TOPIC: New Semi Profile Cutlass for Rapier L-2

Some of you will remember my first 'profile' Cutalss built in 2016:



this was printed T-shirt iron on over balsa and rather colourful, but it meabnt the edges were left square, not rounded. It flew rather well with a Rapier L-2 of the right (lowish) power:



Note vivid colours and sharp lines. But this 'iron-on plastic (it melts with the heat) has drawbacks.

The model responded badly to being over-powered - the iron stuff adds little stiffness and the 1/16" wings were therefore quite flexible. It was destroyed last year at OW Festival of Flight when I chanced my luck with an L-2X in blustery conditions.

So I've wanted to build another one for some time, incorporating modifications to make it more robust and - yes - with a more rounded body and a wing with an airfoil.

Interestingly, the Cutlass is quite a poular jetex.org part-kit, and has been modified to EDF:



Above: a rather larger Cutlass for a customer. He cutomer assured me the flexibility of the wings would be less of a problem with EDF and wanted the nice sharpvivid image iron-stuff can give. I haven't heard from him

Having finished the Gripen, I cut out new balsa parts for my second Rapier powered Cutlass :



Above: this is also larger than my mk 1 and the wings are 3/32" thickness.

Here is progress so far. Flying surfaces are sanded to shape and the fuselage parts glued together and shaped to rough outline:






Above: body and nose ready for gluing together.

With these sorts of 'hemi-demi-semi-profile models things like air intakes and the tail cone add a lot to the look of the finished model :




After final shaping and sanding smooth, I'll apply a coat or two of dope and decide what to cover it with. Paper over balsa looks good, but it's quite tricky (see the first Gripen and heavy. So I'll probably choose printed tissue as the Lansen.

More later!

And so we (slowly) progress. I'm hoping the model will be more than a 'cartoon' of thr real thing, though I love, and have templates for, the old 'jigtime' Cutlass:



Nice, but I wanted better. It's always a good idea to compare with a good 3-view whilst buiilding. But beware! There are many bad inaccurate drawings out there. Here's my guide:



Not too bad (I hope)..

Below is the fuselage glued together. Much care was taken to ensure everything is stright and square. I've made too many 'banana fuselages' in my time!



Next: sealing, filling, doping ready for covering.

After a week of 'doing a bit here, doing a bit there', I've completed covering the doped balsa with printed tissue, sealing and painting the edges and cutting out and making hinges for the elevons. All this takes time as colours have to be matched - not easy!

Here is the coloured 'kit of parts' ready for assembly:



The wings will be joined with a bit of dihedral before sliding into the fuelage slots, after which the fins will be glued in place..

Here are the flying surfaces, note the hinged elevons:



And the canopy with air intakes and the tailcone:





Not too bad. How to paint the canopy on profile models is a bit of a conundrum and I've tried many ways from gloss black/blue to blue/silver. None looked that good. Here I've applied pale blue tissue over silver base. Not sure if this is the 'answer' but it's not too 'inauthentic'.
The jet pipes are still to be added to the rear end and everything tidied up before final assembly.

The weight so far is circa 26 grams - not too worrying as there's lots of wing area (the span is 12") and flying wings generally need less power then conventional plan forms.

The tissue covered parts are a lot stiffer than those of the T-shirt iron on version and making good with coloured paints didn't take too long.
Then the really scary bit. After measuring and checking I glued all the bits together, making sure the dihedral was the same on both sides and the wings are not skewed and the fins straight and true. This is best done with a purpose built jig - these models can fly fast and any inaccuracies can result in a smash up.

So this stage of building is taken slowly! Here's the result, awaiting a calm day and glide testing so that the motor mount can be fitted in the right place (under or just in front of the CG).








Then a coat of varnish and powered tests. At the moment, given stocks of Rapiers are low, I will fit a Jetex 50 mount.

Hmmmmm tasty

The profile Cutlass flies very well, with both Rapier L-2 (nominally 120 mN) and Jetex 50C power.



Above: launching the Cutlass at Old Warden in May 2019. It needs a bit more power than my first profile Cutlass (at least 120 mN, or a Jetex 50C, not a Jetex 50B), but is very steady in flight and is good at flying around trees.