SunDevilPilot

Last one showing the Balsa USA build.

Will be posting more as the build continues.

SunDevilPilot

Zor

I found this thread interesting because _ _ _

I was at the local airport last Saturday and some fellows are converting a full size J3 into a full size Super Cub.

Zor

SunDevilPilot

Not a whole lot to report but I am making progress on the cockpit supports.

I really didn't like how the Balsa USA Cub's supports attached to the cockpit area of the fuselage so I redesigned it for my model. Here is what I came up with for the lower portion. The rods extend 90% the way through the mounting bracket which is drilled to accept the rod. The part is not yet glued in.


SunDevilPilot

do335a

Very simple mod and looks to be far superior to your earlier pic of the BUSA build.

Now those braces will never come out.

SunDevilPilot

Been a little too hot in the garage to be working on the Cub but I did manage to get the cabin wires installed.

I decided it would be best to install the guide tube, or at least the hole in the fiewall, for the throttle linkage prior to sheeting over the cockpit. I was thinking of going with a cable for the throttle instead of a traditional solid rod. My hopes are the return spring on the carb will be enough to keep the cable tight and the throttle constant even when using a thin cable such as Pull-Pull style cable. The ends will be a ball link style clevis. I have already checked and with the arm the way I have it on the carbs throttle shaft the servo will pull the throttle to open it instead of pushing it. I want to have the throttle cable curve down from the firewall and run under the door on the planes right side and a small flexible cable would be perfect. I have never tried a setup such as I am describing but my leaf blower has a similar setup and the throttle adjusts perfect. What do you all think?

FYI: My DA50 still has the return spring on the carb which had been no problem in over two years of service.

SunDevilPilot

resin

My Feedback: (2)

In regards to your throttle set-up, I have used a similar set-up in my Zenoah gas power hydroplane. As a matter of fact, what you described is a common throttle linkage set-up for gas powered boats. You want to make sure you don't have too tight of a cable turn, sufficient return spring pull, lube your cable with light dry lube such as the type locksmiths use, NOT WD-40! Once your set-up has been installed test your system before going too far in securing all your linkage, and always do a double check on ALL your linkage. Don't be afraid to use a good reliable high torque type servo. You certainly can't afford to have a sticky throttle in a full open open position! In other words, make sure you don't duplicate a poorly design automotive type throttle linkage system!

I'm impressed you all your nicely done work. How about enclosing a small work section in your garage, and install an A/C in your work area. I've done that, and often my work area is the coolest place in my entire home.

Keith

SunDevilPilot

Thanks for the info about throttle setup on boats...I never thought about looking there. I found an example of what I plan on doing in a "Gas Outboard" thread in the RC Boat forums...Here are some photos of what I plan on doing. I won't need a bracket as the firewall serves this purpose.

The linkage will be a ball link and not the EZ-Keeper as shown in the photos, I never really trusted that style of linkage.

SunDevilPilot

resin

My Feedback: (2)

In a past throttle linkage set-up, I installed a modified throttle return spring. I had to because, I reworked my crab so I could change it's original mounting position, in doing so I installed a stronger throttle return spring, which meant installing a high torque throttle servo. For fight safety reasons, I would also suggest doing a dry radio flight operation at home the night before gong to the flying flied, Check all flight linkages at home, and not wait until at your model field. This will give you an opportunity to assure your flight system is ready long before loading up for the flight field. I'm sure you'll find a suitable way to install your throttle cable. Also be sure to protect your servo from fuel, and vibration. I would imagine boats would subject their radio gear to maybe more extreme radio conditions than most model planes. Boat generate a tremendous amount of constant vibration due to their normal engine vibration, the continuous pounding of the hull as it races across the water, and the intaking of unwanted water around it's radio gear. Model planes experience their share of flight problems, but a water craft always present a few additional challenges, maybe more than most plane.

Your photos do show how a boat modeler did solve his cable linkage problem. I hope you will consider in your posting the cable solution. This might be a great value to other engine installations.

Happy Father's Day to all the Great DADS!!!!

Keith

SunDevilPilot

Checked my supply an unfortunately I don't have any more tubing to run the throttle, and because I didn't want to waste the morning, I decided to finish up the window frames. The rear curved frame started as a block of wood that had the shape ink printed on it. Few minutes at the scroll saw and the drill press with a barrel sander installed made quick work of the cutting /shaping. The remainder of the framing was 1/2 by 1/4 stock cut to length then sanded flush with the fuselage side after drying in place.

I will post the throttle setup once I start it. I plan on only having some guide tubing on the forward portion of the cabin. From the door back the cable will be out of any tubing. Should operate similar to a pull-pull rudder with the exception of the spring being the other cable. Time will tell.....

The marks for the throttle cable guide tube can be seen on the edge of the firewall. Will be installed once I get the tubing.

SunDevilPilot

SunDevilPilot

Another Angle....

SunDevilPilot

Last of set....

