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joeroberts37

86 Malibu Skier - Stringer replacement - different, trust me...

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joeroberts37

long winded here...

So I have done quite a bit of research on Stringer replacement. I have a good friend who performed the similar task on a Supra TSM6 last winter. He did the "douglas fir" replacement. He had numerous hours on fabricating the wood stringers. Mind you, he has a 40x60' workshop with one full bay dedicated to woodworking (He is skilled and experienced, but also a perfectionist). He estimated his cost of supplies @ $1500 and hours of love in the 80's minimum.

I have a different approach and am always open to critiquing. I will be replacing the stringers with Seacast. I have already ordered the material. That is set in stone. My hesitations for using seacast were making sure the floor is level after the install and engine alignment. Other than that, I am confident in the product and using as a "core" material.

Current plan. Hollow stringer shells one at a time to eliminate hull 'pancaking'. I will be keeping the boat on the trailer for this process as well. I plan to hollow a main stringer and the opposite secondary stringer. Mix and poor. Repeat process for opposite side. I will have the boat level to the point where the main engine cradle is in the same orientation before hollowing stringer shells. Going to add some minor details to control water flow.

My belief is that we do not want to eliminate water into the boat, but control water into the bilge. I plan to add half circle cavities to the main/secondary stringer to allow water to flow to the main galley. Was going to use 1.50" pvc, then cut to 1.50" long (then cut in half length wise) and glass into the the stringer shell.

Leveling the floor-- I am leaning towards using stainless hanger bolts (google image if unfamiliar) driven into the stringers to suspend an alluminum framwork above the stringers. Fabrication is my day job - fyi. Can use aluminum C-channel over the stringers. Was leaning towards making a welded ladder system between the main and secondary stringers. Using the hanger bolts, I could level the aluminum channel using stainless nuts/washers. At my day job, we make a product for a 'Access Flooring' company that elevates floors in office buildings (to allow wiring/ventilation below walking surface). Through there design, they level the floor in a similar fashion. This would take the stress off having a perfectly level stringer from the seacast poor.

Thoughts?

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jk13

I agree with controlling water, not trying to eliminate it. Sounds like you have a plan there.

Only thing I would do is build a foam or wood cradle for under the boat once you get the running gear off. Three reasons:

1) My boat and most others flex differently on the trailer bunks than they do with the overall support of floating in water. The giveaway is how the windshield closes differently on the trailer vs. floating.

2) Ease of entry/exit. Make it lower to the ground. As low as possible. And along with the cradle, I would build a platform or step system around the boat. You will be getting in and out of there hundreds of times and it would be worth the hour or two of build time.

3) If your boat needs attention, chances are your trailer does to. Great time to do it while things are drying inside the boat and you still have energy. Bunks, carpet, wiring, paint touch-ups, etc.

Many, many boats have been done on a trailer and it works fine. Just a suggestion.

Edited by jk13

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Shine

I used the seacast and it worked very well. I pulled all the wood out of the old skin like you are doing.

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Scott N

I have been through a similar process with a key difference being that I didn't do the work myself on the stringers or floor rebuild. You can check out my thread (with link to pics) and you will see that I also considered water control. I was initially interested in drain fabrication but ended up sealing the floor completely (no drains). I don't necessarily think sealing is better, I just didn't want to add a lot of money to my project by paying the shop for custom fabrication.

If you end up going with the ‘control-the-water-using-drains’ methodology here’s a few thoughts that came to mind when I was going down that path:

French drain. Having a perforated drain channel will allow water to come from anywhere and enter the channel. I tend to think this would be ideal if you have undetected water ingress you’re trying to manage.

Venting. Drain will need venting to flow properly.

Close the system with plugs. I wanted the drain for comfort of knowing that undetected water ingress could be dealt with and water would not get indefinitely trapped against my foam/stringers. I didn’t want to create a system that intentionally allowed water to get in. Thus the idea came up to plug the drain openings during boat operation. So you’re basically sealing the system at drain end points. You open it only when you want it to drain. If you seal the floor in properly on your rebuild and you plug the drain ends during operation, then you should not have any water in your drains when you take the boat out of the water and open the drains.

