Chapter 13 - Section 2

Fabrication of NG-30

In this section, I will be fabricating the side panels (NG-30). I did not follow the plan sequence exactly because some of the alignment requirements can be achieved easier with techniques we learned from previous chapters.

Cutting Out the Foam Pieces

I started out by cutting up a piece of foam large enough for both sides of the NG-30. I glassed one side of the foam panel (4 ply), peel plied and let cure overnight. The next day, I cut the foam panel into 2 equal sides. Then I stacked them on top of each other, glass to glass.

I traced out the shape of NG-30 on a piece of paper from M-10, M11 and M19. I used this as a template and transferred the shape of NG-30 onto the foam using my rolling wheel method. Once transferred, I removed the paper and connected up the indented dots with a thin line marker.

Note the 2 screws I put at strategic locations (through the foam/glass/glass/foam layers) so that I can keep them together without shifting around. Then I cut out the NG-30 set with my band saw - tightly along the lines. This way, both sides of the panel will be exactly the same. While the pair is still in tact, I took a hard block and touched up the imperfections.

Since I am using Jack Welhelmson's electric landing gear, I only needed three holes (on both panels) instead of four holes in one panel and three on the other per plan. However, I have not received Jack's landing gear yet, I decided to hold off drilling the required holes.

Note I also left out the 2 holes for the rudder pedals because I plan on using the hanging rudder pedals instead of the plans pedals.

Fabricating the Doublers

The bill of materials in Chapter 13 did not call out for Birch plywood and I did not have any left from previous chapters. I have to make an extra trip for the plywood. The doublers were straight forward. I cut them up with the table saw and put in the 45o bevels per plan.

Fabricating the Aluminum Insert and Doublers

After I cut up the NG-30 foam/glass layers with my band saw, it wouldn't do much with aluminum. I ended up changing to a new bi-metal blade. Just have to save the old one for fiber glass only. I cut up the aluminum inserts and the doublers with little problem.

The plan called for 45o bevels on the 1/8" aluminum doublers - all 4 sides. I tilted my belt sander table to 45o and sanded the edges of the doublers down to the bevels as required. It turned out nicely - I was actually pleasantly surprised. The only challenge with this approach was - How loooooong can you hang onto the doublers before your fingerprints get totally erased by the heat... and I need to get down to DMV to renew my drivers license in the next few days .

After my fingers tips cooled off, I cut a couple square holes on the birch wood doublers and floxed the 1/4" aluminum inserts in place.

Glassing the MKNG-6 Pivot

I made a paper template for the MKNG-6 pivot peel ply and glassing dimensions per plan and traced them out onto NG-30. Then I followed the rest of the effort per plan. Note the big white hole I filled with micro at the bottom left edge - that was one of the 2 'strategic' nail locations I used to hold the 2 NG-30 together...so much for strategic locations!!!

Jack Wilhelmson's Mounting Bracket and its Mystery Holes

Jack's instructions on the three (3) holes needed for his actuator brackets are kind of vague. The bracket came with the far forward hole pre-drilled and it mounts in the second hole back in the NG-30'. I went to M-10 and found the 4 holes for MG-51 (2 at the bottom end, 1 at the middle and one at top of the part). Since I did not order NG-51, the M-10 drawing was my only documentation for the part. I transferred the locations of the 3 holes needed (shown in M-10, ie. the top, middle & second from the bottom) and put a 1/16" hole through the NG-30 just for reference. I did not put in the #12 holes yet because I have not received Jack's parts.

By the time I was ready to remove the foam for the hard points, I decided to look through other web sites and noticed my hole locations did not have the same offset to each other, I was puzzled. Meanwhile, a couple e-mails appeared in the Cozy forum complaining about the lack of information as to where those hole locations should be for the new builders instead of retrofitters. Evidently, a few of the new builders put in their hard points and found out they were in the wrong locations. I revisited all the web sites and no one really talked about how they determined the correct hole locations and their center hole had a different offset than mine. Now, I knew I got the wrong hole and I was really confused...

After some thorough searching, I realized where the confusion was. The four holes the plans refer to are shown in Chapter 13, page 3, the hole that is needed in only one side on the NG-30 (fig 8) is not shown in M-10!!! It is, however, shown in Chapter 13 Page 3. Fortunately, the NG-51 is in full scale in Chapter 13 page 3, so I can transfer the missing hole to my M-10 drawing. The center hole (the 3/4" diameter) is the misleading hole. Once I caught that, it was clear. I just have to plug an old 1/16" hole and put a new one in. That was close...

Here's a picture where I floxed in the doubler onto the NG-30. If you look close, you can also see the 'new found' hole locations for the hard points.

Hard Points

Once the hole locations were established, I was required to build up six 1.2" diameter 15 plies BID hard points. I laid up a 15 ply, 4"x6" BID and let cure overnight. You can see the cured BID in the above picture. Then I used a 1.5" carbide grit hole saw and cut out six round discs (hard points). Since the hole saw has a thick wall, I ended up with ~1.33" diameter discs. I took one of these discs and traced them out on the NG-30 foam surface, centered at each of the six hole locations. With a Dremel and a grinding stone bit, I removed the foam for the hard points and floxed them in. I rounded off the edges around the hard points and am now ready for surface glassing.

[Hindsight: You may want to read forward to Section 3 of this Chapter - under Timing is Everything]

Details...Details...

I caught a couple notable recommendations from other builders. The first one was from Wayne Hicks' site where he suggested beveling the birch and aluminum doubler for the NG-6 at the same time. Since I cut my birch bevel with my table saw and the aluminum bevel with my belt sander, I decided to check its alignment prior to its subsequent glassing operation. Luckily, they were pretty close... but I had to do some fine sanding to make it right.

[Hindsight: I had a tough time glassing over the metal plate edges because I did not round off the sharp edges at the top. I have to clamp everything down for cure.]

NG-30 Reinforcement

The second recommendation was from an e-mail between Jack Wilhelmson and Nat Puffer after Jack's nose gear collapsed into an 8" hole. It was expressed by Nat (later in one of the newsletters) that it may be a good idea to add a couple more plies of BID (preferably UND) at the thinnest point of NG-30. I do not think there was an official plans change requirement. Since I am right at this point, I decided to add the plies as recommended. I got a chance to talk to Jack prior to adding the reinforcement. He recommended that I add a 3" radius at the elbow and 2 layers of UND (to the NG-30) horizontally.

I felt the 3" radius at the elbow corner was a bit small, so I decided to extend it further to give a larger surface for the UND reinforcement. My UND reinforcement starts 1/2" forward of the forward most hard point and ends ~6" forward of the elbow. I shaped and microed a foam radius between those two points (as shown). I added 3 layers of UND (horizontally) on both sides of the NG-30. I weighed down the NG-30 to make sure they stay flat. From the lessons learned above, I rounded off the sharp edges on the top of the second metal bracket and the glass laid down nicely. I also peel plied all surfaces.

Carving Out the NG-6 Cavity

Once the UND was cured, I turned the NG-30 over and carved out the NG-6 per plan. I first used a router to remove most of the glass and foam. I removed the rest of the foam with a Dremel, exposing the peel ply underneath (as shown). After I removed the peel ply, I added a 45o slope to the foam and glassed per plan.