TOPIC: New Models for 2022 Flying Season

Hi Guys,
as the evenings are drawing in, its time to get your drawings out. By which I mean model plans. Models for next year.
Now is the time to start building, and I have had some encouraging emails from Brian Lever, who is building an Aristo Craft, aka Easy Built ... er Keil Kraft Sea Vixen.





Brian had a great time, he says, cutting out all the formers with their hundreds of stringers



latest photo, top:


and underside with tube for TSP L-2:




It is coming along nicely, but Brian has some concerns, " I am Still battling with weight. The booms, fins and tailplane all want to move the cg too far back! I have more sanding to do but my concern is the vulnerability of all the aforementioned structures".

I too, have some concerns about the vulnerability of the structure. The wing root, in particular could do with some gussets and perhaps that first wing bay could be sheeted. Fixing the tail booms should then be more crash proof. A few diagonal wing ribs too would stiffen the structure and the (at least) 1/16" washout built in.

As to the weight of the rear end, the all sheet tailplane could be replaced with an open 'geodesic' structure.

A long time ago, Steve Bage made a version of this model:



Note the built up (if not geodesic) tailplane, diagonal wing ribs, vertical grain balsa between the wing spars, extra gussets around the wing roots and the sheeted areas. Steve also reduced the dihedral, which, he says, was a big mistake!
All further suggestions welcome.

Can the motor go forward another inch or so? And is that really a heavy jubilee clip securing the motor tube?

The DH110 was my first ever Jetex model (Purchased from Dugdales electrical store in Bentham Lancashire around about 1961 or so. Switches to Monty Python mode, "Model shops, we used to dream of model shops...")

Sadly I didn't complete it!

The Terry clip allows Brian to put in a Rapier or TSP motor, but they are heavy. There are better solutions. Putting a motor way in front of the CG means that the CG will move back in flight (one shot motors lose a significant proportion of their weight as they burn, more so than Jetex).
My own solution that I put in the Cutlass, is a Jetex 50 clip and make an adapter for a Rapier/TSP motor.

Making your own motor mounts is covered in this thread:

Motor Mounts

Thoigh these mounts are for profile motors, they also fit nicely in a trough! I'm not fond of Terry clips myself as they really aren't that secure .



Brian's thoughts to date:
"I am now contemplating what I can do to create strength and add lightness. To some extent I am compromised with the model structure mainly completed. I do have 1/2” dihedral and each tip washed out a little. So I shall add diagonal wing spars, leading edge root gussets, maybe some light sheeting to the wing root area. I’m loath to cut out the tailplane from the two fins. My compromise will be to cut some circles out of the tailplane and cover with lightweight jap tissue.
At least I am fully aware of possible future trimming issues.
I treat this as all part of the fun and will not resort to catapult launches but use up my stock of L2 Rapiers in an effort to create flight.
Meanwhile I have identified a DH 108 Swallow for a simpler winter building project after completing the DH 110.


Below is an extract about this model. Note Steve Bage did get his DH 110 to fly and Howard Metcalfe's observations:

This from uber Jetexinista Howard Metcalfe:
To forward mount the motor or not to forward mount the motor?



I built my Aristo -Craft Supermarine Swift 14.5ins wingspan with knock off wings twenty years ago. Not knowing any better at the time, I moved the Rapier half into the next bay ahead of the normal position! You would expect that this would produce a flight profile where the model became ever more nose light in flight and probably ending up in a loop, but that is not the case with the Swift, well not this one anyway. To prove the point, it even won a prize one year at Peterborough for its flight profile. So how come? Well it is a slight enlargement of the KK version and a bit heavy too at 43 grams so it needs all of a 250mN Rapier L2HP to get a good flight out of it. I have concluded that the power to weight ratio is such that it is actually underpowered, it doesn’t appear to fly that slowly but it obviously lacks enough ‘welly’ to speed up into a loop. The ‘down thrust tab’ at the end of the trough probably helps quite a bit too (understatement!) especially with say an L2HP 280. [but try finding one at the moment .... time to move on to TSP!]




Roger adds: there's lot here to think about. Howard's Swift can fly splendidly with the 'right' motor. To conclude: does Brian need to fit a downthrust tab so he can move the motor forward?

Andy Sephton had a KK Panther some years ago with a very forward motor. This flew well and the CG moving back as the flight progressed helped with the glide. Mind you, I don't know how far forward the CG was to start with!

In contrast, I've had models, both straight wing and swept back with motors too far forward, and their flight pattern was: nice climb out ... all set for cruise .... but at this point they spin down like a falling leaf. I explored this phenomenon with an L-1 powered Jetex Wren.



I now put my motor, at least for profile models with thrust tabs, 2/3 in front of the CG, 1/3 behind.

Back to Howard's Swift. This is probably a good model to try a TSP L-2 HP with. These are rated at 300 mN.

Roll on next year when we can give the new TSP motors a real 'beta testing' and try these ideas out.

Motor mounts for these classic built up Jetex models deserves a separate thread:

Motor Mounts

I guess none of us is too happy with the Terry clip!

Hi All!
as part of my free time in the workshop, I built two models: Gripen on L-1 and MIG-19 on L-2 both for the next 2022 season.







Meanwhile, fun with the Duglas F4D Skyray on the L-2 HP:

Yes, I know it still requires a little trim...

Howard Metcalfe adds;

Hi Piotr, it's good to see you having fun! Your Sky Ray's flight pattern It will be transformed if you add a 'down thrust tab' behind the motor.
A typical 'downthrust tab' is shown on my drawing of the profile BAE Hawk:



Roger adds:

This thrust tab, if made of thin metal can be adjusted to prevent looping by bending it down. The right angle for the motor is found by experiment. Be sure to clean off the gunge after each session!