Thorp Air Command - T18.net

Does anyone have a way to seal the flap actuation slot in the fuselage side? With the cold weather I have too much air flow coming in from the aft fuselage. In the past this has not bother me but my wife has started flying with me more now and she gets cold quicker than I.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I cut a piece of the foil backed bubble insulation to slide between the seat backs and the opening to the bagage compartment when it is cold. Helps cut down a lot of the cold coming up from behind me. The only time I notice cold air coming in is when I drop the flaps for landing. I do not have boots around my sticks and with the flaps down some air is forced up around the sticks.

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Matt Smith
Des Moines, IA
55RC

I really like the way Dick Penman did it. NL137.

D

Hi Bruce, I have a 2" hot air inlet right at the wife's feet, that's where my heater blows warm air in the cockpit, keeps her toasty. My baggage floor seals the fall slots from the baggage compartment so I get no draft from them......Gotta keep the wife warm they stay happy that way, Gloria loves to fly with me and I sure enjoy having her along. Dan

My problem is that cold air is coming up from under the seats and out of the slots for the flap handle. All of this air is coming from the tunnel not out of the baggage area. So I'm trying to close off any opennings to the aft fuselage that would allow air to enter and at present it is the flap actuation slots. My cabin heat distributes warm air to both sides on our feet, they are staying warm but my wife complains of the cold air coming up from under the seat on the back of her knees.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I rolled up a piece of left over floor carpet and glued it to keep its shape with some silicone glue . I then placed the rolled up carpet between the front edge of the seat and beam box . It also keeps items from falling thru into the compt. below the seat .

How did Dick Penman do it?

Here's an excerpt from a newsletter suggestion from Tom Kerns ...

There are three T-18's here at Flying Cloud Airport, each with a different type of air seal to close off the flap actuator slot. Without a seal, the slot produces a tremendous draft making winter flight an ordeal. My T-18, NIOTK, uses sheets of 1116" Phoenelic with a one inch hole riding on each flap actuator tube and held against the inner side of the fuselage skin by .025" sheet metal guides. The Phoenelic is cut to butt against the rear spar mounting bulkhead when the flaps are up while extending aft far enough to close out the flap slot. The slider rides on the top edge of the lower fuselage longeron as the flaps move aft (with flaps down, the seals do not close out the forward end of the flap slot). The seals work well and are trouble free but could be a chore to
retrofit to a fully assembled airplane.

Dave Fox, N444DD, worked at adding seals similar to mine but decided there had to be an easier way, and created aluminum boxes covering the flap actuator arms and attached to the inside of the fuselage side skins. The aft ends of the boxes are open to the rear along the cable run. Sewn fabric
cones seal from the open aft end of the boxes to the flap cables. This works
great and may be easier to put into an assembled existing airframe than my sliding seals.

Darshan Karkey, N4MY, looked at our efforts and concluded that there must be a still simpler approach. Darshan cut a 0.9" hole in a sheet of rubber gasket material, slid it over the one inch flap actuator tube so that it is on the outside o f the fuselage, and super glued the rubber to the actuator tube. Darshan trimmed the forward end to clear the rear spar with flaps up, and trimmed the aft end to just cover the slot, The rubber just slides against the side of the fuselage, and air loads hold the rubber against the fuselage side, sealing off the slot when flaps are up.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

I originally had the essentially the Dave Fox method although I have nothing sealing the flaps now. I do have a lot of cold air coming forward from the baggage compartment which I can limit with a piece of poster board between the seat backs against the bulkhead. An interesting data point, I have a smoke system and when I turn it on within 10 seconds I have smoke in the cockpit. I don’t see how the exhaust/smoke can get to the flap actuator holes so it must be coming in somewhere else, presumably the tail cone. I am interested in your thoughts but I brought this up to wonder if sealing the flaps will stop the cold air. I would also be really happy to stop the smoke coming in not to mention I know that means exhaust fumes must be there all the time.

I pretty much assume the exhaust I smell sometimes is coming in through the flap slots. No other holes in the fuselage until I get to the rudder cables but could be coming from there too. Smoke would follow the same path. Maybe putting a camera in the baggage area would show where the smoke is coming in.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I don’t have anything blocking the flap kidney opening. I do get cold air in. I had an active carbon monoxide detector installed for a while and it never showed anything. My thought process was that the exhaust would be well clear of the flap control. I guess I’m wrong. It wouldn’t be the first time I was unsuccessful at telling air where to go.
Cubes

Here's my version of the flap actuation slot seal,

I use a piece of 1" thick foam, don't know what kind it was left over from a previous project. I made a template from the flap drawing -632L


The aft portion is just stuffed up into the end of the flap by moving the flap as far down as posible, it's held in by friction, in six years I haven't lost any parts yet.


I had to remove the wing-body faring to get access to the nose of the flap and stuffed the front portion in.


Flap fully retracted.


Does it work? yes it slowed down the amount of air coming in but I believe the majority of air is entering via the spar box from the wing root.

So far in my quest to reduce the amount of cold air in the cockpit the most effective was to place a "curtain" along the side canopy rail to slow the air flowing out of the cockpit. I used "duck" cloth (thats the stuff the original duck tape was made from) and velcro to hold it in place, don't currently have any photos will have to get out to the hangar and shoot a few.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

See other thread on this for best solution using a shift boot.

Velcro the rubber shift boot below to the inside of the fuselage where the flap arm comes thru. The boot slides over the arm perfectly. Problem solved.


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