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

What is that made of and how assembled ?

It is made of steel tube, only a guess but probably chromoly. I would assume they are made in a jig, cant imagine any other way?

A steel tube 'space frame'.
A common form of fuselage construction.Particularly during the inter war years.
First used for volume production by Fokker in WW1
The jigs can be made as simple or complex as the volume of production requires. Piper made 19,000 Cubs!

Thanks chaps just wasn't sure if it was just a mock up

I have been pondering how to "bulk up" the carbon uprights as they are far from scale diameter. slipping sections of plastic sleeve was tried and nothing really seemed to work, eventually I resorted back to using balsa. So 1/16 square was rounded using sandpaper and a channel filed along one side, just deep enough to take the carbon rod. The balsa was than attached using balsa cement and looks about right.....








I think I will see if I can do the cockpit ceiling tubing next while I am on a roll....

Added the top cross bracing, this is carbon as I may as well use it as opposed to messing with thin carbon and balsa cladding. Stronger than I need granted but there we go.





The rear fus upper formers have been added, they all seemed to want to go wonky on me.... ah well hopefuly not too visible when it is covered in Yellow Esaki.

No idea what will happen around the rear yet, better make the tail surfaces and see if anything springs to mind. I am going to laminate 3 strips 1/32 over an mdf former, using amonia. Not sure what glue to use to do the laminating, tempted with thinned pva, any thoughts?

Cheers
Danny

Thinned PVA should work fine Septic, but don't thin it too much depending on how wet the wood is when you glue it. Also, I'd try bending it around the form after steaming or soaking it in just boiling water first. If that doesn't work, then go for the ammonia treatment.

Soaking the wood then bending it around a hot 'shoe', such as a large soldering iron, also works well for forming balsa. The other 'trick' is to bend it over half a tin can formed into a cone and supported over a couple of candles - it worked quite well for Doug McHard, who reckoned he could form sheet balsa into a complex curve using such a method. So if he can do it, so can you!

Another type of hot shoe is a tube held in a vice at one end and solid bar ( iron is one material used for this ) the bar is heated and slid into the tube and the wood is then bent around the tube. Re- heating the bar as required .Overkill for small balsa models but maybe handy for bigger stuff ( Ply,Spruce ,etc )

Titebond III

Tried Andy's method for laminating balsa into a curved section and couldn't get on with the "elstoplast" technique, I found I was all fingers and thumbs, and the tape kept lifting, I don't know why... I dropped into plan "B" the pinned technique, this worked very well. First I stripped some soft 1/8 balsa into 1/32nd strips with my Kavan stripper.
Wetted three pieces of wood, let it soak for a couple of minutes then formed the first against the former and pinned it. Then I ran glue along the next and starting at one end removed one pin, layed in the next piece and moved the pin to be outside of the two strips. Worked my way around the curve until both strips were pinned snugly against the former. I then repeated the process with a third strip.










Just need to let it all dry now.


And yes I did rectify the error in the third pic

Cheers
Danny

Looks good to me Danny....it's one of those 'whatever works for you' type jobs!

Might be worth considering adding a dummy strip to the outside of the form for the next one, to stop the indents from the pins affecting the outer strip. It's also worth making the formers longer than required so that the ends of the form you're making blends into the part that it will eventually join. However, as said above, it looks good to me!

if forum members are puzzled by the reference to 'elastoplasts', it was a method I suggested in private to Danny last night that's detailed in my Westland Woodpigeon thread here:

www.aeromodellers.co.uk/forum/free-fligh...n?limitstart=0#59414

Hi Andy, good point about the pins marking the outer strip and adding an additional layer is a good one.
I have the rudder to do next so will try the extra on that, it can always be sanded away later.

I do have a slight problem in that the edge is about an 1/8th thick, so some careful sanding will need to be done to bring it down to the 3/32 thickness that I want

But good technique, and thanks for pushing me into using it Andy

Cheers
Danny

The problem I find using pins is that they leave little dings that can be a nightmare to remove when using only 2 or 3 laminations

I now prefer to use small blocks to hold the shape, in the past I have even used a male and female template but I found this method cumbersome and not very effective as there was no guarantee that I could get even pressure to guarantee a good join

Like this.. Used on my Peter Russell STOL








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