Regarding leveling of the floor, my shop fiber glassed the bottom of the floor to the top of the newly-installed and glassed stringer. They followed up by screwing the flooring down. In essence, this pancaked fiber glass and resin between stringer and floor and gave enough play (while resin and glass were still tacky) to level the floor. This also created a water tight seal where stringer meets floor (when resin/glass dried).

Hope some of these thoughts help. Good luck on the rebuild. Post pics!

Edited by Scott N

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joeroberts37

Shine - how many gallons did it take to do your boat? I bought 15 gallons - poured/putty knife scooped the first 5 gallons yesterday. Went well for the most part. Definitely doesn't "pour" out like I thought. The stuff is like a really light 'monkey fuzz' /bondo glass filler. I capped the with Biaxial glass. I just don't feel like I have enough product.

Edited by joeroberts37

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Shine

Mine took 15. Their formuala was spot on for how much I needed. You are correct, it does not pour. I only cut out a 1 1/2 strip before removing the wood. I scooped it all in and there wasnt much need for leveling like you mentioned in your first post. I kept the strip I cut off to realign the engine mounts, then added additional glass over the top of the stringer.

I think I used 2 gallons of the pour foam to refill under the flooring.

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joeroberts37

Gotya. Thanks for the quick reply. For the most part, the top of my stingers was split down the middle for the entire length due to the factory using staples to attach the floor. I also widened the split to 1 1/2" to remove the wood. Would have been great to be able to reuse the 'cap'. Going to rip open the other stringer tonight and start digging. Removing the first stringer really wasn't as bad as I thought it was going to be. A drill and a crow bar/hammer was all I really needed. Patched up any holes and repaired skins with monkey fuzz, mixed seacast and scooped in. Pretty simple really.

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Scott N
I think I used 2 gallons of the pour foam to refill under the flooring.

I used the two-part AeroMarine 2# foam. Second from the top on this page. http://www.aeromarin...m/boat-foam.htm

I replaced all the foam and (think) I only needed one gallon of each part, two gallons total.

Edited by Scott N

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Shine

I used the two-part AeroMarine 2# foam. Second from the top on this page. http://www.aeromarin...m/boat-foam.htm

I replaced all the foam and (think) I only needed one gallon of each part, two gallons total.

Agreed, 1 gallon each part.

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joeroberts37

During my research, I found that some do not replace the foam. The justification is the JonBoat ideology. I know there are purists and safety concerns with not replacing the foam. I'm on the fence. I do not plan to compartmentalize the stringer cavities and attempt to completely seal off any portion of the boat. IMO - impossible to completely seal a section of a boat. Water is extremely powerful. I would rather be able to have air movement above and below the floor. Even thought about the idea of modifying the bow vent to allow air to be piped in to the outer areas of the floor cavities further aiding in air flow.

Here is my $0.02 on foam -

1. Its floatation capabilities are only useful if you have a hole in the boat.

2. The last 8-9 years of the boats life lived without foam in the floor (previous owner)

3. Will eventually absorb water (my belief)

4. I'm a fair weather fan. I do not use a boat unless I plan to get in the water. I'm not going to use a malibu boat to go duck hunting. I don't even own a wetsuit.

The only 'pro' that I do not know the answer to is, did Malibu intend the foam to be a structural member for the hull back in '86? I'm going to use 3/4" ply w/glass for the floor, so the flooring will be strong w/out foam.

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Scott N

In the event of a serious emergency I think it's a question of can the foam slow the sinking process enough to help the people on board. I am sure you can Google and find a formula that will give you the ratios for foam displacement with different density foams.

I personally like the idea of having the foam under the floor as an insurance policy.

To your other point, I would bet the foam could help dissipate vibration and make the ride a little better. It probably does provide some marginal structural reinforcement, too.

Just my layman perspective and I ultimately think this is sort of a subjective decision. For me, I tend to be slightly risk averse and don't usually think 'it won't happen to me.'

Edited by Scott N

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Chuck A

I have the floors out of my '88 Skier and have removed the factory pour in foam completely. The old foam was saturated and holding water like florist's foam. I believe the weight that I've removed by taking out the waterlogged foam to be 400 pounds or more. (6 huge trash bags).

