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Jul 27, 2007, 03:04 AM
Speed King
MarkChinery's Avatar
That looks good biber...

What sort of price will you be looking for for one model(wing)?
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Jul 27, 2007, 03:49 AM
Needs brain lubrication
biber's Avatar
Thread OP
That will depend on how a good working layup will look like.
To make sure it won't flutter at F5D speeds,
there may be other measures neccessary than for a common tailed model with unswept wings.
For the sake of buildability we would aim for a wing skin without sandwich materials,
to avoid the neccessity of a vakuum, but don't know if it's doable with acceptable weights.
So there may be a diversion sensible, into a competition rated version
and one slightly heavier but cheaper fun version with the same or even higher toughness,
but let's say 50 gramms more empty weight than would be acceptable for competition use.
Prices are hard to tell, we'd first have to deal out all participants marges,
including the academic gliding club (for using their facilities, speak: workshop)
and of course tom (for CAD'ing, milling, and the quite expensive premold material).
And we still don't know how much work time will be needed
to get one model ready from zero to boxed, ready for shipping.
I doupt, it will be possible for us to do a competion rated version for 300 Euros.
I'm even surprised how others can do it with more common sorts of models.
Anyhow, it's still sort of an experimental project,
and we will have to see a first prototype successfully airborn yet.

However, I have to admit, I'm very pleased by the positive feedback even at this early state.
That's very encouraging and we will keep the developement going, that's for sure.

Sep 22, 2007, 05:10 PM
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biber's Avatar
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After some weeks filled with other things (for pictures of that click here) there is some progress happening on the Mubu II premolds.
Some more sealing with epoxy resin has been done and the mold halves are now glued together.

I'm thinking about possible layups for days now.
Next steps is waxing anyway, so there is still time to think...

Sep 25, 2007, 03:00 AM
Registered User
Florrain's Avatar
Me want one!!!
Me want one
Nov 05, 2007, 07:11 AM
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biber's Avatar
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Now we finally got to build the first prototype wing out of the premolds.
It's only rated for about 300-500 W or so, as we didn't want to throw
expensive material into a model that only has to prove it will fly well.
So It was a rather quick and dirty approach to it, without sandwich material,
just 4 layers 54 g/mē FG cloth (orientation like +xx+ relative to the LE).
And 10 * 400 tex carbon rovings in each spar cap, tapered linearly towards the tip.

There was no other camera available at that moment, except the one
built into my phone, so the picture quality is rather poor.

Last edited by biber; Nov 05, 2007 at 08:04 AM.
Nov 06, 2007, 04:35 PM
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biber's Avatar
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So we opened the molds today and what came out put a big smile on our faces.

It is rather on the heavy side with 290 g, but who cares, it's just a proto and
has lots of gelcoat on it to enable a finish job by sanding and polishing only.

Next step will be to shape some nice little fuselage fitting the wing.

Last edited by biber; Nov 06, 2007 at 04:59 PM.
Nov 07, 2007, 02:35 AM
Registered User
Uitgeslapen's Avatar
She looks like a killer, I can't wait so see her geared up and ready to fly...
Last edited by Uitgeslapen; Nov 09, 2007 at 01:15 AM.
Nov 07, 2007, 08:06 AM
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biber's Avatar
Thread OP
Well you can definately call it a she, as the Mubu II planform is sort of feminine,
while the good ol' Multibumm I was clearly male, judged by the straight lines it had.

But heck, when it turns out that girls have the aerodynamically better shaped curves,
then, yeah, it has to be so, I guess...

Nov 07, 2007, 04:23 PM
I plan to take over world
sayno2glo's Avatar
I hope she is fast. I too want one but I'm not in hurry.
You can make the vacuum bagging easy with careful design of the final molds. Make them so that you can put them inside a large bag i.e make smooth contours and avoid sharp edges. And think how they match each other in the bag and fill any holes between them so the bag won't stretch and break. Also only one bagging is required but many use two: second for inner glass and spar caps only.
Nov 07, 2007, 04:53 PM
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biber's Avatar
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We have done the one time bagging thing all the way over the last couple of years.
Generally we just sucked thin polyethylene film onto each mold,
sealed off on the parting plane, so not a real bag actually.
Ended using polyurethane sealing mass out of those cartridges, you take to seal your bath tub.
It's quick and cheap and works quite well.
But no vacuum at all is still less hassle and work to do than any onetime vacuum can be.
Without vacuum, it was a piece of cake to get from mixing
the first cup of laminating resin to closed molds in just one evening.

For the F5D rated version we will certainly do a carbon D-box without sandwich and
a rather light FG layup with balsa as sandwich material from the main spar back to the TE.
That construction has proven to hold up well upto F5D speeds in a wing of a normal (tailed) model.

Last edited by biber; Nov 07, 2007 at 05:01 PM.
Nov 08, 2007, 12:32 PM
Registered User
Originally Posted by biber
So we opened the molds today and what came out put a big smile on our faces. ...
That is a truly beautiful creation. I hope that you are planning to make some videos of it in action.

Nov 08, 2007, 01:13 PM
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biber's Avatar
Thread OP
Trust me, there will be videos!

Nov 14, 2007, 10:43 AM
Hi Biber,

I have been following your project, and just one word FANTASTIC.

How can I purchase one of those wings?

At least cores and fuse, just to start up.



Valencia - Spain - 360 days of sun.
Nov 14, 2007, 11:57 AM
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biber's Avatar
Thread OP
Thanks for the nice words and welcome to this board.

Right now there is hardly anything to be purchased except for the one or another fuselage pod that's left over.
There are no cores left and hardly any time to cut new ones.
That's, however, the status quo for the Multibumm I.

As we are working on the Mubu II at the moment, which will hopefully
be even better, we can't throw any working time at the old stuff.
If you would be interested in a Mubu II, once it is beyond
prototype level, then there will certainly be ways to buy one.
Some patience will be required though, I guess it will take
some months from now on, to get it to that level.


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