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Old Jun 10, 2007, 08:31 AM
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Winnipeg, MB, Canada
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Jetset44 175% SU-37 build!

I would like to build a 175% version of Steve's very nice SU-37 but being my first large electric I may need some help along the way. I will be open to any advice or help I can get. Looks like it will have a span of 52.5" and length of 63.5". Some of the stuff I was looking at for it are....

-Motors http://www.bphobbies.com/view.asp?id...84&pid=W815796
9x7.5 props, 72A total, about 6lb thrust, 1060W total and pitch speed of 78mph.
-TV servos http://www.bphobbies.com/view.asp?id...90&pid=S629352
-Other servos http://www.bphobbies.com/view.asp?id...83&pid=S544494
-ESC's http://www.bphobbies.com/view.asp?id...2&pid=B0558275
-8000mah 4S-2P packs

If I can build it with an AUW of 5lb it would be 200W/lb (don't think I can). 6.5lb AUW would give me about 150W/lb (might be able to do). Here are some weights I have so far.....

-Airframe = ???
-2 Motors = 320g
-2 ESC (I wonder if I should use 1 ESC and skip the yaw?) = 60g
-TV servos = 115g
-6 main servos at most = 162g
-8000mah 4S-2P = 704g
-RX = 20g
-RX pack = 105g

1486g, 52.32oz..... 3.27lb so far without the airfrme

-What does everyone thing of the item selection so far? I wonder if 200% would be better?
-Will those TV servo be strong enough?

By the way, I will be building it from 1/2" blue foam... hope I can find it here! I know I can get 1" and 2".
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Old Jun 10, 2007, 11:58 AM
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Racine, WI AMA# 809291
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Good you did start a new thread I think your going to be about 6 lbs, so build light If you can get standard 1/4" blue-cor, you can glue two pcs together. (But that glue adds weight too)

Lowes carries 1/2" sheets of Blue-Cor that are 4ft. X 8ft. Part# 15348

I'd love to build a edf version, but I have at least 3 planes to do first So blaze that trail I'll add this thread to Steve's Parkjets SU-37 page.

Tom - Milwaukee

You can download all of the Plans for the SU-37 at www.Parkjets.com
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Old Jun 10, 2007, 12:02 PM
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Winnipeg, MB, Canada
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Thanks bud. So you think those motors will be a good match for the size and weight of this jet? At 6lb I should still get good flight performance right? If so I am going to order the 175% plans ASAP to get started!
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Old Jun 10, 2007, 12:28 PM
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It should work ok, you won't get blazing speed pushing a 6 lb. jet through the air, but it should end up being "scale-like" The larger prop's would give you more power for aerobatics, though. You also need to find one that's got a counter-rotating match for it too.
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Old Jun 10, 2007, 01:16 PM
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Nerver thought about the counter-rotating props, I will see what I can find in that size range!
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Old Jun 10, 2007, 08:00 PM
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Well I can't seem to find any electric CR props in this range. any ideas!?
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Old Jun 10, 2007, 11:09 PM
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Chapel Hill, TN USA
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After building the 42" ws F4 and 15-% Shumate F-18, I would expect your AUW to be in the range of 6-7 lbs, most probably closer to 7 lb but that's depending on the finish.
A good rule of thumb is airframe =1/2 weight of the plane, equipment the other half. Amazing how often it turns out to be true.
But these big airframes will handle the weight and fly very nice on 100 watts/lb.

J
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Old Jun 11, 2007, 09:22 AM
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Winnipeg, MB, Canada
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Well APC makes 9x6 props in the pusher so I can use those. I would get about... 60A on 4S, 6.6lb thrust, 895W, 65.5mph pitch speed. If it comes out at 7lb I would have 128W/lb. I will still build it at this and I'm sure it would fly great... I just wish I could find slightly bigger pusher props that would be better. I am going to see if I can get the foam today and if I can get it I will order the plans today. They should be here in a couple days!
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Old Jun 11, 2007, 11:07 AM
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You could probably contact APC and see if they make a larger CR prop. Could be that some dealers just don't carry it. From what I've read so far, steve's SU-37 takes a lot of sanding in the first place, so if you can keep the foam thin, you should be OK on weight.
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Old Jun 11, 2007, 11:37 AM
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I'll contact them and see. I am going out soon to look for foam, I think I remember finding the 1" blue foam but not sure about 1/2"... will find out soon I guess!
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Old Jun 11, 2007, 01:43 PM
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Well all is good, I can get the 1/2" blue foam! Only in 2'x8' but I'm sure that will be no problem.... I wonder how many sheets I should get to start!? Also sent an e-mail to APC about the props... see what they say. Plans are ordered so I should start building this week!
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Old Jun 11, 2007, 01:53 PM
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Seattle, WA
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I'll be watching this thread with interest! Sounds great.

For what it's worth, I think it's great to have counter-rotating props if you can, but don't sacrifice too much for it (like using less than optimum props). The prop torque really isn't that bad on these models and can be easily dealt with if need be. I was just lucky that APC makes 6x4 pusher props for my Su-37, which is the ideal prop size for the LSPJ.

Steve
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Old Jun 11, 2007, 02:36 PM
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Ohhh... pressure is on now! LOL. Hope it all goes well, the hard part will be to get it to look as good as your jet! I will start with the 9x6 props then try the 9x7.5 regular props after. May also try 10" props as well but I will worry about that when I get there! For the wing spares I was thinking about 1/4" balsa capped on the top and bottom with 1mm X 5.7mm carbon, what do you think? Any other areas that should get extra attention for strengthening? I have a lot of 1mm X 5.7mm and 2mm X 5.7mm carbon. I think I will also try and put the TV system on bearings.
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Old Jun 11, 2007, 03:47 PM
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Also do you think HS-81 servos would be fine for the rudders... have lots of those!
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Old Jun 11, 2007, 05:15 PM
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Here is something else I was thinking about.... only thing missing from these electric jets is the jet sound! Would it be cool or corny if I build some sort of light sound device that would play jet engine sounds? I think the trick would be to get something light and loud... any ideas?
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