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Question about Boat Construction for you builders

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Old 01-01-2004, 07:51 PM
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Default Question about Boat Construction for you builders

I have a question about boat construction. Every boat that I have ever seen built they made the hull, put in the stringers up to the bow, put in the bulkheads and so on.
In my Formula 302 I am replacing the stringers and it seems to me that they put in the bulkheads first and ended the stringers at each bulkhead. Does this sound correct? Is this common? Seems like it would be a weak spot in the boat but after 25 years the hull shows not signs of problems.

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Old 01-01-2004, 08:10 PM
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Sure the bulheads are not notched for the stringers?
I replaced a stringer in a Glastron where both the stringers and bulkheads were notched and 1/2 lapped(?) at the joint.
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Old 01-01-2004, 08:30 PM
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??

Formula HAS used a floating grid construction in some of their hulls. Don't think this was one of them though.
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Old 01-01-2004, 09:04 PM
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Smile This is less desirable, but...

done on production boat construction. If your formula is like the few others I've seen, they install only one fuel tank in the center of the boat, thats "boxed-in" with stringer/bulkhead material. This "stops & starts" the use of full length stringers, which more serious offshore powerboat manufactures go with. I will say that the material that the stringer/bulkheads is made of is less important than "how" the fiberglass is used over them. Hand-laid glass is always best, as there is less resin used this way. The idea is to used the least amount of resin possible to saturate the glass. Any puddling or excess glossiness to the finished lamination makes for a weaker and heavier finished product. A stringer is only as strong as the glass over the top of them. The proper way to lay glass over the stringer, is to start at the base of the adjacent stringer, going over to the stringer you are covering, up the side of the stringer, over the top, and back down the other side to the bottom & then over to the base of the next stringer. Your first layer of glass goes over all the stringers first, then repeat this layering which results in overlapping glass between the stringers, which is the strongest. Radius the top of your stringer material with a "rounding-over" router bit before installation, so the glass lays nicely over the stringer tops without any air bubbles. Try not to grind off the tops of your stringers later to make the deck fit. How many layers of glass, depends on what material you are using(1708 Biax, 1808 Biax, 3408 Triax, 18 oz. Roving, 24 oz. Roving, etc..) Contrary to what people think, there is nothing wrong with using plywood in a stringer system as long as it is fully encapsulated properly. It will last 25 more years! Hope this helps. I could go on and on... Ed

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Old 01-01-2004, 09:19 PM
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I will be doing a LOT more investigation tomarrow. My boat building friend is coming over to check it out. He is amazed that they would build a boat like this but does NOT want me to cut out any of the stringers tell he has a chance to take a look. Believe it or not I am hopeing that this is the way it is as it allows me to just replace in the effected area and not have to go all the way to the bow.

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Old 01-01-2004, 09:20 PM
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Hey I am not complaining, it lasted 25 years so if I can get another 25 out of it..... I am just trying to figure out the reasoning or purpose to doing it this way. On this boat NONE of the bulkheads are glassed to the sides or deck of the boat. They are glassed only to the bottom and a little up the sides even with the tops of the stringers. From the stringers up there is not connection.

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Old 01-01-2004, 09:50 PM
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Default This is typical of "production" boat building...

Take a tour sometime of a production boat builder, such as Regal, Searay, Monterey, etc...They are open for tours throughout the year. You would be amazed at what you will learn. The hull goes down the production line and is COMPLETELY finished, including complete engines & drives, galley, upholstery, even the throw cushions in the V-berth, before the deck goes on with rivets or screws and caulking. The tops of the bulkheads simply have carpet-type material that the deck sits on with no bonding or fastening of any type. This is normal in a production factory envirement. Ed
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Old 01-01-2004, 10:10 PM
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Thumbs up If you get lucky...

You might not have to cut out your stringers at all, unless the glass has pulled away(delaminated)from the bottom of the boat. If the stringers can be saved by simply adding a layer of glass over the top, you will want to grind the surfaces VERY THOROUGHLY, wash them THOROUGHLY with acetone, and use only "vinylester" resin for the job, as it provides the best secondary bonding characteristics of all resins(other than epoxies). Use the recommended catalyst type & amount. DO NOT try to use less than the recommended M.E.K. levels to allow yourself more working time! This is wrong! Resins need the proper catalyst amounts to cross-link properly. Vinylester resin will feel slightly tacky when dry. This is normal and is part of the reason it has such excellent secondary bonding advantage. Secondary bonding means the "grip" that the next layer of glass has on the previous layer. It also bonds better in all repair work, even though the boat was originally built with GP Resin(General Purpose). Ed
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Old 01-01-2004, 10:39 PM
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Ed why do it this way instead of cutting them out and going all new? I mean if I have to replace the bulkheads and all then why not just cut out the stringers as it will not take that long to do??

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Old 01-02-2004, 10:46 PM
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Smile Well, Jon...You can if you want to. But...

don't fool yourself...It is a bit more work. First make sure the boat can't loose it's shape once you remove its backbone. By this I mean, both twisting from end to end, & the bottom from changing shape. This depends on how you have the hull bottom supported. I don't know how much of the length of the stringers you intend to cut out. If you are completely "de-boning" it, from the engine bulkhead forward(or are you including the engine stringers as well?) Or if you are simply replacing some forward cabin stringers, you don't have to worry much about loosing the hull shape, as the forward vee-section has a lot of natural strength by design. Mostly, you will be doing ALOT of grinding, to remove most of the original stringer glass & to make any glossiness of the original resin to go away. There are no shortcuts in this process. Use the most coarse 8" grinding disc they make. A 24 Grit will do, on a high speed 8" grinder. Make sure your wearing a full monkey suit, a full head sock, goggles, respirator(not a dust mask), with masking tape at your neck, wrists & pant cuffs. Also tape up your complete exposed socks & shoes. Set up a large fan to blow everything away from you as you work or you will not be able to see anything. Vacuum everything out when finished(do not use the garden hose), then THOROUGHLY clean with acetone in preparation for your carpentry skills. If I can help any further, feel free to ask. Ed
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