A Record of important things…

Drilling and Aligning Fins


To get the horizontal fin at the correct 5° angle, and to keep the relationship of the vertical fin reasonable and the position of the rear mounting hole centered in the doublers (don’t worry, it would make sense if you were building one), I found things to work better if I placed a 0.125” spacer under the front vertical fin mount. This also allowed for the milling of a tilt to account for angular mismatch between the fin and the frame mount.  Quick job on the Grizzly.


When I first started making these tubes I thought I would simply use my fabricated tubes as templates and then go have a welder make “real” tubes with a welded endplate, but I must say that I am actually pretty pleased with the results.  The double MAP torch trick seems to work as Home Depot MAP torches do not seem to burn hot or concentrated enough to thoroughly melt the tube, but the flame temp (3600 degrees) is well above the annealing temp (1590 degrees) of 4130 steel.

I may redo this one lower tube as the distance between the bend and the bolt seems a little long on the lower end.  It is curious how things look worse in the digital photos than in reality.  I guess this is good - like having a critical eye looking over your shoulder.

The finished (almost) fin mounting job.  I just need to redo the single lower tube, final rivet the central fin doublers, drill the horizontal fin to its mounting stub tube and fashion a bracket at the rear of the horizontal for added support to the vertical.  One evening.

Of course during flight checkout all these may have to be boogered around a bit, but for now I am pleased that they are spot-on the planned dimensions and angles.