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Old Dec 28, 2010, 10:20 PM
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john_53_70's Avatar
south alabama
Joined Dec 2010
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Question
90mm edf with around 8 lbs of thrust

Hi I'm new here and I am building a scale fiberglass F-18F superhornet it will be about 35 inches long and I have a target weight of 7 lbs I would like to use a 90mm size fan and I'm wondering what kind and set up would make about 8 lbs of thrust, hoping to use a 8s lipo thanks for your help
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Old Dec 28, 2010, 10:41 PM
efflux RC's Avatar
United States, CA, Santa Clarita
Joined Aug 2009
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The ARC 36-75-1 motor in a Wemo Midi fan pro (90mm) will give you 8.8 lbs thrust on 8s.
~3kw @ 105-110A
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Last edited by efflux RC; Dec 28, 2010 at 10:48 PM. Reason: spelling
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Old Dec 28, 2010, 11:36 PM
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Steve C's Avatar
United States, CA, Lodi
Joined Feb 2001
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That sounds a bit small for 90mm these days.
Got any pics? We love pics!
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Old Dec 29, 2010, 12:01 AM
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south alabama
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Yeah Thats kinda of the idea for me at least it is for now, is to keep it kinda small, it's the first time I'm trying to tackle fiberglass mold so I figure the smaller the less it will weigh but no pics yet I will put some up once I start to build the plug
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Old Dec 29, 2010, 12:11 AM
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St.Catharines, Ontario
Joined Jan 2009
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I would increase the size for 90mm. you are only going to add several ounces by going to a larger size. remember that most of the airframe is air/space, so the only added weight is in the few extra square inches of airframe materials. 7 lbs is an overkill guestimate for that size an airframe, considering that my foamie of roughly that size only weighs about 2.2 lbs. you'de be able to power that size plane with a decent 70mm. I'm guessing you could build a slightly bigger model at around 5-6 lbs. consider that the WM400 makes just over 5 llbs of thrust on 6S and the efflux speed is higher than a 90mm, which means a theoretically higher top speed. you'de have a fairly light model, with a thrust to weight of nearly 1:1, if not greater than 1:1 if built light. do a quick calc of Watts to weight and you'll have a good idea. anything over 200 Watts/lb is going to give sparkling performance. all pluses IMHO.
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Old Dec 29, 2010, 12:16 AM
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St.Catharines, Ontario
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you can guess the weight of the plane if you are building a FG fuse. if it were me, I would build with 2 layers of 2oz cloth. count roughly how many square inches your entire airframe is and multuply by the weight of the cloth.............it'll either be 4oz per square yard, or square foot. do the math to convert from square inches to square feet/yards and that'll give you a weight of your bare fuse. then add the weight of your radio gear, fan unit with motor, battery, etc and you'll come up with an AUW weight (roughly). then you'll know how to progress with the design...............70mm or 90mm. you'll be fine at that size with a 70mm on 5S or 6S though.
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Old Dec 29, 2010, 09:14 AM
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south alabama
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You know now that I think about it a plane that size would fall out of the sky with the power off at 7 lbs so yeah think I'll hit up the drawing bored again, but thank you for that info that helps me out alot
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Old Dec 29, 2010, 11:10 AM
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Why not opt for a high powered 70mm?
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Old Dec 29, 2010, 11:48 AM
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United States, MO, St Charles
Joined Nov 2002
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Quote:
I am building a scale fiberglass F-18F superhornet it will be about 35 inches long and I have a target weight of 7 lbs
Hi John,
35 inches would be a good size for a 70mm ship and at that size I don't think you'll have any problem keeping under your target weight. On the other hand, if there was a typo and you ment 53 inches that's about the size of my 90mm legacy Hornet or Ed Waldrep's proto Hornet kit.

In my case, I'm using a 90mm Wemo fan powered by a Neu (formerly Medusa) NEU/MR 036/060/1300V5 motor on 8S with the option of going to 9S if I need more power. Just don't try running it on 10S as a number of folks have found out.

Please tell us more about your project. I'd be really interested to see your work.

Dan Eaton
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Old Dec 29, 2010, 02:40 PM
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south alabama
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Well the whole idea got started by me looking for a true scale F-18F or a E model I could make an F model out of. Well after a long search I've had no luck with a true scale because I have this horrible habit of finding some thing that throes it off scale I hate it by the way. So I said well if you want something done right Gotta do it your self, so my thought going in to this project is to have a true scale plane the flys like a fommy with the durability of a composite, and one that flys scale but I really want a 1:1 thrust ratio so that's way I was thinking small frame big fan, I don't plan on putting on landing gear but I will have all control surfaces as the real jet does and using the same airfoil as the real one so now that I know a little more about the fans thrust I'm going to rethink the scale and start on the plug and hopefully after I get a good flying jet maybe start to sell some kits in the $200 price range 
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Old Dec 30, 2010, 02:49 AM
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United States, MO, Warrensburg
Joined Feb 2008
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Quote:
Originally Posted by AceMigKiller View Post
Why not opt for a high powered 70mm?
Sounds like the TJ70 would fit the bill nicely. Impressive numbers.

Jetnfast
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Old Dec 30, 2010, 02:52 AM
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if there's one thing you'll learn, it's that you can't plan on selling kits. you'll never get your money out of it, without asking a huge price. build it for yourself and then see where it goes after that. I'm finding out all this now with how many hours I've got invested in my Jaguar and I'm nowhere near finished. in fact, I haven't gotten past the plug stage and I wouldn't even want to count the hours. do it for fun, but don't think about doing it to kit, or you'll lose your mind. LOL.
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Old Dec 30, 2010, 05:05 PM
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Skunk Water, Rhode Island
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A kit mfr once told me..How to make a small fortune in the model airplane kit bizz..Start with a large fortune!

Fuzz
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Old Jan 16, 2011, 11:05 PM
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south alabama
Joined Dec 2010
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Quote:
Originally Posted by LuvEvolution7 View Post
if there's one thing you'll learn, it's that you can't plan on selling kits. you'll never get your money out of it, without asking a huge price. build it for yourself and then see where it goes after that. I'm finding out all this now with how many hours I've got invested in my Jaguar and I'm nowhere near finished. in fact, I haven't gotten past the plug stage and I wouldn't even want to count the hours. do it for fun, but don't think about doing it to kit, or you'll lose your mind. LOL.
lol good advise but if anything it would more or less just be to share with ever one just not for free lol
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