Sparky 2X Speed 400

[Konrad]

That's coming on well Konrad.

I agree with your comments on the use of masking tape and sanding bars.

Masking tape must be the unsung hero of the modeller's tools. masking for paint or sanding as you are doing here, temporary support and jigs, surface for adding alignment marks etc.

I also use as sanding bar or trammel sander a lot. Sanding bars are particularly useful when working on straight tapered wings or geodetic - angled ribs. I use finished ribs at the root and tip and blanks in between. Tape over the root and tip ribs provides protection while trammel sanding the blanks to shape using the sanding bar riding on the root and tip ribs.

John

That is becoming a lost art, being able to loft the intermediate ribs between the tip and root ribs.

[Jmk89]

That's coming on well Konrad.


Masking tape must be the unsung hero of the modeller's tools. masking for paint or sanding as you are doing here, temporary support and jigs, surface for adding alignment marks etc.

Another good use is instead of double-sided tape - stick masking tape to both surfaces you want to attach temporarily; then put a few dots of CA on one of the masking tape backs and put the two pieces together with the masking tape strips back to back.  The CA glues the masking tape strips together but you can peel the tape off the pieces when you've finished.  Often much easier than using double-sided tape.  Also you can make law-tack  tape just by using low-tack masking tape!

[Konrad]

Now we come to one of the reasons I put this aside for 3 years. I found that the fin mounting was inadequate with only 1/16 pins going across the joint. I hate butt joints and try to avoid them. Also there is no purchase for the stab covering on ether side of the fin. This will make repairs on the stab difficult to recover. I have yet to redesign the 1/4 center rib and rudder structure to allow for proper mounting of the fin.

[Konrad]

Here I'm starting to build the structure that holds all the parts together, the fuselage.

This is a ladder type construction. I was shocked at just how large a building area I needed. In fact I'm build on the diagonal and still have some overhang I have to deal with. Another surprise was just how fast this fuselage is eating up the 3/16 square strips!

I'm also practicing the old technique of building the the second side over the first side. This is claimed to make identical sides, as the pins are placed in the same location for both sides. I find that in reality this is a false assumption as the stresses in the longerons vary drastically between the pieces of wood.  In the end I have to heat (steam) the sides and manually manipulate the ladders to get identical sides prior to moving the fuselage build into the 3rd dimension.

Not sure if shows up, but I'm changing the decalage as I fail to understand why the incidence of the stab (Datumed from the wing) is negative with a lifting airfoil. Here I lowered the aft end ot the stab 5mm (over 3/16").You might recall that the purpose of the stab is to provide a force counter the pitch moment of the airfoil. This lifing stab a force arrangement I don't understand. Heck most full size transport aircraft have the stab's airfoil "upside down".

With this Sparky and my Benny Boxcar a lot of this force to counter the wing is provided by a very aft CG. This results in an aircraft that is very speed sensitive in pitch.

[Konrad]

This isn't to just show my poor joinery. Rather I want to show what I do to improve the joint and at the same time improve the prep for the covering.

The first photo shows how mis-matched the side are as I pull them off the building board. Some of this is just poor craftsmanship but most of this is as a result of the different stresses in the wood.
I will be making slight adjustment to the ladder structure and steaming the ladders in an effort to make matched sides. I really have to say that the kitchen is often the best room for hobby work as it has both water and heat. (You might be hearing the wife steaming  mad in the back ground!) I've learned that an induction hot plate is near perfect for a source of steam . This is because there is little radiant heat that might burn the structure.

There is often a glue web often left behind against the parting film (Saran wrap) that offers no strength. It does have a bit of mass and can at times be seen distorting the covering. I remove this web with the tip of a number 11 blade. I then come back with some glue to make a full depth glue fillet. A proper fillet can add strength.  One needs to be careful with the fillets to make sure they don't interfere with the bulkheads to be added later.

[OZPAF]

I will be making slight adjustment to the ladder structure and steaming the ladders in an effort to make matched sides.

I have had similar issues in the past but now prefer to select matching strips for the longerons and also soak them in hot water and pin them to the curve before adding the uprights etc, leaving them to dry for at least a day.

John