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Old Apr 04, 2015, 11:52 AM
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Question
Suggestions for Building a B-66 Bomber

Hi,

As you will see from this posting, I'm new to RC modeling. I know my first project will seem a bit ambitious, but I expect to learn a lot along the way.

This thread continues from one I started in the Scratch Built forum, before realizing that this forum--for EDFs--was available: "Would Like First Impressions of B-66 Project" (http://www.rcgroups.com/forums/showthread.php?t=2381385

In short, I want to build a foam, 50-inch-wingspan B-66 Destroyer. Because I want it to be as close as possible to scale, I'm considering using two 50mm EDFs since anything larger probably wouldn't fit in the to-scale nacelles.

Attached is an image showing three different sized nacelles and the diameter of the interior tube from each nacelle. I see that the Dr. Mad 50mm external diameter is about 2.09 inches, so that would seem to be about right for the to-scale nacelle.

Also attached is a spreadsheet showing my initial estimates for the weight of the plane--about 32 ounces.

So, I have a few questions:

Do my weight estimates seem reasonable? If not, what might be expected for a foam plane of that size?

Is it reasonable to expect that two 50mm EDFs would have sufficient power for this plane? For what I've read, I realize there are a lot of variables, such as design and power set up.

I should mention that I'm not looking for super performance. The actual, full-sized plane had a thrust to weight ratio of .35, and I'd be happy if performance in the model mimics that of the real plane.

If the 50mm units will do the job and if there is some excess capacity, I would like to add retracts, which are not included in my initial weight estimates.

If 50mm units will work, I'd like suggestions on good makes/models of fan and motor. I've seen a number of them mentioned in this forum's threads, but some of the posts are old, and the technology is constantly changing, with new units coming on the market.

Let me know what else you need to know to make suggestions.

Thanks,
Bill
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Old Apr 04, 2015, 12:25 PM
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A couple of things that might be helpful here. OK , so it has wheels, but I guess no retracts-- do you fly off grass , or do you have a paved surface?-- Secondly, if your using thrust numbers from HK , don't believe them --these are the most optimal the fan can get--
I'd giveThe Don a call or e-mail to see what a 50mm really puts out-- http://www.donsrc.com/cart/

Another thing that helps everyone, is to put you location in your profile-- are you at sea level or up in the mountains--how do we even know. That certainly can make a difference .
Cooler
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Old Apr 04, 2015, 01:15 PM
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Cooler,

Re: "... do you fly off grass , or do you have a paved surface?"

Truth be told, I'm just getting started flying. Got a HorizonZone Super Cub for Christmas and flew it in Arizona.

HobbyZone Super Cub S--First Flights for Plane and Pilot (Feb 25, 2015) (10 min 57 sec)


You of all people will know why I wasn't flying it at home in January/February, because, neighbor, I hail from Minnesota.

Actually, at one point I tried to figure out how to add my location on this forum but couldn't find the place to do that. Could you give me some directions on that?

But, to get back to your question, I'll be scoping out flying clubs and local areas to practice my flying skills. I'll have plenty of time to do that, because I expect this project will take a long, long time. Given the marginal power of the B-66, I assume I'll be using paved surfaces. I doubt if even the real aircraft was much of a soft-field plane.

Concerning thrust numbers, yes, I see what you mean. I have found some threads where people have done actual tests.

Again, if anyone has any info on 50mm units that they would recommend, please let me know. And please note my other questions in my initial post.

Thanks,
Bill
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Old Apr 04, 2015, 02:58 PM
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Bill , just go here: http://www.rcgroups.com/forums/usercp.php
on the left of screen you have these options:
Your Control Panel

Your Profile
Edit Your Details
Set Location- -go here
Profile Privacy
Edit Profile Picture
Quote:
You of all people will know why I wasn't flying it at home in January/February, because, neighbor, I hail from Minnesota.
With out a location who would know?

Personally , I think location should be a mandatory inclusion, to register .
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Old Apr 05, 2015, 09:55 AM
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I noticed that Rocketman1092's (Eric) CS100 Bombardier is configured similarly to the B-66, having the motors in pods attached under the wings by pylons. Because it's powered with two 50mm EDFs, I sent him a personal message for input on my project. Below, with his permission, are the key points of the exchange:

Me: I'd be curious to know your thoughts--either posted here or at the thread--on the feasibility of my project. Especially, suggestions on which EDF to use and how to set it up.

