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Old 03-08-2009, 07:36 PM
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Join Date: May 2003
Location: Iowa City, Iowa (again!)
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Default RE: Charlie Kellogg's TBM Avenger Build

Hi, Chic (and anyone else that reads this!)

So I will receive my motor on Tuesday, but last night I spent several hours measuring from the plans and drawing new plans for the front of the airframe. Everthing looks like it'll work now, although I will have to have a machinist friend of mine turn a hub extension so the cylinder bank on the RCS/Moki 150 will clear the tapering cowl. Aside from that, and based on my measurements and new plans for F1 through F4, I think that it's going to work out pretty well.

Anyway, after I sorted the business end of the Avenger out, I then got to checking the PCK parts against Charlie's drawings. Most everything was fine, although a few stringer- and crutch-notches had to be re-worked on a few of the formers.

This afternoon, I started on the crutch. Charlie's plans call for a balsa crutch, but PCK provided spruce instead, so I just went ahead with the spruce. First step was to splice two pieces of 1/2 x 1/4 spruce to get enough length for the full crutch. To do this, I cut an angle across each piece to be spliced and then tacked them together with CA. Once set, I then drilled through the joint and then pounded a toothpick to pin them and hopefully get some more strength at the joint. After that was done, the cross-members were added. These are just 1/8 x 1/2 balsa. While the crutch was still pinned to the board, I ran a sanding bar down the crutch to ensure all the balsa cross-members were even with the spruce (another advantage of using spruce for the outer splines). Last step was to transfer the former locations from the plans to the crutch.

Next, I accurately cut 5 pieces of 2x4 lumber to 9 inches in length. These serve as supports for the elevated crutch. Instead of working over the plans, as Charlies suggests in his instructions, I simply drew some reference lines on my building surface... one long, straight line to demarcate the fuse centerline, and a few 90 degrees to the centerline. At one of those perpendicular lines, I tacked two of the 2x4 supports to my building board. By doing this, I was able to clamp former F10 to the supports, and F-10 is where I started gluing. As long as the 2x4 supports are perpendicular to a flat building surface, then having the reference lines and tacking the supports to the building surface makes lining up and gluing very easy. It also helps make sure that the first former is absolutely perfectly aligned.

Right, then I just started sliding the formers on the crutch. Each was glued after verifying it was vertical, 90 to the crutch. I then began to fill in other material (F-19 turret floor, F-22 cockpit side-supports, etc...). I also added a little bit of 1/4 triangle stock to help support the ball-turret floor, as well as a bit to support F-22 where it abuts F-8.

I stopped short of gluing in F-14 at the rear, and F-3 at the front. These and the adjacent formers have not yet been glued because they all will require some modification to accomodate the Sierra tailwheel and the motor I've selected. I want to have the actual motor in hand before I start modifying F-3 and F-1 and I need to do some more thinking about the Sierra tail wheel installation. The Sierra tailwheel is considerably larger than the Robart 160WC that Charlie used, so I'm going to have to make some changes back there. I know that Jim (Gibb), who also is building this Avenger and has posted to this thread, has installed the Sierra tailwheel. I PM'ed him today for some feedback. Hopefully he'll check back to the site soon. The installation should not be a major pain, but it would certainly be more efficient to get his thoughts and perspective on the matter.

That's it for now. I'll poster more later this week or weekend, depending on when I can get back to work on the plane. I also should add that Charlie Kellogg has done a teriffic job engineering his design. It all goes together very well and it's clear how carefully he has considerded his design. I am particularly impressed with how the wing center section is locked into the fuse. Simple, yet very clever!

How did you come along this weekend, Chic?


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