Robin Stevens

Yeah, the mass build for me will just be "the stuff I would have run out of time on this winter"

I'm in a similar boat, got a couple of builds that have been on the shelves for a while that I'm taking the opportunity to work on. Might as well make the best of a bad situation. If doing an isolation build then something smaller and simpler would probably be more appropriate. Something like a limit EX or a mini tyro.

Just to prove I am still working on this I'll show my progress. Things have just been a little slow, real life always gets in the way. Having a look at it I think Martin's suggestion of sectional anhedral is a good solution, but for the time being I'm concentrating on the fuselage. Most of the formers are about ready, I'm just planning out the stringers so there's a minimum level of fettling. The tail obviously needs to be planned out and the parts modelled. Given that this is taking a bit longer than I'd hoped I'm thinking of doing a simple PSS model of the XP-79 so I have something to take to events and the like.

The Sabre jigs are very impressive, definitely a technique I'm willing to copy. The only thing I'm unsure about on the Frogfoot wing is whether to have the scale anhedral angle or to make it a flat wing, dihedral would look wrong so that's not an option

Going for E374 with the wing centre section built into the wing as advised. So far I'm around half way through planning out the fuselage profiles, hopefully will have something ready to be cut in a couple of weeks. Thanks for the link Martin, interesting read with some things worth bearing in mind. Washout seems to be a key consideration, the Su-25 has a slight sweep to the wing so around 1 degree washout seems appropriate. The plan is to have the fuselage being self-jigging where possible, the key advantage of CNC cutting to me is that accurate interlocking surfaces can easily be produced.

Will keep the pylons in mind, for the time being it looks like the fuselage should be draggy enough but like I said I can always change my mind later. The opportunity to have weapons all over it as variable drag/ballast is tempting though... 3d print of my CAD model is done (1:72 scale), I think I've got the shape and proportions right. The print is just as a test to make sure I'm happy with the shape before I start to take profiles from the model. Thanks for the offer Martin, there's someone in my club that's already offered the use of their CNC router but when I have the profiles and plan complete I can share the dxf files if 1.8m sounds about right for you. As far as wing section goes I'd been recommended Eppler 374, which looking at airfoiltools looks like it's comparable to Eppler 205. However 205 has a flatter base which would be more convenient for building. Had a look at different methods of wing detachment on the CAD model, I think having the port & stbd wings detach at the root is a better way to go than having a continuous detachable wing. The wings are very deep in the shoulder mount so there isn't much structure left if the entire wing pops off.

Hi Phil, thanks for the info. I had seen the Steve Griffiths plan on Sarik but without an image on their website I didn't pay much attention to it, looks a little on the small size for what I'm thinking but it's good to know what's out there. As you say the Frogfoot isn't exactly a speed demon but it is pretty fast (around 850kph / 460kts). At the moment I'm thinking that the only concessions to scale I'll do is eliminating the weapon pylons to preserve the overall look of the plane, could always add them in later if needed. Nothing would be slimmed down for performance, the real thing can carry it's own weight in weapons and fuel so there should be plenty of overhead there. In terms of construction I'm currently leaning towards a balsa stringer and former construction with a planked and glass skin. Currently 3d printing the CAD model (scaled down) I made yesterday so I have a good indication of whether I have the right shape.

Hi, I've been thinking of getting into PSS for a while and could never find a model for a subject I was really interested in, so recently I've started to take the plunge and start to draw my own plan for a 1:8 Su-25 Frogfoot (about 1.8m span) The Frogfoot is a Russian ground attack aircraft of similar (but not quite the same) role to the A-10. I quite like the Russian designs and the Su-25 seems like a good plane to start with for PSS. The fuselage is almost rectangular all the way through it's length and doesn't really taper significantly so construction should be pretty simple. Does anyone experienced with PSS have any recommendations on wing section to use? At the moment I'm thinking that the wing area should be sufficient with simply scaling down the design, no tweaking of the proportions. As far as I'm aware this doesn't get modelled often, if there's anyone out there with another I'd be keen to hear from them. Edited By Robin Stevens on 16/02/2020 18:17:23

Thanks for the recommendations I think I'm going to go with the SC 0.40 two stroke glow that I have from another aircraft that I'm retiring. Looking forward to having the toot sweet finished, everything I've heard about it makes me think it'll be a fun flyer. My club isn't fussy about noise, we're fortunate in being in the middle of nowhere. A trusty glow 2-stroke will likely give me all the power I could need and be relatively practical.

Nice colour scheme, looking good liking the eyes on the side rather than a cockpit. Looks so fish-like it could be Guppy Love I take your point on KISS, was worth asking though just in case.

I might be best to just stick with glow then, throttle response will be critical on an aerobatic model like the Toot Sweet. I'll think about it again when I'm closer to finishing the model. I don't expect there to be any massive improvements in the small engine offerings but it could happen.