Boomers!! Parkflyers for Beginners to Pros! Vid post 125 - Page 61 - RC Groups
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Mar 31, 2013, 11:07 AM
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builderdude's Avatar
Forget it, I'll keep looking.
They want $112 for shipping. The heck with that!
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Mar 31, 2013, 11:53 AM
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Okay. Park Zone sells Stryker wing/fuselage and nose cone for $22.49.
That looks like a nice way to build a boomer. The slots for the fins can be used for the twin CF booms. The nosecone can be extended out a little further for weight balance.

It's a little smaller than I was hoping for, at 37" wingspan, but it looks really boomer-friendly. So I'll post pics as I get my Stryker-based boomer assembled. More later.
Last edited by builderdude; Mar 31, 2013 at 12:11 PM.
Mar 31, 2013, 12:49 PM
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The Stryker makes a good Boomer, although EPO, not EPP.
If you search Stryker in the Boomer Thread, you'll find the Stryker Boomer I built.

Also, RiteWing recently has produced a 54" Wing, molded EPP for around $100+.
Mar 31, 2013, 01:04 PM
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I'll try out the Stryker boomer first. I'd still like a larger one, but 37" isn't too bad.
I've noticed you keep your tail moment short on most of your boomers. Still should improve pitch control over a pure flying wing. I also noticed your elevator and ailerons are pretty large. Also, you don't use rudders. They're bank and crank planes.

Okay cool. I can do this. I don't have access to bumper foam like you do, but my son might. He works in the body shop of a BMW dealership.
Mar 31, 2013, 02:38 PM
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The pitch stability is improved over a Wing, because of no reflex and C/G is about 28% back.
The large control surfaces are for the parkflyers. They really help at slower speeds and in gusty winds. If you plan on building a fast plane, you may want to make them smaller or use duel rates.
When mounting the aileron servos, I adjust the servo arms to give me some aileron differential, so a rudder is not really need and because its a grass lander.

I work on corvette's at different body shops and they save me EPP foam.

If you look back a couple pages, here on the Boomer Thread, you'll see a Stryker-Lite, with forward strakes. I used a chunk of EPP to carve/sand out a longer nose for it.
Apr 01, 2013, 11:17 AM
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Thanks for all your help and input, Butch.
I've got my Stryker wing on order and will work on it as soon as it comes in.
I don't have access to EPP foam. At least not yet. My son could possibly get me some from a ganked up BMW bumper or something, but by that time, I'll have my boomer done.
I think in my case, I will extend the nose with balsa. As long as I don't make a habit of doing frequent lawn dart landings, the balsa should hold up fine. I'll either carve it out of a solid block, or else build it up. Haven't decided yet.

I do have one other question for you.
It would seem that using the carbon fiber tail booms to support the horizontal stabilizer directly to it rather than at the top of the fins, would make it structurally stronger. Is there a reason why you go with a high-mounted horizontal stabilizer?
If it's because it looks cool, you're right, it does. Or is it to get the elevator out of the same plane as the wing? If that's the reason, that's a really good reason.
I just thought I'd ask.

By the way, no. I'm not going for blazing speed. I want something that will handle the wind and actually be fun flying in a stiff breeze. It would be nice if I were able to keep it light enough so that the stall speed isn't so high, but maybe a high stall speed is part of this plane's ability to fly in the wind. The Stryker is advertised as a 30 oz airplane when it's done. If that's the case, no doubt I'll have a few ounces added to that once it's got the extra weight of being converted into a Boomer. So inherently, it's going to be fast.
Also, the motor from the AXN Floater Jet was extremely powerful. I used to be able to take off from its belly on pavement, no problem.
For this reason, it's tempting to come up with landing gear.

Another reason for the landing gear is that where I live, it's very barren and desertlike. There just aren't that many nice grassy areas to choose from. So I need to protect the prop from landings, otherwise I'll be buying a lot of props. This is nice because I can do ROG take offs and touch and goes too. That being the case, I can use channel 4 to steer the nose gear.
Last edited by builderdude; Apr 01, 2013 at 11:25 AM.
Apr 01, 2013, 01:12 PM
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Murman's Avatar
Hey Builder, check out the "Light Stryker " thread below for lots of good ideas for building it light...
Apr 01, 2013, 01:27 PM
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That's what I have in mind, Murman. I could not believe a 37 inch Stryker typically comes in at 30 oz, ready to fly. I was wondering to myself, what are those guys doing wrong? A 5 ounce wing should not be gaining 25 ounces, ready to fly.

I am going to try to build mine light too. I know coming in at under 20 ounces with a boomer will be a challenge, but I'm going to really try. Thanks.
Apr 01, 2013, 02:58 PM
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Builder, Pm me your address and I'll send you a chunk of EPP to carve on.

The horizontal stab is mounted about 2/3's up. If at the bottom, the tails are weak.
If at the top, the whole assembly is weak and its more of a pain to install the elevator pushrod. I used EPP fins, with a carbonfiber rod stiffener 2/3's up.

