Carlson Skunk Works

October 12th, 2011

AMF Maranda 14-H SN:1026 Making Sawdust October 12, 2011

Posted by Roger in AMF 14H Maranda SN1026, news

Things have been quite busy this summer. The fuselage is nearing completion! At this time I have only about half a dozen wood pieces to glue to the fuselage and it will be ready for sealing.

Let’s see … the last time I posted was on June 20th, so there are a lot of pictures to show.

That worked quite nicely. Ben has been busy fixing WordPress and loading the picture went very quickly! I am impressed!

Anyway, as you can see the fuselage cross members have been glued in place as well as the roof. The tail fin is just clamped in place in this picture. I just wanted to see what it would look like.

This shows how I joined the fuselage top stringer to the center roof support. There will be stringers like this one on the bottom and on each side. Without the stringers the fuselage would look VERY square. The stringers push the fabric out from the “surface” of the fuselage sides just enough to give it a bit of a rounded look. They also add just a little extra support for all the spacers and diagonals.

Here is a better view of the top of the fuselage. This is from near the tail looking toward the front.

This shows the way that the firewall will fit with things. You can almost start seeing it start to look like an airplane.

Once the nose sides were glued in place things started to really look like an airplane!

Before the firewall could be fitted in place and the nose sides glued to it, it had to be filled with fiberglass and the front sheet of plywood needed to be glued to it. The fiberglass is for noise absorbsion according to the plans. I intend to wear a good headset, so that may be as secondary issue. But anything that can make the cabin a bit quieter is worth the effort.

OOPS! Well, I guess this is the first spot of “hanger rash” for my plane. One of the pipe clamps that I had leaning on the frame started sliding and the handle bumped the inside of the 1.5mm plywood. Fortunately, there will be a plywood window retainer glued to the inside of this area, so this boo-boo will get fixed. In fact, I installed that piece this afternoon and I think things will be just fine when the glue dries.

Here are the floor supports. They are sort of like the floor joists in a house except that you don’t stand on them. The main purpose is to support the seat(s). I am not sure if I will build bucket seats or a bench seat. I have qute a bit of time to think about that yet.

I have had a number of people ask how I make my scarf joints. This shows how they start. To begin this section I should probably explain what a scarf joint is. A scarf joint is a joint where the two pieces of material (in my case wood or plywood, and in this example plywood) are tapered then glued together on the taper. This provides a very wide glue joint and the resulting joint is just as strong as (sometimes stronger than) the material being joined.

This is a picture of two sheets of 3mm plywood that will make the floor of the plane’s cabin. The top sheet was set back from the edge of the bottom sheet by 1 1/2″ then clamped in place. I used my hand held belt sander to sand the taper across both pieces of plywood at the same time. Plywood is made up of several layers of wood that area glued together. The glue shows up as the dark lines in the picture. Since all the layers are the same thickness, the glue lines should end up being evenly spaced and parallel to each other. I didn’t get everything perfect, but it is close enough for what I am doing.

The joint will be “clamped” against a piece of plywood. I have a 3/4″ thick piece of plywood that I use for lots of things and it works very nicely for this application as well. First I cover the 3/4″ plywood with wax paper so that it won’t become part of the floor. Then I place one of the pieces of floor plywood that I just got done sanding on the wax paper. Next I smear glue all over the area that I sanded and fit the sanded area of the other piece of plywood into the glue. Then I grab my staple gun and put a staple near one end of the joint to hold that end in place and I proceed to run a series of staples along the joint. The staples are my “micro-clamps” and they work very well.

This shows the way that the joint ends up. Notice that I put in two rows of staples to ensure proper contact between the pieces of plywood. When the glue cured I pull all the staples and sand the joint to remove the excess glue.

The finished scarf joint. The floor has been glued into place and the scarf joint will be under the seat(s). The joint is not invisible, but it doesn’t look too bad.

The floor is in place.

The instrument pannel is in place.

Snice these pictures were taken the brackets to hold the landing gear to the fuselage have been completed. Once the last pieces have been glued to the fuselage, we will be able to apply sanding sealer. Then it will be on to the landing gear!

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