Safeair 1 Pitot Mast...

danielhv · #1 07-17-2010, 08:22 PM

May be a stupid question but better than a stupid mistake!...

Is it a possibility to cut the mast to shorten it and still have acceptable readings from the pitot? I'd like to take 1 - 2" off this thing... its a little to long for my taste.

Bevan · #2 07-17-2010, 11:25 PM

I'm putting a more robust style pitot tube on too.

For those with the standard Van's style pitot tube, what is the vertical distance below the bottom wing surface to the center of the pitot tube inlet?

Bevan

PCHunt · #3 07-18-2010, 12:06 AM

Quote:

Originally Posted by danielhv

May be a stupid question but better than a stupid mistake!...

Is it a possibility to cut the mast to shorten it and still have acceptable readings from the pitot? I'd like to take 1 - 2" off this thing... its a little to long for my taste.

My philosophy, which seems to work for me, is: "If it ain't broke, ......don't fix it."

My guess is that the length is there for a reason.

danielhv · #4 07-18-2010, 12:32 AM

Quote:

Originally Posted by PCHunt

My philosophy, which seems to work for me, is: "If it ain't broke, ......don't fix it."

Now where would the fun be in that?

AX-O · #5 07-18-2010, 09:35 AM

Quote:

Originally Posted by Bevan

Van's style pitot tube, what is the vertical distance below the bottom wing surface to the center of the pitot tube inlet?

Bevan

6 inches. (extra words)

danielhv · #6 07-25-2010, 09:30 PM

Well, I know some will say just leave it as is, but I'd still like more input on this idea... Im not up to par on airfoil dynamics etc... so can anyone help me out?

Is there a NEED for the pitot to be so far away from the bottom of the wing? And if I DO cut the mast to shorten the distance... how close is too close? I'd like to get the BOTTOM of the pitot tube itself 3" or so from the bottom skin. Is this realistic?

schristo@mac.com · #7 07-25-2010, 09:48 PM

install the mast and move on... if you really find it bothersome when you are actually flying cut it down an inch or so, reinstall the pitot and test the airspeeds against your benchmark... repeat until the deviation is too great or you are satisfied with the overall height.

AX-O · #8 07-25-2010, 11:34 PM

Quote:

Originally Posted by danielhv

Im not up to par on airfoil dynamics etc... so can anyone help me out?

Is there a NEED for the pitot to be so far away from the bottom of the wing? And if I DO cut the mast to shorten the distance... how close is too close? I'd like to get the BOTTOM of the pitot tube itself 3" or so from the bottom skin. Is this realistic?

You may be able to cut it down from 6 to 3 inches and may not have any problems. Some people have used Piper blade pitot tubes without any problems. However, the only way to get a definitive answer will be by wind tunnel testing ($$$$$$$$$) or actual flight test ($$$).

You want to try and place the pitot tube in as clean and undisturbed airflow as possible. The nose of the aircraft or the leading edge of a wing work well but place the pitot tube in the way and can get damaged by people in a variety of ways. Placing the pitot under the wing provides shielding from people and at a certain distance (depending on wing and airflow surrounding the area) from the airfoil can function in undisturbed flow. The closer it is to the airfoil, the dirtier the air is and the more possibilities for errors in pressure (meaning errors in airspeeds).

In flight test, sometimes we spend years (even after CFD and modeling) trying to find a location that provides good results. The current program that I am involved in has had 3 different locations for pitot tubes. Now the air data computer uses correction factors to account for pitot tube location errors.

Hope this helps.

chris mitchell · #9 07-26-2010, 05:12 AM

I have a SafeAir mast installed with a Dynon AOA pitot head.

Personally I couldn't see a reason to shorten the mast - the pitot is in the same position as the Vans system, risk of damage seems minimal and shortening the mast is only likely to introduce position errors, with no way (wind-tunnel testing aside) of assessing what the error was likely to be before flight testing.

Now I'm flying (about 110 hours so far) and I'd rather go flying than take it apart, shorten the mast, go check the position error (tedious process), find it was significant and then have to find some way of making the mast longer again.....

Maybe some things are just better left????

I'm sure you plenty of other parts to work on?

Chris

RV6AussieNick · #10 07-26-2010, 06:00 AM

The Pitot is more than likely designed to be a certain length away from the under surface of the wing to eliminate erroneous air speeds, remember there will be a bow wave (compression wave) coming off the wing leading edge.

Personally I wouldn't mess with it.

If its an aesthetic thing then you might have to learn to live with it or you could ask VANS for there ideas.

Cheers,

Nick..