Nigel R

Thanks Nick. Sadly the proof of the pudding is likely to be a ways off, going by how long previous builds have taken me. Tonight's job was simply to stick the rib templates to some wood. Managed to squeeze them on to 3 sheets of Ecuador gold: it has to be said, I am not relishing the thought of the next bit, it is my last favourite part of an airframe build.

Unbranded aren't worth the saving if you're only buying one or two for a refurb. Get a decent brand and have done with it.

Sounds like the average build cost for a scratch build at present.

And to catch up with progress to date, the wing in devWing: and the internals: The taper is fairly mild - the tip is around 2/3 of the root. I'm using strip ailerons, of 1-1/2" width. There's a secondary spar there to help carry the load around the cutouts for retracts - if I've done my sums right there is space to get a 3" main wheel tucked away.

welcome aboard matt

...and some sheet on the fins... I then put some 1/4 x 1/2 around the outside. Later on, this will be sanded to a nice rounded outline: Time for a mock up! Fins pegged to the tailplane with cocktail sticks: ...looks good so far, I think. You can see the ply insert on the rudder is lining up nicely with the tailplane 👍 And a view from the top. At this point I have now hinged the fins/rudders, dry fitted the M3 rod, cut the nylon horn down a bit, and opened up the TE of the tailplane in order to allow free movement. Phew! Sadly I forgot to take a picture with the snake in place, but, it's all nicely enclosed in that pocket. I'm rather pleased with my efforts so far. So much so I promptly stopped work on the thing for about three weeks! This pause in building activity was the point I spent the kids inheritence on a small stack of balsa and started drawing out the wing in CAD.

Time to make some fins and rudders, or vertical stabs as they say over the pond. Internal structure from 1/8"; I'm adding a hard point of ply to receive the M3 threaded rod: Starting to get some 1/16" sheet on the rudders and taper the 'ribs': The rudder's LE has the ply scarfed to some 1/4" balsa: Rudders now sheeted: More soon...

So would i

you must have a very large flight box!

They're very good. They could use a slightly longer spigot for the vent/breather. One can always use those little clamps, I guess. The thread for the clunk feed sometimes has some moulding cruft that needs cleaning up.

Asymmetric thrust can be a thing. Depends on the spacing of the engines, clearly. My twin fuselage effort, it is barely even noticable, on my conventional twin it needs some rudder to keep it tracking straight. With more airspeed comes more response to rudder and with that comes easier single engine flight. As Jon says, if you lose an engine, keep it moving. One thing it is well worth doing is practicing your deadstick landings. You may not truly need to "land from anywhere" if you have one stopped and one still turning, but knowing you can pull a greaser out the bag if everything goes quiet will give a lot of confidence when piloting a twin.

Plastic tube also works. Or, SLEC make those rectangular tanks that use no brass tubes at all, and are all moulded nylon.

About 10lb of battery right there. Join the 21st century, use a 3s2200 lipo... weight 1/2lb.

Rc primer is dated now but was an excellent book.

Starter? Let the printer take the strain: https://www.thingiverse.com/thing:2884920 I made a simple frame from cheap b&q ply but I didn't have a printer at that time.

Somewhat recently, my dad proudly gifted me his dad's drafting equipment. It was quite clearly a very nicely made set of dividers and compasses and parallel rules and so on. "Now. This is what a professional draftsman uses," he said. I hadn't the heart to tell him that hasn't been a career for forty years. (obviously, it's now family heirloom status)

My views are precisely two twin engine models old, do with them what you wish. First, twins get attention. More than any other model I've had. Maiden it when its quiet, unless you like an audience! Also, twins with electric power seem like cheating 🙃 Thrust angles: Dead ahead works. Some right thrust on the right engine also works. Don't overthink it. It's not a deal breaker as far as I can tell. If you have counter rotating props, the funny thrust angles argument vanishes in a puff of (magic?) smoke. Downthrust, do whatever you do normally. I use a degree or two, but, that works for my specific models. What are you building?

3S2200 lipo on my starter, works ok. On a 10cc 2 stroke and upwards, you need the prop turned back as Paul says, but is otherwise perfectly ok, and I'd rather not hit the engine with a starter that has "way too much" TBH. I like an electric fuel pump, I'm lazy. Mine's on a 3s1000. My glow driver is a home made widget that runs from the same 3s lipo. Manual pumps also work. Plugs fail with age - take a spare, and a plug spanner to change it with. You don't need heaps of kit. A well adjusted engine starts quite easily, or, there is something wrong that probably needs a workshop/bench/kitchen-table environment to investigate and fix. That said, don't forget something to clean your toy with after you finish playing with it. Lastly, castor oil, if you say the word three times, Jon of Laser Engines will appear in your workshop and remove all your fuel.

You could switch to veneer for wing sheeting... it might need some sort of semi-solid substrate... maybe lightweight bead foam... (reinventing the wheel department) balsa cabin are listing poplar veneer for under £8 a sheet of decent size - 15" x 60"... that's heaps cheaper than balsa

When I was small, I wanted to do the "RM Flight Training Course"... although I ended up learning on a Precedent Flyboy, Junior 60 and then an aerobatic trainer I cannot remember the name of. Many moons later I finally built the pair... Part 1... RM Trainer (and sheep): Part 2... RM Aerobat: Both electrified on 4S 2200, 300W and 400W respectively. The Aerobat is lightly modified (mainly style - I made the deck a little more rounded, and moved the tailplane upwards a couple of inches).

If it's built up, it might be a lighter model... 😈

Just pulling a random WW2 example, Hurricane, the elevator was an appropriately sized metal torque tube - able by itself to resist the twisting forces it would experience when the elevator was moved, and tapered metal ribs, which I believe were capped (which would then form an I beam structure, and also aid in resisting racking and warping) were attached. I'd imagine this had some degree of analysis applied. Note, there are loads on an elevator, just like every other part of an airframe, your statement that it is not a load bearing structure is not true. A slab of balsa is an easy route to making something that works for us. It is, "good enough". Is there better for a particular application? Sure.

Wings are quite long and thin, so maybe the skin having a grain oriented in the direction of the longest measurement is quite useful. We wouldn't run the grain fore and aft, for instance, as it would leave all the spanwise strength to the spar structure. With the skin grain spanwise, it can contribute more usefully to the whole structure.

Required twist resistance will be linked to, I think - * Maximum speed (where flutter might be an issue) * Aileron deflection (3d? regular sport aerobat? stooging-around-scale-like-performance?) Horses for courses, as usual. Some models want lots of torsional rigidity, some not so much.

A few more shots of where I am up to with the business end of the inner tailplane workings. Snake entry into pocket... ...and the other side of the tailplane... ...and a different angle, now with sheeting on both sides (well, except for the ply insert) ... ...with that (nearly) done, time to put the tailplane itself down and make some fins and rudders. The above process actually took quite a long time - the few working prototypes I made didn't come for free (sadly). I also spent a bit of time playing with the dimensions of the tailplane to find out what the widest curve I could get for the snakes was. This was a case of balancing off the span and chord of the tailplane, and a bit of suck-it-and-see to find out what curve would fit. In the end, I think I wound up with about a 6" radius in the snake, and the tailplane itself is about 20" in span. As I'm shooting for ~150 sq in on the total tailplane/elevator area, that gives 7-1/2" average chord, of which around 1-1/2" will be elevator, leaving 6" chord on the tailplane... Hence the "about 6" radius" on the snake itself...