusher I would expect more like 2/3 rule power to weight ratio as minimum, Joe.
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Old May 27, 2012, 09:49 PM
Now in TN!
J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
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47 oz WL for a plane this size is nothing. It will fly just fine, larger planes handle larger WL easier.
I have a 1/10th scale F-104 that I built, it has a 38 oz WL, flies great and floats on landing. The 38 will do even better.
Get her in the air Andy, it will be fine.

J
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Old May 27, 2012, 10:57 PM
Capt. Z
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Tonopah, Nevada
Joined Dec 2004
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Originally Posted by J Morgan View Post
Get her in the air Andy, it will be fine.

J
Will do boss...

Cool stuff Fitz thanks..

I ran it on 10s this evening for the first time and she sure feels like she has some get up and go. I never held back 25 pounds of thrust before..pretty cool. !! I may put a digital fish scale on it tomorrow just to see how many pounds it pulls in the horizontal.

Just about have all my OMG it weighs 40 pounds madifications all done. Another day or so of finishing that stuff up and she should be getting close to lets go fly time. !!
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Old May 27, 2012, 11:55 PM
Official Boat Bum
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United States, NV, Reno
Joined Mar 2000
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Awesome. Kick the tires and light the fires. I'm not being flippant, I really strongly suspect this is going to be a successful and enjoyable model to fly. My money is on a nicely flying jet due to the solid construction, use of good hardware and some fantastic detail work. The heavier than expected wing loading is really common ground for this size of a jet model.

Going with your earlier references!!! Trailers below to set the theme for some flying.

Leslie Nielsen maneuver - Airplane! (0 min 9 sec)


Looks like I picked the wrong week to quit smoking... (0 min 50 sec)


Airplane thriller! (1 min 57 sec)
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