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Thread: Alum Hull design/leak containment question?

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    Default Alum Hull design/leak containment question?

    hi all! Are hulls like this designed for strenght only, or to contain a leak if the hull is punctured in one or two+ of these sections?....if the top is sealed up with marine plywood(flooring) etc, would it give a guy a chance to at least make it to shore some how, and the bilge pump taking on any leakage?..thanks larry

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    Member DMan's Avatar
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    Thats allot of structure. The hull needs to be able to flex some to prevent cracking. What kind of boat is that?
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    Member Maast's Avatar
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    Aluminum hulls, with the exception of two builders, are built for strength and not leak containment, its impossible to "contain" a leak.

    However a boat may contain sealed compartments or globs of foam for flotation, boats 19 feet and smaller are required to have "level flotation" which means that if the boat swamps it will stay afloat in a relatively level position. Boats bigger than 19 feet arent required to have any flotation built in.

    The two aluminum boat builders that do build in flotation for their larger boats are Stabicraft and Aluminum Chambered Boats, they have sealed metal flotation chambers around their waist that are designed to keep them afloat no matter what.
    You could take those boats and submerge them to 30 feet and when you let go they'd bob to the surface. Very nice, but spendy boats.

    Whichever kind of boat shown in your picture it is, it's being built really robustly, almost too robustly.
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    That looks like a Wooldridge and not too much structure at all. This is why they can use 3/16" AL with all the supports rather than 1/4" with much less support. My last boat had a 1/4" bottom with box stringers and I personally like this type construction much more than the box stringer route.

    Mike

  5. #5

    Smile What boat you ask????

    I can tell just buy looking at the welds,bracing, and general construction, but first to set the record strait I am not a marine engineer. Just a regular guy that works hard for my money, saying that I want a boat that is WELL made, safe, excellent performer, and like a tool or any piece of equipment that does the job I expect it to do. I read year after year, boat show after boat show how good a deal people think they got, two years down the road (2ft itis sets in) time to sell and move up.. That is when the real shock sets in, RESELL my goodness I am not getting much for my INVESTMENT!! The cookie cutter boats parts (motors, electronics, aluminum all that it takes to build a boat) basically cost the builders the same. The cost difference is the time it takes to BUILD, as in man hours engineering WELDING WELDING WELDING. Go to any lower price boat builder look under the hood. Nine times out of ten 1/4'' plate a few cross braces and your in the water. A little touch on the bottom with a very rigid plate; time for repairs. If you want a water tight compartment, you need a bulkhead. In this size boat it is not practical. If you are in the market a little advice, do your homework, check resale values, warranty claim. If you are spending that kind of money meet with the builder, ask for references. A quailty builder will take the time to answer all your questions. If that is not a Woolridge, than I owe you a lunch. I have owned 3, getting ready to order #4 knowing full well i will get the boat, and performance, not to mention resale, when I move up again!!! Good luck

  6. #6

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    Quote Originally Posted by bcriverhunter View Post
    hi all! Are hulls like this designed for strenght only, or to contain a leak if the hull is punctured in one or two+ of these sections?....if the top is sealed up with marine plywood(flooring) etc, would it give a guy a chance to at least make it to shore some how, and the bilge pump taking on any leakage?..thanks larry
    The rear floorboards rest on these braces ahead of the side fish box on a 26 pilot wooldridge. They are not welded all the way acrossed just to the top of the stringers so they are not water tight.

    A better pic



    Here is another type of construction, on a different brand of boat.



  7. #7

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    good guess, fish hog!!...yep, she's a wooly!...so i take it you like the brand?....thanks everyone for the info!!...larry



    Quote Originally Posted by FISHHOGG View Post
    I can tell just buy looking at the welds,bracing, and general construction, but first to set the record strait I am not a marine engineer. Just a regular guy that works hard for my money, saying that I want a boat that is WELL made, safe, excellent performer, and like a tool or any piece of equipment that does the job I expect it to do. I read year after year, boat show after boat show how good a deal people think they got, two years down the road (2ft itis sets in) time to sell and move up.. That is when the real shock sets in, RESELL my goodness I am not getting much for my INVESTMENT!! The cookie cutter boats parts (motors, electronics, aluminum all that it takes to build a boat) basically cost the builders the same. The cost difference is the time it takes to BUILD, as in man hours engineering WELDING WELDING WELDING. Go to any lower price boat builder look under the hood. Nine times out of ten 1/4'' plate a few cross braces and your in the water. A little touch on the bottom with a very rigid plate; time for repairs. If you want a water tight compartment, you need a bulkhead. In this size boat it is not practical. If you are in the market a little advice, do your homework, check resale values, warranty claim. If you are spending that kind of money meet with the builder, ask for references. A quailty builder will take the time to answer all your questions. If that is not a Woolridge, than I owe you a lunch. I have owned 3, getting ready to order #4 knowing full well i will get the boat, and performance, not to mention resale, when I move up again!!! Good luck

