Tailless F5D Limited? Multibumm! - Page 2 - RC Groups
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Jun 26, 2006, 11:43 AM
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to be exact the slopes are around aubel around 35 km from Aachen, lots of Dutch and Geman pilots are flying there...
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Jun 26, 2006, 02:39 PM
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Florrain's Avatar
Hi Biber,

I'm interrested in cores too ... I'm not going to let Daan fly laps around me...

"Mubu rules!!!" , it's so much faster then a Turnleft in the straights and I was very impressed by the turns it could carve.

Apart from trying to keep the flow laminar on most of the fuse length and trying to avoid braking props, is there any reason why you decided on a pusher prop?
The reason I ask is that launching power off means you loose 1 or more seconds compared to a launch with power on like the Vampire does.

Do you think the prop wash could affect the special pitch control system?

@+
Francois
Jun 26, 2006, 03:12 PM
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Uitgeslapen's Avatar
About the launching...wouldn't it be possible to use some kind of launch-system or is it not allowed?

http://images.amazon.com/images/P/B0...CMZZZZZZZ_.jpg
Jun 26, 2006, 04:03 PM
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WimH's Avatar
Quote:
Originally Posted by Uitgeslapen
About the launching...wouldn't it be possible to use some kind of launch-system or is it not allowed?
Not allowed. I see no problem in lauching power on with this one though...
Jun 26, 2006, 05:02 PM
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Florrain's Avatar
Quote:
I see no problem in lauching power on with this one though...
I think it would be ok too but for some reason they launched power off and it seemed a bit tricky that way.

The single blade prop seemed quite good in top speed too but the acceleration was a bit poor in the first lap. It might be a feature of single blades because we experience the same slowish acceleration with our single blade FAI setups.
Jun 26, 2006, 05:51 PM
Needs brain lubrication
biber's Avatar
The reason for power off launching is the psychological component...
We do know people who don't mind to throw push proped models with power on.
And It seems to work quite well.
But I'm a coward.

The main reason for the pusher setup was the CG.
If we had chosen a pull prop setup, the heavy motor would have required a battery location way back behind the wing.
That would make a big fuselage neccessary, with lots of unused room under the wing,
excess weight, excess wetted surface and more inertia especially around the pitch axis.
The pusher setup avoids these penalties.
It offers the smallest possible fuselage, minimum wetted surface,
with the chance to keep at least parts of the boundary layer laminar.

For a molded hot F5D version, a pull prop setup could be considered as a valid option, though.
The motor would be less heavy and the battery more heavy, wich could change the issue.
I'd guess the prop stream could even improve the effectivity of the elevator, not that it would be neccessary.

Edit: For the slope locations, in Belgium I knew only the site at the military cemetary in Henri Chapelle.
And in Germany/Aachen the best slope I've ever flown, at the open cast coal mines, doesn't exist any more.
You know, they are digging for coal right there, what a bummer...

And the cores, well, I guess we have to make another some...

biber
Last edited by biber; Jun 26, 2006 at 06:04 PM.
Jun 28, 2006, 08:17 AM
Needs brain lubrication
biber's Avatar
Quote:
Originally Posted by Uitgeslapen
Maybe we can arrange a Multibumm crash course.
Daan, I can very well give you a Mubu crash course,
since I'm one of the very few guys in the universe, that have actually ever crashed one.

biber

P.S.:
We will cut some cores next week,
and will try to make some more photos during the building process,
so that it can be seen more detailed how we did the buildung.
But we don't claim our way to build it to be the only working one.
We are still trying to find better ways (less complicated) to make them.
Jun 28, 2006, 11:47 AM
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Uitgeslapen's Avatar


Sounds great, looking forward to the build...
Jul 08, 2006, 08:02 AM
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biber's Avatar
No more cores cut yet, but we made some spinner cones from plastic.
They save about 7 gramms compared to the aluminium ones.
And they require less time on the lathe.

And we continue building some spare fuselages,
so anyone who wants to have cores, can get a fuse pod too.

biber
Feb 19, 2007, 03:21 AM
Registered User
It is old thread, but: how did you RDS setup work? What was the diameter of the shaft? Did you have any support on the hingeline? The coupler was not attached to the servo using screw - it was just pushed over the output shaft of the servo?

regards,
Arne
Feb 19, 2007, 05:43 AM
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biber's Avatar
Hi Arne,

nice to see this thread revived.
The shaft is 1.5 mm piano wire.
There is no support at the hingeline and no need to have one either.
It is glued with Z-poxy (5min) onto the servo's output shaft.
That gives quite a tight fit.
You can pull it off and on again, but it will stick right there during flight.
Only in crashes we had some of them going loose.

biber
Feb 19, 2007, 06:06 AM
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Uitgeslapen's Avatar
How is it going with the Multibumm??
Feb 19, 2007, 07:44 AM
Needs brain lubrication
biber's Avatar
Oh, I will have to repair one of the existing Mubus to go with it into this years competitions.
That is because right now I have little time to do more than just the neccessary.
Our plans have gone through some twisting and changing during the last three months.
But I'm sure we will meet in Leverkusen, right?

biber
Feb 19, 2007, 02:01 PM
I plan to take over world
sayno2glo's Avatar
Are you developing a F5D version that's all composite?
Feb 19, 2007, 07:35 PM
Needs brain lubrication
biber's Avatar
We are indeed planing a molded Mubu II which should be suited for F5D.
But at the time being we have lots of other work to do,
so nobody even knows when a first proto might get airborn.

biber


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