Saturday, September 27, 2014

Ch 9.1: Main Gear Reinforcements (1 of 3)

By the time I'm done with Chapter 9, I'll have the main landing gear, wheels, brakes, and speed brake installed.  It starts with reinforcing the area around the landing gear bulkheads so it can hold the main gear bow and take loads from landings.

Strength in Numbers...of plys!
This will be a three part post because there are 3 areas that are reinforced.  #1, the front of the Forward Landing Gear Bulkhead; #2, the area between the Aft LG Bulkhead and the Firewall, and #3, the area in the middle between the Fwd and Aft Landing Gear Bulkheads where the gear bow will be mounted.  These are tricky to glass because of the number of corners to glass around and the limited space to work in for the latter two areas.

Fwd LG bulkhead
For the front most reinforcement, I followed the technique used by Bernard Siu.  Instead of making paper templates and trying to cut the glass to fit, I cut three 10" x 24" rectangle of BID and laid it in starting from the bottom/forward and working aft/up being careful to keep the glass pinned in the corner.  Additionally there are two additional BID plys that cover the hard point up to the bottom of the tall tabs for a total of 5 plys over the hard point.  In the pictures, the sharpie marks outline the reinforced area.

Pilot side reinforcement looking aft.  Stray
sharpie marks are misaligned edges of glass
Fuselage, back seat looking aft at the Fwd Lnd Gear Bulkhead.
The reinforced areas are at each side, extending from 2"
on the side, along the floor 6",  then back to the bulkhead
and  all the way up the tall tabs. 

With a little patience, and slow curing epoxy (I used the Aeropoxy 3665 hardener which has a little
longer working time than the 3660 I usually use), I got all 5 plys down and peel ply'd in 2.5 hrs.  The copilot side went slower...but that was because I had a six month lapse in working on the project and had lost a little glassing efficiency.

As I was wrapping this reinforcement up, I came across an archived email discussion from Marc Zeitlin.  The plans, Ch 9, figure 1, shows an additional 2xBID tape to be run from the floor to the fwd bulkhead...but the text never discusses it.  I thought it was because this layup was already done in Ch 6 when the fuselage bottom was attached.  According to the email however, Marc Z stated that the additional 2xBID tape should be done.  He said that this far into the plans, it assumes you know to 2xBID tape any place two parts come together.  So if it actually shows one, even if it's an additional tape, do I did.

The plans have you reinforce the area between the bulkheads next, but you need to turn the fuselage on its side.  So I went ahead and did that while I had easy access.