Rick6a

Rick6a

Well Known Member
Today, as I was just about to drill the static port locations on the -8 side skins, I decided to review the instructions that came with the SPF50 static ports purchased from Cleaveland. The instructions include the following words:"...drilling a 1/2" hole into the .025" skin of the tailcone assembly.......It is important not to prime the inside of the skin......the thickness of the primer will also cause the port to not function properly......."

From what I gather from reading the instructions, it is important that the static ports protrude from the skin by a specific amount. I get that. The trouble is the side skins on the -8 are .032 thick. The ports are obviously machined to accept an .025 skin just like on my 6A where the Cleaveland static ports perform acceptably.

A call to Cleaveland resulted in "Go ahead and install them." I did not receive what I consider a satisfactory answer as to why the instructions are worded in such a way as to caution the builder to install them in a very precise manner. If the thickness of a primer coat is such an important consideration, why on Earth would .007 thicker skins not make any difference?

I guess what I am looking for here is validation. Have other -8 builders installed the Cleaveland ports and are they acceptable with the thicker skins?
 
Rick6a said:
From what I gather from reading the instructions, it is important that the static ports protrude from the skin by a specific amount. I get that. The trouble is the side skins on the -8 are .032 thick. The ports are obviously machined to accept an .025 skin just like on my 6A where the Cleaveland static ports perform acceptably.

I guess what I am looking for here is validation. Have other -8 builders installed the Cleaveland ports and are they acceptable with the thicker skins?
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Rick:

I installed the Cleaveland static ports in my -8. I didn't prime the interior so this was not an issue. When I installed the ports they were flush with the skin. Cool, I thought.

Being a first time builder, I didn't think ahead to when the aircraft would be painted. The paint shop very carefully masked off the static ports so that paint would not clog the hole. Problem was I now had several layers of paint that effectively raised the aircraft surface so that the ports were now ever so slightly recessed. When flying with friends I noticed I was indicating about 10 mph slower than they. Hmmmm?

After having my airspeed indicator checked (and my altimeter, too -- static system stuff) and being told they were perfect, I started looking for other answers. Where's an engineer when you need one?

I finally figured it must be the ports. At first I tried painting the ports (with the holes plugged of course) to bring them flush with the finish paint. But this is easier in theory than reality. So next I took a look at Van's rivets as orginally supplied. I simply cut the heads off with a Dremel tool and glued them (3M Weatherstrip adhesive) over the holes. Essentially this is nothing more than adding an extension to the hole so that now the port (rivet head) protrudes slightly above the painted skin.

Voila! My airspeed increased, my altitude climbed, my truck started working again and my dog came back home. Okay, I don't have a truck or a dog but heck, I live in Texas. :D

Moral of the story: Van is giving us all a hint with the rivet trick. You need the static port slightly above the skin level for proper readings at least when using the recommended location.

I think this is extremely important as incorrect static pressure may cause erroneous readings on your Mode C encoder, and baby around "Big D" airspace that ain't good. Or anywhere else for that matter.

Go ahead and use the Cleaveland kit if you like. Just keep what I said in mind. If you haven't installed them yet, consider a kit that has domed shape static ports such as the ones Safe Air offers (advertiser on this site).

Chris
 
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Westwinds

Hi Rick, I have a similar static port setup that i bought from A/S. I have a small lathe that i was able to turn the rim down on. This left plenty to cs and rivet the rim to the skin and gave me about .045 above the skin when installed. If you think there is enough rim thickness to allow me to take off anywhere from .020 to .050 let me know and i may be able to do the same for you. Tony
 
Cleaveland's Ports

I am sending this to Rick also, but I will post it here to update builders on our current ports.

For well over a decade builders were using our ports with great results. I am not sure if paint changed or standard practice but a couple of years ago we started getting calls about the ports not getting accurate measurements. We quized these builders on how they were installing the ports. The top three errors that resulted in the port being 'below skin level' where: buildup on the inside in either primer or installing them with RTV, lack of proper countersinking to accept the dimple in the skin thus pushing the port inboard, and finally not painting the port with the rest of the airplane.

The original ports were flat with a .035" step on them to protrude into the airstream (on early RVs) by .010". We did two things to solve this problem, we wrote instructions on how to install them and what people usually did wrong. And second taking Van's static design into account we went from flat to a .035" dome on the surface of the port. So now if installed correctly they should stick out .035". If not the builder will have .020" to play with before they start to show an error. Hopefully this is enough to account for lack of paint and glue in factors. Since making the change a couple of years ago there have been no problems.

Please email me if you have any questions: mike (*at*) cleavelandtool.com
 
westwinds said:
If you think there is enough rim thickness to allow me to take off anywhere from .020 to .050 let me know and i may be able to do the same for you. Tony
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Tony,

Thanks for your generous offer to remachine the step on the ports. As it is, Mike Lauritsen from Cleaveland offered to do the same thing if I want and I'll probably use his services. I have done much business with Cleaveland over the years and Mike was quick to get back with me with a truly informed answer to my questions. He made it clear he will review how the instructions are written and will make any adjustments required to satisfy the customer.
 
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