Hostetler 40% GeeBee Model Z

[Phil Clark]

The latest project was started here at Fighteraces last week in the form of a 40% scale GeeBee Model Z based on the Wendell Hostetler plans.

Basic spec is as follows...............

Span - 112"
Length - 72.5"
Engine - Moki 400cc (yes, 400cc is a 6ft long model!!!......the client is sticking religiously to the GeeBee philosophy of the biggest possible engine in the smallest possible airframe)

I say based on, because the 40% plan is a straight enlargement of his smaller 29% plan, but no modification to structure has been made at all. Certain areas are very lacking in structure employing 'small model' construction techniques, so a lot of attention will be given to the base structure to re-engineer it to cater for the significant increase in weight & the power of the Moki 400.

This project will be delivered 'turn key' ready to fly. We've been tasked to replicate the scale fuselage structure so it's visible when the cockpit hatch is removed + the various removable metal panels, fixings, rib sticking, tapes etc etc.........the whole nine yards basically!!!

The final scheme will be this......

[Phil Clark]

There are no moulded parts available for this model, only the 29 & 33% versions......so before any of the main construction is done, patterns are to be made for the cowl, wheel spats & canopy to allow us to make the epoxy glass moulds.

The cowl is 468mm diameter & is made from 3 x 1/4" lite ply formers around an 8" sq lite ply box to ensure alignment, 1/4" sq balsa stringers, 1/8" balsa sheeting with a shaped yellow Styrofoam nose ring. The spat pattern is yellow Styrofoam around an 1/8" lite ply core.

With the 1st side of the spat pattern shaped, this is glassed in 160g twill weave glass. Once cured, template patterns will be taken from side 1 to allow side 2 to be shaped symmetrically.

[Alan Cantwell 1131]

image.jpg (72.49 KiB) Viewed 16013 times

Superb, what are you doing about these Phil?

[Phil Clark]

You man these Alan!!!

Slight problem though......these 40% struts from Sierra come supplied with 7" wheels. The plan shows 8's but checking my scale 3-views, they should actually be 9 1/2's.........so not only have we got to source new wheels that are slim enough to fit inside the fairly skinny spats, but the lower forks are all going to have to be remanufactured to cater for the bigger wheels.

Nowt's ever simple!!!!

Phil

[Phil Clark]

You man these Alan!!!

Slight problem though......these 40% struts from Sierra come supplied with 7" wheels. The plan shows 8's but checking my scale 3-views, they should actually be 9 1/2's.........so not only have we got to source new wheels that are slim enough to fit inside the fairly skinny spats, but the lower forks are all going to have to be remanufactured to cater for the bigger wheels.

Nowt's ever simple!!!!

Phil

[Alan Cantwell 1131]

That makes both the yoke, and the swiniging arm useless, may as well start from scratch, and sell these on, hell of a project Phil, v nice

[Alan Cantwell 1131]

I love these things, seen this lot?

http://rogerritter.com/images/aviation/Mu1GeeBeeZ/

[Phil Clark]

That makes both the yoke, and the swiniging arm useless, may as well start from scratch, and sell these on, hell of a project Phil, v nice

Naaa.....the welded steel structure + the oleos will be fine. Drawing new yokes & swinging arms up and having them machined will be far simple than starting from scratch.

Phil

[Phil Clark]

I love these things, seen this lot?

http://rogerritter.com/images/aviation/Mu1GeeBeeZ/

Yep.......there is stacks of good stuff online......a lot of which has been saved.

[Alan Cantwell 1131]

Well, hope you enjoy building her Phil, really looking forward to this one

[Phil Clark]

Progress has been made on the basic fuselage structure for the GeeBee this week........the plan shows 1/8" ply sides from the TE forwards, laminated to 1/8" balsa nose to tail (uuggghhhhh).......we've changed this to give 1/4" ply sides up front, mated to a cyparis/balsa rear framework with ply gussets.........it's not identical, but it's following the basic structure of the full-size fairly closely.

Wedges have been added to the firewall front & rear to give 2 degrees side thrust for the big 400 up front....this results in the engine being offset 10mm from the centreline at the firewall.

[Phil Clark]

Fuselage jigged up with light weight balsa formers + diagonals added to help stiffen the basic box structure.

Cowl & spat patterns also ready for initial priming & main surface prep following glassing in 4oz cloth + a coat of U-Pol 'Reface' spray filler (basically sprayable P38 body filler.......fantastic stuff for fast build up)

[GrahamKennedy]

Phil
I have about 20 random shots I took of the full size when I was at Fantasy of Flight a couple of years back.

If you think they would be of any use to you, then drop me a line.

Graham

[Phil Clark]

Hi Graham

It's well documented online, but YES PLEASE......the more photos & info the better. If they are e-mailable.......phil@fighteraces.co.uk.......or if you can put on a CD, mail it to the works address (address is on my website)

The Z is trundling on........the fuselage has basic rectangular balsa formers with diagonals added to stiffen. Before all the stringers go on, mounts have been added for the twin elevator & rudder servos......again, these have been moved from the plan location as 1) we'll need the tail weight with 20lb of Moki hung off the front & 2), we want all control linkages either hidden (elevator) as per the full-size, or closed loop cables exiting the fuz in the correct location (the rudder cables are shown incorrectly position on the plan). Access to these 3 servos will be via the canopy hatch with the pilots seat removed.

With these in, we've been on with adding the multitude of 9 x 3 Cyparis stringers in the outer formers (which are all added in 1/4's). The plan isn't the best so notches were cut in the 1st & last formers then a straight edge was used to determine the notch positions in the other formers to ensure they went in straight.

The cowl & spat patterns are also well on.......after glassing (4oz cloth & L285 resin), they were sprayed with a heavy coat of U-Pol 'Reface' (basically a sprayable version of P-38/U-Pol car body filler). This levels beautifully with 80/120 grit paper. After this, on with the KK epoxy primer......1st coat flatted with 120, 2nd with 240 etc etc.........these are now ready for a final coat and a 600 wet sand prior to applying a gloss coat ready for waxing/moulding.

[Phil Clark]

Fuselage stringers done ready for the forward fuz sheeting to go on.

[paul needham]

Looking really good Phil, is this one staying in the UK or is she destined to go abroard ?

[Phil Clark]

UK

[paul needham]

Looking foward to seeing her in the sky.

[Phil Clark]

Still progressing well in the back ground with another very large projects taking up the rest of the workshop!!!!

The fuselage is now complete ready to have the centre section mated to it + the glassfibre nose 'glove' (with louvers) moulded & fitted. The st/bd outer panel & aileron are also complete. These are of all conventional construction around Cyparis spars, ply/balsa shear webbing, ply & balsa ribs & 1/8" sheeting. Joiner tubes are 16 and 10mm respectively......not huge but all loads will be taken by the swiss 4mm st/st streamlined flying/landing wires.

Port panel is now well on & almost ready for sheeting.

[Phil Clark]

With the port wing panel now at the same stage, the centre section could be mated (dry) to the fuselage and that unmistakable 'GeeBee' outline is clearly visible for the 1st time.