Draft ??

[Skippydiesel]

First flight day is getting ever closer. The excitement is building.

The wings will be installed for the final time and I am wondering about those 2 big holes on each side of the fuselage - how drafty is a Sonex??

What have builder/pilots done to reduce uncomfortable cold air drafts coming in to the cockpit at hip and calf hight?

[ldmill]

That area is really drafty - and that is an understatement. During the winter it blows enough cold air on me that it's uncomfortable. I haven't addressed it yet, but it's literally next on my list. Some folks have talked about a leather covering over those areas, I've pondered super soft/stretchy type convoluted boots - or even just basic felt retained with velcro. Whatever I end up with, I want easily removable however as in the summer time - it's really nice to get that level of ventilation.
Lorin

[mike.smith]

Yes very drafty. At the fuselage holes at the leading edges, I filled those holes with some deftly shaped 1" thick pink rigid insulation, and that has worked well.

Where the flap and aileron pushrods go through the fuselage, that is trickier, since the stick pushrods need to move in several axis. I tried making a witch's hat of faux leather to close that up, attached with velcro to the fuselage. It's very tricky detailing, and I did it after the wings were installed, so it never worked well. It would have been much easier to work in that area if I had done it before attaching the wings.

So I stuff a hand towel between the seat cushion and the fuselage (pilot and passenger sides) to keep the worst of the draft off my legs. It's tolerable in the winter, but not ideal.

[Rynoth]

So I stuff a hand towel between the seat cushion and the fuselage (pilot and passenger sides) to keep the worst of the draft off my legs. It's tolerable in the winter, but not ideal.

This is all I've done as well. Provided I'm dressed appropriately for the weather, the only real issue with cold I was having was the draft directly on my left leg. A hand towel did the trick, and it doubles for use in the summer to wipe the sweat off my brow.

[Skippydiesel]

My thanks to you all for confirming that the fuselage/wing ports can be drafty (as I suspected). Timely advise as it facilities my attempts to reduce the draft before the wings are attached.

I am just starting to research draft mitigation materials. So far I have asked for samples of "Engineering Felt" in A Grade , Firm White & B Grade - all 4.8 mm thick. As I understand it the Grades refer to density/stiffness.

At this erly stage I have chosen felt because ;

Its is both stiff & has a degree of flexibility (allowing movement of aileron rods and flap mechanism)
Durable
Fire resistant
Unaffected by environmental temperatures.
Can be shaped/cut using a sharp tool (box cutter, scissors or similar) & will retain its shape.
Available in a range of thicknesses from 1.6 - 24.5 mm (space between first wing rib & fuselage side is approximately 20 mm)

I welcome your on going advise/comments.

[Onex107]

In the Onex the wing holes in the fuselage are one source of outside air but the draft from the rear fuselage is equally big due to the negative pressure in the cockpit.

[Skippydiesel]

In the Onex the wing holes in the fuselage are one source of outside air but the draft from the rear fuselage is equally big due to the negative pressure in the cockpit.

Good points Onex107.

I like to be able to control air flow in the cockpit. My, yet to fly Sonex Legacy, has two NACA ducts, feeding through SCAT ducting, to eyeball air vents. I hope this will be sufficient for in flight comfort.

The last thing I want, on a long cross country trip, is a blast of uncontrolled cold air onto any part of my anatomy - the discomfort detracts from the wonderful experience of flying.

As for rear fuselage air flow - as long as its not a blast of air, this will be just fine. If it turns out to be a blast, I will find some way of reducing its impact - probably curtain of the second bulkhead behind the cockpit.

[Skippydiesel]

Have been trying to come up with a draft excluding design for the aileron push rod circular holes.

Obviously there must be no restriction on the aileron push rod movement. It seems to me that two fabric (possibly felt) cones/rod might be the way to go.

The cones would be secured by a "doughnut" of some light weight material (expanded polystyrene/EPDM sponge/etc). The doughnut (100mm/4 " centre) will be held/stuck in the 20 mm gap between the first wing rib & the fuselage wall/skin.

One cone would go onto the wing , the other into the fuselage (duplicated on each side of the aircraft).

The cone hight/length would be sufficient to accommodate full lateral movement of the aileron push rod.

The flexibility of the cone material will allow for vertical movement.

The tip of the cone would be a close fit (not clamped) on the push rod. This would ensure/with cone hight, that there will be no rod movement restriction.

It may be sufficient to have one cone per rod - I would assess this at the time of installation.

The flap hole (which in my case also has wing tank fuel and pitot lines) is much easier to "fix". I figure a sheet of semi rigid felt (or similar) can be stuck to the outside of the fuselage (if necessary duplicated on the inside). The felt would have carefully sized holes for flap mechanism, fuel & pitot lines.

Comments please.

[Skippydiesel]

Making a paper cone, to use as a pattern for my felt draft excluder idea should be easy.

I can make a cone okay, even checked out some "How To..." videos (there are heaps) but do you think I can make one that has just the right dimensions??? Nooooo!

FRUSTRATION!!! - just have to make more cones, in the hope one comes close to my careful measurements.

[Skippydiesel]

Wing root to fuselage/cockpit draft exclusion complete. Looks good - tried to load photos - no luck.

I will not know how effective my draft mitigation is until the Sonex flies - sometime within the next month or so. This will be middle of winter for us, so best time to test.