Jumbo Survey

[builditright]

okay guys, I got in touch with Carl Risteen the designer of the Jumbo and he
has given me the green light to make a kit if anyone is interested.

If you are looking for a really big Classic model with flaps here's your chance.

The Jumbo was featured in M.A.N. back in 4/56

This is a really big model for a .49-.60
with a 63.75" wingspan
AutoCAD is showing the area to be 963.38 sq.

Would anyone be interested in this one as a kit

[wwwarbird]

 WOW, Jumbo ain't kidding! Cool plane, would be a fun one to do. I could see one with a big Saito on the nose.

 Too many on "The List" and already in inventory for me right now though.

[john e. holliday]

I have one scratch built hanging on the hook.  Fox .45 for power.   Flying on .018 X 65 foot lines puts me at the limit.   As long as I am doing manuevering of anykind it is okay.  But, if you fly level for more than a lap or two it disappears from flexing.  Is covered with Super Coverite on the wings.  Double layer of carbon veil on the flaps.   I am using an APC 13-3 prop trying to slow it down.   If I can keep it over 5.3 laps or more it is okay also.   Not enough tank for a complete pattern.   By the way it is big.  Lonestar sent me two blocks for the fuselage that felt like soft pine, but were hard balsa.   It was perfect for the job.  Have not done a total weight on the thing.   Guess I will have to pull it off the hook and weigh it.  No more Jumbo's for me, as they take up too much room.

[rustler]

Would anyone be interested in this one as a kit

Possibly. What sort of fus. construction do you envisage?

[builditright]

Possibly. What sort of fus. construction do you envisage?

I am trying to make it like a normal box built fuse with some triangle stock internally to
allow for the more rounded shape fuselage.
 

[rustler]

I am trying to make it like a normal box built fuse with some triangle stock internally to allow for the more rounded shape fuselage.

Sounds promising. (Only thing is, after a ruthless clearout things are beginning to pile up again!).
I'll keep an eye on this thread.

[builditright]

Let's show a little progress on the Jumbo drawings...   

[john e. holliday]

Can't really tell about the construction on the fuse drawing.   Myself I used two blocks of balsa for the fuse.   Yes a lot of carving and sanding, but everything was on the zero incidence when I got done.

[Dennis Adamisin]

Can't really tell about the construction on the fuse drawing.   Myself I used two blocks of balsa for the fuse.   Yes a lot of carving and sanding, but everything was on the zero incidence when I got done.

Doc:
That brought a whole new meaning to the idea of "LOGging In"!  With all that carving, you must have been releasing a lot of internal stresses in the blocks - did you have any trouble with it warping?

I'm afraid I am NOT old school enough to carve/hollow a 3" x 36" hollow log fuselage!     

[builditright]

This a little better to see?

[Jim Rhoades]

     I too, have thought about building the Jumbo and also talked to Carl Risteen some years ago about it.  I wish it were OTS legal rather than Classic as there are too many much more modern ships out there.  Some of my thoughts on the construction are as follows.  The fuselage is symmetrical for the most part and would lend itself to being molded.  The same mold buck would suffice for the top and bottom.  With the light free flight style multi spar wing construction the covering must be rigid, no plastic films.  Silkspan or polyspan preferred.  I would build up the flaps as a sheeted truss envelope rather than a flat open bay truss.  Being as big as they are I'd cover them with carbon veil for stiffness.  Same for the stab and elevator.

     I think it is a really neat and unique design and would be a fun ship to fly but it would be an awful lot of work and balsa for a sport plane.  I'll stick to the more modern classic ships as the competition I fly against is pretty stiff and I don't build enough to make a project this big for fun.  Don't get me wrong, I think the Jumbo could be made to fly quite well.  I'd be sure to make the controls adjstable as the huge flaps may not need to have much movement.  A large bellcrank and tall horns would seem to be very desireable.  I'd like to say I'd be interested but realisticly I think not.

Jim Rhoades

Looking closer I note that the flaps as you show them are sheeted rather than open bay.

[builditright]

I am not saying the Jumbo would not be a nice flying or even a competitive stunter
but one thing I think is being overlooked is that Carl has made it clear to me that the
Jumbo was designed for doing tricks. The kind of stuff that is being done with Bi-Slobs.

Now with stiffer flaps and a modern control system
I think the Jumbo would make a really good larger classic stunter.

[dennis lipsett]

I don't know Walt, Given the short lifespan of many Bi Slobs doing tricks I'd hate to build a Jumbo for the same return as a Bi Slob. Cost wise it wouldn't work out.
Still it really would look neat in a hover as long as it isn't followed with a tail slide.  LOL

Dennis

[Ty Marcucci]

Personally I'd rename it "the balsa overcast". I've alwsays wanted to build one just to hang on the wall if nothing else.  I have carved a very accurate fuselage for my 1949 "Fireball", but I left the interior smooth, so carving a round fuselage is a no brainer. Just sharp #6 blades, and lots of sand paper... 

[Dennis Adamisin]

Enough of my hemmin & hawin - I'M IN.  No sense letting Doc have all the fun with the Jumbo!  Will figure out how to build it with plug-in wings so I can carry it in the econobox.  Fuselage with the stab removed would be quite small.

Hey Ty, mine will be "mylar overcast".  There is remarkably little balsa in this thing considering it is almost 1000 squares!  Monocote will stiffen it nicely and make it easier to correct te inevitable wing twists.  Electric power will help make sure it does not wind up in the wind - hopefully preventing the wing flutter Doc talked about.

YEEE HAW!

[gordon tarbell]

Really good engine for this would be?  The oldest big engine I have is a fresh V60 supertigre. Or do I need to find an old Mc coy 60  or some type of sparker engine. How critical is engine weight on this airframe, and fuel capacity.

[Dennis Adamisin]

Hi Gordon
Despite its size the Jumbo does not looks like a real power hungry airframe.  Note Doc Holliday said he used a Fox 45 and was "propping down" to try to slow down the airspeed.  The original plans call out a McCoy 60 - I cannot imagine it.

I think Walter's plan shows a Tiger 51, that is probably a reasonable choice, your V-60 is likely stronger but you should be able to use a 5" or 4" pitch prop to check the speed build-up.

Better still if you find the 60 is too much choke the venturi way down to curb the power - and increase your fuel economy.

[john e. holliday]

Well the original was flown on 100  foot lines according to the article and the power was a McCoy Redhead 60.   By the way Dennis the carved blocks have not warped and neither has any of the rest of the plane.  Fuel tank area is not big enough to fly full AMA pattern.   But, the plane is an attention getter.   With electric I would imagine putting the battery in the wing and the other stuff in the fuel tank area.  May take it to Topeka for the Ringmaster Marathon in Oct.   Just need to limber up the old IC engine.

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