Jan 30, 2024     Elevator - (4 hours)       Category: Empennage

Fabrication of Elevator End Rib forms for part 75T3-1. MDF was used for the form. Practice part made to determine the depth of flutes for nose curve.

  Jul 17, 2023     Consultation with Roger - (0.5 hour)       Category: Empennage

I spoke with Zenith's Roger Dubbert by phone regarding the H.T. Brackets and Gussets. I explained the alignment concern and issues with the part profile and attachment point and requested some input on how to proceed. Roger was helpful and said that Zenith could provide the Cruzer style one piece Bracket part without holes. This would allow me to align the bracket and locate the holes with the current fuselage holes. The Gusset parts were of particular concern and these parts were later returned and materials purchase to fabricate the one piece forward and rear gussets. Note in the photos that the fabricated Gusset for the Cruzer is positioned rear of the STOL. I will make one piece gussets using one piece for the added benefit of strength but order the one price bracket.

I also inquired about having hand rivet gun tips correctly profiled by Zenith. Roger said they could do this and I later sent my tips in to Zenith and later received profiled tips in the mail.

  Jun 29, 2023     H.T. Brackets & Gussets - (4 hours) Category: Empennage

Ordered H.T. Bracket materials and inventoried available on hand materials for fabricating H.T. Gussets. Materials on hand for the gussets ordered other materials. Thought process in determining whether or not to order fabricated parts or to fabricate locally. My decision point is whether or not the price of pre-made parts is if the cost of fabricating on my own exceeds 50% of the already fabricated part and whether or not I have the necessary tools and experience to construct to an equal or better standard.

H.S. Upper and Lower Horn I identified as having issues with spacing and placement of the drilled rivet holes. These two parts are made from 6061T6 t = 0.063 which I have a good quantity of so I will be making these parts.

I fabricated a new Seat Support (75F11-2) which had been omitted by previous builder. I also verified to insure proper rivets were used and replaced those which were a concern.

  Jun 26, 2023     Horizontal Stabilizer Mounts - (2 hours)       Category: Empennage

On June 26 I called Zenith with my list of questions regarding the mounts for the Horizontal Stabilizer, the forward and rear fin alignment on the rear Fuselage and the availability of plans / parts for the four-point seatbelt. After a very short hold I spoke with Roger and went through my questions. First we discussed the H.T. I expressed my concern about the parts currently installed and really wanted to know if it would be more beneficial to replace these parts with those for the Cruzer which include a one piece fwd one piece rear gusset and a once piece bracket, R & L? A short discussion and the answer was yes. So this resolved my question on the H.T. mount. Second item, the fwd and rear fin on my 750 were not aligned in line with the aircraft centerline. I asked options for resolving this. Roger agreed it needed to be fixed and he suggested just correcting the alignment, re-drilling and riveting. The previous holes I should just rivet to close. This resolved the second question. Last item was the seatbelt parts plans. Roger said he would send me some documents.

On June 27 I received an email from Roger with attached plans for my questions. The horizontal stabilizer plans looked as if they could be easily construction so I researched the price of materials and upon comparison I found the materials would be at least 50% of the already fabricated price so I chose to purchase pre made. I placed the order on the 29th of June. Price is $102 plus tax and shipping, so roughly $139. My general rule is I will try and fabricate a part if the price of purchase is more than twice the materials cost or complex bending, machining of assembly beyond my capabilities is required. Sometimes I take on the challenge but in this case the goal is to get in hand a part to install.

The plans for he four-point seatbelt were not very helpful as they just illustrated the assembly. I'm pondering this option for the time being. I believe I have sufficient aluminum to make these but drawing don't reflect component thicknesses. So if I chose to fabricate I will need to determine fabrication details not available in the plan.

  Jun 15, 2023     Horizontal Stabilizer and Rear Fairings - (4 hours)       Category: Empennage

Today I looked over the Horizontal Stabilizer attachment to the rear fuselage (75-ZA-1). This has been on the list of concern due to poor profiling of the H.T. Attachment Gusset (75F2-5 and H.T. Attachment Bracket (75F2-6). I removed the Forward and Rear fairings on top of the H.T. to enable better viewing and was able to get good access. I found that the profiling, which really seems to be unnecessary, is inconsistent and unsightly. I was able to measure the locations of the bolt (AN3) placement and it appears the the setback is less than advisable. I also found the rivets in the Gussets are A6 instead of the A5 and it is not quite clear as to why. I'm not sure if this was an error in selecting the correct rivet of if it was done to resolve a problem in assembly. More research is necessary.

