Bunks already carpeted...what bolt/screw to use from underneath?

bassin_louisiana

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I needed to replace two center bunks on my 1998 Tracker trailer. The boat is a light, aluminum 1997 Tracker Pro Team 165. I bought two treated 2x4s and carpeted them beautifully. The problem is, I now noticed that the current bunks are bolted from above with a lock nut on the bottom. I cannot counter sink anything at this point because my carpet is already in place. So, my question to the group: what is my best option for bolting or screwing from below up into the 2x4? I realize that this is not the ideal option because it won't involve a bolt and thus have greater chances of coming loose. My plan will be to check this each trip. I need the biggest baddest thing that will hold these boards from below. I welcome your suggestions. Thanks, guys!
 

GA_Boater

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Welcome aboard.

Well the bad news first - Toss your nice, new treated bunks. The chemicals, specifically copper, used in treated wood will eat your aluminum Tracker. The copper will leach through the carpet and work on the hull.

The good news is you can now replace the bunks with non-treated wood and install the same way the factory did.
 

four winns 214

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Bad news broken record here, but aluminum and pressure treated lumber are totally incompatible. There is no other option but to start over. This time, drill and countersink carriage bolts before carpet.
 

bassin_louisiana

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Can I go a year or so before replacing the treated 2x4s? I put a few hours into this weekend and just don't want to spend another $40 on materials.
 

JASinIL2006

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I would think the first year would be the worst. That's when there are the highest concentration of chemicals to leach out and corrode your hull. Is it worth the risk to save $40 and a couple of hours?
 

bassin_louisiana

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I found this on another forums, which speaks about a new type of treated wood: MCA. That's what I have. Apparently, this new type of treatment is OK with aluminum.

"''New to the forum, but have seen numerous posts regarding the use of pressure treated lumber, and its potential corrosive qualities. I am in the pressure treating industry, and want to educate those folks who may not be clear on this topic.

About 4 years ago, a new treating chemical was introduced that was designed to eliminate the corrosive qualities of the chemical that was in current use. Any lumber purchased at the retail level with an end tag labeled ACQ or AC2 has corrosive qualities and is not designed to be used in direct contact with aluminum. With that, typical metal fasteners like deck screws, nails, joist hangers......had to be "hot-dipped" to protect against corrosion so that any structures being built wouldnt eat the fastener and jeopardize the integrity of the structure. If you tried to use a standard galvanized fastener, or attach aluminum flashing for a deck project, in direct contact with an ACQ or AC2 product, it would dissolve the fastener and
aluminum over time.

So an new chemical was introduced; MCA-Micronized Copper Azole, that is approved for direct contact with aluminum. This is a much less corrosive chemical compound and is more similar in design to CCA that was the industry standard prior to the introduction of ACQ and AC2.

Bottom line.....if you want to use pressure treated lumber for your boat deck mods, you can do so by simply making sure that you purchase any product that utilized the micronized copper treatment. Check with folks at the lumber yard and ask them what treatment was used on their product. Most of the industry has moved to this newer chemical, but 1 of the big-box retailers still uses the old stuff.

Good luck with your projects''!

later he said this

"The MCA treatment is approved for direct contact with aluminum.

I would rather not mention which store(s) stock the ACQ or AC2 products. These products are effective against rot, decay and termite infestation, which is what all pressure treated lumber is ultimately designed to do. Just ask which type of treatment they use and decide for yourself which is the best way to go. It is also very easy to tell simply by looking at the color of the
pressure treated wood.....Dark Green is the old stuff. The lighter colored product has almost no green tint to it at all; which also makes it more appealing to home-owners who want to use a light stain to get a more natural wood look on their decks or fences.

As far as the copper reacting with the fasteners, you are correct. As the copper that is used during the treatment process leaches out of the wood, it reacts with the unprotected metal. Hot dipped galvanized or stainless steel fasteners are recommend with the ACQ and AC2 products. Not necessary with the MCA. Not sure about any conflict between the simpson fasteners and the aluminum. I do believe that some, if not all of the simpson products are actually hot-dipped galvanized rather than zinc.

Something totally unrelated......for anyone wanting to stain or paint pressure treated wood, you dont have to wait a year to do so. Once you have completed your project, give it a couple of good sunny days and then sprinkle a little water on the wood. If it absorbs the water within 15 seconds or so, then the wood is ready to be protected. If the water sits on the surface of the wood, then the moisture content is still too high, and staining or painting will not be effective''.
 
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bassin_louisiana

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OK, folks: just an update here. I called two different, large lumber treatment plants. They both told me the same thing: 1) ACQ treatment is alkaline based and causes corrosion upon direct contact with aluminum. 2) MCA treatment is defused copper with no alkaline and is perfectly safe against aluminum. I asked if I should coat the lumber with paint or something else and they both said "no": the aluminum would be perfectly fine. Older treatments were the problem. MCA treatment is safe for aluminum. I'm going to keep getting some opinions but this makes me feel a little better.
 

