Stringer Crack - Opinions needed. (Pic)

I called Four Winns directly. There were no reported problems arising from that stringer/engine mount design. He said it was used on many different models.
 
So I've been reading a little...

It seems that, though not ideal, if stringers are unusually thin and high, they need to be, more than thicker stringers, vertically stabilized with framing. That may be the case with this boat. If there is no delamination of the stringers, and there is no bending, then the stringers are performing adequately.

This boat has been banging around in Lake Michigan for 400 hours, with no noticeable delamination or other symptoms. If I go ahead with this boat I will get the surveyor to pay particular attention to this issue, and check for proper framing, hull stress cracking, stringer delamination, and during the sea trial to check for flexing and bending. If the stringers are not moving during a good sea trial then the stringers are fine. If there has been no problems in 9 years on Lake Michigan, then I believe she will be good for me on the waters I boat for a long time to come.

Thanks,
Shel
 
I agree, never saw such a flimsy stringer supporting an engine. They beefed it up where the mounts are so it must work for them. Ernesto, I can't see your pictures, but Crusader produces their own motor mounts. Sure makes alignment adjustments easier.
 
I agree Greg, even my old 1987 has a wonderfully tall and sturdy box stringer system with those mounts. I had to move an engine that was in place for almost 20 years to align it after replacing the cutlass bearings and re-bedding the struts, nothing to it.
 
I don't see it as a problem. Most boats in that category are built the same way. Four Winns is one of better builders.
 
IMHO, that stringer is a poor design. Remember, stringers don't just take an up an down load, they also take a side to side load. A thicker stringer is needed with a consistently thicker profile along the entire stringer to spread out the static and dynamic load of the engine weight. IMO, the reason the gelcoat is cracking where the thick section meets the thin section is flexing of the stringer under dynamic loads (when the boat pounds, etc.). This is comparible to a horizontal beam in a house that supports the ceiling joists. Depending on the span of this beam, you may need double 2x10's or 2x12's or even micolams and a builder wouldn't just make the beam thicker at the point where the ceiling joist meets the support beam, he needs the beam thickness consistent along the entire length to spread out the load of the ceiling weight. Have a mechanical engineer of even better, a certified professional engineer look at this and see what he says. Not all surveyors are well versed in mechanical engineering and may not recognize this as a potential problem. I would stay away from this boat.
 
FW is generally thought of as a good boat, but even on my old 88 FW Horizon 200, the engine mount pads are about twice as wide as the mounts themselves, glassed into a 3/4 in thick stringer. As others said wtih the age of the boat, if there has not been a problem the design is probably fine. I'd be tempted to look at a new model of the same or similar size boat and see what they are building now. If it's substantially different, that might give me pause.
 
I would check for delamination under the gelcoat by tapping the entire stringer with a phenolic hammer. If you find an area that sounds hollow compared to other areas, its delaminated. Delaminations don't always show up at the surface of the laminate. Another poor design feature of that stringer is that the severe and sudden change in thickness from the doubler to the thinner area. They should have beveled the edge of the doubler so it gradually gets thinner as it integrates with the thinner area so the load would be spread out better. Fiberglass/composites don't like sudden changes in thickness and when they exist in a heavily loaded area, it will eventually fail there. Why don't you go to a FW dealer and look at a new 338 (which I belive replaces the 328) the and see if they still use the same stringer design...I bet they don't.
 
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