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Old Oct 24, 2002, 07:02 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
Hobby Lobby Three Dee



Okay, shes all done, rf installed, motor mounted, controls all set up, and computer programed.

BUT , the CG is really bad ! Its a good 10 MM to far to the back. The instructions call for 65-70 MM i have atleast 80 unless i add 3/4 oz weight to the nose.

Sounds like way too much weight to add. I have moved the batt as far forward as i can, the reciever is right behind that. I have the speed control right behind the motor and still its too far rearward as per the instructions.

So my question is, is 10 MM or 5/16 too much ? Or will i never notice this when i take it to the fied on friday ?

I dont want the first flight to be a disaster.

Thanks Guys !
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Last edited by Koenig; Oct 24, 2002 at 08:02 PM.
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Old Oct 24, 2002, 09:25 PM
Flying slowly along..
Northern Ca.
Joined Dec 2000
1,336 Posts
Hmmm I was looking at this little plane, and thinking about buying one. I really can't answer your cg question, but please let me know how well the plane flies. Thanks--Rob
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Old Oct 24, 2002, 10:24 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
no problem Rob, Im gonna give it a go in the morning ad we will see how bad the CG is. Ill post a follow up here on the flight. Keep in mind im running a s400 not a brushless system..

Cheers !
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Old Oct 25, 2002, 08:47 AM
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Boise, ID 83703
Joined May 2001
266 Posts
Batteries

What battery pack are you using? I'm using 8-1100AEL's and my CG is mighty close. Can't imagine anything you did wrong to produce it. Probably a change in battery pack will do it.

You are going to need some air to the motor though. I cut a red plastic spoon about in half with a dremel. Makes a great scoop for air. I put one on each side. Looks cool too.
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Old Oct 25, 2002, 09:50 AM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
New Bern, NC
Joined Mar 2001
3,012 Posts
Tail heavy !

My Three Dee 400 from Hobby Lobby was tail heavy too, even with the 8 cell 1100AELs. I lightened the tail as much as I could, but still had to add 1/2 ounce of lead to the nose. Cooling holes are a must. I made the spoon scoops too like Tim did. They worked out well. Remember to put a few outlet holes in the rear of the fuselage. Cool air in, with no way out, is useless. I drilled 3, 1/2" holes in the bottom of the fuse back by the tail to let the hot air out. It isn't a screamer with the speed 400, but it flies nice. It goes exactly where you point it. Rolls like crazy too. I had to tame my ailerons down some. It was to quick for me. It is built very nicely, and flies very well if you have aileron experiance. This model is not for beginners. Tom
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Old Oct 25, 2002, 11:36 AM
Registered User
KVNY
Joined Oct 2002
338 Posts
i have 2 packs, both using the HR-AAAU 720mAh NmHi Batt. they are 7 and 8 cell 4 on 4 and 3 on 4 stacked. Seems like because of the light weight of these pack i have to pay and ad 3/4 oz to the nose.

Maybe I can hunt down some cells and build a new pack with some more weight to help keep the CG right and add flight time too.

I think the cooling holes are a great idea. There is nothing to help cool the motor.

I think after i get back from the field i will have to do those mods..

Thanks !
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Old Oct 25, 2002, 01:50 PM
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Boise, ID 83703
Joined May 2001
266 Posts
Tail Difference

I did not follow the instructions on the tail skid. I mounted a small piece of plywood to the rear and put on a really light wheel used on the tail of the Firebird XL. That may have lightened me up a bit in the tail. On a long fulcrum, that may have made quite a difference.
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Old Oct 25, 2002, 03:29 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
Yes the tail skid does ad some weight. I just may remove this and to a tail wheel mod to it.

The CG problem wasnt much of a problem, It flew perfectly fine with the CG a bit back then recomended in the instructions. I had added the 3/4oz to the front of the plane and it made it very nose heavy. Once I removed the added weight, it corected and was still stable.

Okay, I just got back from the field ! Had a bunch of fun flying, but I am trully disappointed in the performance of the S400.

It took full throttle to get it going, climb and get some alt. Once altitude was achieved I could finally cut back on the power and fly. Inverted was okay, but doing any rolls or loops was without a great loss in speed and alt. Then climbing back up as a chore !

