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Jun 24, 2006, 03:11 AM
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biber's Avatar
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Tailless F5D Limited? Multibumm!

Multibumm is our tailless aproach to the german F5D Limited class.
I'm going to use this place to add new pics of it
and describe the ongoing developement.

Some information on the model is already available in my blog,
but its kind of a bit hidden there,
so I thought I'd start a thread here to continue this.

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Jun 24, 2006, 03:42 AM
Hallo Biber,

Nice to see you guys here!
Very nice blog you have, many pictures of the things you explained to the belgian team in Uelsen :')
I am very happy to have met you there and also to see your wing fly and eating up some turn left,... and of course the nice sound of your home made single blade prop.
I didn't even know rc-groups blogs even existed so it is for sure a good idea to start a regular thread on your magic multibumm wing design.
I would love to see F5D limited grow in popularity over the world.
Jun 24, 2006, 04:04 AM
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biber's Avatar
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Thanks Novy, for the kind reply!

As there seem to be planned a european open campionship in F5D Limited,
next year in germany, that may push the popularity of the class somewhat.

And I appretiate your efforts to eventually install that class in belgium, too.

Jun 24, 2006, 09:45 PM
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jetdryvr's Avatar
Very cool Biber, When you get one back up and running I would be curious what kind of radar gun numbers you are getting. They are very nice planes. Make one for me
Jun 25, 2006, 04:01 AM
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Neil Stainton's Avatar
Excellent design, well done. I love the spinner! So often people use blunt nosed spinners in a pusher config and don't realize they would be better off without one!

I'm sorry it broke on landing. Is the landing speed very high? Also at high angles of attack the tips will be the lowest part of the plane, making a cartwheel difficult to avoid.


Jun 25, 2006, 04:29 AM
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biber's Avatar
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Thanks for the nice words!

We still have one running and building a new one can be done in about 4 days of work.
I'd expect the radar gun to give readings of about 120mph on course,
maybe 150mph and more out of a dive.
We don't sell models yet, but If you really need one (might be the case ),
You could get hot wire cut cores from us
(depending on where you live, that might be an option or not, because of shipping costs ).
Or you make one yourself, as I will make a drawing with all the needed numbers
and post it soon in this place.
A molded version is maybe to come later this year,
then we might sell some wings to get off the costs for making the molds.

The next spinner cones will be half the weight (Delrin is about half the density as aluminum)
and may become even a little longer and less blunt at the end.
Cartwheeling is not a big issue with that wing,
only if you make a low pass with hooking the weed with one wing, like I did...
So it was no landing intended.
Landing speed is about the level of similar models.
As said, usually there is no cartwheeling during landings and once it did,
there was merely on of the taped on winglets gone off.
Nice thing is, that we don't seem to break any props, due to the pusher setup.

Jun 25, 2006, 08:16 AM
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biber's Avatar
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That's what the Mubu's wing and winglet planform looks like.
It has 3° anhedral each side.
The control surfaces should be somewhere in the range of 22%-30% chord.
The drawn winglets are rather to big, it may be neccessary to decrease their size until the wing stops snaking and tail wiggling in straight flight.
The only important requirement to the aifoil is a moment coefficient close to zero.
Try a MH44 with thickness and camber rescaled to about 8%-8.5% and 0.7%-1.1%.
(I'd go with 8.5% and 1%)
D60 servos will fit quite well into the wing.

Last edited by biber; Jun 25, 2006 at 08:24 AM.
Jun 25, 2006, 09:20 PM
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jetdryvr's Avatar
Biber, I would have some soccer spectators bring me back one of your planes from Germany but for some reason they have already come home
Jun 26, 2006, 02:45 AM
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biber's Avatar
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What is soccer?

Jun 26, 2006, 05:55 AM
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MarkChinery's Avatar
Nice model..

has this got variable C of G?
Jun 26, 2006, 07:02 AM
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biber's Avatar
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No it doesn't, Paul and I don't think that the effort would pay off for this kind of wing.
But Paul had such devices installed in some of his wings over the last few years.
It's definately worth to be considered for high performance wings.

Jun 26, 2006, 08:29 AM
I think he means "football"
Jun 26, 2006, 08:59 AM
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biber's Avatar
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Ahhhh, eez eet foootebol!

Jun 26, 2006, 09:46 AM
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Uitgeslapen's Avatar
Hello Biber,

Daan here (the noob from the Belgian team). Nice to see the Mubu again. I would be very intrested in a mubu core. According to Aachen and Leuven are only seperated by 140km of freeway. Another great source has told me that you guys have a nice slope overthere. Maybe we can arrange a Multibumm crash course. I would be nice to get one of your ships flying overhere.

Best Regards,


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