Winter build project: Wolfgang Matt’s ATLAS

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?

I must need new glasses, because I can't see section HH or II. However, the vertical stab and the block at the base, were just butt jointed on the BA. Plenty strong enough unless you cartwheel it, in which case you've probably got more to worry about than a broken fin.

As for the single 15mm or laminated 1/4 1/8 1/4...I'll probably go for a single soft sheet in order to eliminate glue lines. A sheet that thick will be warp-resistant, IMHO.

And you asked about contest grade balsa. All you're getting with contest grade is someone sorting through the pile of light balsa and hand-picking the lightest pieces. It might have been worth it years ago, but the quality of light balsa from Balsa Cabin is good enough to not bother with paying the premium, IMHO.

MikeSeale wrote: .... Plenty strong enough unless you cartwheel it, in which case you've probably got more to worry about than a broken fin.

You've seen my landings haven't you?

Thanks for the details regarding what you did on the Blue Angel, and intend to do on the Atlas. I'll start work on a wood list, but maybe once I've done it I could look at yours before I order just in case I missed something.

Here is H-H and I-I:

I still can't see where you're getting the sections from. The only pdf at the start of the thread is the RCM&E article and the sections you show must come from a kit with numbered parts.

Once the fuselage rear end is nearing completion it will become clearer whether it is necessary to let the fin drop all the way to the top of the tailplane or just go with a butt joint on top. It might be necessary to drop a shaped piece of 15mm balsa into the gap between the numbered pieces 34 in order to sand it to shape. Than remove the infill and replace it with the real fin. You certainly can't sand 34 to shape if the fin is already there.

Hi Mike,

The original Outerzone link in the first post no longer works! so here is the new link:

www.outerzone.co.uk/plan_details.asp?ID=5517

This is the PDF plan we were originally looking at before I got the RCME plan. Sorry for any confusion.

Plenty of time to decide what to do at the tail end.

As for F4, I've worked out that it probably serves to stop the fuselage sides bowing out between F3 and F5 when you pull in the rear fuselage sides. I didn't use it on the BA, but if you do add it, you might end up removing it after planking the turtle deck in order to make space for the battery and/or servos

Most model designs from early 40s to late 80s were very over designed and ended up fairly heavy due to the materials avaliable. Modern day designs fly soooooo much better using lighter materials thus giving a lighter wing loading.
I am a great fan of using liteply instead of birch ply but with an understaning you are not going to compromise structural integrity.

I've had a look at the plans and made a provisional list for a wood order, and being a metric design some of the sizes have to be approximated and substituted for imperial alternatives.

The wing and tail will be sheeted in 1/16 soft balsa.
I'll make the rudder and elevators using soft aileron stock, 5/16 x 1 1/2, with 1/2 inch soft sheet making up the front part which will be sanded down to the aileron stock.
The ailerons themselves will be 1/2 x 1 1/2 aileron stock cut to size and sanded to shape.
The fuselage sides will be 3/16 c-grain
The top and bottom fuselage sheeting will be 3/8
The fuselage base will be 1/4
The wing and tail leading and trailing edges will be 1/4
The fin will be 1/2
Wing tips will be 1/2
Tail tips will be 3/8
The lower blocks either side of the nose retract will be 1" x 3"
The under wing fairing will be 1/4 with some triangular fillets
The wing dowels will all be 6mm

Excluding the plywood, this gives an order of:

Soft 3" x 36" sheets
20 of 1/16
2 of 1/2
3 of 3/8
4 of 1/4

Soft c-grain 3" x 36" sheets
3 of 3/16

Soft aileron stock
2 of 1/2 x 1 1/2
1 of 5/16 x 1 1/2

Soft block
1 of 1 x 3 x 24

Soft triangular (not sure what size needed)
1 of 1/4 x 1/4
1 of 3/8 x 3/8

Birch dowel
1 of 6mm

Hope this helps

I made a start on it last night, but half way through realised I was working out what wood was needed to build it, rather than simply using the standard sizes balsa comes in and working out how many sheets are required, which is actually quite a bit quicker! So I'm half way though my list, and you've just answered one of my questions, if the plan says 10mm is 3/8" (9.5mm) close enough? Which it appears it is.

Thanks for your list Mike, it has helped, and matches mine except that I've still to work out the wing sheeting and blocks that are needed.

Do I need any triangular stock to brace between the formers and the fuselage sides? Or would that be over building it?