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40% Extra 300 Construction by-the-numbers - 4/6/2006 4:38:26 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		Several have asked for this kind of "by the numbers" thread for building the Extra 300- to supplement the PAK instruction booklet.

After reading the instructions several times through, construction started.

With the front bulkhead on the 300 now full size one uses the edge of a table to get the engine compartment aligned while gluing. I used the wood glue for construction of the box. Several clamps in place.

Al, forgive me. While visiting my father two weekends ago, we did some engineering. Three engineers around the table talking about statics. My sister came down and gave us her input. We are all EE's but still remember our statics enough to give it a shot. The results are 1/4 lb off of the engine box sides. Holed drilled then a band saw to take out the triangles and center area of the box sides. This was carefully done. The model was tested somewhat in the prototype, which had equal amounts of material in the front- wing tube mount area as this new one.

The fuselage sides were assembled per instructions The 1x1x72 inch aluminum triangles were purchased at Lowe's. The fuselages were joined and doubler added. A scrap 3/8 inch piece was spaced for top and bottom of the fuselage joining point. The 3/8 squares glued on the tops and bottoms with mostly wood glue, skipping about an inch every 6 to 8 inches and putting thick CA at those spots. THis allowed construction without delay of waiting for the wood glue to set.

Finally the vertical stringers were glued in with 3/8 inch square pieces, and the rear doubler glued into place.


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       Post #: 1

RE: 40% Extra 300 Construction by-the-numbers - 4/9/2006 3:10:11 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		Mating the fusleage sides to the engine Box structure.

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       Post #: 2

RE: 40% Extra 300 Construction by-the-numbers - 4/9/2006 3:19:35 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		I drew a center line down the center of the worktable (an unfinished door). Used a SMART LEVEL to double check how close the fuselages were (tops parallell). Basically if you use the long aluminum straight edge or 78 inch corner aluminum stock this ensures the fuselage front and back piece are glued together straight. A hint. When you splice two pieces of balsa 3/8 stock together for the longerons, glue them with the splice opposite the glued surface. Basically this makes a stronger joint. The plywood sides will flex in and out, but not top to bottom. I had to put a shim under the back of one side since the door was about 1/8 inch off on one side as compared to the other. When the front box is glued in place straight, the back of the fuselagee (rear) will come together perfectly.

I put the triangle 78 inch stock in the corners and then clipped the fuselage sides to them in a few spots. Then carefully cut top and bottom pieces so they were the same size. Then glued in the bottom pieces (F3 F4 and f5) The balsa cross-pieces (cut the top piece first then cut the bottom one to match it). This insures the fuselage is square.

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       Post #: 3

RE: 40% Extra 300 Construction by-the-numbers - 4/9/2006 3:25:12 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		As you can see above, before gluing in F3, F4 and F5 (the bottom bulkheads), first put the tailwheel plate in, and then a small piece of balsa at the rear of the fuselage. This rectangular piece was 1 1/2 inches wide. Taking in consideration two 3/8 squares pieces and the 1/8 inch fuselage sides, this put the rear of the fuselage at 2 1/2 inches per the plans.

There were a lot of triangles in the kit. Lay them out by size. They go in front and back of each of the forward three bulheads, and around the engine box. As you can see I took a hole saw and put a few lighening holes in the back area as well.


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       Post #: 4

RE: 40% Extra 300 Construction by-the-numbers - 4/9/2006 3:28:54 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		I put the wing and stab tubes in place and checked alignment. It was very close. The triangle stock has to be shaped when going in the corners around the engine box and the fuselage sides. I put wood glue in the corner and a few drops of CA on the edges of each triangle. The CA set quickly while allowing the white glue to dry.

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       Post #: 5

RE: 40% Extra 300 Construction by-the-numbers - 4/9/2006 3:36:40 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		After I put the stringers in, then I put the diagonal- cross pieces in. They are staggered so the top and bottoms cross opposite. I went ahead and built a pipe tunnel out of light 3/32 balsa in case I go with long tuned pipes. Marco Benincasa did this at the Tuscon Shoot Out last year and I was really impressed with his power setup. I heard that the long pipes make the idle a bit tempermental, but since there are no tailslides at the Don Lowe Masters, this should be no problem. I had to remove the center of bottom bulhead to make room for the pipe tunnel. Will put the rudder servo tray up higher to clear the pipe tunnel.

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       Post #: 6

RE: 40% Extra 300 Construction by-the-numbers - 4/11/2006 5:42:32 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		Some additional pictures of the pipe tunnel.

Canopy deck. Make sure you allow 1/8 inch overlap for the two 3/8 inch side stringers. I glued the bottom 3/8 inch side stringers on, placed the canopy on the airplane, then glued the front three bulkhead/formers in place. I used a clothespin to clamp to the front fuselage bulkhead. Next is to mount the ply mounting tabs (its easier to get to them before sheeting the top of the canopy deck).

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RE: 40% Extra 300 Construction by-the-numbers - 4/19/2006 6:14:12 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		Rough assemble the canopy deck. Glue in the formers. Now, what angle do you put the rear former? Align the rear former so it's parallel to the back deck. It does not have to be exact. Just close enough so you can glue in the stringers in place.

The sheeting was straight forward. Cut two pieces, glue them together with some thick CA. Immediately sand the joint with a sanding block, then flip it over and sand the other side. I cut about 1/2 inch off each at the rear, tapering up to the front. That way the side pieces glued in are at about the right angle to fit on the canopy deck. See pictures. I put a litle water on the underside of the sheeting and set it on top of the deck, with some books on each side, to help shape it generally to the frame.

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RE: 40% Extra 300 Construction by-the-numbers - 4/19/2006 6:19:51 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		The next step is to glue the sheeting to the deck, trim the edges, then position it. Before gluing on the sheeting, I will mount the tabs for the six 6x32 cap screws and mounts. Its easier to get to them before its sheeted. Finally once everything is positioned, one can glue on the back deck to get a clean interface with canopy deck.
BTW. I glued the 1/8 x 3/8 pieces to the underside of the rear deck pieces, added additional 1/16 pieces to fill the rest of the gap, only to find that I had to trim about 1/32 off the front and back for a flat mating surface (flat with the tops of the fuselage sides). A little sanding and it fit very well.

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       Post #: 9

RE: 40% Extra 300 Construction by-the-numbers - 4/23/2006 1:37:28 AM   
Don Szczur



Posts: 950
Joined: 1/6/2002
From: Chantilly, VA, USA
Status: offline 		Canopy deck sticks are glued in, then the 6 tabs for the mounting blind nuts. A 3/8 spacer is glued in at each location. Finally sheeting is glued on. Make sure you sheet on a flat surface so the deck will not warp. I used wood glue for the stringers and then thick CA on the edges. After wetting the balsa on the outside, it provides for bending of the bala at the bottom part.

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