Chick Ludwig Posted January 14, 2015 Report Share Posted January 14, 2015 Well, the great grey whale is in my driveway. Now, in my spare time, I gotta flip it to sand the bottom and re-paint it. Then flip it back to start the cabin, interior, cabin, etc. It is an aluminum boat. Question for you guys. If I grind the paint off with an 80 grit disc, can I epoxy bulkheads in place like I would with a plywood boat? My intent is to build a cuddy cabin on it. It's a 1971 Crestliner. Here's a picture: https://fbexternal-a.akamaihd.net/safe_image.php?d=AQCMrQ_0-ezLdmSW&w=470&h=470&url=http%3A%2F%2Fimages.craigslist.org%2F00D0D_4rYAvvdDOzS_600x450.jpg&cfs=1 Quote Link to comment Share on other sites More sharing options...
Ken_Potts Posted January 15, 2015 Report Share Posted January 15, 2015 I'm not sure but I think it's tricky getting epoxy to stick to aluminum. Are there frames that you could rivet to? You could put a blind rivet through a washer then through a wood panel and finally into the hole in the aluminum frame. The washer would spread the load from the rivet head onto a larger surface area of wood. Maybe someone else will chime in with a tested way to bond to aluminum, but I don't have experience with it other than making the tapered sections of Southbound's masts. Quote Link to comment Share on other sites More sharing options...
LennieG Posted January 15, 2015 Report Share Posted January 15, 2015 Chick- Well it is about time you started a new boat! I think it's been since late October when you finished sport boat/ turtler. Man you do boats like I do food shopping. Best of luck.....look forward to the progress. Always fun to see your threads. Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted January 15, 2015 Report Share Posted January 15, 2015 What about using 5200 and wooden cleats instead of glass tape? Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted January 15, 2015 Author Report Share Posted January 15, 2015 Grrr@#///#*---sorry y'all. I just finished typing a reply to you guys, and my stoopid computer shut down for a windows update. Lost it all! Oh well, let's try again... Ken, yes, I'll attach frames and panels to the aluminum structure wherever I can. But I want to seal and bond in between too. and there are some places that there is nothing to attach to, mainly foam boxes, shelves, etc. Lennie, yep, I've been "going nuts" not having a boat project to work on. I'll need to get enough stuff done on this one to hang my 25 hp Tohatsu on it so I can use it while working on my main project for the year, my CS-15 Mk-2, in time for the B&B messabout. Mainly paint on the hull, floor, a steering console, flotation, etc. I can finish the cabin and other stuff next fall and winter. Hirilonde, Hmmm, hadn't thought of that. What do you other guys think? Thanks for your thoughts and suggestions. Keep 'em coming! Quote Link to comment Share on other sites More sharing options...
Docpal Posted January 15, 2015 Report Share Posted January 15, 2015 This might be over kill, (or not even possible), but what about TIG/MIG welding aluminum angle iron to the hull where you want to connect things? Quote Link to comment Share on other sites More sharing options...
ricknriver Posted January 17, 2015 Report Share Posted January 17, 2015 Chick I was able to seal up some leaky rivets with epoxy on an old tin boat way back. Seemed to hold ok, but I didn't have it long term. Maybe Gflex? Nice deep hull. "Interesting" project . Rick Quote Link to comment Share on other sites More sharing options...
PAR Posted January 19, 2015 Report Share Posted January 19, 2015 The problem with attaching things to an aluminum structure is the dissimilar materials and their various expansion rates. Aluminum can move a lot, so can wood, so attachment needs to have a reasonable elongation quality that can absorb the worst of the two. Epoxy can do a good job, though I'd think welding a better choice if the hull shell or structure is thick enough. I mean you can weld thin sheet, but it's a pain in the butt, which is why you see lots of riveted sheet alloy boats. A welded flange would kill a few birds with the same stone - locally reinforcing the area and offering a place to mechanically attach whatever, which can also offer movement compensation. Lastly, it's import to not make this new cabin structure very tall or heavy. Do some simple math and figure out what the displacement and PPI is for this boat, to give you an idea what you have to play with. To calculate the PPI (pound per inch immersed), multiply the LWL by the WL beam, then multiply by 80% (.8), this is the "water plane area" (sq. ft. of water plane), next multiply by 5.34 to get pounds per inch immersed. So assuming it's got a 17' LWL and a 7' WL beam, this is 95.2 square feet and the PPI is about 508 pound per immersed inch. Of course topside flare affects this figure as the boat sinks or rises, but it gives an idea of how many well fed friends and their coolers of beer, you can bring aboard and more importantly how it'll affect loading and trim. Figuring displacement is about as easy, take the LWL, the WL Beam, plus the depth of the underwater portion of the hull and a good guess at her coefficient (use .7 for this type of hull). Multiply all three together and then by the coefficient, which will give you the weight (64 pounds per cubic foot for salt water) of the volume of the hull immersed (within a few percent, because of the guessing stuff). Close enough for home builts. Now you have something to work with and assuming the previously used figures, you might be off by a 100 - 150 pounds either way, but this isn't enough to get pissy about. Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted January 19, 2015 Author Report Share Posted January 19, 2015 Thanks Par. The entire cabin structure that I have in mind will be very light. Probably not much more than 100~150 pounds. The seating in the cockpit will be less that the stock boat. The load will be a couple of adults and a young teen and a lunch cooler, and for cruising, just me and stores for a couple of day cruise. Mig/tig welding would be more that what I paid for the boat, and beyond what the budget can endure. The structure will primarily bolted to the frames sole, and deck framing. The the glass/epoxy bonding is more for sealing the cabin from water and cold air from entering around the edges of the aft cabin bulkhead than for strength of the attachment. I'm about ready to remove the old sole and flip the hull to strip and repaint the hull. I'll get a couple of pictures first so you guys can see the internal structure. Quote Link to comment Share on other sites More sharing options...
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