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    Member jrogers's Avatar
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    Looking at Sportdrifter' version of the picture leaves me with a couple of questions.

    It seems like the front half of the cockpit is boxed from the hull skin to the floor. Doens't this leave the boat without a lot of below deck space? It seems like it would be hard to access and use these little areas.

    Looking athe aft portion, are they going to box that as well, or are they fish holds or something. If they are not going to support that area futher, then that seems like a weak area to me.
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    Default Errr

    The second set of pics with the 1x2 upright tubing, I would have problems with a boat built like that. If the uprights were welded to the BOTTOM of the stringers it looks like it would be ok but side welded like that I see someone rewelding a lot of cracked supports in thier future. Almost looks like they were in too much of a hurry or lazy to measure correctly and place them underneath.

    I know I spent a winter rewelding and bracing a M*r*i*n 20 ft boat a few winters ago. welded the same way (on the sides) Almost every single cross stringer and support had cracked at the weld.

    Thge first set looks sturdy and well thought out.

    Here is the boat I hope to have made for me one day (or get the plans and build it with my sons)
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    Member Maast's Avatar
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    Sportdrifter, what brand of boat was your second set of pictures? If its not PC to post here please PM me.
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  12. #12

    Thumbs up pictures

    Quote Originally Posted by jrogers View Post
    Looking at Sportdrifter' version of the picture leaves me with a couple of questions.

    It seems like the front half of the cockpit is boxed from the hull skin to the floor. Doens't this leave the boat without a lot of below deck space? It seems like it would be hard to access and use these little areas.

    Looking athe aft portion, are they going to box that as well, or are they fish holds or something. If they are not going to support that area further, then that seems like a weak area to me.
    Yes those are large fish holds on the sides, center space belly fuel tank and there is more then enough storage fore and aft. Under bunks in the cuddy, under floors, over head. If you have time go to the boat show in Anchorage take a look every square inch is utilized and well planed out. And ask to see or go on line and check out there performance bulletins I think you will be impressed.

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    Member jrogers's Avatar
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    My boat uses a bit different method, I think because it uses heavier gauge aluminum. The supports stay down low so all of the space can be accessed for storage.




    It would take a pretty big hit before have to worry about leak containment. The more common thing to worry about is thru-hulls, and how many of them they are. My through hull transducer is mounted off the back of the boat instead of through a hole for this reason. I do agree that Wooldridge makes a nice boat. I am surprised that I donít see more of them up here as compared to Hewescraft.
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    Member DMan's Avatar
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    Here is the GlacierCraft Hull/Bulkhead setup.



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  15. #15

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    I love seeing all of these construction pictures. I wish I had pictures of mine before the deck went on. Anyhow here is a picture of the engine bay and then a picture of the main hold that is between the engine bay and the cabin. They are separated by a bulkhead that is not waterproof at this time. So far it is the only boat I have seen that the box girders used for the engine mounts continue that far up into the boat. My hull has limber holes at all of the bulkheads so there are no water tight compartments but I may change that.




  16. #16

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    thanks for all the extra pics!...i will ask grant at wooldridge to send me the construction of thier 29 footer pilot(same design as the 26'..)...it uses .250 '' thick allum instead of 3/16"..., interesting to see what the difeerece is!...larry

  17. #17

    Default Rear deck

    Quote Originally Posted by jrogers View Post
    Looking at Sportdrifter' version of the picture leaves me with a couple of questions.

    It seems like the front half of the cockpit is boxed from the hull skin to the floor. Doens't this leave the boat without a lot of below deck space? It seems like it would be hard to access and use these little areas.

    Looking athe aft portion, are they going to box that as well, or are they fish holds or something. If they are not going to support that area futher, then that seems like a weak area to me.

