Hull Strength??

[Skink]

Guys, I picked up a 1974, 21' Seacraft CC with the intent on restoring it....

After I brought it home and cut out the deck, I noticed how flimsy the sides feel(From the outside)

Is this normal for an older boat? My 90' aquasport seemed solid as a rock, this Seacraft doesn't feel that way at all.

Opinions? Anyone with an older SC with an opinion?

[workinpr0gress]

At that time period many boats just kept piling on resin and layers upon layers of heavy fiberglass fabrics. SeaCrafts are fairly light and are strong and thick where they need it and thin where it isn't needed. In it's entirety it is very strong when everything is right and most times when everything isn't right. Problems definitely add up over time with some boats when things like delimitation, rot, poor hull to deck joints, glass breaking away in corners etc...

I assume you have a 20'?

[bly]

Originally Posted by Skink

Guys, I picked up a 1974, 21' Seacraft CC with the intent on restoring it....

After I brought it home and cut out the deck, I noticed how flimsy the sides feel(From the outside)

Is this normal for an older boat? My 90' aquasport seemed solid as a rock, this Seacraft doesn't feel that way at all.

Opinions? Anyone with an older SC with an opinion?

No core in the bottom or the hull sides. The hull sides are thinner. The stringers are foam with fiberglass. No plywood there like many others back then. The boat was built with a 2 piece construction. So there is an outer hull and a skin also on the inside on the sides. No core. On most newer boats they core the hull sides today especially on 3 piece construction. The transoms were all plywood back then so that usually goes bad after many years. The Floor is also cored with plywood back then and usually needs replacing.

[Bushwacker]

If your boat is a '74, has to be either a 23 or, more likely a 20. The only SeaCraft 21 was the grandfather of them all, the rare Moesly 21 http://moeslyseacraft.com/SC21Brochure.aspx built in the 60's, or the later Tracker 21 (built in the 90's?)

As a highly experienced pilot from WWII, Moesly knew how adversely weight affected performance, so he designed the 20's sort of like an airplane. He came up with a light but VERY stiff structure when the hull/stringers, inner liner and deck cap are all bonded together. He then raced his designs in the very rough offshore powerboat races in the 60's to find out what worked and what didn't. Did you remove the top cap or cut out the entire inner liner? If you remove the cap and inner liner, yes the individual pieces are fairly light, but that doesn't mean the final assembly isn't very stout.

If you want a very detailed description of the hull construction, click on Classic SeaCraft Home at the bottom of the page and go look at the Boating Magazine article on the '69 Seafari in the Literature section. If you find it hard to read, PM me with an e-mail address and I can send you a good .pdf file of the article. It contains sketches showing the layup schedule and thicknesses for the hull and stringers. The hull bottom is naturally very stiff at each vertical step, but notice how the 4 stringers, which are installed about half way thru the layup, attach to the hull in the center of each panel, locally thickening the hull in what would otherwise be be the softest spot. As a retired aerospace engineer, I would say it's a structurally brilliant distribution of material! In 1974, Potter changed Moesly's original 4 stringer design to 2 wide box stringers, which I have to believe is a cheaper but less uniform and therefore a less optimum distribution of material. However there is no history of any hull problems on any of the 20' models that I know of. Some of the later Potter 23 and 25 models have had some rare quality control issues, and workmanship on the later Tracker models doesn't seem to be up to the Moesly/early Potter standards. Don't know if it's in the Literature section, but I have a factory brochure from about '78 comparing the SeaCraft laminate schedules to Bertram, Formula, Pursuit, etc.; the SeaCrafts typically had the same or more layers of the comparable size Bertram, which were noted for being "overbuilt"!

