Thorp Air Command - T18.net

Ran into a product called Plastifix. Urethane.com handles it. They have repaired a B25 canopy with it.

Bill,
Could not find a web site Urethane.com. Searched for Plastifix and found http://www.urethanesupply.com, looks like good stuff. Has anyone used this for a repair.?

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

The RV guys have used it. I think a B25 glass was repaired.

** admin posted for Bill Williams ***

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Forum Administrator

Hi Bruce,
Plasti fix is available at aircraft spruce,I have used it to repair
several cracks in my windshield,it is not the easiest stuff to work with but it works.---It melts the plastic and seals the crack,it does not look too good but seems to be a sound repair!
Dick Schaub---Thorp C-FSBD Welland Ont.

Hi All,
During the walk around I noticed some play at the wing root attach point--in the pin holding the wing to the fuselage
on the passenger side only.-Here is a stupid question,should there be absolutely no play there ? or is a little bit acceptable?
Also what is the best way to remove the pins and drop the center wing? I would like some opinions and expert advice from
you experienced Builders and Pilots,-as I did not build the Plane just re assembeld it after purchase!
Where could I buy a new pin should it be necessary,or may be a Bolt and Nut.---by the way the existing pin seems to be quite tight!
I flew the Bird approximately 230 hours since purchase in 2003---not many but very enjoyable hours!

Dick Schaub C-FSBD (Tigermouse)

Disconnect wing fillets. Remove baggage floor. Disconnect flap cables. Remove flaps. Disconnect any electrical and pitot connections, remove mount bolts and the whole wing comes straight down.
I don't think you need to do that tho.
If there is any movement, fix it. I would attempt to ream and replace, if I could.
Cubes

I'll offer my thoughts ; I believe you are referring to the pull pins in the main spar. I installed bolts in my S18. Les Conwells S18 had the pins installed and had about 1/8" play at the wingtip for the 20 years he flew it. Somewhere I was told 1/8 play was acceptable at the wing tip.

Close tolerance bolt to take up the slack ?

RB

Bill, are you referring to the horizontal?
Cubes

The main wing tip. I flew mine with this up and down end play for a few years , then installed bolts and the play went away. The think most builders use a hand drill or a light weight drill press to finish the spar fitting pin holes and the tolerances are not held. I drilled mine with a Bridgeport mill. Also the cad plate on the pins can add a little slop as it wears.
As for the tail I would not let it get much more than a 1/16".

Why can't a person machine with a lathe a ring into a AN bolt shaft so that the close tolerance of the bolt diameter and reamed hole can be matched, and the ring act as the stop just like the pull pins? Seems like the best of both worlds.

Can you get slightly oversized bolts in the event the spar fitting holes need to be re-reamed to get close tolerances and of course the matching bolt diameter to get a tight-tight fit.

ALso, what is the standard difference in diameter for a close fitting bolt and hole? obviously the hole has to be SLIGHTLY larger than the bolt diameter. But by how much? 1/64 of an inch?

Most close tolerance bolts I have found on the order of a few thousandths of and inch smaller than the designed hole.
I have never heard of any allowance of movement in the wing. I believe I have a note from JT that allowed small movement in the horizontal. I want to say less than 1/8 inch.
End result, I would ream to fit new hardware.
Cubes

When I took the wings off of 'Feisty' the bolts were rather snug. I drifted them out with a wood block and modest taps with a hammer. I am very confident these are good. I intend to install new bolts as a precautionary measure (cad plating looks old), but if the old ones have the superior fit, I'll stick with them. The lower gear mount bolt on the left side seems a little bent (no suprise), it needs to be replaced, and the motor mount bolts have slight wear marks, they will be replaced as well.
I looked at an S-18 before I bought 'Feisty', it had lathe built pins with a spring retention device, for ease of removal (folding wings)
These pins are easily made, but the material specification would be the important part. These are probably spec'd in the plans. Ream the holes 'clean', then build the pins, presuming the over sized hole does not compromise the strength of the part.
PS; How did wing pins/bolts end up in "Canopy"?

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Scott Emery
EAA Chapter 326
T-18 N18TE

Probably time to make wings,pins,bolts a new subject and get out of acrylic ?

RB

FWIW... 1/64" is much to much. Close tolerance bolts are within a few "tenths" (10/1000's) of an inch of stated dimension. In this application you don't want a fit that is too tight, but one that does require at least light tapping to install... I'm unsure of the exact terminology, but perhaps a "light, or medium interference" fit. A little light lubrication would then be good to facilitate installation & removal, as well as to minimize wear. You really should have no discernible movement at the wingtip.

Perhaps the administrator (Lee) could move these posts into an appropriately named thread?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE