Chapter 13 - Section 9

Piping the Pitot & Static System

Pitot Tube at the Nose

The pitot tube per the drawing construction method is pretty flimsy and I prefer a more beefy one. There were plenty of discussion on the Cozy Forum regarding alternatives. I liked the one Wayne Hicks used and I ended up getting the same from Aircraft Spruce ($27). I marked the pitot tube extension location at the nose carefully with my lasers and opened it up with a drill and Dremel grinding wheel. Since the pitot tube is husky and I plan to extend the tube out the nose by 1 1/2" only, I see no reason to make it removable. Hence, I put a groove onto NG-31 such that I can seat and flox the pitot tube in place. I will eventually have to cut the pitot tube shorter and put a thread at the cut end for the fitting. The picture showed the original pitot tube and the groove on NG-31.

Preparing the Pitot Tubing

I cut the 1/4" aluminum tubing from Aircraft Spruce to 38" & 6" per plan. Then I drilled the necessary holes through F-0 and F-22 and threaded the tubing up hill along the left side wall. The tubing was easy to bend. I just bent it by hand and it hugs along the side wall readily. I had to get a flaring tool (McMaster-Carr) to connect the tubing to the blue fitting. I hope we will be using a lot of tubing down the road because the flaring tool set me back $90+ for one shot ... so far.

Here's a close look of the pitot tube after Jamie cut it to length and threaded it for the fitting. Jamie owns a machine shop close by and he had been providing machining support for us for the past 16 years. I have gained tremendous amount of knowledge in material properties and its machining processes from him - a very talented person. He also helped me with my rudder pedals in Section 6 of the Chapter. You can see Jamie can get a bit artistic with his work sometime ... Note the groves and dimples he added onto the surface for floxing. He even buffed the exposed tip, just for appearance !!!

Pitot tube extending out the center of the nose cone.

Static Port

The 6" aluminum tube cut earlier is for the static port. I pinched one end of the tube with my rivet squeezer (it worked well). I made a simple bending fixture and bent the aluminum tubing to shape.

I had a lot of difficulty clearing all the foam between the glass layers with a drill bit and not going through the outside wall. It looks like I have to put 2/3 of the tube (i.e. 4") inside the foam - I can't see how a drill bit can do that. Matter of fact, I did put a small hole through the outside wall ... I made a small hole digger and it didn't work very well. After hours of struggling with it , I finally gave up. See the top half of the slot?

Instead, I took the Fein tool and cut a strip of the glass out, dug out the foam and was ready to bury the static tube in a matter of 15 minutes. The wider hole at the top part was from the 1/4" drill bit and the lower straight part was from the FEIN tool. See that small hole I put on the outside wall with the tip of my 1/4" drill bit - at the middle?

I marked the pitot tube position on the outside of the fuselage (with the help of a flash light), made some wet and drier micro. I partially filled the cut out with wet micro first, then I inserted the aluminum tube, making sure it is set tightly against the outside wall of the fuselage. Then I sealed the rest of the slot with the drier micro. Once it cures, I patched it up with 2 BIDs of glass and all is well.

Ballast Compartment

According to the plan, the nose cone compartment is used for lead ballasts - to keep the plane's center of gravity (cg) in check. Since I put the landing light in the nose, I need the opening (at NG-31) for replacing / removing the landing light if required. However, I still wanted to make the best use of the remaining space for the ballasts - I need to figure out how I can keep the lead ballast from falling through the hole. In addition I need to figure out how much weight/space I need? A removable 'floor' is required...

I found my answer through Rick Maddy's search engine (Newsletter #84 per Nat Puffer). Based on the weight of Nat's plane and his weight (160 lbs), he showed how he determined the amount of ballast needed for his plane - a total of 24 lbs at the nose. I would expect my plane will be somewhat close to his, but I am about 20 lbs lighter than he is. With a moment arm of 2.5 (per the Newsletter), I need a total of 32 lbs at the nose (its simple calculation if you read the Newsletter).

I also learned that lead is ~0.41 lb / cu. in. The 32 lbs can be in the form of a bag of lead pallets or in a 2" x2"x19.5" block. Since my nose cone door and space would not allow a 20" long block, I just have to make shorter blocks. I cut up a bunch of 2"x2"foam blocks and did a trial fit. The 4 longer blocks are 2"x2"x4" and the shorter ones are 2"x2"x3". I can fit 22" of blocks that equates to ~ 36 lbs of ballast. - giving me a small margin of flexibility - just in case I lose some more weight ... If I add one more 4" at the middle, it will make it 42 lbs of ballast.

As noted above, the removable 'floor' over the landing light access hole consists of two aluminum strips mounted across the landing light access hole. The 3/4" and 1 1/2" wide aluminum strips are being held down by 4 bolts and nut plates built into the NG-31 floor. I had to notch out the wider strip to fit under the L bracket to provide some freedom for the landing light. An alternative is a wire mesh / net of some kind... if I come across something better. If I stay with the aluminum strip approach, I will drill a few holes through the aluminum strips and up through the lead blocks, stick a long threaded bolt through them (vertically) and secure the whole assembly with a wing nut at the top. That will keep them somewhat secure during flight. I also added a nut plate on the top of F-0. This will be used to hold an L bracket, which in turn holds the top end of the threaded bolts for the ballast.

Here's a picture of the pitot tube floxed in place. I also sealed off the hole at F-0 where the aluminum goes through with silicon sealant.