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Old Jun 11, 2009, 04:18 PM
ParkScaleModels
zbrubaker's Avatar
United States, PA, Loganville
Joined Feb 2002
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1/12 scale F-84F Thunderstreak

I was challenged to get this project (started several years ago ) finished up and with any luck, the prototype will fly at Warbirds Over Delaware.

I had originally intended to design this as a light weight parkflyer, but with brushless motors and LiPo's being as cheap as they are now, I decided to do a complete redesign from the ground up around the available 68mm fans like the Wemotec Minifan.. Remarkably (for me), I have completed this design in just over 2 1/2 weeks. I plan to cut parts and get them sent off to the guy that's going to build the prototype this weekend. While I was going along in the design, I did build a wing, one half of the horz stab and the vert stab.

Controls will be standard fare - R/E/A/T with optional flaps and it has a full flying stab. I have not designed in LG at this point. Wing area is approximately 320 sq.in and I'm estimating the AUW to be around 32oz or so with a 3S 2200mAh LiPo. As it stand, I've calculated the bare airframe to weigh around 14oz...so this leaves 18oz for fan, motor, electronics and batteries. We'll see how it comes out.

Fuselage will be fully sheeted with 1/16" as will the stabs. Wing is a 'D' tube construction with some sheeting at the trailing edge for additional strength and rigidity.

I'll post some pics of the wing and the stabs that I have already built tonight or tomorrow.

Zeke
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Old Jun 11, 2009, 06:31 PM
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Winterthur, Switzerland
Joined Aug 2003
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Hi Zeke!
Very interesting project! I always liked those not so much seen early jets..Especially like the details of your stab construction!

As of now Im finishing my scratchbuilt 1/13 Thunderjet (straight wing) also designed around the Wemotec Mini. I posted some pics and remarks here. Hopefully it will take to the air this month, however it turned out rather heavy (>40oz) for the size and upscaling to 1/12 would have been the smart choice in the beginning..well i now know for next time ;-)
I also took down the weights throughout the construction process, i will post them as soon as the bird is completed! As a small advise: be careful with positioning all the components, I had troubles (read: required ballast) achieving proper CoG.

Good luck with your build, Ill be following!
cheers,
Andy
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Old Jun 11, 2009, 06:55 PM
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St. Martin's Avatar
Skunk Water, Rhode Island
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Last edited by St. Martin; Jun 12, 2009 at 03:21 AM.
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Old Jun 11, 2009, 09:54 PM
ParkScaleModels
zbrubaker's Avatar
United States, PA, Loganville
Joined Feb 2002
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Quote:
Originally Posted by Dotcom
As a small advise: be careful with positioning all the components, I had troubles (read: required ballast) achieving proper CoG.
Thanks for the advice Andy...that was a concern for me as well, but I've been doing a fair amount of calculations, so I hope I should be in good shape as far as getting it to balance properly.

Nice work on your F-84...I read through your thread a couple of days ago. I'm looking forward to the completion of your project.

Zeke
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Old Jun 12, 2009, 08:46 AM
ParkScaleModels
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St. Martin....what happened to your post?!? I had typed up a nice long response and was going to post pics last night when Firefox decided to hang right as I was uploading the pics grrrrrr - decided it was time to go to bed before I beat the snot out of my computer.

I'll have to look into the motor you suggested (if you can repost it). My flying preference leans heavily towards scale flying. I've never been interested in all out speed that many EDF pilots are. I found a 3900kV motor from Hobby City that looks like it will do what I want it to. With the 3S pack, it looks like I would be pulling about 35A max, but I'm sure I'd spend most of my time at 2/3 - 3/4 throttle anyway. But who knows, maybe I'll get bit by the speed bug too.

MotoCalc (numbers taken with a grain of salt) shows my intended setup to top out around 50mph - which is just fine for my tastes!

Laser cutting should commence later this afternoon.
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Old Jun 12, 2009, 09:37 AM
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Lawton/Fort Sill, OK
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Very interested in this project.
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Old Jun 12, 2009, 01:05 PM
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Las Vegas, NV
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Nice work Zeke, looks great.

What CAD software did you use to draw that, Rhino or something else?
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Old Jun 12, 2009, 02:41 PM
ParkScaleModels
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United States, PA, Loganville
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Quote:
Originally Posted by Ed Waldrep
Nice work Zeke, looks great.

What CAD software did you use to draw that, Rhino or something else?
AutoCAD 2009
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Old Jun 13, 2009, 04:53 PM
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St. Martin's Avatar
Skunk Water, Rhode Island
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Sorry, Zeke, I jumped the gun. There are a few folks on this forum, who choose to ignore my posts. Could not remember if I had made the mistake of posting on one of those members threads. My apologies, Sir.

My thoughts were in relation to your batt size requirements. You cannot beat a 4s system, when in the 2000-2500 Mah size batt arena. If a mtr Kv size of 3000Kv is used, such as the inexpensive HET 3W, will give 450W. The positive here is the 30-35A load. Perfect for a 2200Mah batt. I run a Astro 805W on 4s, in the mini, and it draws 40A @ 550W. Good cooling, and a larger ESC of 45A is required. The HET 3W only uses the much smaller 35A ESC.

The whole idea is in using the lower Kv to produce good watts but at a low system weight. Any mtr with a Kv value of the 4000, or more arena, will require a larger batt to avoid the voltage drop. My reasons for not using 3s packs to get a system to produce 400+watts. The added weight, or loss of duration should a bigger pack not be used, is self defeating.

I'm sure if you could fit a 3s-2200, a 4s-2200 could be fit. And the cooler running system, better efficiency, longer duration, would beat the 3s hands down, with the same power(W) levels.

JMHO.. And the design is coming along fantastic!

Fuzz
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Old Jun 14, 2009, 02:38 AM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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whats that ....balsa wood ? ...i remember that stuff ......where the depron ? .....it's the new balsa , nice project good luck.
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Old Jun 14, 2009, 10:34 AM
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Larry Dudeck's Avatar
Williamsville, NY, USA
Joined Sep 2000
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I second St. Martin's comments about the HET3W motor on 4S. My TBJ (avatrar) uses a pair of MF480's with the 3W motor and get 840 watts for the pair using a single 4Sx3300 TP pack.

Using mixed throttle, 7 minute flights are easy. Calculated top speed is 70 mph but I have no way of verifying that.
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Old Jun 14, 2009, 12:33 PM
ParkScaleModels
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United States, PA, Loganville
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Thanks for the Info Fuzz and Larry. I'll definitely look into that setup.

Air Sally...some of us still like doing it 'old school'!
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Old Jun 14, 2009, 12:39 PM
ParkScaleModels
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United States, PA, Loganville
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OK...cut some parts on Friday and yesterday...and did some assembling (I'm like a kid at Christmas!) What is pictured below represents about 5-6 hours worth of work. All that is left to do on the fuselage before exterior sheeting is doing the intake ducting. And in case anyone is interested...current weight of the fuselage in the pics is 4.3oz.

Almost forgot to mention...it was built entirely freehand...no jigs or plans required!
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Old Jun 14, 2009, 04:34 PM
Big gov never Works
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Skunk Water, Rhode Island
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I'll definetly build one of these,Zeke.

Fuzz
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Old Jun 14, 2009, 05:19 PM
ParkScaleModels
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United States, PA, Loganville
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I just finished getting the ducting in. I put in the EDF shroud with the motor installed. Weighs 9.5oz so far. Will post pics as soon as the batteries for my camera finish charging.
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