Target weight for geo xl?

[rob biddle]

 Hi folks,

 Finally back after an extensive layoff due to a massive family upheaval. New chick, new house etc.etc.

 I'm currently building a geo xl at 90% size squeezing in an mvvs .49re for power. D-tube construction for the wing as it's being scratch built from a scaled down plan.

 Just wondering what the ideal weight range would be? I was hoping to get it under 50oz but it is a real challenge with the heavy powertrain.

 In hindsight I probably should have built it fullsize, under 60oz would have been ok with the .49, The 90% version is 2/3 built now so I guess I'll just have to suck it and see.

 Look forward to hearing your thoughts, thanks in advance..
 
 Rob...

[PJ Rowland]

Really depends on the power.. weight isnt as critical as it was a few years ago.

Under 50 would be nice.. but its cerainly not going to stop you from performing at a good level ( if thast what you want ) My '51 .61 Nobler weighed in at 53 oz and is extremely competitive.

With your intentions, it comes down to power.. I dont know too much about the MVVS however if you were to put a PA 61 or even 65 in it you could comfortable move toward the 55 - 58 oz mark without any problems of performance.

[rob biddle]

 Thanks PJ,

 I had the .49 in a 64oz shark 45 for a while and it performed quite strongly. The model had an inverted tracking problem that i couldn't figure out so it eventually got shelved. (Was never going to get a decent refinish on it without it becoming too porky anyway lol)

 Pretty much built the geo xl on a whim to get the engine back in service and to confirm a finishing technique i've been working on. (Last couple of models had issues with chemical compatibility).

 At the moment it weighs 34oz but I'm yet to add cowl, flaps, u/c and moulded top and bottom shells. I'm guessing 53-54oz will be about where it ends up. I do have a pa.61 slated for another project should the finish on this one work out as planned but I'm not opposed to trying it should more power be needed.
 
 Cheers, Rob...
 

[Allan Perret]

My '51 .61 Nobler weighed in at 53 oz and is extremely competitive.

Did you calculate the wing loading on that Nobler ?  I have been curious about what the upper limit of a competitive wing loading would be.

[Derek Barry]

Really depends on the power.. weight isnt as critical as it was a few years ago.

Under 50 would be nice.. but its cerainly not going to stop you from performing at a good level ( if thast what you want ) My '51 .61 Nobler weighed in at 53 oz and is extremely competitive.

With your intentions, it comes down to power.. I dont know too much about the MVVS however if you were to put a PA 61 or even 65 in it you could comfortable move toward the 55 - 58 oz mark without any problems of performance.

I agree, 50-53 would be ideal. 53-56 good. 56-60 will probably still fly but you will have to speed it up a little. My Staris (Randy 40 size plane) weighed 61oz with a PA 40 RE on a pipe. It flew awesome! Wish I still had it.

Derek

[rob biddle]

 Thanks Derek,

 I was fairly fussy with the wood selection knowing that more weight would be gained using the d-tube wing. If the finish goes well I might be able to make sub 52oz.

 The mvvs has plenty of power for a ship this size, the fun part has been squeezing a big enough tank in without extending the nose from the plan outline. The engine is over 12oz so I'm doing my best to keep the nose as short as possible.

 Cheers, Rob...

[Louis Rankin]

My 92% Geo XL, AKA the Geo Jr weighed 49oz with a PA40UL.  The sq inches of the 92% are 608.

[John Leidle]

   My  GOXL was 74 ounce with a PA .65  it flew probably as good as anything I ever had  untill the wind came up. So if you come in at under 65 ounces with a strong engine it will be fine.
                  John

[rob biddle]

 Hi john,

 The version I'm building is at 90% original size. Roughly 595sq''. Pretty confident I can get it under 55oz so by the sound of things it should be ok.

 I imagine louis' 92% geo xl would have been pretty awesome at 49oz with the pa .40.

 Cheers, Rob..

[John Leidle]

 Mine was well over 700 square inches  ..

[Bill Little]

HI Rob,

Get it as close to 50 oz. as you can.  Billy's full size was only 53-54 oz. with a piped system.  The airfoil is straight USA-1 with a slightly blunter LE.  The airfoil is thin for modern standards, so it needs to be light for optimal performance.

Our Geo Bolt XL was 64 oz. using the more modern Geo Bolt (P-47 Billy/Randy) wing from Billy.  The older (Geo XL, Junar, USA-1 and before) designs from Billy usually have to be built very light to perform as Billy designed them to work.  They will still "fly" and work pretty decent, but not up to the standards that they are capable.

Big Bear

[rob biddle]

  Hi Bill,

 I simplified the construction somewhat but added a heap of wood in the process ,

 Pretty sure I can make 55oz ok, sub 50 would be a real big ask at this stage.

 If ever there was a test for a new finishing method, this is gonna be it!!! LOL

 Cheers, Rob.

[Randy Cuberly]

HI Rob,

Get it as close to 50 oz. as you can.  Billy's full size was only 53-54 oz. with a piped system.  The airfoil is straight USA-1 with a slightly blunter LE.  The airfoil is thin for modern standards, so it needs to be light for optimal performance.

Our Geo Bolt XL was 64 oz. using the more modern Geo Bolt (P-47 Billy/Randy) wing from Billy.  The older (Geo XL, Junar, USA-1 and before) designs from Billy usually have to be built very light to perform as Billy designed them to work.  They will still "fly" and work pretty decent, but not up to the standards that they are capable.

Big Bear

I know this is an older thread...but it just caught my eye.
I've been flying a Geo XL for several years...a full size one that is 720+ Sq in.  It weighs 53 oz like Billy's original and is an incredibly good flying airplane.  Very forgiving and easy to fly well.

I would reiterate what Bill L. said.  Keep it as light as possible.  I'm sure it will fly OK at 60+ oz but it is a real eye opener if kept light.  This is not a design that works better in the wind if it's heavy.  It works better everywhere if it's kept light.  Incidentally I beliebe that part of it's secret to great flying is the very torsionaly stiff Geodetic wing construction.  Too bad you decided to make it a D-tube...more weight and less torsional stiffness.

Randy Cuberly

[Allan Perret]

Anybody remember what magazine / issue had the construction article for Werwage's Thunderbolt ?

[Bill Little]

Anybody remember what magazine / issue had the construction article for Werwage's Thunderbolt ?

Hi Allen,

Model Aviation: July 2006.  Great article and the plans are true art.  I am very happy to have the first Lost Foam fixture for a Geo Bolt Wing used in the Razorback.  I happened to call Bob while Billy was there and they were cutting the Lost Foam fixture.  It is a GREAT wing, we used one in Aaron's "Geo BOLT XL" 

Bill