HK Specter 1800 - Page 8 - RC Groups
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Aug 22, 2012, 03:35 AM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
One last tinker with the engine before turning in...

With a 1300 mAh 3S battery, turning the 10x6 prop, I see 201 watts peak and 17.7 A peak. It looks like I can step down the ESC to a 20A and be fine. I can feel lots of wind blowing past as I hold on to the fuse and my guess is that it'll fly nicely with this combo. Probably not vertical but fast enough to leave plenty of battery time for soaring.

Peter, I tried to attach the props I bought to the hub you suggested and they do not fit, perhaps I mixed up pieces when ordering but what I have now is just a bit too large for the fuse. It looks ok and does mount but that other one would look a touch better but the forks on the blade holder are too narrow for the blades I have.

This is how I have it mounted up now.
Last edited by SoarWest; Aug 22, 2012 at 03:48 AM.
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Aug 22, 2012, 11:07 AM
Registered User
Hey, SW.

If you get a 10X6 swinging anything over 9000 RPM you should get near vertical performance. I chose my motor before I made my final decision on which glider to get. I figured that I could under prop it on a lighter ship but have enough margin that I can swing an 11X6 or even, possibly, a 12X5 if I needed more thrust. I'll probably pick up a bigger prop sometime to see if I get ridiculous vertical performance, just for kicks and curiosity, but a 10X6 at anything over 200 watts should be great.

I might have gotten confused when I was mixing and matching spinners and adapters but I was able to make any combo work aside from using the wide blades with the narrow yoke. (I thought i had mentioned that but I'll go back and cleanup the post if I was wrong. I hope i didn't mislead you on that.) There was one collet that I had to machine down just a tiny bit by chucking it in my drill and running it VERY gently on a fine sanding block. Going back the other way the adapter does pull into the back plate a bit but it still gets tight. My final fit looks identical to yours. I can't notice it at more than a couple feet. It looks like your wires will work just fine. Is there room to make a shield out of plywood or a chunck of a plastic bottle? Just for insurance.

I ran into the same issue with tightness on a rudervator and an aileron. I was able to loosen them up by just running the iron over them while holding them at full deflection. You won't need a whole lot of throw on the ruddervators, 6-8mm is plenty, so I would try that before going through the hassle of replacing the whole hinge.

Oh yeah. I also ended up using the shorter yoke that came with the 28mm spinner.
Aug 22, 2012, 11:33 AM
Earthbound Skyhound
StarHopper44's Avatar
Originally Posted by SoarWest
Star, I can't turn the motor 90 degrees as you suggest or the holes for the engine mount don't line up. I hadn't noticed it before but the X mount for the motor holes aren't evenly spaced. One set of screws is father out than the other, that is the case for this mount and motor too. .
Okeydoke - I see. It's one of those mounts you can use 2 different motor spacings using only 2 screws. Well, I'll take one more shot then. If you can determine what kind of adhesive that's holding the mount in , there's surely a solvent even if it's hot glue (hot water) or CA (de-bonder) or whatever...and rotate the whole motor mount & you're home free for re-routing the wires. Of course I'm just speculating on possibilities - you might have determined what youv'e done will work perfectly fine. Whatevers....good luck with it, & hope she does well by ya! I really wish I didn't have other priorities standing in my way so's could get me one on the way! (Somebody start singin' "Some Day"....)
Aug 22, 2012, 02:06 PM
Registered User
So many planes and so few thumbs. Right, StarHopper? On any given day my wish list is always at least 4 gliders, a stunter, and a warbird.

I think I'm going to start by getting another good, strong, 28mm motor and some metal gear servos. Then, when I finally decide on a glider, I could go with a smallish, 4 cell, warmliner but still have the ability to swing a 11 or 12 inch prop on 3cells if I decide to go with a 2.5meter floater. I would be perfectly happy to give up the screaming vertical climbs to keep the motor under 100grams in an Avia, for instance. There are a couple motors in that class that should provide more than 1,500g of thrust and the Avia is listed as under 1,400. If one can keep it closer to the 1100g minimum without needing ballast it should be possible to match the climb performance of the Specter with well under the 120g-175g, 38mm, motors most people are using.
Aug 22, 2012, 02:13 PM
Registered User

Re: How much current?

I'm still learning about power systems in general but, based a small sample size; I think that any combination of motor, ESC, and battery that can deliver a burst of 20 amps or more will give excellent performance for a Specter. I knew the 40amp ESC I used was overkill but, not having actually tested stuff with a watt meter, I didn't want to take any chances. Plus it has a 4amp switching BEC. Now that I'm certain about the motor's and radio's needs; I'll be ordering a 30amp to go in the Specter and I'll use the 40amp in the next project.
Aug 22, 2012, 04:19 PM
Earthbound Skyhound
StarHopper44's Avatar
Originally Posted by peterlngh
So many planes and so few thumbs. Right, StarHopper? ...
And the moneys. And the time. And the moneys. Da weather. & moneys.
And...and...and.... Oh, did I mention the expense?


