Is this overkill or a proper design?

I have a bassboat (1993 Vision) that I got essentially for free (I bought the engine and the boat and trailer came along as part of the deal). Instead of cutting it up and taking it to the dump I talked my son into rebuilding it with me, and he'll get the boat as a graduation gift when he finishes college.

I'm wondering about the design, to me it looks like they went way overboard. It has 5 stringers (plus 2 little 2" thick ones that are about a foot from the edge of the hull), a transom brace plus 4 transom knees. Here's a couple photos that show this:








ALSO, the hull is constructed with 3/8" balsa core, but the core only extends from a couple of inches on each side of the stringers. Here's a very rough sketch showing that:




That just doesn't seem right to me (and it's different than I've ever seen before).


I'm hesitant to redesign a boat, but if I do I'd just make it very similar to my Checkmate which I rebuilt a couple of years ago (uninterrupted balsa core, transom brace, 2 knees, 3 stringers.

Thoughts?

 

Your post has been up for several days with no reply. Most of us are sociable and friendly sorts but the nice guys have failed to comment. I'll start. Though I claim to be a nice guy, I am also a frequently practical one. OK, lets face it , people smitten with boat fever are not famous for being sensibly motivated.

If you are into self flagellation then I think that you'd ought to restore the boat. If not, then the chainsaw is a more practical altenative.

 

Which answers none of his questions...

I'm not qualified to answer them, but I'm sure there are people here who can.

 

If the old girl doesn't show any signs of cracking or crazing in the glass or gelcoat in those areas you are puzzled about, I'd say it isn't a problem.

 

I'm not sure about the laminate schedule or power expectations for this design, so couldn't tell you if it's over kill, but with cored projects, you can go over the top a bit without as big a weight penalty.

Consider how long it survived like that and ask if this was sufficient service span or if you more. Most things should be apparent, as Mr Efficiency has noted, but building her as she was, seem on the surface a reasonable approach.

As to the core arrangement, it's difficult to see what you're concerned about. You could skip the core and bulk up the laminate or you could use a different core material or you could do as was done. The tapered sections that I think you're worried about was (IMO), to put solid laminate in the stress riser areas, so the core wouldn't be involved. This is a common practice with core at corners and hard transitions, to eliminate point loading.

 

Thanks for the replies. I've been working on the de-construction some more and have learned a bit more about this hull.

First off the areas I showed in my sketch between the core and stringers had a lot of voids where the glass wasn't contacting the hull layup. I'm sure that was bad from a structural standpoint, plus it accelerated the spread of water and rot. What it looks like to me was that it was too tight of a corner for the heavy biax cloth to conform to.

Also, I had assumed that the core was balsa (up 'till tonight I had only taken glass off of one small area of core so I could measure the thickness, and it was totally rotted there). Turns out the core was just 3/8" plywood.

Anyway, unless someone can talk me out of it I'm planning on roughly copying how my Checkmate was constructed. I'll do a continuous balsa core covering the entire area that was originally cored, layup 2 plies of biax over the core, then place stringers over that.

Once we get done this should actually be a pretty decent boat. The hull itself is in good shape, and the gelcoat is great, so with some elbow grease it should look pretty good.