Winter build project: Wolfgang Matt’s ATLAS

If you read the thread title you'll see that no building is allowed until the end of autumn.

Poor excuse Mike

Give us a break, Buildingpete, 'aven't even got the plans yet.

Well I guess a good starting point is working out what wood is required, now there is a plan.

Mike was telling me that in the olden (some would say golden) days there was no such thing as lite plywood, and so the Atlas plans only stipulate the use of 'plywood', can I or should I use lite plywood in any of the construction of the plane, or is it best to stick with birch ply as would have been originally used?

With regards to balsa, you can get three densities; light, medium and hard, I assume we want light for most things, but what about the tail fin and rudder? Also is there any where I should be using C grain/cut Balsa?

Is 'contest' balsa a super light balsa, I've found info on A, B & C cuts, but not contest sheet.

Thanks

To my other conspirators in this little project, could you have a look at the vertical stabiliser on the plans and on the PDF at the beginning of this thread, the PDF seems to show the vertical stabiliser extends into the fuselage (section view H-H & I-I), where as the paper plans seem to show it just stuck on top, I assume it does extend into the fuselage and that it is taken for granted that the builder would know this?

The plans also suggest two ways of building up the vertical stabiliser, either with 15mm balsa or 1/8" core and 1/4" either side, would I be right in saying the second option is the way to go and that the grain orientation of the core should be at 90º to the 1/4" sheeting.

Sorry for all of the questions

I've just had another look at the plan and the construction is going to be very similar to the Blue Angel (BA). Here's what I did regarding the ply:

F1 - 2mm ply - yes
F2 - 5mm ply - probably OK. BA used 6.5mm ply since it holds the motor in place and my only other option was 4mm, which is too light to hold a 1.5kW motor in place
F2a - I omitted this part in the BA because my retracts were bolted to the fuel tank floor, not a vertical bulkhead.
F3 - 5mm ply - OK. BA used 4mm since this is what I had
F2b and F3a - 1.5mm ply. This will be fine, but I will use 2.5mm liteply since it will sand and not leave an edge showing against the balsa
F4 - I omitted this part in the BA. Not sure what purpose it serves.
F5 - 4mm ply - yes
F6 - 3mm ply - Fine, but I will use liteply since it cuts easier
F7 - 2mm ply - OK, but I'll use litelpy since it will sand easier and not leave an edge showing against the balsa
F8 - ditto

The fuselage double will be fine with ply, but I'll use liteply since it cuts and sands to shape easier.
I'll use 6.5mm ply with lightening holes for the fuel tank floor since this will take the nosewheel retract.
4mm ply facing for the leading edge of the wing is what I used on the BA
I used 2.5mm liteply for the trailing edge facing.
I used 6.5mm ply for the retract bearers in the wing.

I placed an order for all the BA wood at balsa cabin. All of it was light balsa. I did use c-grain for the fuselage sides, not because it carves easier, but because it pulls in at the tail without twisting. But this is just a preference and I'm sure others will scoff at this idea.
I ordered aileron stock for the ailerons and the rear-end of the rudder and elevators. The front of the rudder/elevators was then soft block balsa sanded down to the triangular sections. The advantage of this is that most of the surface is light but the thin trailing edge is harder and warp-free.

I'll sit down and make up an order for Balsa Cabin tomorrow. I mentioned to Steve on Sunday that it would be interesting to see if we all end up with similar orders or not?