On any given day my wish list is always at least 4 gliders, a stunter, and a warbird.

I think I'm going to start by getting another good, strong, 28mm motor and some metal gear servos. Then, ...
I've got a couple gliders I wanta snag, & my next big buy I've about decided is, I'm gonna stock up on some servos, a few motors, linkage hardware...already started w/ a few ESCs, Rx's, & props.....and start building myself a few scratchies. Lord it's gotta be cheaper'n the planes at the rate I'm accumulating 'em! And there's gotta be a bit more satisfaction flying something you built with your own hands rather'n just pullin' 'em out of a box & throwing together.
Aug 22, 2012, 04:54 PM
Registered User
Yeah. The money is just a given. Still, I can get a plane every few months if I (mostly) deprive myself of beer!

I used to enjoy building as much as flying but my aged neck, eyes, and intolerance for CA fumes (Even "odorless" CA.) makes it pretty easy to stick with ARFs. I can still get some enjoyment out of modding the color schemes and I'm looking to hook up a deal on a "ready to cover" when I decide to go bigger and floatier. It would be a chore to beat the price on a lot of ARFs but one can spread the cost over time rather than buying all the accessories, and generally replacing some or all of them, in the box. Of course, they just about give away the airframe when one goes with a foamy PNF.

I'm doing the same thing with electronics. A couple servos here, a ESC there, and I still need that big roll of Velcro. I'll just try and stick with components that will work in a small fast ship or a big slow one. I figure I can use my current gliders as test mules so I know I have dependable electronics before I decide to launch a bigger, more expensive, plane. I already have a couple 12g metal geared servos I'm dying to try out in the air.
Aug 22, 2012, 08:50 PM
Registered User

May I know what motor and KV you are using?

Aug 23, 2012, 12:19 AM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
Hello Yeap,

The motor I have installed is this one from HK:
Turnigy Aerodrive SK3 - 2830-1130kv Brushless Outrunner Motor

There are others such as the one Peter is using but it's been out of stock for so long that I picked this one. There's another similiar to the one I have but larger and with much more power, the SK3-2836. I think the 2830 will be enough. I am building this plane out of HK stuff for fun to see how it'll work out. Trying to keep the total price under $150.

I have to wait for a few more pieces now and hope to have her flying in a week or two. It's been raining here every day anyway so no flying time is lost yet ;-)
Last edited by SoarWest; Aug 23, 2012 at 01:23 AM.
Aug 23, 2012, 01:17 AM
Registered User
Hi, Yeap.

If I were to do it over again I would go with something more like the motor SoarWest picked up. The KDA22-20 is a bit overkill and, although it's fun being able to climb straight up, I would just as soon save a little weight.

Aug 23, 2012, 02:00 AM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
I decided to do a little more testing with the motor by changing the prop. I have numbers now for 2 prop combos.

Turnigy Aerodrive SK3-2830-1130Kv (187w) 58g, 2-3s, 20A max (rating)
tested 3S w/Turnigy AE 25A ESC; 10x6 folding prop; 17.7A peak; 201w peak
tested 3S w/Turnigy AE 25A ESC; 10x8 folding prop; 22.0A peak; 243w peak

For quick 10-20 second climbs reaching 243w peak which is well over the 187w rating is probably ok but time will tell.
Aug 23, 2012, 02:15 AM
Registered User
Hi SoarWest and Peter

Yes I think a motor like SoarWest would be ideal. It is after all a glider : ).

Thank you both for your expeditious replies.

Aug 23, 2012, 12:03 PM
Registered User
I would start with the 10X6", SW. I think you're close enough to my numbers for a near vertical climb and the extra pitch with the 10X8" would only help in level flight. It might even be enough to bog down the motor and hurt the climb performance.
Aug 23, 2012, 12:17 PM
Registered User
I'm always happy to help, or try to help, Veap.

There are many motors that would work great in the Specter and mine is just towards the top of the weight range. I'm still learning about modern motors so I figured I would go with a powerful one. Plus, I hadn't really decided on a glider when I picked up the motor and I wanted something that would handle an 11" prop if I wanted to go with a slightly bigger plane.

The Specter has a wide speed range and I would think that most any 28mm motor between 50 and 100grams should work great. Mine even flies well with a 9X5" prop and, if you went with a kv of 1200-1400 it might even work better than my setup.

Aug 23, 2012, 09:26 PM
Registered User
Thanks Guys,

I have being keen on the Spectre for a while now. Your testimonies have certainly tip the scales for me.


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