I became a believer in SeaCraft's hull integrity after my first return trip across the gulf stream from the Bahamas in the late 70's. Winds varied from NE to N to NE, producing steep breaking seas of up to 6-8'. I quickly learned why the old salts always said "If the wind is out of any northern quadrant, stay the hell out of the gulf stream!!" Took us 4 hours to run the 60 nm from West End to Palm Beach (Lake Worth) Inlet. Our "flotila" included a Moesly 21, my 20' Seafari, and a Wellcraft V-20. The 21 had zero problems and had to slow down so the 20's could stay up with him. When we got to the ramp, my friends V-20 had virtually disintegrated . . . the seats had come apart, there was a big crack in the cabin bulkhead, his twin saddle tanks had busted loose at the welds, and when he got it out on the trailer, there was a 4' crack in the bottom of the hull!

On my Seafari, a few of the screws in the cabin bulkhead were loose, but that was it! I was totally beat, but the boat held up just fine!

As for the Aquasport, another friend of mine told me that after making a rough crossing to West End in his Moesly 21, he saw an Aquasport being hoisted out of the water with water pouring out of numerous cracks in the hull! It didn't sink because of all the foam, but it did not appear to be a very robust hull! He said there are some good glass repair guys in West End with a lot of first hand experience of which boats had problems crossing the stream. SeaCraft hulls were highly regarded by those folks! The Aquasport? - not so much. Denny

[Skink]

You guys are outstanding, the 21 was a typo, it is a 20 with the two large foam filled stringers. I was thinking about filling the void between the hull and the liner with 2lb foam, mostly for my peace of mind. What do you think? Good idea?

[gofastsandman]

Originally Posted by Skink

You guys are outstanding, the 21 was a typo, it is a 20 with the two large foam filled stringers. I was thinking about filling the void between the hull and the liner with 2lb foam, mostly for my peace of mind. What do you think? Good idea?

No.

If you wanna foam, fill under the gunwhale, but not around the filler hose. I suspect they do that for a reason however. Where Wolves of LLoyds or some such authority.

FRP is designed to flex for a looonng time.

The old racers are what I would think to be thin.

I would be wrong.

Here we are these many years later, and they are still in our thoughts and desire.

Gobble,
GFS

[bly]

Originally Posted by Skink

You guys are outstanding, the 21 was a typo, it is a 20 with the two large foam filled stringers. I was thinking about filling the void between the hull and the liner with 2lb foam, mostly for my peace of mind. What do you think? Good idea?

It would be impossible to put expanding 2 lb foam into that small area to I guess stop what you perceive as a weak area?? No it is not. Yes you can have what they call an oil can effect because both pieces are not extremely thick or cored. But as Bushwacker said and documented. No failures. Expanding foam would only cause probably the inside liner to bulge in different areas and look ugly. Yes there are many things that need improvement to the 1960s moseley hull. They used 20 inch engines back then but now all want 25 inch engines and the added safety height for water control. Also plywood was the only material available back then for transoms and floor. Now many of us are using coosa foam glass type high density material. If your boat gains any weight with water absorbtion of closed cell foam or plywood cores getting penetrated by water. Then the floor will be two low to self bail. Especially with new 4 stroke heavy engines. There are improvements that can be made but injecting 2 lb expanding foam into the liner void is not a good move.

[Skink]

Ok, thanks!

My plan is to raise the deck 1.5" and have a large scupper going out each side.

The transom has been redone by a professional(guy I bought it from), but he only went back to the 20" transom, didn't raise it all.

The plan right now is to hang a new suzuki 140 4 stroke back there...

I was just going to have marine plywood used on the deck, completely encapsulated, do you guys really think coosa makes that big of a difference? I hear it is VERY expensive...

Thanks for the insight so far!

[Bushwacker]

Originally Posted by Skink

Ok, thanks!

My plan is to raise the deck 1.5" and have a large scupper going out each side.

The transom has been redone by a professional(guy I bought it from), but he only went back to the 20" transom, didn't raise it all.

The plan right now is to hang a new suzuki 140 4 stroke back there...

I was just going to have marine plywood used on the deck, completely encapsulated, do you guys really think coosa makes that big of a difference? I hear it is VERY expensive...

