Lead Sled Alley - February 2003
Since the name of this column is 'Lead Sled Alley', I thought it might be fitting to talk about lead sleds this month. Actually, my next few columns will be a multi-part series on the creation of a new Me-109.
By Russ Thompson |
Feb 13, 2003, 01:00 AM
Since the name of this column is 'Lead Sled Alley', I thought it might be fitting to talk about lead sleds this month. Actually, my next few columns will be a multi-part series on the creation of a new Me-109. This plane will replace my old Me-109, which does not have the wing fillets built in and has been stretched and skinnied. The goal behind this project is to build the new one as scale as possible, with the exception of stretching the wings a little to help with stability.
I wanted to get the plug finished for this article, but due to time constraints, I did not quite make it. However, it is about 80 percent finished, and I think I can finish the last few details in the next few weeks and get it ready for the mold.
Because I wanted this plane to be nice and scale, I decided to work from a set of plans rather than just blowing up a three view as I had done in the past. I contacted Dave Platt about buying a set of his plans and told him that I ultimately wanted to use them to build a mold for a new slope plane. Because my intention was to reduce them in size, I would not be able to use the vacuum formed parts that normally come with the kit, and he agreed to sell me just the plans.
The night they finally arrived, I was jumping up and down like a five year old; just looking at them really got me motivated. Dave's plans are for a 1:5 scale plane with a fuselage length of 72"! I raced down to Kinko's and reduced them until the fuselage was 39" long. There is nothing magic about this number, except that it is the same length as my Spitfire. The next day, I cut out the bulkheads and used 3M77 to glue them down to a sheet of 1/8" balsa. I was only concerned with the outer shape, so I did not worry about all the interior pieces.
The plans show a spine running along the top of the aft ribs to keep the tops of them in line. However, in order to build the fuselage that way, I would have had to notch each rib by hand. Any error would have translated into a warpy looking fuselage. I thought it would be easier to use a carbon fiber rod to line them up, so after cutting out all the bulkheads with a razor blade, I stacked them from front to back and pinned them together. Then I used a drill press to drill a 7/32" hole straight through them. You can see here that the rear bulkheads have a single foot in the middle to set their heights above the building board, while the front bulkheads have two feet at the sides.
In most kits that I have seen, the lower half of the fuselage is upside down on the building board. Then the turtle deck is built on top of it. This allows you to pin the bulkheads down squarely on the board and makes it easy to keep everything straight. Dave's plane is not built this way, and I could see that it was going to be nearly impossible to apply the sheeting without turning the fuselage into a banana. After grappling with the whole unruly thing for a while, I finally decided that the only way to keep the bulkheads aligned would be to glue them down. I laid another sheet of balsa on top of the building board and glued them to it. I also created a track to keep the feet of the rear bulkheads aligned by pinning down two more pieces of 1/8" sheeting on either side of them.
Even with the bulkheads glued down, they were still too flimsy. I needed to be able to apply a fair amount of pressure order to bend the sheeting around them, so I added some braces to help make things sturdier.
To sheet the other side, I had to move the braces to the opposite side. The large chunks of balsa form the forward deck.
Here the top sheeting is finished.
I decided to turn the spinner next. I cut the spinner profile from the plans and used it to check the shape.
I also wanted to get the vertical glued in place before I cut the fuselage off the building board. This would make it much easier to get it straight. I tried building the vertical from the ribs on the plans, but had a hard time getting the sheeting on without warping it. I finally cut a foam core and sheeted it in its own saddle.
The dimensions for the canopy are not shown on the plans because Dave has a vacuum formed canopy. Since I could not use this, I had to improvise. I bought a plastic model of a 109 and measured the angle of the canopy with a protractor. Then I setup my table saw and cut that angle on both sides of a block of balsa. I used that to make three individual blocks, one for the front, one for the middle section and one for the rear. The front block was the trickiest because it has all sorts of compound angles. At this point, my wife told me it looked like a fish.
I cut the fuselage off the board and planked the bottom. Planking is not exactly my strong point, but I was not worried about getting it perfect. The whole thing would eventually be glassed and bondo'd to fill any imperfections.
At this point, I realized that although the side profile looked good, the top profile was completely wrong. The problem was that the fuselage is supposed to curve inward slightly just behind the spinner, but mine was straight. I studying the plans for a while, and realized that there was a mistake in the front bulkhead. It was too big by the thickness of the sheeting. After spending a few days in denial, I finally faced the fact that I would just have to hack the front of the fuselage off and reshape it.
This also meant turning a new, smaller spinner. Unfortunately, I got carried away and made the spinner too small the second time around. This made the side profile of the fuselage wrong. Notice the dimple under the chin; the real 109 does not have this.
To make a long story short, I finally made a third spinner that was bigger than the second, but smaller than the first. I then had to build out the sides and bottom of the nose to match it. It took some effort, but I am much happier with the way the nose looks now. With all that done, it was time to glass. I laid the glass on with the weave running 45 degrees to the centerline of the fuselage. This helped it bend around the sharp corners of the canopy without having to cut it.
In anticipation of building the wing saddle, I had also been working on a wing to use for this stage. I like to build the wing saddle right onto an actual wing so that it fits perfectly. Here I have tacked some 1/64" plywood onto the wing and set the plug on top of it. After squaring everything up, I glassed the plug to the 1/64" plywood.
I also added some plywood gussets to help fair the fillet into the fuselage. The only purpose these really serve is to hold the bondo.
After gobbing on five or six coats of bondo, I started shaping. It still needs a little work, but at this point, the fillet and saddle just about done.
When I blocked up the wing and fuselage at zero incidence, I noticed that the trailing edge of the wing hung below the fuselage about 3/16". I tried blending it locally, but that made the profile of the plane look strange, so I ended up building up the whole underside of the fuselage.
Next, I added the radiator scoop under the nose. This detail is also not on the plans because there is a vacuum formed part for this area. Once again, I resorted to my 6" model for reference. After getting it shaped, I glassed over it with 1.5oz cloth. The light cloth bends around the corners more easily and should be strong enough to keep the plug from breaking as long as there are no mold locks and nothing sticks.
This is the state of the plug at the time of this writing. Remaining details include carving the gun ports, adding the exhaust pipes, adding various small scoops on the sides of the nose and other parts of the fuselage, and adding the gun blisters that were just in front of the canopy. At some point, I will also have to build the scoop that was on the left side, but that will be a separate mold so it can be done later. I still have plenty of building to do on this plane so stay tuned!