Eric: My CS100 is around 40oz and has plenty of excess power with the Mad Thrust 50mm fans with Turnigy Plush 40A ESCs and a 4S 2200mah pack. It's a bit overkill really, as I fly around at about half throttle most of the time. They're nice fans and would probably be a good choice for your build. Plus, you'll have plenty of wing area with a 50in span so it should still fly fine even if the model weighs more than you expect - which happens with pretty much every build.

Ducted fan units have changed a lot in the past few years and it's now possible to build models with scale-diameter power systems. You do pay for it in efficiency and power consumption, but that's not much of an issue unless you want long flight times.

The 3300kV inrunners are what I'm using on 4 cells, and they work well. I think they're re-branded RCLander motors and are of pretty good quality. There's a 4000kv version for 3 cells, but it doesn't seem to be as popular.

__________________________________________________ _______

Encouraging. Anyone else with suggestions or observations, please let me know.

I'll start a build thread once I have enough to be worth posting.
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Old Apr 06, 2015, 07:56 PM
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I would use depron foam to build the B-66 . Mark knows his stuff and has given you good info. he's really good at searching out info .
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Old Apr 06, 2015, 08:21 PM
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Thanks for the kudos's Rodger. I have never used depron myself so, I didn't go there.. Changing over to a new OS. has left a big hole in my data base--

Mark (Cooler)
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Old Apr 07, 2015, 09:06 AM
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I was a maintenance officer on the B-66 in France, 1965. We had ECM jammers, they went to Viet nam when the first SAMs were fired. The B-66 had Allison J-71 engines (no good) compared to the J-57 in the original Navy A3D airplane. A nice modeling subject. You might consider upsizing the nacelles a tad over scale and putting 65 mm fans in it. ! real tight fan housing would mask the out of scale affects.
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Old Apr 07, 2015, 11:59 AM
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42" plans for a B66 in "Vintage" section Post# 13977

Regards Ian.
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Old Apr 07, 2015, 07:12 PM
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Re: "42" plans for a B66 in "Vintage" section Post# 13977."

It's a small world. Before starting this thread, I started one in the Scratchbuilt (not EDF one) thread titled "Would Like First Impressions of B-66 Project."

(http://www.rcgroups.com/forums/showthread.php?t=2381385

In it, I say,

When I was a teenager, I built a free-flight B-66 from a plan ordered from Model Airplane News magazine. In those days (circa 1955), kids mostly built either U-control or free flight. For those of you who don't know what U-control is ... Oh well,
never mind.

Anyhow, I built this free-flight B-66, but it was underpowered, having only a single .049 glow engine in the fuselage and a ducted fan blade you cut out by hand. Oh, those were the days! The plane couldn't do more than taxi slowly. Howard Hughes at least got his Spruce Goose in the air for a few seconds; but not me.

The plans are still available on eBay! The attached image is a screengrab of one of those sets, which I captured for old-time's sake.

So, now that I've been rebitten by the model-building bug, constructing a B-66 that can actually fly is on my bucket list.

________________________________________________

Thanks for the reference. Now I know I wasn't far off when I said circa 1955. The magazine was published in 1957. For anyone interested, the link is

http://www.rcgroups.com/forums/showt...=B+66&page=932

Bill
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Old Apr 07, 2015, 10:16 PM
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Re: "You might consider upsizing the nacelles a tad over scale and putting 65 mm fans in it."


As you might expect, I'm getting advice about 50/50 on both sides of this question. Fortunately, I can hold off making a decision until I've come up with a more precise picture of how much the model will weigh, etc.

Worst case, I can build new nacelles if 50mm fans doen't provide enough power, but I hope it doesn't come to that!

Bill
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Old Apr 08, 2015, 12:38 PM
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You don't need Fleebay Bill, the PDF is full size.

Regards Ian.
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Old Apr 08, 2015, 01:34 PM
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Re: "You don't need Fleebay Bill, the PDF is full size."


Yes, I downloaded it. Will be of minimal use, however, since the design is completely different than the one I envision. The .jpg version that I attached in my previous post I had grabbed free of charge. It is essentially the same as the .pdf. At that time, I wasn't aware of its existence at RCGroups.com.

As far as I can see, the .pdf is of the plan only, not the entire article. Too bad.

I recall that in the magazine article there is a photo of the plane in flight. Too bad YouTube wasn't around then. As I mention, I never was able to get the plane to fly. If I had that model today, I might strap a more powerful motor on it and try again.

Bill
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