Horizontal tail mounts

xtricity · Post by **xtricity** » Sat May 03, 2025 9:20 am

Post by **Tony Spicer** » Tue Jul 12, 2016 7:28 am

Sacpilot wrote:Tony/Dan/Paul,

My rear mounts were too long. Now that they are at 3.5 inches, I have managed to get my stabilizer clamped and aligned to the point where I have about .8 down. I assume the .8, is down toward the front, and not up? I don't know that I can get .8 up without having the front mounts reasonably below flush on the front spar stiffener. So, if it's .8 down, bingo.

Per the prints, the 3 1/4" brackets go in front and the 3 1/2" in the rear, making the leading edge sit low. If the angles are correctly installed and the HS skins allowed to rest on the tops of the angles per the BM, then the incidence will be what Dan intended. As to the actual measured angle, I suspect that will vary depending on how the measurement was done.

Need a small, accurate, inexpensive digital level? Here's one:

https://www.amazon.com/gp/product/B002L ... UTF8&psc=1

I'm eagerly awaiting Dan's upcoming post on HT incidence settings.

Tony

Sacpilot · Post by **Sacpilot** » Mon Jul 11, 2016 10:56 pm

Tony/Dan/Paul,

My rear mounts were too long. Now that they are at 3.5 inches, I have managed to get my stabilizer clamped and aligned to the point where I have about .8 down. I assume the .8, is down toward the front, and not up? I don't know that I can get .8 up without having the front mounts reasonably below flush on the front spar stiffener. So, if it's .8 down, bingo.

Post by **Tony Spicer** » Fri Jul 08, 2016 8:52 am

Good read:

http://www.flyingmag.com/pilots-places/ ... -incidence

Tony

Post by **Tony Spicer** » Thu Jul 07, 2016 4:53 pm

danweseman wrote: Rest assured if you follow the BM your aircraft will fly fine and be able to be trimmed to any speed.

Dan,

Being able to trim pressure away at any speed doesn't really cut it.

My HS is mounted per the prints. The angle is .8 degrees. CG is at 27.4% (58 lbs engine ballast). The issue is that at 150 mph TAS (my cruise speed) the trim tab requires 1" of nose down trim (tab up) measured at the trailing edge of the tab. That's a lot of unnecessary drag. At 180 mph TAS the trailing edge of the tab is up 2 1/4", where it's more a speed brake than a trim tab.

My Sonex, RV-3 and RV-4 all had the trim tab close to neutral at cruise speeds. What's the issue with shimming the HS to achieve the same thing with the Panther?

Tony

Sacpilot · Post by **Sacpilot** » Tue Jul 05, 2016 11:01 am

Thanks Dan and Paul! I believe I checked the HT lengths as per my full scale plans. I will check again. If I still have a problem, I will give Dan a call today or tomorrow. I feel like I need to push HT down and then get 3-5 degrees with my digital level. Will check again. Maybe I am somehow misinterpreting tooling holes and reference point for measuring angle. I put an3 bolts in holes and lined up points of bolts, then measured across.

Thanks!

Post by **danweseman** » Tue Jul 05, 2016 10:46 am

HI guys
Hope you all had a great july 4th weekend !

First thing to mention is ,if any of you have any questions like this your first stop should be a support ticket or phone call to Us. (Christopher has a opened a ticket ) Other builders and are a great source of inspiration and support , but not so great at spreading accurate information. The below thread is and a few others hear are great examples.
Next SPA will always issue notices when revisions or service notices are needed through the same venue as the plans updates and revisions. Notice i said needed. We are very cautious to make changes on things when the info is coming from builders. It takes time to verify the information and then see if its a isolated condition,then to decide if its really a "problem" or just a "preference" or "opinion". Again please come to Us first and we will do what we can to give you accurate relevant information! (PS it may take a little longer to answer tickets on holiday weekends, as we have builders trying to pack in workshop time over long weekends which generates higher than average questions, and these Holidays are important to The SPA family also !)

HT Incidence settings. We are working on a post to cover this in more detail, the short answer is that if you build per the plans your HT will be At approximately .8 degrees. This will fly fine, and allow the aircraft to be trimmed at any CG condition and speed from stall to full throttle level flight at sea level. we have 4 aircraft flying at this setting 2 Corvair 2 lycoming . All can be trimmed hands off at any speed to 200 MPH. We have one aircraft flying at .5 degrees and one at .25 reported by builder (but not verified by SPA). They are also able to be trimmed through out the Range. The update to this will detail how to optimize this for your particular combination of wing and engine choice ,and your "opinion" about what is correct.
Note: We didn't not initially give the HT incidence in degrees as we didn't want the builder to need a expensive , accurate digital level. This turns out to be helpful with many other aspects of building so will include the info in the revision to the BM and Plans sheets.

Look for this before we depart for Oshkosh in a few weeks.

Rest assured if you follow the BM your aircraft will fly fine and be able to be trimmed to any speed.

Post by **psalter** » Tue Jul 05, 2016 10:30 am

The first thing for setting proper HT incidence angle is checking that the forward and aft mounts have been cut to the proper height with this drawing. https://flywithspa.sharepoint.com/sites ... 20prep.pdf. As of the time of this writing, the forward mount is cut to 3 1/4" tall and the aft one is 3 1/2", but always check the drawing. Most problems with incidence angle to date have been because these dimensions were not followed.

After they are cut to height, you mount the rear ones per the manual to the fuselage. Mount the forward ones to the HT. The mounts are cut so the HT top skin can rest on the mounts, this will align the top of the mount with the top of the HT spars, and automatically set your incidence angle correctly.

The current incidence angle has worked pretty well for all aircraft from the Jabiru, Corvair to the O-320 powered aircraft. It allows the aircraft to be trimmed throughout the range. Dan may offer some information on minor variations to incidence angle for some special conditions, but what is out there now works fine.

Sacpilot · Post by **Sacpilot** » Tue Jul 05, 2016 10:17 am

With Rear HT mounts clamped to top of rear spar, and front HT mounts floating above deck and clamped to top of front spar stiffener as per the BM, I pushed down on the whole HT to bring it to the deck. By my calculation, this brings me to a 3-5 degree down incidence as the mounts float about 1-4-1/3 of an inch above the deck. Can anyone assist? I am under the understanding from Brent, that HT should be level to .5 down. What am I missing? rear HT mounts are fitted and bolted to the deck properly so that they don't move during HT front mount fitting.

Sacpilot · Post by **Sacpilot** » Mon Jul 04, 2016 11:27 am

Can someone post what they find out? I am ready to drill front HT mounts.

Thanks

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