PA-18 Super Cub for the BMFA R/C Scale Indoor Nats

Hi chaps, useful discussion thanks for your thoughts
I have reworked the fuselage drawing to incorporate the carbon rods, and some carbon tissue re-inforcing. I have also made the stringers in the correct position to allow the lower door to be open, should I wish to go that far!!
I am seeing Dylan this weekend, I will ask him if he could cut all those ribs, I could also let him have a sheet of competition grade 1/16 balsa to cut them from




Cheers
Danny

I might be (I am! ) being super picky but doesn't the Super Cub have a slightly under cambered wing section? USA-35b

I haven't seen a reference for the unflapped wing, mind you I havent seen a section for the flapped wing. Of all the plans i looked at they have all used a flat bottom section.
Cheers
Danny

I have chatted to my A/C engineer friend and he is adamant that the wing section is basically a clark Y, and flat bottomed like the Pawnee etc.
On the grounds that I cannot find concrete proof in any direction I am going with the profile used on my three view and that is flat bottomed. I have made the rib height as per the three views.
Andy S has sent me a note suggesting my fus is over engineered and I am thinking like an outdoor modeller :woohoo: So I might have to reduce some parts
Cheers
Danny

Septic
This site tends to be my source for wing sections.
I try to back it up with other references if I can find any.
However the issue with Cub/Super Cub appears to be even more complex in that Piper officially referred to it as "USA 35B mod".
The last post in this forum suggests the modification was to increase the vertical coordinates of 35B by 4% which appears to be referencing a reliable source.
I can find no explanation why Piper did this over the standard USA 35B used on the Taylor craft wing that the Cub evolved from.
Of course apart from the slight under camber the USA 35B and Clark Y are very similar and I would suggest completely unnoticeable at the scale of indoor RC.

My only reason for raising the topic of wing sections would be to allow you to impress the judges (or maybe not!) on the level of its detail accuracy.

Well I am really impressed with your tenacity in finding the facts, and as you say it is USA 35B modified with the 4%. I will try and break it to my engineer friend gently
I will needless to say not do the undercamber bit, as i doubt you would really even see it at the scale i am working too

Thanks again for your help much appreciated

Cheers
Danny

Well take 4,279........
the final ribs, using USA35B




Cheers
Danny

Hi ! See you went for true scale in the end .However I stood under one displayed in flight attitude.I never noticed any undercamber so I'm sure it won't be noticed at that size. However well done so far. :woohoo: :whistle: ::

I reserve the right to not always follow a suggestion, but in this case what the heck, I couldn't resist the challenge
Cheers
Danny

I hope you intend to sand off all those little steps in the section! :lol:

Of course i will

I too have been looking at full size photos on the net to see if the 'bulge' was noticeable in the fabric between the ribs due to the under camber. So far it doesn't show, indeed it looks very flat!
What it does show is the washout!

Oooo great pic thanks for that

It is really wonderful to have sucha wealth of expertise helping here thanks for that. If anybody has any profile or plan pics of a Super cub/L-18 (Must be the greenhouse version) then please stick it on here. My docs are not complete yet

Thought I would start with the fuselage formers:

I am sure this is all old hat for you guys but just in case. Vertical lines are drawn up from the profile view, where I want bulkheads. These lines are reflected in my 45 degree reference line to draw horizontal lines across the fus on my plan view showing the bulkhead position there.

I draw a reference line under the profile view and I transfer a line showing the bottom, the datum and the top boundaries of the bulkhead. The lines are referenced to the datum. Then you draw lines showing the width of the bulkheads on the plan view, where the bulkheads are. These lines are then also transfered to the datum under the profile view. This will give us what I call bounding boxes. These boxes are the maximum outside size of the bulkheads. Hopefully that will become clearer when I draw them in tomorrow.







Does that make any sense at all?

Cheers
Danny

A word of caution, Septic.

This type of aircraft is normally regulated by the Light Aircraft Association (ex-Popular Flying Association). Owners are allowed to make whatever changes they see fit provided that they are 'signed-off' as fit-to-fly by the local LAA inspector or for major changes, the LAA Engineering Department. As a consequence, no two aircraft are the same.

As the model is being built for competition, a look at the rules before you make any design decisions is essential.

During static judging, the judges will compare the model to the photographs you have of the subject aircraft. So, even if your photographs are limited, make sure that whatever you do matches the photographs you have, especially if you decide on adding something that is found on a different subject aircraft.