Thanks for the insight so far!

Can't comprehend why a "professional glass guy" would go to all the trouble to replace a transom and not raise it to 25", but maybe he already had a 20" motor for it!

If you're removing the original Potter vertical through-the-bottom scuppers (which drain VERY well underway IF you have the original suction-creating wedge in front of them on the bottom), I think they'd drain better out the transom instead of out the side, plus that would give you the option of using the ping-pong ball check valves. You might even consider crossing the drain lines under the deck as Moesly did on some of his boats, so that stbd scupper drains out port side of transom and vice versa. That way water won't run in when you walk to one side at the stern.

I didn't know they even made a 20" shaft Zuke 140! It's about the same weight as the 150/175/200 E-Tec, and the only 4-stroke I would consider for the 20' hull. If you're putting that much weight on a 20" transom, I would definitely add the full height splashwell tub that Pianewman and Don Herman are working on. More outboard boats are sunk underway by a wave over the transom than any other single cause, so you're tempting fate with that heavy motor/low transom combination; if you go offshore much, that simple piece of fiberglass could save your boat one day!

As for the deck, why not use 1/2" balsa core like the original. Much cheaper and even lighter than coosa, and nothing wrong with it provided you don't drill holes in it and leave them unsealed. (If you have to put screws into it for leaning posts, etc., just drill them oversize and fill with epoxy cabosil, then redrill and tap for machine screws, which hold much better than sheet metal screws anyway. You'd have to do the same thing with coosa, which doesn't hold screws well either.) The original 39 year old balsa core deck and plywood transom in my boat are still in good shape, so nothing wrong wood provided you take care of it. The only plywood in my Seafari's deck is the area where the pedestal and galley seats mount, which appears to be 3/4". Don't know where they used plywood on the CC models. Denny

[bly]

Originally Posted by Bushwacker

Can't comprehend why a "professional glass guy" would go to all the trouble to replace a transom and not raise it to 25", but maybe he already had a 20" motor for it!

If you're removing the original Potter vertical through-the-bottom scuppers (which drain VERY well underway IF you have the original suction-creating wedge in front of them on the bottom), I think they'd drain better out the transom instead of out the side, plus that would give you the option of using the ping-pong ball check valves. You might even consider crossing the drain lines under the deck as Moesly did on some of his boats, so that stbd scupper drains out port side of transom and vice versa. That way water won't run in when you walk to one side at the stern.

I didn't know they even made a 20" shaft Zuke 140! It's about the same weight as the 150/175/200 E-Tec, and the only 4-stroke I would consider for the 20' hull. If you're putting that much weight on a 20" transom, I would definitely add the full height splashwell tub that Pianewman and Don Herman are working on. More outboard boats are sunk underway by a wave over the transom than any other single cause, so you're tempting fate with that heavy motor/low transom combination; if you go offshore much, that simple piece of fiberglass could save your boat one day!

As for the deck, why not use 1/2" balsa core like the original. Much cheaper and even lighter than coosa, and nothing wrong with it provided you don't drill holes in it and leave them unsealed. (If you have to put screws into it for leaning posts, etc., just drill them oversize and fill with epoxy cabosil, then redrill and tap for machine screws, which hold much better than sheet metal screws anyway. You'd have to do the same thing with coosa, which doesn't hold screws well either.) The original 39 year old balsa core deck and plywood transom in my boat are still in good shape, so nothing wrong wood provided you take care of it. The only plywood in my Seafari's deck is the area where the pedestal and galley seats mount, which appears to be 3/4". Don't know where they used plywood on the CC models. Denny

Also the leaning post. They never bolted things down so they used plywood and screws. I know because I have repaired a few. I also just last winter repaired a 2001 or 2 23 ft regulator with water in the balsa cored floor.




Sorry Bushwacker but I am a strong advocate of no wood or wood products in boats. Especially balsa wood. Thats just my opinion tho.