Back to the Bobcat

[Jim Fruit]

Hi Guys:

Sorry for the change in title. I tried to post in the old title and the system would not let me do it. Something about not having posted in the last 120 days. Oh well. It has been a while since I last posted, so I thought I would show you the progress (or lack thereof) to date which consists primarily of the nacelles and landing gear. It is slow work. It took me two weeks of tweeking to get the gear retracting properly. At least she is sitting on the wheels now.

Photo 001 is at the right front quarter, showing the configuration of the nacelle to the wing. The top of the nacelle was accomplished by shaping styrofoam blocks and then covering that with fiberglass. the bottom was done by the more tried and true method of formers and balsa strips to form the shape. After sanding that to shape, it also was glassed for a continuity of finish. I used this hollowed out method for the bottom nacelle because I needed more room for the retracted wheels, ESC's, etc.

Photo 003 is from the left rear quarter, showing how the top portion of the nacelle fits into the wing. Nothing very exciting here.

Photo 004 is lower to show the relative position of the extended landing gear. The gear retracts into the lower nacelle, but not completely. In fact, in the retracted position, the wheel protrudes by approximately 3/4 of its dimension. It makes me wonder why they even made the attempt. In fact, I think I could land the airplane with the gear retracted as long as the motors are shut down (props not turning)!

My next project is a decision of if I should do the two cowls or the cockpit enclosure. Currently I plan to do the cowls with the formers and strips method. However, If I wait long enough that might change to the lost foam method. That is the beauty of scratch building. The cockpit will be done by the pulling of hot plastic method. I have to decide if that will be the entire area or just the compound curved area above the pilot's head that will be hot pulled. That is the beauty of scratch building.

Enough for now.

Jim Fruit

[Will Hinton]

Jim, you are a man after my own heart!  That is looking fantastic!  I forget, what brand gears are you using?

[Jim Fruit]

Thanks, Will. The retracts are E-Flite, 85 degree main gear retracts. Funny thing though, they are super quiet while operating in my hand. But when they are mounted in the plane, they literally yell when operating. Especially when there is a restriction that won't let it go through full range. At that point it stops and gives you three loud electronic "beeps". I suppose the added noise is because I have them hard mounted inside the balsa wood "trumpet" of the nacelle. Maybe I will have to wrap the operating motor in foam rubber to attempt to calm the noise down. It sounds very far from scale. I don't think the judges will like that. These electronic retracts do operate nicely. I think that my favorites, however, are the mechanical retracts that are servo operated. They don't make any noise and can be operated at any speed.

JHF

[Fred Cronenwett]

I have noticed the same thing with the electric retracts I am putting into a AT-6 wing, the Hobby King electric retracts are not as quiet has the E-flite but noise is louder when mounted to the wing. I am not concerned because I don't think the judges will hear it or notice.

Fred

[Dick Pacini]

That looks like the Songbird!  Remember Sky King?

[Jim Fruit]

Fred:

I disagree, since our electrics are so quiet, I think the judges will comment about the noisy retracts. Now I can see how effective the mounting of a small speaker to the inside of the body to simulate real engine noise can be. The whole airplane extends the sound.

Dick:

That is exactly what it is. It will be more recognizable when I get the cowels made and mounted.

JHF

[Avaiojet]

Jim,

You're a world class model builder and I cannot wait to see this Bamboo Bomber, completed.

[Russ Popel]

Jim, you are right about landing with the gear up.My partner and I rebuilt/restored a Cessna Crane ( Canadian name for the Bobcat) in the early 80's and after hundreds of trouble free hours ,he had to land gear up. Only the props suffered, the airframe was unscathed. Although the gear did not retract all the way into the nacelle, there was a significant decrease in drag.

[Jim Fruit]

Russ:

Wow!!

JHF

[Jim Fruit]

Hi guys:

One more belated post:

I wanted to show you a tool that I made to work on the somewhat fragile cowls without holding them in my hands. It allows me to do the rivets, painting, details, etc., while turning the cowls over and doing the other side without smearing the other side. Sort of like some of the paint stands I have seen on this website, only smaller. It is nothing more than 1/4" balsa from the scrap pile. It has a rather extended base for stability. I then drilled the two uprights concentrically with a 1/4" drill. I then placed a long piece of 1/4" aluminum tubing into those holes without gluing it. I then glued a balsa "cross" onto the aluminum tubing that matches the inside dimension of the cowls. I now slide the cowls onto the assembly and can work on all sides of the cowl without touching it by simply rotating the tube. I experimented with the application of some of the first rivets. I used white glue. Even though it is called "white glue", they dried out a harsh orange/yellow. I think I will go back to RC/56. It dries clear.

The cowls are somewhat light in the interest of overall weight. I used three layers of fiberglass and polyester resin. I constructed them by making them by stringers and formers and then covered that with glass. I then removed all of the balsa except for some left in the extreme front for strength. They are somewhat flexible, but I believe they will firm up by the time I add the engines, mounting brackets, etc.

My apologies for this late post, but my Chron's recently put me in the hospital with a bad infection. The infection did a number on my kidneys and now we are fighting to get them back. If we can't get them back, I may have to start a dialysis regimen. The only reason that I mention this is because if I have to go to dialysis, I may not be able to go to any more scale events even if I finish this plane. Rats!

Jim Fruit