SetSail » Construction Issues

Exterior use of 6061 alloy

Steve Dashew — Sat, 16 May 2009 06:42:25 +0000

Hi Steve, As a long time builder, user and owner of aluminum alloy boats perhaps you can answer this question: How does the odd bit of raw 6061, above the waterline , but on the exterior, fare visually over time in comparison to 5086? In particular, we’re building a Dix 43 Pilot House and I’m looking at using a 3″ half pipe extrusion as a rub rail down each side and it is only available in 6061. The hull plating is 5086 H116. The alternative is to buy vastly more expensive 5086 schedule 80 pipe and rip it on the table saw. I don’t mind spending when it’s justified but don’t want to waste money. We love the look and practicality of unpainted alloy, but my experience in non-salt environments with 6061 is that it can look pretty nasty after awhile. Perhaps it’s just a matter of an occasional scotchbrite rub-down. The other place we’ll be using 6061 is for the rudder shaft . It’s a spade rudder with a 115mm diameter shaft and Jefa self aligning bearings. Appearance is not an issue here, and I think the 6061-T6 will be stronger than 5086 . Do you think corrosion could be an issue on the 6061 rudder shaft? We will have a comprehensive anode system. Thanks so much-I love the new site format!

6061 is OK above the waterline in most applications. The 5000 series is tyically stronger in welded condition. For rudder stocks we prefer 5000 series but 6061 can be used, you just have to account for the difference in mechanical properties when welded. There will be some visual difference as the two alloys oxidize differently.

Windows Attaching to Aluminum Structure

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Dear Steve, I have just read the glazing section for your FPB boat with much interest. Can you tell how the windows where attached to the aluminum structure? Many thanks, John H.

Hi John: We used a Sika system which included a primer first and then the "goop". There are very specific details on how this has to be done, environment, thickness of adhesive, etc. But it makes for a very strong bond.

There are a number of different companies who have systems for this. Regards – Steve

Finding Leaks on Newly Launched Boats

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

(We just launched)…an Angelo Lavranos 43 (Barefoot) in British Columbia. It is unpainted. However, I was surprised to find a couple of deck leaks: One in an interior corner of a deck locker, one where the weld was apparently polished too far, and a burn-through where the genoa track flat bar is welded to the 3/16” deck plate. The builders are good welders so I was surprised by these. In your experience with unpainted aluminum boats have you seen this before on new boats? Regards, David

David: It is not unusual to have one or two things that are missed. Best way to fins them is with a fire hose. Once they are welded tight there should not be more problems. Enjoy your new boat! Steve

Insulation Approaches for Alum. Hulls

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Steve, First let me say I have appreciated the wealth of information in your books and website. Thanks!

In considering an aluminum hull for use primarily in the tropics and temperate zones, I was intrigued by your reference that on Beowulf you chose to use no insulation. You reference careful attention to the head and hull liners. Was there any attempt to provide insulation via the head and hull liners or did you just eliminate the insulation that would have otherwise been used and use standard liner materials? Also, you reference the reveals between the liner panels to promote ventilation between the liner and deck. Did you use a specific % of open space design spec, or just go more with looks? Given your experience in the tropics, would you go this route again, or use insulation? Anything else to consider if choosing to use no insulation?

Thanks for sharing your insights. David

The head/hull liners were from Ultaleather, a material which does not itself breathe. We left 3/4" gaps between the head liner panels and gape top and bottom of the hull liners. There seemed to be enough airflow that we never had mold or mildew issues and there was still some heat barrier from trapped air – at least we never felt inside heat in the tropics. That said, we also had good awnings which were used at sea as well as at anchor. – Steve

Lifelines/Stanchions

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Good day, I am enjoy your site and also using as a reference source as I am presently having a 42′ aluminum cutter built.

I was wondering if you have and could post a detail/close-up look at your stanchion/lifeline setup. There are several pictures on your site which show an overview and it looks like you used SS pipe going into aluminum pipe stanchion bases welded to the deck. One picture looks like you used SS pipe for some of the lifelines. I would appreciate any details you can provide.

