Back to the beginning: Project Tiger Cub Story part 12

Some work in the cockpit

Following Ben’s visit I set to finishing the front section of the fuselage. The front end I’d left pinned together with old bolts and I had done no riveting until Ben had seen my newly fabricated front tubes. So I completed riveting up the new throttle quadrant so that the throttle support tube could be fitted. I offered it up to strike a problem, it didn’t fit. Humm, it had fitted before when back in the mists of time I had dismantled it. Then I got it, despite the trouble that I’d taken with labelling everything up I’d fitted the starboard upright to the port side and visa versa, Idiot. Ohh well, stupid but curable with care. By cunning use of the triangulation of the structure I was able to remove both main uprights replacing such bolts as held other tubes in place in the right order so that I could swap the offending tubes over while maintaining the structure. Those in place, the right place this time, the throttle support tube slid neatly into place. Then working my way methodically though the assembly I replaced the old bolts with new ones painted with Zinc Chromate and wound on the new nylocs. 

I really could now feel that I was starting on the fun bits and get started at installing the controls. First off, the rudder pedals, I fitted them to the brackets that I re-installed on the cockpit floor after crack testing. They moved smoothly on their pivot and the end float was exactly as specified in the build instructions,

 I was starting to get a good feeling about this. Next, install the front cockpit floor, no room for error here, as this is structural giving triangulation to the front of the cockpit. I slid it into position and clamped it up only to find that I had pinched the monel rivets that I had bought hold it into place for another job. A bit of a pain, but not a disaster nothing that a call to LAS wouldn’t sort out. So clamping it into place I moved on to the rudder pulley in the rear of the cockpit section. No sign of wear to the pulley bearings so after a bit of a clean up the pulleys spun as merrily as new. Fitted with nice new bolts I slotted them into place and another little job was sorted. The next thing to re-fit was part of one of Jim Romains mods. It was just as well that I had taken pictures of the bits before dismantling. For this one Jim had changed the non-differential cable driven aileron circuit for a rod controlled system that provided some differential to the control.

For this one Jim had changed the non-differential cable driven aileron circuit for a rod controlled system that provided some differential to the control. To achieve this he had fitted a sleeve with two offset arms around the outer tube control column. Attached to these control rods ran to bell cranks that were mounted on an additional tube fitted athwartships.

These provided the differential and another rod each side ran to the bell cranks which are detachable to allow wing folding, these fit to the ends of the aileron control tubes. As I am missing one of the control rods I’ll have to get one made to the original spec. As I have been cleared by Ben to get this done at an aviation workshop to only real problem will be the cost. As the second tubes will be easy to fit later as long as the cockpit sides are left open I can still press on.

The hiccup with the rivets for the floor proves to be to my advantage as Ben is unhappy with the use of monel rivets in that position. He had gone away a worked out the rivet loading, because it was right behind the front bulkhead it was subject to considerable side force from propeller torque and a good deal of vibration. According to the “Big White Book” the FAA standards for inspection and repair, pop rivets should not be used in places where they are subject to vibration unless the rivet walls, without the central mandrill, are up to taking the load. It seems that monel rivets are not, all was not lost though as Ben found some stainless rivets that met all the requirements of the “Big White Book” and the bit in the CAAs own ‘Section S’ that covers side loads on engines.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s