Czmelak building

[kjkavaney]

BUMMED....the Czmelak plans for the horizontal stab show the rear of the ribs gets a 1/8" x 1/4" balsa sub rib, top and bottom according to the plans...only AFTER all the glue is dry did I discover Pete had put in the kit, two pieces of Spruce....1/8" x 1/4" labeled " stab rear spar"... long enough to cover the whole stab...... other builders...do NOT Make this same mistake...my stab is now obviously weak, so I plan to add some 1/8" balsa shear webs all along the back part of the horizontal stab to try to make up for the lack of a Spruce rear spar....

My Bad..I should have made a better effort to inventory everything before I started gluing.

[ARUP]

Can you just layer some CF tow with epoxy both sides where the spar is located?

[kjkavaney]

Thanks Mike...the area is very big...I think the shear webs will likely tie things together better than carbon tow...I know you can't see the design with OUT the plans, but the height is about one inch and 2.5 inches across...for each bay and there are 20 of them....no biggie but it will take forever cutting each shear web by hand and fitting them...each will be a tad different width...
Had I spotted the labeled Spruce pieces, I would already be done with all this part of the building......I guess I am the pioneer out there in front making all these mistakes so those that follow will be spared the mess ups I am making...be sure to check labeled parts versus the plans...they sometimes do NOT agree.

I was hoping I would be spared the scratch building I had to do on the 108% Pegasus....but this one is turning into some scratch building as well...

[kjkavaney]

Have been stumped with how I was going to sheet the vertical stab since I can't use CA...how could I get the sheeting to turn 90 degrees with glue that takes an hour to set up ??
I decided to try adding 3/8" triangle stock and will put a bevel on the front of the sheeting which is 1/8 " balsa that covers the whole width of the stab...I will wait till I can get help to do this..Tim lives an hour away but will try to rope him into helping on this part of the build..
once this is all set up, will of course round off the LE..

[Tango Juliet]

That should work just fine. I think if it were me, I'd apply the sheeting first to the edge as you have it in the second photo, then sand the whole leading edge flat before gluing on the triangle stock. Rather than putting on the triangle stock first and trying to butt the sheeting to it.

[jfrickie]

Apply the Titebond or whatever glue you are using to both surfaces and let it dry and then position the part and iron it down with a hot iron. Worked great on a plane I'm building...

[kjkavaney]

Too late..the triangle stock is already glued in place...but I think your idea is a better one...the sheeting is actually about 8 inches front to back and all the way across the vertical stab so it will be a handful to keep it in place while praying the glue sets up in the right way..

[kjkavaney]

HOw to NOT do this...I was fearful that the leading edge of the stab sheeting would NOT stay in place once I started gluing and bending the sheeting, so I chose to glue 3/8" triangle stock to the LE so the sheeting would have something to butt up against...i glued just the front edge of the balsa sheeting and let it dry..I followed Jim Frickies advice on using titebond ahead of time and then using heat iron to stick down the sheeting. At first I was moving all around the sheeting much like one would if putting on Ultra coat...did absolutely nothing...then I began to hold the iron for many seconds directly over the ribs on top of the sheeting. I used a Kevlar glove to hold the area of wood till it cooled down to try to maintain the glue joint....to get the sheeting to bend I sprayed water on it...I did NOT appreciate how much that wood expands when wet..yes it curled but when I ironed the sheeting down, it was now too long and I was left with gaps between the ribs and the sheeting...
I was convinced that the sheeting was not wide enough to reach the LE in the way I thought it needed to do...again with adding water it would have. Tango had the right idea and I should have
started at the back of the spar and back edge of the sheeting and worked my way forward so the wood could expand or contract as needed and not be boxed in. I spent about another hour heating up the entire LE area hoping the heat would constrict the balsa sheeting and it seems like it did...I re glued the ribs from below the sheeting...I am tempted to sand off the whole triangle stock before doing the bottom and do it the way Tango suggested...worst case scenario a bit of epoxy and micro balloons if I end up with a gap at the LE...

elevators are done...soon onto the wings...servos on order...

[Tango Juliet]

It's all part of the learning process. I'll bet you never try to do it that way again.

[lenb]

Kevin.
The process for sheeting something like this is to start at the spar, or wherever the sheeting ends, then roll it forward along the ribs. Let the excess overhang the LE And sand it off later.
Another great trick is to soak it with either vinegar or amonia and use a hot iron to roll it down. IT will holds its shape

len

[kjkavaney]

I tried Jim Frickie's method and that seemed to work well. However, I should have trusted my belief that the sheeting was too narrow....I think maybe a more experienced builder would have started the
1/8" sheeting half way across the spar...not completely covering it...could make up that lack of covering with the cap strips that glue on next...you can see from the closeup that the sheeting just made it to the LE but not enough over hang to complete the curve...

I raced with aggressive taping to keep the glue joints closed at the LE while the glue was still setting up.

I've finally come to terms that there are a thousand ways to build a kit...a few ways are optimal, but in the end it still becomes scratch building to a point. I messed up on Elevators and had the plywood ribs in the wrong place so I just made more plywood ribs and glued them in places where I thought strength was paramount...I am fighting my instinct to build STRONG....my mentors keep telling me: build it just strong enough"

Pretty soon will start the wings once the horizontal Stab is done...

kevin

[lenb]

FYI Kevin,
The stabs I built for mine are balsa rear spar and they're plenty strong.
This plane does not need to be built any stronger. Excess strength mean one thing... WEIGHT

[Mosquito]

Keep going on it Kevin. Once hunting season ends here in the Midwest, I can offer you some help with CA gluing etc.

[ARUP]

Build it like Colin Chapman would build his famous cars but just a wee bit stronger! He is rumored to say the car should be strong enough to fall apart from wear and tear just after it crossed the finish line in first place! Well... we want your tow plane to be a first place winner but to keep on keepin' on! Don't be tempted to build a brick.

[kjkavaney]

HELP....I am confused...you can see that my elevators are wider than my horizontal stab. I did not miss any ribs. my horizontal stab is about 1/4 inch narrow on each side compared to the plans...the elevators a a smidge wider than the plans show...the last laser cut hole for a robart hinge will not even be with in the stab's dimensions.

Pictures I took of Pete's plane in September show the elevators and the horizontal stab to be flush on the sides ...

Obviously I can glue some balsa side pieces onto the stab make things equal but this seems weird to me and I am not ready to glue anymore until I can get some clarity..
I have already drilled another hole more inboard for the last Robart hinge ...

[lenb]

Kevin,

I ran into this initially too, and then realized it was because I had the pieces mixed up, after flipping things around and mixing them up I was able to get everything to line up. Of course I did all this before glueing anything together.
I would just glue on some fillers and move forward. It's a model airplane and its modeling. Do what you need to make it all fit together.

[kjkavaney]

Thanks Len...will do as you say...heck I am used to scratch building but got confused when nothing was lining up...I DID flip things around but I was never any good at Rubix cube or whatever so must have not landed on the right combination...
LE glued on and shaped today...just do the hinge facing and onto the wings next...any pointer there ??
kevin

[lenb]

yes,
Spend time with the plywood angle joiner. Test stack all the pieces and be sure what the next step is before completing the first step.
The two joiners must be identical. The more time and patience you spend now will pay off when you join the panels.
Its really fun to build the wings. I've built a lot of planes over the years, these wings were the most enjoyable I've done.