With the forward and rear fairing being removed I was able to more clearly see the center alignment of the fairings. They appear to be off center which I am currently unable to explain. The off-center is noticeable quite clearly. I will need to review the assembly guide and plans to determine if this is intentional. The removal of the fairings was necessary regardless due to the gusset and bracket issues. I have emailed Roger at Zenith with a question on these parts and a question about change the bracket to the single piece part as seen in the 750 SD and the Cruzer.

Lastly, I removed the rudder cable fairings on both side due to the omission of the nylon bushing material in the assembly. The cable was up against the side skin and would have damaged the skin rapidly if this is not addressed.

  Sep 15, 2022     Elevator Skin Repiar - (2.5 hours)       Category: Empennage

I continued work on the elevator. I fully separated the nose skin from the elevator structure. I noticed immediately that the nose skin had two rows of holes drilled in the skin, corresponding to the alignment with the 75T4-2 and spar 75T3-5. It appears that the skin misalignment may have been recognized after drilling and an effort was made to salvage the original skin by completing riveting under 75T4-2 and re-drilling in the new position. I am unsure at this point if I should purchase (or make) new nose skins or trim.

In order to remove metal chips and shavings I removed more rivets than should have been necessary in order to get a vacuum into the crevices of the elevator. The Elevator rear channel 75T3-10 was drilled with 7/8" step drill to allow access to the closed in area between spar 75T3-5 and the rear channel. I made a small curved tube out of electrical conduit and attached to my vacuum to remove rivet head and shavings. I riveted an access plate over the hole.

  Sep 04, 2022     Elevator Skin Repair - (4.5 hours)       Category: Empennage

Completed drill out of rivets holding the incorrectly assembled nose skin of the elevator. I began the process of deburring skins and internal structure components which had been overlooked. On 9/5/22 I spent time just cleaning out metal shavings and dust which was inside the elevator. Several spots were also marked for fit adjustment when elevator is reassembled. I was not prepared to complete corrosion protection and reassemble so I prepared a storage rack for the elevator and placed the elevator on the shelf.

  Aug 30, 2022     Elevator Nose Skin repair - (2.5 hours)       Category: Empennage

During inspection it was determined that the prior builder had riveted the nose skin 75T4-3 over the Elevator nose skin 75T4-2. The assembly instructions indicate that the above assembly procedure is used to located the nose skin rivet holes but in this case the prior builder completed final riveting without repositioning the nose skin 75T4-2. I drilled out the >100 rivets and separated the skins which will be reassembled after corrosion protection.

  Aug 13, 2022     Elevator / Horizontal Stabilizer - (2 hours)       Category: Empennage

I removed transport bracing used during the move from storage to my shop. I then inspected the elevator and H.S. and identified several issues which will need to be addressed. The Elevator top and bottom skins were left on top of the nose skins and then riveted. Per plans the nose skin should have been positioned on outside of top and bottom skin. Resolving this issue will require the removal of the elevator and repositioning the nose skin over the top of the top and bottom skin.

During rotation of elevator up and down a scraping noise was apparent. I located the problem which is the inside nose skin on the right side which is rubbing against the H.S. Resolving this clearance issue will require removing the elevator and trimming either the inner mount at the pivot point or trimming the nose sheet at the inside. , reference 75TA-1 and 75TA-6.

I disassembled the Elevator attachment points (outside and center) and determined the signs of incorrectly pulled rivets and pivot bushing was excessively tight. I suspect that by correcting the rubbing of the inside nose skin and resolving some rivet installation issues the position of the elevator will change slightly and resolve the nose skin scraping and binding currently observed. Elevator was fully removed and placed in a work area for later date.

The H.S. mounts to fuselage were profiled (by the previous builder) on the outer edges in a way which left each different from one another and one extra hole serving no purpose was located on the metal mount. I will need to verify the level of assembly and determine if replacement is required.