November 04, 2013

Building Season-F-105

Hello again after a pause with my F-105 construction. The last few months have been a little slow with progress on the Thud due to my short flying season here in the upper midwest. The call from my Mibo A-10 and Me 163 Komet have required more time at the runway than in the shop with the Thunderchiefs. Now with the leaves on the ground and the threat of snow in the coming weeks, I'm back into an aggressive build mode in the shop. First I'll address the "progress" side of things with the F-105.

I finally completed the chute door mechanism that now reliably ejects this 48" drogue from the jet. The unit consist of three air cylinders and an ejector/flapper which lifts and tosses the contents out of the confines of the fuse. As always, space presented the largest problem to overcome.

As you'll see in some of the pictures, I needed to add a sharper trailing edge to all flying surfaces. The existing trailing edges were just too thick.

The main fuse hatch and canopy hatch work is now complete.

As good as the glasswork is from the mold, I have a technique that with a little work can make all the hatch lines practically disappear from view when fitted. The secret is using plastic food wrap from your kitchen. I'll give some detailed pictures on my technique a little later.

The lion's share of work to date has been with the actuation of the landing gear. This falls into the chapter of "STRUGGLE AND LACK OF PROGRESS". The main problem I've encountered with the landing gear is the lack of uplocks designed into the geometry. These are fairly hefty gear and keeping them secured in the wheel well while pulling two or three G's is a challenge if you're relying on air pressure or an electric drive motor to hold them into position. The situation has been two steps forward one step backwards with a pile of parts/money and time being wasted with unacceptable results. The retracts were designed to actuate with one large air cylinder. This concept proved to be inadequate due to a slight geometry problem along with the lack of uplocks.

"ROUND TWO" was my idea of using electrically actuated threaded shafts to pull things into position. The with this idea was that when the electric motor hits the stop switch, the threaded shaft and motor would unwind a turn or two allowing the gear to sag into the slipstream. So, time/money and ideas are getting frustrating with no good results so far. I decided to start over and cure the lack of uplock problem by contracting with a machinest friend to design a set of retracts from the ground up. The new retract system is now actuated via dual air cylinders and uplocks. Now my gear is "locked" in the wheel well untill I hit the extend switch. My canopy now opens/closes using a servo to lift and lower. The canopy locks are nextproblem