Most of my several Strykers-Lite's and Stryker-Boomer were 8-12ozs flying, with most having better than one to one thrust ratio, meaning, pure vertical.
Most were easily good to over 20mph winds.

The stryker stock fins and elevons are heavy, so replacing them with depron or balsa Boomer parts won't hardly add any weight at all.

To help protect the prop, I added a rear lower dorsel fin.

What size motor are you going to use?? Butch

My old Stryker-Cat Thread, before we called them Boomers, using a GWS brushed 350 motor!!
Apr 01, 2013, 07:31 PM
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Butch, PM sent. Let me know if you don't get it.
Thank you!

The motor for the AXN Floater Jet, off hand, I don't know. But it would launch a 16 ounce AXN right off the pavement and was very powerful. Let me see if I can find anything online on that motor...

Yep...found it. Here it is:

Floater-Jet Replacement Motor (AXN-2208-2150)

RPM/V: 2150kv
Max Watts: 180w
Max Amps: 20A
Max Volts: 11.1 (3s)
Turns: 16t
Resistance: 0.085Rm
Magnet type: N45SH
Idle Current: 1.52A
Shaft: 3mm
Weight: 44.0g
Suggested Prop: 5x5 / 6x4

I ran a 7x4 3-bladed pusher prop on mine. I think next time, now that I have the specs, I'd better put a wattmeter on it.
In fact, maybe I'd better mock it up tonight and see what it's drawing with that prop.
Apr 01, 2013, 07:46 PM
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You really don't want to run a 3 blade prop on a pusher, unless it will completely clear the ground on landing. On a 2 blade prop, when the lower blade starts to hit the ground, it moves up, which keeps it from breaking upon landing.

That motor should push it along quite well.
On one of my faster Boomers, I ran a 3200Kv inrunner and it flew a lot different than the WildWing parkflyer type. I had to give it much more room to land.
Apr 01, 2013, 08:28 PM
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Okay, here are the results of the wattmeter test. On a fully charged 2200 mah 11.1 V Lipo, using the 7x4 3-bladed prop, it drew 27 Amps and 280 Watts. So I've been drastically overloading this little motor. I will need to find a different prop for it. I'm lucky this hasn't burned up the motor or the ESC. It is only a 22 Amp ESC. So I almost screwed the pooch.

Okay, I don't think I have a 6x4 prop. I'll look, but I'm going to have to order one. Darn, I just put in my order for the Styker wings already. Oh well...

Oh, by the way, with a 6x4 prop, I calculated that theoretical top speed for this motor at 11.1 V will be an astonishing 90.4 mph. Now, I knew the AXN was fast, but I didn't think it had THAT much potential.

I think this will be a great choice of motor for my "Strike-Boomer".
I'm trying to decide what color I'll make it. Thinking about a sinister black color with USAF stars and bars decals....maybe.
Apr 01, 2013, 08:54 PM
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(Message cancelled. Continued in next post)
Last edited by builderdude; Apr 02, 2013 at 12:24 AM.
Apr 01, 2013, 09:22 PM
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A totally different 11.1V Lipo. 130 Watts, 14.5 Amps, on a 5x5 prop. No problem.
Apparently, not all 11.1V Lipos are created equal. The 5x5 prop will work fine, provided I'm careful what battery I use. But I don't really want to use a 5x5 prop. I don't want too much top speed.

Anyway, I think I know what's going on. Someone check me on this.

The battery that really makes this motor run hard is rated at 30C continuous.
The battery that actually works with this motor is only rated at 13C continuous.
That's a big difference. But I didn't know the C-rating could make that much of a difference in power consumption.
So I can't just throw batteries around from plane to plane with different C-ratings without checking things with a wattmeter apparently.

Anyway, it just so happens that I had a folding 8x4 prop that I was experimenting on making into a folding pusher prop.
So if I use that prop with the smaller of the 11.1V Lipos I tried tonight, the 13C (20C burst) battery, everything works pretty good.
The folding prop uses 20 Amps and measured at 180 Watts. This is a 180 Watt motor and a 22 Amp ESC.
So it'll work. It's neat because I can have a boomer with a folding prop, so all I need is a skid instead of landing gear. I kind of like that better.

Enough about me and my motor experiments.
Obviously, I'm more than ready to get my wings in the mail and start building.
Last edited by builderdude; Apr 02, 2013 at 12:26 AM.
Apr 02, 2013, 04:52 PM
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I took this up in the appropriate section of the forum and got a lot of help there.
I don't want to use the 13C battery because it can only support 17.2 Amps of draw, and if I'm pulling 20 Amps, the battery won't last long.
I had another battery and I tested that. It's a 20C battery and with the 8x4 prop it was drawing just a little too much current, 21.1 Amps. It's a 180 Watt motor.

So I ordered the two smallest folding props that APC makes, a 7x4 and a 6x3. One of those should lower the load on the motor enough. It'll probably end up being the 6x3, which would still result in a 68 mph theoretical top speed...more than enough.
Until those props come in, or until the wings come in, my work on this new boomer has to wait.


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