I did find the 10x7 prop to work better for the s400 on this plane rather than the 9x6 I started out with. Yes you did loose some flight time, but atleast it helped in the climb rate.

Now Im wondering has anyone used a brushless setup in this plane and had good results. Because with the s400 a ThreeDee it is not. I would have to call it a "Slow Flyer"

Im going to charge up the batt and put the astroflight whattmeter on it and post the results. Maybe someone can post their results with a brushless set up ?

I will have to go to a brushless motor unless i can tune this thing up a bit, its just too slow.

Cheers !


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Last edited by Koenig; Oct 25, 2002 at 03:56 PM.
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Old Oct 25, 2002, 03:37 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
New Bern, NC
Joined Mar 2001
3,012 Posts
Slow !

I felt the same way with mine. It took off OK with the 10x7 APC Slow Prop, but the climb rate was weak. It is a rather heavy model, and truly needs more power. Maybe a long can 400 or a 480 that will fit on than gear box would do. I sold my plane at the NEAT Fair. It flew nice, but it should be called something other than Three Dee 400, because there is no way it will do any 3D stuff with the stock setup. It's a very nice flying airplane, but needs more power in my opinion. Tom.
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Last edited by Tom Smith; Oct 25, 2002 at 06:49 PM.
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Old Oct 25, 2002, 03:42 PM
Registered User
Boise, ID 83703
Joined May 2001
266 Posts
Motor Hop Up

Mine seems to have more power than yours, but then I'm not doing much for aerobatics yet either.

I think a 480 Race BB would be awesome, but by the time you spend about $55 on the motor & GB, I would think a brushless would be in order. That would also add a little weight to the nose.

I did buy a different GB for mine. I put a ball bearing one in place of the one they sent with 3D. I disagree with the 7mm length of the motor shaft too. I have to cut to about 6mm to keep the end of the gear from binding a bit on the GB. I always test for motor speed before I add a little adhesive to keep the motor from coming out of the GB.
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Old Oct 25, 2002, 03:43 PM
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USA, CA, Martinez
Joined Feb 2001
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Are u still using the 720s? Cause that may be a problem. I think those cells are good for 6 Amps or so max.
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Old Oct 25, 2002, 03:59 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
Re: Slow !

Quote:
Originally posted by Tom Smith
I felt the same way with mine. It took off OK with the 10x7 APC Slow Prop, but the climb rate was weak. It is a rather heavy model, and truly needs more power. Maybe a long can 400 or a 480 that will fit on than gear box would do. I sold my plane at the NEAT Fair. It flew nice, but it should be called something other than Three Dee 400, because there is no way it will do any 3D stuff with the stock setup. It's a very nice flying airplane, but needs more power in my opinion. Tom.
That about sums it up ! Im not selling it though. I know I can make it fly like it should !

"Keep the rubber side down when landing !"
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Old Oct 25, 2002, 05:14 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
Quote:
Originally posted by mumblety-peg
Are u still using the 720s? Cause that may be a problem. I think those cells are good for 6 Amps or so max.
Yes.
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Old Oct 25, 2002, 05:59 PM
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budzilla's Avatar
cornwall,uk
Joined Nov 2001
48 Posts
hi all
iv'e flown my three dee a few times b4 the crash
i also had cg problems & had to add weight.i think its the cells i'm using.the stupid hobby shop sent me ni-hm's when i asked 4 ni-cd's.iv'e got a 4 on 4 cell config.flies ok on 8 of these cells but iv'e not had enough flights to judge performance due to bad weather hopefully this weekend

cya
chris
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Old Oct 25, 2002, 06:41 PM
Registered User
KVNY
Joined Oct 2002
338 Posts
With my astroflight "whatt meter" here are the results.

Both props are APC electric. Grupner S400 7.2V

With 9X6 prop :

5.1 Amps
45 Watts
8.5 Volts
.002 Ah Sec

With 10X7 prop :

6.5 Amps
53 Watts
8.1 Volts
.003 Ah Sec

this is using an 8 cell 720 mah AAA pack.
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Last edited by Koenig; Oct 25, 2002 at 07:16 PM.
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