Fanny dented Strut

[Cajun Joe]

I know this guy who has a friend with a cousin named Henry with a PA18. While Henry's back seat passenger was climbing out fwd of the struts he slipped and planted his elbow in the front strut 3 feet out from the fuselage. Henry asked me if there is a reg that can be found to describe what size dent (if any) is permitted in the forward strut. Can a hole be drilled in one side of a strut to have the dent "massaged" out by one of those "dent master" guys.????

 

[sj]

Joe,

My only thought would be that drilling a hole in them is that they are sealed struts and you would be unsealing them.

But what do I know?

Sounds like passenger training is in order.

sj

 

[behindpropellers]

I know this guy who has a friend with a cousin with a PA18. guys.????

Probably get that cousin to buy a new strut. You can sell your old one to some crazy experimental guy, they will buy anything.

 

[Steve Pierce]

Small dents are acceptable. Univair sells slightly dented struts at a discount. They might could give you the criteria for usable vs. scrap. I wonder if one of those spot welded dent puller things might work?

 

[Charlie Aileron]

"Probably get that cousin to buy a new strut. You can sell your old one to some crazy experimental guy, they will buy anything."

I resemble that remark!

 

[Speedo]

The engineer in me says to be very careful with dents. The struts can fail in compression mode, and the dent can be the origination point. Very small dents, say the size of a dime, probably aren't a problem. Bigger dents, say with a 2" diameter, would be a problem in my eyes.

Dents with creases or sharp edges would be a big problem, too.

 

[SuperUrsus]

I agree with PA_12pilot. Sounds like you need a new strut and the passenger needs some cub counseling.

 

[cubscout]

Look at the Strut A.D. for guidance. Some specific text on dents and corrosion. As I read it, NO dents are acceptable, but then it's from memory, and I'm ususally wrong.

Thanks. Cubscout

 

[bob turner]

I don't remember any discussion on such dents, but a lot of older cubs have them, due to mis-handling while off the aircraft. You know; they slip off the sawhorse while you are sanding, etc. They don't seem to hurt anything.

My first thought is that if an elbow put a dent in a strut, it probably bent the entire strut. Then it is a throwaway. So, of course, is the elbow.

Second thought is that a standard length strut has relatively little ability to withstand compression even without dents. Don't pull more than a half-negative G on a Cub, unless the struts have been shortened.

I show everybody my "No Step" stencil, and tell them that it really means "don't even touch this strut". We then laugh, and avoid the struts altogether. Stepping on struts is why we have all those ADs on them.

 

[Lawn Dart]

You might try mentioning to your passenger how much it cost you to replace the strut and see how they respond.

Or you might do as this guy did and just repair it yourself

 

[Jon B.]

One of the rear struts on '57B had a 'patch' welded on it. I presumed it was to cover a dent . Wouldn't that be a legal and less expensive option to replacing the strut?

Mine all turned out to be rusty on the bottom ends, so they were all replaced anyway.

Jon B.

 

[AV8R2]

Dented Lift Strut

I asked and aeronautical engineer the same question and he asked me if I would use that strut if the dent were a hole. Of course I said no. He then said that is exactly what that dent was in this application; a hole! The strength of the strut is compromised; especially in compression loads.

For what it's worth...............

Burl

 

[CubCouper]

My pucker factor would make me replace it, but that said, wouldn't a strut only be under compression when the plane is not flying? When the wing is generating lift the strut would be under tension. Just asking, in the off chance that a guy has to return from the wilderness with damaged parts some day.

 

[Aviator]

- G.

 

[Speedo]

Much of the time the strut will be in tension, but there are many times during a flight when it will be in compression. This will be particularly true in rough air.

We've all seen how an empty soda can will support the weight of an adult, provided the load is applied gently and in line with the can's axis. And we've all seen how the same can will collapse in an instant if someone taps the side of the can. This is an example of a compression failure.

An dented strut will fail at a much lower load than an undented strut, but it's impossible to calculate how much lower.

Having a strut fail in flight would ruin one's day. Why take the risk?