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Old Sep 25, 2003, 10:40 PM
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davis, ca.
Joined Sep 2002
493 Posts
A new twin on the block.....

here is a new twin that i hope will be the fastest of the bunch. i just finished the build and will maiden tomorrow. the wingspan is only 36". i made up for some of the needed wing area by increasing the chord a little. its auw is 28 ounces. i can shave 2 ounces when i get my extra li-po pack. but for now the 9-cell ni-mh will have to do. the wing is also slim as you can see in the photo. please excuse the hideous covering job. i have a few colors and no patience. the esc is a gws 30 amp with 2 gws 400 motors. the servos are the gws park units. i used them in another wing and was very pleased with the performance especially at $13 each. these motors sound awesome when spun up. if it flies well, ill hire a couple of broads for the photo shoot
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Old Sep 25, 2003, 10:40 PM
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davis, ca.
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assembly
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Old Sep 25, 2003, 10:41 PM
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davis, ca.
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fin'
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Old Sep 25, 2003, 10:42 PM
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davis, ca.
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slim
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Old Sep 25, 2003, 11:27 PM
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Westborough, MA
Joined Apr 2003
280 Posts
Bring it on Mike!!! This one really looks like fun!!

Be careful with your esc though - you seem to be pretty close to toasting it. I just ran the numbers through PCALC ( http://brantuas.com/ezcalc/dma.asp ) and it says you're going to be pulling exactly 30 amps at WOT using those Gunther props and 9 high-output cells. ...Although I could be a little off here as I used the stats for a Graupner 6V SP400 because I couldn't find the ones for the GWS motor.

Anyway, hope the maiden flight goes well. I'm sure this little rocket is going to be a handful to fly. Can't wait to get my grubby paws on one!!!

Later,
Joel
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Old Sep 25, 2003, 11:49 PM
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davis, ca.
Joined Sep 2002
493 Posts
joel!!!

thanks for replying! if all goes well tomorrow, ill fly the heck out of it this weekend and get some video. i was hoping to get my website up this week but, a new(1996 fzr 600) motorcycle has taken up my time this week. maybe this weekend i can find some time to do it. anyway, i may get to box you one up this weekend. i benched a motor with the gunther props at 10.8 volts(3 series e-tec li-po voltage when sagging) and it pulled 15 amps. my 9-cell ni-mh is less than that when it sags so i have an amp or two margin. im not too concerned because the gws esc'seem to be under rated from my experience. and if i burn it up, oh well, ill just get somthing bigger. i want to use and abuse this setup because these are the parts i want to recommend with this setup. i post some more tomorrow.
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Old Sep 26, 2003, 02:19 PM
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davis, ca.
Joined Sep 2002
493 Posts
as usual, i get a little nervous when i toss a plane for the first time. i put the c.g. where i thought it should be. gave it about 3/8" reflex. looked it over, and threw it. it was almost perfect! im on a good streak! the c.g. seemed spot on. a little trim adjustment and i was off. the flight characteristics are great. very smooth and agile. yeah, yeah, you want to know if it was fast. well, it wasnt as fast as i thought it would be. the motors dont sound like usual scream i hear on my terni(3sx2p e-tec). im going to check voltage to the motors to make sure im not loosing too much through the esc since im running at its limit. im also going to get the extra e-tec pack today. that should add another volt or so to the motors and shave a little over 2 ounces over my ni-mh. more tomorrow........
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Old Sep 26, 2003, 02:43 PM
Rehab is for quitters
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West Middlesex, PA, US
Joined Jun 2001
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Geez Corn and I was gonna pose with your twin in some speedos!!!!


Dave...
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Old Sep 26, 2003, 02:45 PM
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Westborough, MA
Joined Apr 2003
280 Posts
Mike,

Maybe the issue is one of amps…. Two sp400s spinning Gunthers are going to need a pack capable of delivering around 30 amps continuously to really get screaming, like a 8-9 cell pack of CP 1700SCRs (which is what ships with the Zagi XT). There aren't too many nimh cells under 2000mah capable of 30 amps, which ones are you using? Anyway, you'll probably get much better results with the li-pos.

later,
Joel
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Old Oct 13, 2003, 02:15 PM
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Westborough, MA
Joined Apr 2003
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Mike,

Just wondering if you’d still like me to beta your twin. I bought a couple of packs of those new CBP2100 high-output A-cells that are just fine at 30+ amp draws. They’d probably add a little weight, but would certainly get those 400s screaming. I've been using them on a 48" epp wing with a Mag-Mayhem and a 7x5 prop - flat out speed is probably only slightly better than your Terni, vertical performance is hilariously good however. I also have an extra 50 amp esc looking for a home so I’d really just need the cores and motors.

Then again, maybe you’ve moved onto other projects, in which case I might be interested in buying your twin prototype if you’d like to let it go. I think a flat pack of those 2100s would give it a nice kick in the tail.

Let me know. Later,

Joel
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Old Oct 13, 2003, 07:01 PM
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davis, ca.
Joined Sep 2002
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hi joel,

im sorry buddy, ive been so busy lately. i think i may be abandoning the twin, not sure yet. ive got two kits available now. the 32' TERNI, which is now available in epp with a carbon spar. just add $9. and the MINI 400, which is only available in eps. its a 24" wingspan flying wing. the leading edge angle is less than 90 degrees. its about 85. it looks almost like an arrow head! only 7/8 thick. its pretty quick. it flies amazingly well for such small wing area. its made for someone who wants something thats alot of fun, inexpensive, and easy to take anywhere. you can see it on my webite which is finally up. it still needs alot of work. www.corndoghobbies.com
i am not ready to part with the twin yet. i am still interested in you beta testing it. design wise, its ready. ive got the c.g., reflex, and all that stuff dialed. im all out of foam. ive placed an order. ill have more in about a week. ill be in touch. sorry again for not cotacting you.
-mike
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Old Oct 14, 2003, 04:50 PM
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Westborough, MA
Joined Apr 2003
280 Posts
No worries Mike – I’m fine with putting off the beta for a while, if not indefinitely. We’ve only got another month or so of flying weather up here in New England anyway.

Your new site looks great!!! The 24” speed wing looks like fun, but I think I’ll stick with the Terni – it’s enough of a handful as it is. I think the EPP version of the Terni is another great idea – even though EPP tends to get a little “flappy” at high speeds (without a spar), I much prefer wings that bounce to those that shatter (especially given my flying style).

Anyway, good hearing from you. Take care!!
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Old Oct 14, 2003, 06:13 PM
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USA, HI, Honolulu
Joined Jan 2003
2,886 Posts
Best bet for lite weight battery pack would be the KAN 1050's. With 8 cells it should be enough. If you want to stick with li-poly you would need at least 3S2P TP 2100 but that would be 9 oz. The 3S2P should be fine with bursts at full throttle and continuous at 3/4 throttle.
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Old Oct 14, 2003, 06:46 PM
FLYER spelled I-squared-R
fliir's Avatar
Grand Rapids, Michigan
Joined Sep 2001
1,622 Posts
The HR1950FAUP is about the smallest 30A continuous NiMH that I have used.

I run two 480s off of 8of those, for a peak of almost 40A.
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