SunDevilPilot

Here is the guide tube I installed for the throttle linkage. The tube is glued in but the linkage is just loosely attached for testing only. This method of using the carb's return spring inherent to walbro carbs and the small gauge (Flexible) cable seems to function properly and goes smoothly from full closed to full open. I have never tried to set-up the throttle in this way but from what I can tell it should work pretty well. I would have preferred a direct link via a carbon rod but due to the shape of the fuselage, and because I don't want a rod going across the door, I had no choice. There will be a cable running along the fuselage just below the door to the servo but this was acceptable.

The throttle cable will continue aft until it is connected to a servo mounted just rear of the door.

Now that this is done I can cover up the upper and lower portions of the forward fuselage. Once that is done the fuselage is almost complete and I can move onto the tail feathers.

SunDevilPilot

SunDevilPilot

Second Photo:

SunDevilPilot

The Carb Side:

(I will use a different bolt and lock nut on the ball joint when the final installation is done, the one shown is the only one I had that fit at the time I took the photo)

do335a

The throttle linkage looks nice.

I use a similar system on my G-62, except that at the carb I've put the ball link on top of the throttle arm. In your case, it looks as though the bolt is a tad long. If that's the case, you'll have a devil of a time getting the ball link off, since the bolt will not be able to drop out. Of course, a shorter bolt would be a good solution when you do replace it.

SunDevilPilot

Hopefully it all works.... The bolt shown in the picture is the only one I had in metric. The throttle arm is from a helicopter so I need to purchase a smaller allen key style bolt for the linkage. I am not leaving the long philips head style bolt in there as it was just to test the setup. I decided to put the ball on the bottom because I thought it would help reduce the torque on the arm itself. By lowering the ball the tendency to pull arm over instead of just rotating it is reduced.

The bolt does look a little cheesy so fear not, it will be a proper fastener when I do the final installation.

SunDevilPilot

Flytoolow

My Feedback: (17)

Can you put the linkage on top with the bolt going down? it may be harder to do, but gravity will always win if something happens...

SunDevilPilot

I could put the ball link on either side but when the ball is on the bottom there is far less stress on the arm. When the final installation is done the bolt will have lock-tight and a nylon insert nut keeping it in place. I am not concerned about the linkage coming loose. Remember.......The photos are just the test and not the final installation. A long road of building and painting ahead before I install the motor again.

If you really look close at the carb photo you can see the cable is not even crimped. I simply bent it over itself to conduct the test..

The point of todays exercise was to get the guide tube installed and test the carb's function. The motor is no longer on the plane.

SunDevilPilot

SunDevilPilot

In preparation for closing in the dash / forward fuselage I fiberglassed the sides and bottom of the firewalls interior. With the fiberglass tape and the dowel pins on the sides I am confident the firewall will never come loose. I also took the opportunity to add a few rails on the fuselage sides, where the bottom edge of the forward sheeting will meet with the sides. I added them as a gluing surface and to prevent the possibility of the dash coming undone.

The upper sheeting is 1/8" thick and I believe that will be difficult to bend around the dash without cracking. So....I plan on sheeting the forward fuselage with two layers of 1/16th balsa sheeting. I will add the first layer, allow it to dry, then add the second layer locking in the curve. I need to stop at the Hobby Shop tomorrow and purchase some more balsa to continue.

Some of you may have noticed a slowdown in the progress of this plane. A new house, the loss of my building table (Wife got a new kitchen table deemed off limits to building!), and the summer heat in the garage. Hopefully things will accelerate coming this Thursday. The base for my Maple Top building table arrives Thursday. After that I can build and not have to clean off the table at the conclusion of each step.

SunDevilPilot

SunDevilPilot

It is a little hard to see in the photo but I was trying to photograph the fiberglass tape on the lower portion of the firewall.

SunDevilPilot

SunDevilPilot

Got the first layer of sheeting put on the nose. The 1/16th balsa was easy to bend and almost went around the curve itself when I wet it just prior to bending. To install the sheeting I cut each half to roughly the correct side, added a notch for the cabin wires, and glued it to the centerline. After the initial glue on the centerline dried I used a micro-plane and a sanding bar to get the lower edge of the sheeting to match up with the top of the fuselage side. Was not hard to get perfect but it did take some care. Will do the second layer of sheeting tomorrow.

SunDevilPilot

SunDevilPilot

Another angle...

SunDevilPilot

Close up.

SunDevilPilot

WacoNut

Nice clean work, your Cub is going to look great!!
Anthony

SunDevilPilot

Added the second layer of sheeting to the nose and trimmed it all up. I used wood glue on the edges and CA in the middle. I chose to use some CA because I didn't want to risk the wood warping due to the water in the wood glue. I wanted to use wood glue on the edges because it sands much better than CA.

The only parts left to build on the fuselage is the side stringers and the lower floor on the nose.

Because the nose of the fuselage was more or less stable due to the sheeting I decided to remove the brace still present in the door. Was happy to see no shifting when the brace was removed and the forward cabin area seem extremely resistant to twist. Looks like my solution to the forward fuselage is going to work.

SunDevilPilot