Now I’m considering three options for replacing the flotation foam. The first idea I found on a pour in foam manufactures web site suggested filling in large areas with ridged Styrofoam and then using the pour in foam to fill the gaps. This reduces the amount of pour in foam needed and I believe regular Styrofoam would be less likely to absorb water and hold it.

The second idea would be to use flat sheets of Styrofoam custom fit to the below the floor areas.

Now, I see a third option; no foam at all.

I’ll be watching this thread to see what the experts say.

Chuck A

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risky1

Good afternoon,

I read this thread with interest as i will need to do my boat after this season, (well, i intended to do it this past winter but ...) I consider my self handy and willing to do just about anything ( I did build a complete kitchen- cabinets drawers etc, as we remodeled, I just ordered the doors done because my wife wanted raised panel. and the cabinets looked dang good BTW I was very proud ... of course a good finish can hide a multitude of sins.... ) anyway, I am thinking about the seacast route as the actual fiberglass shells around the wood stringers is fine, but the stringers are done in many places (motor mounts are still solid, but drivers seat floor is toast. I figure i have at least 2-400 lbs of water in the foam by the way the boat sits in the water. (ballast? we don't need no stinkin' ballast")

are there pictures of how you guys did this? you removed the floor, and cut just the tops of the stringers off and then dug out the wood as i understand it? then just mixed the sea cast, filled up the fiberglass shells, leveled the tops and recovered with bi-axle cloth? then re-installed a new floor?

i realize i just way over simplified it... but i just want to make sure i have the general idea. is there anything that would turn you away from doing seacast again had you known going in?

Thanks,

Jared M

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Shine

Good afternoon,

I read this thread with interest as i will need to do my boat after this season, (well, i intended to do it this past winter but ...) I consider my self handy and willing to do just about anything ( I did build a complete kitchen- cabinets drawers etc, as we remodeled, I just ordered the doors done because my wife wanted raised panel. and the cabinets looked dang good BTW I was very proud ... of course a good finish can hide a multitude of sins.... ) anyway, I am thinking about the seacast route as the actual fiberglass shells around the wood stringers is fine, but the stringers are done in many places (motor mounts are still solid, but drivers seat floor is toast. I figure i have at least 2-400 lbs of water in the foam by the way the boat sits in the water. (ballast? we don't need no stinkin' ballast")

are there pictures of how you guys did this? you removed the floor, and cut just the tops of the stringers off and then dug out the wood as i understand it? then just mixed the sea cast, filled up the fiberglass shells, leveled the tops and recovered with bi-axle cloth? then re-installed a new floor?

i realize i just way over simplified it... but i just want to make sure i have the general idea. is there anything that would turn you away from doing seacast again had you known going in?

Thanks,

Jared M

That is the jist of the project. You'll need lots of space and a way to remove the engine and top half of the the boat. If you plan ahead of the floor cut out, you can leave yourself enough of a lip to put the floor level back to where it was originally set along the outboard edges and near the the transom.

If I had to do it again, I would use the pour foam before I put the floor down and use a file to level it. And I would use HDPE sheets instead of Marine ply for the replacement floor. I would also come up with a custom seat mount instead of going with the factory set up.

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Shine

In the event of a serious emergency I think it's a question of can the foam slow the sinking process enough to help the people on board. I am sure you can Google and find a formula that will give you the ratios for foam displacement with different density foams.

I personally like the idea of having the foam under the floor as an insurance policy.

To your other point, I would bet the foam could help dissipate vibration and make the ride a little better. It probably does provide some marginal structural reinforcement, too.

Just my layman perspective and I ultimately think this is sort of a subjective decision. For me, I tend to be slightly risk averse and don't usually think 'it won't happen to me.'

This is a good point and was my main reason for adding the foam back in.

At one point I began planning to plumb bags under the floor but came up with tons of reasons not to. The biggest reason is making a ski/barefoot tractor into something it is not. Kudos to those like rugger and MA that have been very innovative, but we dont surf and only wakeboard when we are too tired to ski/barefoot.

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