Jupiter Junior vintage style biplane - Page 28 - RC Groups
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Aug 10, 2017, 12:22 PM
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I did a search to find prices for the MPF - 6 sheets certainly is within budget for the raw material.
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Aug 11, 2017, 09:30 AM
Retired CAD guy
birdofplay's Avatar
Here is a layout for a 54" version.
I just scaled the originals to a reasonable size with respect to MPF size and shipping considerations.
As it is this will take two of my boxes to ship.

1. It uses 6 sheets of 48x24 MPF or fanfold. more sheeting for KFM needed.
2. It does NOT have provisions for KFM (x) sheeting. (yet )
3. I am worried at the Lack of bracing when things get this large.
i.e. no spars, no N-struts, no X bracing

Although all that "could" be done with just X bracing if lightly built.
On my LARGE SimSymSam I used Kevlar thread which worked nicely IMHO.

Once one starts building for strength things tend to get heavy very quickly.
I already can envision Ply doubling on the cabanes and possibly removable wings.

We Could straighten out both wings, loosing the dihedral.
That would make them stronger and more easily Spared
The top wing "Could" be changed to a Polyhedral at the tip like the Slowly.
My Slowly has simple LE and TE spars and nothing else and it's very slow flying.
The UC foil shape also adds quite a bit to the "strength" of the wing.

It's a decision between ROBUST and Durable vs Light and Floaty

Bob @ Hoosier Cutout Service
Last edited by birdofplay; Aug 11, 2017 at 09:44 AM.
Aug 11, 2017, 10:00 AM
Registered User
Looks good Bob!

I have been putting some thought into things like bracing and removable wing attachment.

In your estimation would a KFM airfoil allow slower flight?

Would it provide enough stiffness that X bracing wouldn't be required?

If it provides one , the other or both I would do it.

For wing removal I was thinking good old rubber bands for simplicity, cost and low weight.

On my Jr. the floats are held on by music wire and come off easily to change to conventional gear.

I think they would pop off with little or no damage in a crash as well (I'll post some pictures this weekend).

I would do something similar here where the floats or landing gear comes off with the lower wing.

If X bracing is required I was thinking CF tubes with AL tube ends glued to the CF, pinched closed, drilled, bent, and bolted through the wing.

I like your Kevlar thread idea if the problem is tension only, but it may make it difficult/impossible to remove the wing

I considered N struts, but they would also make wing removal difficult unless they slide on/off the ends of the wing.

CF rod or tubes in the wing with no X bracing is a possibility too.
Aug 11, 2017, 10:07 AM
Registered User
Hmm, visualizing it at 54" it isn't really giant and isn't bigger than the 60" Beaver I have now.

I want GIANT! lol
Aug 11, 2017, 10:19 AM
Registered User
Make the wings longer, make the trailing edge of the wings on another sheet, that way ailerons could be easily added if desired

that might get us to 90+"

the upper wing section of the fuselage needs to be one piece with the lower fuselage (IMO), having a separate rear section is ok (or maybe go back to a 4 x 8 sheet of 1/2" XPS for the fuse?)
Aug 11, 2017, 10:25 AM
Registered User
At the speeds I want, it might be worth going to a flying elevator and rudder too
Aug 11, 2017, 11:16 AM
Retired CAD guy
birdofplay's Avatar
OK here is a scaled to max foam size without too much part separation.

I added the 50% sheeting for KFM
Aug 11, 2017, 02:42 PM
Registered User
I don't have the right tools to draw it correctly, but was thinking a 80" span (40" wing) could be cut like this:
Aug 11, 2017, 04:05 PM
Retired CAD guy
birdofplay's Avatar
The original has a very high Dihedral.
I was thinking that possibly Kite Braces that allow for CF to PLUG IN would be viable.
Kite supply places have them all molded up and ready to build with.
Or we can invent something out of Metal tubing


Aug 11, 2017, 04:51 PM
Registered User
cbalgra's Avatar
Why deal with all the bracing.? Just build up a fully ribbed, built up wing!

My wings for my Beeker are 43 1/2". A 16% thick airfoil. They have 4 ribs per panel. Have balsa wood leading edges sanded to shape. Upper and lower 1/4"spars. Have a lite ply spar joiner. 5 degrees of dihedral. They are covered with brown paper and Titebond II glue. They are painted with acrylic pant. This wing is super stiff and has no twisting whatsoever.

And the wing only weighs 6.3 ounces. Double the size of that, and the weight would be negligible with that much wing area.

If I were to build a giant Beeker, or any other slow flying large plane, I would only use this method. Too easy to build! Zero complexity and flies wonderfully.

All this "giant" talk is almost enough to make me want to build a 200% Beeker!
Aug 12, 2017, 02:04 PM
Thomas B.'s Avatar
I like the beeker!
And I like your wing structure.
Kite braces seem to be a good idea for an undercambered wing, too.
I use 4mm wooden struts with wire hooks at the ends and ply fixpoints on my 200% Jupiter Duck and this works fine, too.
Aug 12, 2017, 03:25 PM
Registered User
cbalgra's Avatar
I appreciate the kind words Thomas. That means a lot coming from you.

I love the under cambered wing on my Big Duck also. This plane never fails to draw attention whenever I fly it!
Aug 12, 2017, 05:53 PM
Retired CAD guy
birdofplay's Avatar
Thomas has made the Sponson/floats easier to mount ad much more robust
by using Thru-Fuse Cf tubes ( I presume ) .
Plus the quick disconnect Struts make this an easy plane to get ready for flight.

Possibly this winter for a Big Jupiter Duck ;>}


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