    The rear has 2 side fish box's like fishhogg said with a 150 or 185 gal fuel tank in the middle. Where the rear door/bulk head starts the front half does not get these type of supports it is more open to allow for under floor storage. The interior is not aluminum decking like the rear it is standard marine plywood with vynil covering.
    Their are 4 storage compartments in the middle if the boat, under the front seats, under the floor in the walk way and below the dinett table and under the dinett seat not counting under the cushions in the cuddy.















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    Member JOAT's Avatar
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    Quote Originally Posted by bcriverhunter View Post
    hi all! Are hulls like this designed for strenght only, or to contain a leak if the hull is punctured in one or two+ of these sections?....if the top is sealed up with marine plywood(flooring) etc, would it give a guy a chance to at least make it to shore some how, and the bilge pump taking on any leakage?..thanks larry
    It is built that way for strength. And contrary to other opinions, you don't want an aluminum boat to have any flex in it at all. A bullet-proof aluminum boat is completely rigid. Any place where aluminum is allowed to flex will break. Not "might" break, but it "will" break. A rigid hull doesn't flex and thus will not break. And in order to be completely rigid, there can't be any flat spots in the hull. Everything must have curvature to it. I can show you a number of completely rigid aluminum hulls that are up to 30 years old that have never once had to have a flex-crack repair. All flexible hulls will eventually need repairs if they are ever actually used in the water and/or trailered very much.

    If you want it to also be flotation compartments, they must be stitch welded all the way around, which those are not. Since they are not welded all the way around, they won't stop any water flowing under them from one compartment to the next. Note that the USCG in their complete lack of wisdom doesn't consider trapped air to be flotation. If you want to seal them for flotation purposes, laying plywood over the top will do nothing for you. Finish welding up the inside seams and then cap them with an aluminum sheet welded down to each individual compartment (so the top of each is also sealed all the way around.
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    Member DMan's Avatar
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    Quote Originally Posted by JOAT View Post
    It is built that way for strength. And contrary to other opinions, you don't want an aluminum boat to have any flex in it at all. A bullet-proof aluminum boat is completely rigid. Any place where aluminum is allowed to flex will break. Not "might" break, but it "will" break. A rigid hull doesn't flex and thus will not break. And in order to be completely rigid, there can't be any flat spots in the hull. Everything must have curvature to it. I can show you a number of completely rigid aluminum hulls that are up to 30 years old that have never once had to have a flex-crack repair. All flexible hulls will eventually need repairs if they are ever actually used in the water and/or trailered very much.

    If you want it to also be flotation compartments, they must be stitch welded all the way around, which those are not. Since they are not welded all the way around, they won't stop any water flowing under them from one compartment to the next. Note that the USCG in their complete lack of wisdom doesn't consider trapped air to be flotation. If you want to seal them for flotation purposes, laying plywood over the top will do nothing for you. Finish welding up the inside seams and then cap them with an aluminum sheet welded down to each individual compartment (so the top of each is also sealed all the way around.


    Flex isn't really the right word to describe what I was referring to. I agree a rigid hull will last for sure.

    What I am referring to is the energy tranferance when a hull is in the water or pounding in the waves. I don't remember what the engineers call it speciically but the concept is that the hull has to be designed in a way to allow that energy to smoothly disapate throughout the hull. Much in the way the bulkheads look in the Wooly (I didn't notice that it was only welded to the top of the stiffeners). In talking to a boat designer (the one that designed the aerohead) I understand more now why certain boats are designed certain ways. He believes that in a mojority of boats the bulkheads should not be welded to the bottom of the boat as this creates an enviromrnt where energy is immediately stopped which puts more pressure and stress on the welds but if the bulkhead is welded on top of the stiffeners and the energy is allowed to transfer down the stiffeners and up into the bulkheads disapating throughout the boat then there is less concentrated stress.

    Either way you put it I agree it needs to be a rigid hull. I think there are allot of different concepts out there and enjoy hearing them all.

    Forgive the grammer errors. Trying this from my iPhone!

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  20. #20

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    What I have been told by Wooldridge is the most strenuous thing we do to the jet boats is load them super heavy and head down to Yukon in rough water, it is the most demanding thing we do to them. Typical use hitting the grarvel bars, logs, a few rocks is not as stressful as the heavy loads.
    Dman is right you can see wooldridge does not weld the cross bracing down to the bottom to where if you hit a rock it would catch and do more damage than letting it slide along the bottom distributing the impact. I hope that made sence.

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