Thank you for considering this request. Cheers, John

Hi John: Details of this are in our Offshore Cruising Ency under the aluminum details chapter. Basically we use welded alu. Pipe bases, with support of some sort (usually on a frame) and then stainless stanchions. A plastic isolation sleeve is used between the two metals. Most of our life line stanchions are 30 to 32" in height and are of 1.25" diameter medium wall pipe. Regards – Steve

Ferro Cement

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Hi Steve, I am looking to buy a plan of a sailboat with between 38 & 40 feet with small draft (1.20 to 1.40 m). I know Hartley boats but I would like to contact other designers that have plans to be made in Ferrocement. Do you know any? Best Regards, Eduardo

Hi Eduardo: I don’t know of anyone doing Ferro boats these days. Our advice is to use a different material, of you are going to custom build. The hull is only 20% of the total cost and ferrocement is not a good material when you are aground. There’s a section on materials, and ferrocement in our Offshore Cruising Encyclopedia. Regards – Steve

Sandblasting an Aluminium Boat

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Hello from New Zealand, We are a 40ft aluminium sailboat called Wyndeavor. We’ve sailed from the Pacific Northwest to New Zealand with our two kids and have recently put our boat on the market. The paint on our boat was chipping terribly so we decided to go with bare aluminium in order to help the boat sell (low maintenance). We recently had the boat sandblasted and are not too happy with the outcome. We have covered most of the deck with a nonskid product (Treadgrip) but the rest of the deck and hull to the waterline are bare. The bare aluminium is very rough and our feet and fingers leave marks. We understand that you have a lot of experience dealing with aluminium so we were wondering if you had any advice regarding these issues. Should we sand the decks? Will it get better as the boat oxidizes? Should we just leave it be? Can you help? Regards, Kelly

Hi Kelly: Yes we do have some experience, in fact exactly the learning curve you have gone through! Our first unpainted boat was sandblasted. Moving if from the build shed to the water it was marked by some tree branches and I realized we’d made a mistake. The concept is to be easily able to refinish a rough spot, which means grinding, not sand blasting. So, we ground off all the expensive sand blast finish!

For the deck, the nonskid material, as long as it gives you a good foot hold, is the best approach. Otherwise, what we ended up doing on Sundeer was using the edge of a cut-off wheel and grind the decks to put a tooth into them. But a good plastic tread would give better traction.

The sandblasting leaves a porous finish, and until this naturally oxidizes, probably four to six months, it is going to show more things like finger prints. I am not sure why, but the smooth mill finish, or a ground finish with heavy Scotch Brite pads seem not to have the same problem.

Seems like you have two options. Stay with what you have for now. Or get out the grinder and lots of Scotch Brite and go to work. Beowulf, at 78′, took about 80 hours to polish the topsides, grind the decks, and polish the coamings.

Good Luck with whatever you decide you do – Steve

Keel

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Hello Steve & Linda, I just watched Offshore, and enjoyed it very much. I have been looking around on your website, and I think it is fantastic. Well done. I dream of having a lifestyle like yours one day.

I’m 22, and have a 34′ custom riveted aluminum round bilge, Terhou, built in England in ’59. Within the next decade or so, intend to weld something bigger (and faster) for myself.

This goal has me thinking about design, best practices, etc. You mentioned in Offshore that Sundeer’s keel is welded on. How is the ballast installed? Is it poured inside? I assume it is lead? – Ryan

Hi Ryan: Our normal practice has been to weld the keel on. Some times the lead is poured into the keel before welding it to the hull and sometimes the lead is poured after.

In the case of Beowulf, the keel was fabricated, lead poured, and then after she was delivered to her launching point on a truck the keel was welded in place. Steve.

Building Trawler in China

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

Good Morning Steve: I have a 98 Valiant 42. I’m selling her and moving to the trawler mode. Most trawlers are just ugly–too high off the water, too much windage. I’ve found the Dieselducks designed by George Buehler and built at Seahorse Marine in China. Please look over these and let me know what you think. Here is their website: http://www.seahorseyachts.com/ Go to the dieselduck 44 and take a look at them. Please let me know how you feel about steel boats and if the design is sound. I respect your opinion more than anyone out there. Thanks again, Roy

Hi Roy: I would take extreme care with buying a boat in China, as there is little legal redress in case of a problem. First, I would use a letter of credit for the full contract price, with the exercise of the L/C based on your acceptance (usually with a surveyor involved). Second, make sure the specifications are detailed, and cover everything you expect and how it is to be accomplished. The price sounds very attractive, so there’s some room for cleaning up problems, but you want to be sure the basic boat is sound. There’s a lot of detail on this subject in our Offshore Cruising Encyclopedia towards the back. If you go ahead, let us know how it turns out, and good luck. – Steve

Pilothouse Windows – Best Material

Steve Dashew — Tue, 30 Nov 1999 05:00:00 +0000

What do you consider the best material for pilothouse windows? Lexan, Tempered or safety (laminated tempered) glass?? Phillip

There are no silver bullets – any of these materials will work. You need to calculate the hydrostatic pressures as a start, and then the spans involved, which will lead to the thickness of the various materials required. Easy engineering for anyone familiar with the process. – Steve