Decalage angle

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poormansairforce

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What would you do with manometer data? No doubt low pressure, but what is normal?
If we know the pressure and the vector we can calculate approximate drag as well as moment of drag under the thrust line. That would give us the stab down force needed to balance for this specific area.

I offered it since he so far doesn't seem to have a clear path forward.
 

Eugene

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My logic was much more primitive than that. I was simply thinking if we know difference on pressure drop from one point to another we can simply determine how really bad things are and which direction to go. I have no idea what is expectable from pressure drop Standpoint and what will be acceptable range
 

Eugene

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Ok, I will ask same question from different angle.

In my every day life I use a lot of numbers: delta T°, temp. rise, temp. drop and so on. Pressure drop is also on the list. If you know and understand relationship between this numbers = you can explain any problem out there.

So, in aviation world must be some kind of roles for fuselage pressure drop between point A and point B at 100 MPH if this 2 points lets say 12" apart pressure drop should not be grater than 5" WC or so. Otherwise you are entering separation zone and start creating more drag.

If we don't know about that role, Then my readings not going to do us any good. I wouldn't know what to do with it.
 

poormansairforce

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Well, in a normal plane the fuse bottom wouldn't have the sharp curve that the Skyboy has. So if there is a pressure drop of 5" WC then that equates to .18 psi so if you have 2 sq.ft. of fuse surface on the curve then that equals about 51 lbs of extra force pulling down and back.

Its not really about a pressure difference between two points because all planes have a nose that air will push against. Its just that yours has a bubble bottom exerting an extra force. The question is does that force have a serious impact on the plane?

Once you have a force you can plug it into one of your patented drawings and check the down force needed at the stab.;)

Please don't do this if your not comfortable with it!
 

Eugene

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Please don't do this if your not comfortable with it!
Not comfortable with what? Drilling some holes in my airplane? I can do that all day long!!! Its not my problem at all!!!

Trying to understand what we going to with my measurements, when I will find the way to get it done.

Piter Garrison was telling me that fuselage position in flight not making big difference at all. That wing is by far biggest drag producer.

But I think most very knowledgeable guys were dealing whole life more or less with normal airplanes. I think Skyboy situation is unique. Nobody really know what to do.
 

poormansairforce

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I think Skyboy situation is unique. Nobody really know what to do.
Those are the magic words. It was designed for a mission and now the mission has changed. As you have seen the pressure recovery of the fuselage isn't very good. Its just a matter of deciding what your willing to do about it. And info helps make that decision.

If my hunch is correct then you'll understand better why fixing the stab didn't work very well. Any drag under the thrust line adds to the stab down force needed. Any negative lift adds a load for the wing to carry.

The question is which fix returns the most benefit? Do you think fairing several small locations will return better results than one large area? These decisions are yours to make.
 

Eugene

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Any drag under the thrust line adds to the stab down force needed. Any negative lift adds a load for the wing to carry.
Agree 100%!

The question is which fix returns the most benefit? Do you think fairing several small locations will return better results than one large area? These decisions are yours to make.
I am not looking fast or easy fix with best result. This is project for next 10 years. Feel free to call me crazy. But to get to the bottom of it would be very big accomplishment for me. Let them log 100-200 hr every year of straight and level flight, have fun and be proud of themselves. I will be OK with only 30-50 hr and every year flight to Oshkosh. Straight and level for more than 20 min is boring for me. I am sitting up there and thinking about things I can change or improve. Here is 10 year program maybe in different order:

- different rear cowling
- engine cowling
- new horizontal tail with 9% airfoil and larger span
- wing swept 1-3° to move CG forward as compensation for new tail
- front wheel fearing
- improve main wheels fearings
- new 20-25 gal tank vs 15 gal
- build large door for baggage compartment
- build all new IFR instrument panel with 2 GRT 7" EFIS
- autopilot with altitude hold
- replace glass on doors and windshield from 1/16 to 3/32
- build new winglets
- replace wing fabric
- extend hard leading edge from 10% to 25-30%
- when nothing else to do get IFR ticket using Skyboy
- convert engine to injection using Edgeperformance $6000 kit

P.S. looks more like 15 years already
 
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poormansairforce

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Feel free to call me crazy.
Nope, I'm jealous you have a plane to do these things and that your doing it. You and I are much alike. Solving problems is like a drug for me. Makes me think.:cool:

P.S. you'll need to change the name of the plane after all those mods since it won't be a Skyboy any more. How about SkyRusky?:D
 

Eugene

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At only 4800 rpm and relatively high AOA on this picture main wheel fearing acting like air scoop with pretty big distance from engine.

fullsizeoutput_1717.jpeg fullsizeoutput_1716.jpeg
 

Eugene

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fullsizeoutput_1718.jpeg

This picture was taken from far away. Skyboy in level flight position.

Just want to make sure that everybody agree with statement, that horizontal tail operating in the shade of wide fuselage and not getting good airflow.

I don't see it that way. Fuselage at this level is only 30-32".

I do see however that tail is outside of propeller air stream.
 

BBerson

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That fuselage bottom is quite a bit wider than most. If the fuselage was narrow on the bottom with small gear legs sticking out it would be much less separation on the short fuselage. Also the down visibility is much better if you can lean your head over and see over the side.
 

BBerson

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It's not the wheels. You can't lean over the side to look straight down without hitting your head on the top of the door.
The widest point of the fuselage should be where your head is. Some airplanes and helicopters have bubble side windows so they can see straight down. The Skyboy tub is much wider than needed and that is extra drag.
 
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