JASinIL2006

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Good info, thanks for sharing so we all can be current! Glad you have the safe kind for aluminum!
 

BRICH1260

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Knowing that the bunks are safe, you will have to anchor the bunks with lag screws from below. While I prefer thru bolting, lags will work. Just make sure that the tips do not protrude through the carpet to gouge the hull. Drill as small a pilot hole as possible to get the best bite on the wood.
 

211libwtfo

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Jus cut ahole in the carpet where the carriage bolts will go counter sink the bolts then use E-6000 to patch in the cut out carpet. I think lags won't work as well
 

Scott Danforth

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copper and aluminum dont mix

just google aluminum and copper galvanic corrosion.
 

JASinIL2006

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Leaving aside the issue of corrosion, you can just use lag screws as mentioned above, although I think carriage bolts would be superior. My bunks were held on with with lag screws and when I recarpeted them (the wood was still in good shape, so I reused it), I simply used lag screws again. Just be sure to get something that won't rust or interact with wood. I used stainless steel.
 

Stumpalump

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"Much less corrosive chemical compound" but still corrosive. I'll be number nine. Don't use pressure treated wood. Throw those away. Your big box stores sell or can get you redwood for about the same price.
 

oldjeep

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Lags work fine, the custom trailers that come with 100k wake boats are lag bolted.
 

bassin_louisiana

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Thank you all very much for your feedback. I really appreciate it. Please allow me to finish up with this. I called the specific company who treated these 2x4s with MCA (they were listed on the lumber tag). They provide me with a safety sheet?what they call a MSDS?and I took that to a chemist at the university where I work. He read the chemical makeup and has assured me that there is nothing to worry about. A company manager said that even with water immersion, leaching into the carpet would have no real negative effect on the aluminum. He said MCA was created in part to be compatible with metal contact, including aluminum. One boat service department just told me to watch for corrosion around the lag screws. After much consideration, I have decided to mount these boards. I will mount with 5/16 x 1.5in galvanized hot dipped lag screws. Now, I need to figure out what kind of washer I need. Thanks, everyone!
 

wahlejim

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Be sure to keep us updated over time on how the bunks perform. There seems to be a lot of conflicting opinions about this lumber and I am sure it will help someone in the future if you keep us up to date on any corrosion issues you encounter.

Thank you for doing your due diligence and being the guinea pig for the forum on this one.
 

Boomyal

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........ One boat service department just told me to watch for corrosion around the lag screws. After much consideration, I have decided to mount these boards. I will mount with 5/16 x 1.5in galvanized hot dipped lag screws. Now, I need to figure out what kind of washer I need........

Here is what I did 15 years ago. I did use pressure treated wood but my boat is glass. Although my bunks are 2 x 6, I used 3/8 x 1 1/2 stainless lags with stainless flat washers, from underneath. I like the larger diameter lags because they have more surface area to bite the wood. I pre-drilled the holes to depth. I do not remember what size they were but I used a large enough bit to allow the bolts to cut good, clean threads in the board. I did not want them so small as to have the bolts distort the surrounding wood fiber and make it weaker.

I ran the lags into the holes to cut the threads, then backed them out. I then filled the holes with a penetrating epoxy until they quit absorbing it. I then did a full wrap of the boards using indoor/outdoor carpet, wrapped entirely around the board and secured it with Arrow Monel 9/16 staples.

I also did my side boards the same way. Just two days ago I removed one of the boards because the sun (on one side) had deteriorated the carpet. The bolts were all tight and showed no sign of any deterioration. When launching, my sideboards get as wet as the bunkboards.
 

trailking82

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I lagged my bunks down, but i used 1" length galvanized lag bolts with lock washers. So far so good but i dont think i used pressure treated wood either. Your 1-1/2" lags will be too long if your bunks are like most, laying flat. Nominal thickness on a 2x4 is really 1-1/2x3-1/2. I went with the princible of having the bigger lag screw with the smallest pilot hole i could achieve.
 

frantically relaxing

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I must echo what the other have said, copper + aluminum = bad... And I even have proof...
Most of you know I run an engraving shop from our home. This is my big CNC engraver, with aluminum work table...

7000.jpg



Not long ago I engraved some nickel plated copper plates for a customer. I flood cool with water soluble Trim Sol when engraving metal, so the shavings were wet. The nickel plating was only about .0002" thick, and engraved into the copper about .012", so the amount of nickel, even though it may have helped, is insignificant. This pic I took the next day when I had the mess mostly cleaned up, and noticed what was going on, so I left the rest of the cut shavings where they sat and took this pic. Notice to the left of the shavings you can see the discolored area where the other shavings were---

7000b.jpg



Closeup---hey, the aluminum is not just discolored, it's visibly pitted! This was only ONE day of the wet copper sitting on the table.

7000c.jpg


That's quite a bit of galvanic corrosion for one day. After finding our houseboat full of holes 2 years ago due to stray current corrosion, I've done quite a bit of research on corrosion in general. It's nasty, fast, and the short of it is, better safe than sorry...
 
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