Tail of the Dog
Happy Holidays folks! Been working on the rudder installation now for weeks - among some other things - and I’m sick of it! The issue is some binding as all the bolts are tightened up. We’ve adjusted shims and played with tightening sequences to no avail. Some of the things we did helped, but nothing we have been doing is totally fixing it. So, after much frustration and quite a few cuss words, we’ve thought about the best way to make new hinges for this rudder. Unfortunately, we can’t replace the hinges completely unless we build a whole new rudder (that thought has crossed my mind). We do have a serious Haas mill at our disposal and it can make quick work of aluminum billet.
The issue: Prior to covering the rudder, we had decided to bring the airframe to Sun N Fun and Oshkosh. So we had to hurry and temporarily install the tail surfaces. Well, we never fully installed the rudder until now. The vertical was not perfectly located and the rudder post wasn’t meeting the aft fuselage frame at the same exact angle. So, when tightened, the rudder post had a very slight bow in it. This created a non-axial condition for the three hinges. Not an issue when snug, but an issue when fully tightened. The rudder would swing pretty nicely until bolted-up snug. Then it has some major binding and requires a bit of force to swing it. Leg strength on the rudder pedals could easily overcome it, but it isn’t acceptable.
Attempts to fix it: at first, we were excited to bolt it up for the first time with all the zeal of the plane “coming together”. Well that quickly faded as it was pretty heavily bound-up. Its an hour to install the rudder and about an hour to remove. Several of the bolts are almost impossible to get a wrench on. Well, maybe it is sequence, undo them all and tighten from side to side. Didn’t fix it. Ok, one more time another sequence. Nope. What the heck? Consternation and cussin’. Ok, uninstall, check the vertical for alignment. Not straight. Oh boy! So we checked and rechecked. The vertical was not correct - fore/aft due to the fwd spar being about 1/8” higher than designed and a smidge to far aft. This caused the top of the rudder post to be aft 1/8” as well. Ahhhh, that would do it. So we designed a fix for the vertical stabilizer’s fwd spar mount to the fuselage - which required some adapter plates due to new hole locations. Installed that and checked alignment. Beautiful. Ok, install the rudder and - still binding. Arrrgh! Well then we adjusted the shims at each of the hinges and re-installed the rudder each time. Nothing is working. Ok, check the rudder for straightness - it was built in a fixture so it should be. Yes, it is straight. What the heck?!? I finally gave-up entirely. Had to think about it. Thought about making a new rudder. Thought about palm trees and hammocks. Ok, back to reality! Fix this!!!
First, the hinge design is novel and we should have just done it like on an RV-8. But, this should work. Installing and removing the rudder is a total pain in the a##! Redo that for the production model for sure! We have a large mill, can we make a new rudder post from a solid billet? No, too heavy and would likely change the way the rudder aligns with the vertical. Sight lines would not be right. However, we can make new hinge receiver blocks that bolt up to the existing rudder post and can be individually adjusted at assembly. The existing hinges on the rudder just slide over the receivers and then we can drill and bolt the rudder independently from the side. Installing and removing the rudder would only take a few minutes and allows us to bolt all the structure together without having the rudder in the way. Easy access to the hardware and checking of alignment. That way we can adjust everything to be perfect before the rudder is installed.
Scott got busy after Christmas and modeled up the new receiver blocks and machined them out. They look awesome and fit perfectly. We installed them and tightened them up. The structure of the rudder post and vertical was now complete and we checked alignment - fully expecting to have to add shims. None were needed. Straight in all axis between all three receivers by like .010” or so. Well within our tolerance on the hinges themselves. We then attached the rudder to the vertical and the rudder slid right on - with just a little resistance. No binding at all. We drilled and pinned the hinge brackets to the receiver blocks and re-checked for binding - none! Wow! First time in weeks! We are super happy now with the rudder installation. Time to finish the rudder cables and tail wheel steering cables.
We also removed and remade new aft spar attachment brackets on each side of the fuselage. This will help with as built alignment of the wing spars to the fuselage and with the seat belt attachment area. Checks and double checks of the mounting alignment and tolerances showed we need to shave the front mounts by .050” to have the spars slide in perfectly. So we will do that over the next few days.
Static ports and hose is going in the aft fuselage. Wiring for tail lights and trim is going in. Our engineers Paul and Aaron worked on the bolt sizing calc for the spar. The calculations for the wing attachment brackets are complete and we are way strong - good to go for wing installation! Having to wait for two bolts of the 16 that are on back-order from Aircraft Spruce means we will not get the wing on this weekend, but will be able to by the end of the first week in January. Tough break, but we will not sit idle. On-ward!
