How much flex is normal?

[keelhauled]

Hi all,

I noticed an interesting phenomenon last time we were out on the water. I was sitting on the rear bench and allowed a friend to drive (rare occasion) and he crossed a rather sizeable wake at speed, at about a 45 degree angle. It wasn't much of a bounce, no more than a typical 'wub wub wub', if you know what I mean.

I witnessed a noticeable amount of flex of the hull, almost as though you could see it absorbing the impact of the wake the entire length of the hull. To better describe it, I could see the deck and gunwales move side to side independent of the sole. This is harder to describe than I thought.

This may not be something new and could possibly be characteristic of the hull design, but I've never noticed it before. I know the obvious answer is rotten stringers, but Lancers have hollow stringers therefore no wood to rot. If we want to split hairs, the engine support stringers do have a wood core, as does the transom. Both of which are confirmed solid.

Am I making a big deal out of nothing? I suppose there has to be flex or it would just break or crack, but how much?

I'd appreaciate your discussion!

 

[Frank Acampora]

Re: How much flex is normal?

Ever been on a commercial airliner and watched the wings flex up and down during weather?

A small planing hull is not a rigid monocoque body and some flex is inevitable. How much depends upon numerous factors including integrity of the hull and stringers, quality level of the hull itself, and engineering design.

Because of flex, a well engineered hull will NOT have any "hard points" where bulkheads meet the hull sides.

Even though they tend to get waterlogged, a foam filled floor (wow! Can you spell alliteration?) will tend to make the hull much more rigid

 

[Lyle29464]

Re: How much flex is normal?

I think you should check it out more. Not much flex in the early 60's stuff.

 

[ajgraz]

Re: How much flex is normal?

Check the deck, the connection between the deck and gunwales, the gunwales inside and out, and the hull bottom for cracks and/or soft spots. If you don't find anything, then IMO you're OK.

 

[Sharp Shooter]

Re: How much flex is normal?

Some boats flex and some don't. It all depends on how they're designed and laid up.

If you're worried do as others have suggested and do an inspection. Look for seperation and delamination. Use a quarter and tap the hull. You don't want to find soft spots.