Piper Super Cruiser for OMFC Rubber Scale Duration

[Squirrelnet]

I have started a new build and something a little different for Scale model builders.  It's a 36" Piper Super Cruiser built for the Oxford MFC's new Rubber Scale Duration Class. This is a duration class for scale models with a max time set at 90s so very much a scale/duration hybrid class. For this model I've used under cambered wings borrowed from a Coupe and I'm fitting a D/T . The design is basically a double size KK Piper SC
For the D/T I've used the same method that I've used on several FF sport models for a flip up tail DT where the fin fits into a slot in the rear of the fuselage in the DT position. This locates the tail and fin assembly and stops it coming off in use ...not a good thing
The same structure to create the slot is used to locate a 1/8" dowel for a rubber band that simply goes through a hole in the fin. The pivot point is the LE of the tail against rear former, I'll add some small retainers later just above the LE to stop it riding up but this arrangement creates an over centre pull by the band to pull the tail up . It's held down by the D/T line tensioned with a band to the timer
DT is activated by a mini timer from Mike Woodhouse Free Flight Supplies based on the TOMY timer mechanism. I have several of these now and they work well , I'm a bit of fan of old technology - no batteries to fail, no RDT TX to forget, no fuse to light, just a simple clockwork mechanism. They get left in a box all winter, then just wind them up when you need them and off they go
If you want to know more there's a webpage on the Oxford MFC site that outlines the class and the rules https://oxfordmfc.bmfa.club/omfc-rubber-scale-duration/

I'm currently at the covering stage , having just finished the basic airframe with Asuka tissue and doped with 30/70 Non-shrinking dope

[TheLurker]

It's not yellow enough.

Do like that, shame that it's far, far too big for Trinity.

[Squirrelnet]

Well Christmas Day wouldn't be Christmas Day without sneaking in a  bit of aeromodelling ... not much just a tiny bit of trim in black tissue after all it was only wafer-thin!

[Squirrelnet]

Managed a bit time in the workshop this afternoon and added the tissue markings. I need to fit the Dt properly, glaze the cabin and make a prop and hub ...nearly there

[billdennis747]

To all intents and purposes it's the same now as the 40" KK power model, which also featured a rubber conversion! Should go well

[Pulserudder]

Model looks great. Really appreciate the translucent quality of the doped tissue.

Also, great to see this new version off HPA up and running.

[Steve85]

Lovely model.  Any plans for the maiden yet?

Steve

[Squirrelnet]

Thanks Steve. Still a bit to do but hopefully I can at least test glide in the next few weeks

[Squirrelnet]

A bit more progress today with the D/T being fitted.


The timer is held in with small bamboo 'nails'which are cyano'd in. The line is held captive by 2 U shaped staples from 26swg wire with a dressmakers catch which is too large to go through the staple to take a rubber band to the timer. Another u shaped staple takes the turn to the fin where a simple hook is attached to the fine. I've added some half round balsa dowel to the underside of the tail as well to loctate it in the same position each time. The tail has been set to the usual 45 degs for DT which is governed by the band hook being stopped by the u shaped staple


One thing I have added as well to the timer is a guard for the waggler as on a previuos model I found an errant strand form the motor can and did find it's way to it and wind itself round it stopping the DT from functioning !!!

[Squirrelnet]

A pilot from the cut out Paul Plecan Pilots sheet has been added and the left side glazed.


 I started making up the hub but realised I didn't actually know what I was doing 


I have two laminated balsa blades and was going to attach them to a carbon tube hub but realised unlike the coupe prop I was thinking of I need to add a freewheel clutch of some sort ...any ideas


 I have a bearing set from Mike Woodhouse for the thrust as well and a hlaf moon hook to take a Tim Grey Hook but lack of a plan for the free wheel brought me to a halt ...I'll go and do some research 

[Squirrelnet]

The glazing has now been finished. It was packaging clear acetate stuck on the canopy glue and swearing. Canopy glue would be so much easier to use if it had some tack 

 Many thanks to Mark M who sent some pics of Ivan Taylor's prop he made for his very similar Auster. That allowed me this afternoon to copy the design with dowel to hold the blades and a tube hub. I was hoping to use some Carbon tube but typically I didn't have any the right size so in the end resorted to the heavier brass option. I have drilled the nose block with 5 deg down and 3 deg side thrust but it will be adjustable. I will make up the two brass plates to hold the rear of the prop shaft tube bearing tomorrow. This will be to the same design I used on a Miles Falcon, a design sent to me by Mike Mulholland in build thread on the old HPA . It's simple and worked very well on the Miles

[Squirrelnet]

The driver for the freewheel clutch will just be the prop shaft bent to 90 degs but I need to finish the adjustable rear mounting and spray the prop black before I can do that. After that I think I'm done apart from balancing ...it seems promisingly ballpark at the moment but we'll see, particularly once there's a motor in it

Oh and paper undercarriage fairings need to be made. The biggest remaining job is probably to build a transport/storage box for it

[OZPAF]

The neat glazing in particular caught my eye Chris - especially the front section. It looks great but as Lurk mentioned - it's not yellow enough .

Good luck withe trimming.

John

[Squirrelnet]

Thanks John


Well I'm calling that done now. I'll wait for the weather to warm up and ground to thaw out before I try some test glides. The nose block now has an adjustable palte at the rear. I couldn't find or don't have thin sheet brass so I made it out of an old food can lid. The larger plate locates the rear of the brass prop shaft bush in a slot to allow side thrust adjustment while downthrust is adjusted on the the slotted mounting holes. Another smaller plate locks it in the side thrust adjustment

[Squirrelnet]

It's a big old prop but the same size as Ivan Taylor's on his Auster so we'll see how we go. Weight is now over 100g but it balances out pretty well with the CG on 35% MAC without balast

I even got time to make a transport/storage box