Stringer Question - Poor Design?

[atengnr]

I have a 1968 SAFTMATE, 15 ft fiberglass boat. Several years ago, I replaced the floor and stringers due to rot, but have a question about the boat's design....It has three stringers, one on the center line which is perhaps a 2x6 (cross section varies along the length of the boat), and two 2x4s on either side of the centerline.

BUT, these (2) 2x4s, rarely contact the underside of the floor anywhere along their length, due to the shape of the hull (they contact near the back of the boat, where the hull is fairly flat, but are on an inclined angle and are about 1 inch below the bottom of the floor near the front of the boat. What is the purpose of these two "stringers"?? Was this a common design back then, or is this simply poor design??

It seems like only the centerline stringer significantly provides structure to the boat given that its level on its top surface and the floor is in full contact with it...

Thanks.

 

[Frank Acampora]

Re: Stringer Question - Poor Design?

My interpretation of your post leads me to believe that the designers were trying to save some weight and perhaps some money in raw materials. The maximum load on a planing hull bottom is within the last three feet of length so my guess is they made the stringers contact the floor there to re-inforce both the floor and hull bottom. Further forward they probably figured they did not need so much support.

Remember: if a factory must cut a stringer to a taper, it takes a paid employee to cut it. Then they need to ensure that the stringer is glued in correctly. So, it is quite a bit cheaper to use a straight 2X4 than a custom cut one. It is not good to manufacture a product that no one will buy because it is just as good as, but more expensive, than the competition. So a lot of things are done at the manufacturing level to keep costs in line.

The mark of a properly designed product is: Does it do the job for which it was intended over its expected lifetrime.

Poor design? If the hull and floor are adequately supported--no. If you have problems--yes

 

[RotaryRacer]

Re: Stringer Question - Poor Design?

I wouldn't consider that part of it a poor design.

I redid a 73 Saf-T-Mate.

I rebuilt mine using the same basic geometry in that area. What bothers me about the design is that the stringers were not attached to each other. I added some "bulkheads" between my stringers to tie the whole structure together.

The 2x4 is actually tapered at the rear also.

Make sure to allow a way to get any water out from under the floor. That part of the design was really poor.

 

[atengnr]

Re: Stringer Question - Poor Design?

Make sure to allow a way to get any water out from under the floor. That part of the design was really poor.[/QUOTE]

Indeed this is the reason why i had rotted out stringers and floor in the first place....I have spent much time tilting this boat up and using a siphon pump getting any water out of this area over the last 15 yrs. Though it may get less than an ounce of water in each use, it never comes out without significant effort.....i think i found the leak source and repaired it (lousy patch from damage while removing the floor).

Is your 73 a well-built boat?? Mine does not seem to be, as the (deck) cap does lots of flexing when hitting waves. Is this not a sign of a poorly designed boat??

 

[RotaryRacer]

Re: Stringer Question - Poor Design?

I wouldn't say that Saf-T-Mates of the late 60s to mid 70s were overbuilt boats. They were adequate and nothing more.

My boat now seems very solid. I have some finish work to do and will try to sell the boat next spring.

I will also say that when the company was purchased by the Four Winns they improved the designs a lot.

I just bought an 81 Four Winns. Very solid, heavily built boat.

 

[atengnr]

Re: Stringer Question - Poor Design?

I wouldn't say that Saf-T-Mates of the late 60s to mid 70s were overbuilt boats. They were adequate and nothing more.

My boat now seems very solid. I have some finish work to do and will try to sell the boat next spring.

I will also say that when the company was purchased by the Four Winns they improved the designs a lot.

I just bought an 81 Four Winns. Very solid, heavily built boat.

Can you send me pics of your saf-t-mate?? What is the model name, size, max HP?

Thanks.

 

[RotaryRacer]

Re: Stringer Question - Poor Design?

Under the sole:

How I rebuilt the stringers:

I guess I did change the design some. However, I could have just used 2x4s as the original design.

In the Water:

I am not sure what the model name is. There is no ID plate on it. It is 15' long and obviously a tri-hull. I have been told that 70hp is its max rating.

 

[atengnr]

Re: Stringer Question - Poor Design?

Nice boat. It looks like saftmate really improved things by the 1970s. My boat is closed bow, but is much flimsier looking than your boat.

BTW, what is the purpose of the metal caps over the lower motor mount bolts...just anti-rotation??

Do you typically get water in the subfloor area of your boat??

 

[RotaryRacer]

Re: Stringer Question - Poor Design?

Thanks for the compliment.

I'm not sure what the metal caps do. They were there when I got the boat. They seem to work just fine.

I don't get water under there now. The only water that gets into the boat is from wet people getting in or wet life jackets and stuff. I left a 4-5" gap in the floor under the splash well so I can get any water that gets in, out easily.

 

[atengnr]

Re: Stringer Question - Poor Design?

Thanks for the compliment.

I'm not sure what the metal caps do. They were there when I got the boat. They seem to work just fine.

I don't get water under there now. The only water that gets into the boat is from wet people getting in or wet life jackets and stuff. I left a 4-5" gap in the floor under the splash well so I can get any water that gets in, out easily.

So you have left a hole in the floor so you can access the subfloor area?? Cant water get into the subfloor area easily if it splashes onto the deck?? I assume that everything in the subfloor has been waterproofed so that it can get wet? Could you provide pics?

Im wondering if it would be of value to cut a few access holes and install like some sort of access hatch - something that seals, but can be opened to access the area. Your thoughts?

Thanks.

 

[RotaryRacer]

Re: Stringer Question - Poor Design?

I don't have pictures of the inside of it finished right now. I'll see if I can get a few this weekend.

Basically I just cut the floor/deck piece about 5" short at the rear. So the stringers are exposed between the edge of the deck and the transom. I can now get any water out very easily. I just tip the boat up after using it to make sure all the water runs back and use a sponge to get it all out.