Frame/Hull flex how muck is OK ? ?

Hi all,

I vaguely remember seeing similar questions but was unable to find the posts. So I`ll ask them again.

I am trying to determine how much flex is acceptible in my H16 (1977) frame. While sitting level on 4 blocks (rear blocks are about 1 foot forward of rear pylons), I can lift the nose of one hull exactly 5 inches (at the very tip of the bow) before the opposite hull starts to lift up as well. Is this good or sloppy?

I also have a little bit of side to side slop/rocker of the pylons in the castings. How critical is this type of motion? Should there be zero side to side rocker or is that unrealistic?


Dave

There are a couple of ways to take care of this problem. 5" isn't that bad. First, the motion of the pylons in the castings. You will hear people tell you to epoxy them into the castings. This will give you a great custom fit between the casting and pylon. I don't like this idea as it makes removal more difficult. I like making shims from old soda cans to insert into the gaps. This allows easy removal and adjustment.

Second, tramp tension. This will help tighten up your entire boat. The tramp adds rigidity to the frame like a gusset in a 90 deg joint. There are posts on this site and the hobie site abotu using your main blocks to get some prebend in the frame.

I think you will notice an improvement with just tightening the tramp. Doing the shim/epoxy to the pylon casting joint will help reduce wear caused by the parts moveing against each other.

Thanks Nick,

I am well aware of the methods you have mentioned. I also tend to agree with your wiews on permanently bonding the frame. However, it is not too difficult to use the epoxy so as to bond to one surface only - filling all/most gaps; reducing movement and allowing easier disassembly in the future.

A while back I read your technique with the soda cans - liked it too. Especially how you hook the edges of the can over the lip of the pylon.

My tramp is quite tight already (used ratchet straps instead of mainsheet technique...same result).

You mentioned 5 inches not being too bad. By comparison, do you have an idea what a new boat would have for flex in this regard?


Dave

I've actually never seen a new H16 so I have no idea. Matt Miller will be able to tell you.

I've seen some boats with as much as 13" of flex. It was awful. tightening the tramp took care of most of it.