Malibu RCB trunk delete

[MNshortliner]

Bought a 2012 RCB last fall and wanted to change up a few things. Kind of ridiculous that a ski boat would need 100# of extra weight in the nose to get a better wake, the lack of floor space kind of sucked. With two skier’s gear not much room for moving around and hated stepping over the rear trunk to get to the platform. And why would they have that said trunk open forward so you can only access it from the platform? So the wheels started turning and the fiberglass in the rear was minimal compared to other boats with “built in” gas tanks or rear trunks and I was bored and needed a project.

A pic before the project started. My son skiing 28 mph. And you can see a ski barely fits from the driver seat to the backrest of the trunk.

 

So started taking out all of the upholstery and panels.

 

[MNshortliner]

Don’t know why they designed it this way but they sure stuck with it, for like 15 years.

 

 

[UWSkier]

Different strokes. I love the trunk on my RLX and it's one of my biggest issues that it's gone from newer boats. That and I regularly have two skis on the floor behind the drivers seat with little issue.

 

I'm the only one who uses my trunk and I only use it when I am on the platform getting ready or getting done with a set so it's perfect for me.

 

But I do love a good boat modification thread! :)

[PurdueSkier]

So what is your plan after the demo?

[skimtb]

OK, occupation not listed, but @MNshortliner is clearly in the advertising or marketing business. He baited us and now we have to keep coming back until he posts again.

[Deke]

I'm with @UWSkier, the trunk is my favorite thing about my 99 RLX! Looks like you're going for the 98 RLX look. Don't forget to design some sort peep hole for the gas tank!

[6balls]

Gull wing trunk is nicer, accessible from in the boat or the platform.

[DavidN]

@MNshortliner

Yes.

Go on please ...

Audience is waiting!

[MNshortliner]

Let me just say, this was my last winter project, it is done, this is just my build, wanting to share what I did, some like to see boat projects just for fun.

So starting out thinking about the project, I had a number in mind of 250. That’s how much weight I thought I could get rid of all behind the motor.

I have always skied with 3/8 of a tank or less to get an optimal wake and don’t have unnecessary equipment in the boat. The ski boat is used 100% for slalom skiing so no need for other gear. So I got down to tank removal and the gas gauge said under 1/4 tank. When I disconnected the hoses and took the hold down brackets out the tank was still very heavy. We got it out of the boat and took about 8 gallons of gas out of the tank.

 

So taking out the trunk/tank the side panels were not going to work how they were stock so those had to come out also.

 

Getting measurements for what kind of gas tank I was going to be looking for. Also those were the 2 sand bags that had to be in the nose to get a little better wake.

Disclosure, I am going to drag this out for about a week or so. Haha

[ReallyGottaSki]

 

[DW]

@MNshortliner - I am sure you pleased with your project, I did a similar one on my Echelon. Moved tank in to ski locker, created a ski locker where the old tank lived. Really helps the wake and removes a significant amount of mass off the transom.

[PurdueSkier]

@MNshortliner Reading live builds is fun. Reading a completed build in bits and pieces is just annoying. Post some pics and tell the story.

[Bill22]

That extra floor space would be nice when installing a portable course.

 

I’ve had a full six buoy Insta-Slalom course, three adults, skis, ski gear and a cooler in my RLx. Yep, space gets tight fast.

[Kevin89MC]

Very interesting thread, at least to me! I just got my hands on a '99 RLX and love the trunk. We keep 2 slalom skis and binding slime in there and it's all readily accessible for hitting the course. But I do see the advantage in saving the weight. One quick question, do you still have your old trunk cover? Mine is pretty soft at the hinges, and I plan to re-build it this winter. An existing one would make that much easier! I'm in Minnesota, thinking you might be as well considering your user name. PM me if you'd like so we don't clutter up this thread.

Thanks,

Kevin

[MNshortliner]

So after getting measurements for how much room there was in the nose I started looking at fuel tanks online. I decided on a 12x10x32, 13 gallon tank. When we go out skiing 90% of the time it is 2 skiers and between 2 sets each we use about 6 gallons total. I wanted something that wasn’t going to take up the whole bow area and something that was going to offset the driver a little bit, also wanted it as far forward as possible.

 

So I cut the appropriate size hole in the new tank where I wanted it, and made a HDPE backing plate ring to fit inside the tank so the stainless screws had something to bite into. The fuel pump in my boat is the in tank bucket style assembly and quite large but it worked out really good. I put it in the rear part on the tank so when on plane the deepest part of the tank would be at the pump to pick up the most gas possible. The old tank was only 8” deep and the new tank was 13 inches so the bucket style fuel pump assembly would not reach the bottom of the tank. This is a stock fuel pump assembly.

 

I had to take apart mine and extend the arms where the springs were.

 

I welded on new stainless 3/8” tubing to extend the fuel pumps down another 4” or so and did replace the filter socks at this time. The lock washers rest on my welds and the springs push on the lock washers to obtain about the same spring pressure and travel as before.

 

 

[MNshortliner]

So with the theme of dropping weight, moving around the swim platform is ridiculously heavy. I mean holy crap after 20+ years of ski boat building in the new age you think they would do a lightweight platform. The platform sits behind the hull and as far as a leverage aspect is more important than weight loss inside the boat. With that, I like working with aluminum, so an all aluminum platform only makes sense to me. The aluminum I used is 1 1/8” x 6”. It is the same stuff that is used for outside bleachers and joins/hooks together to make it very strong and light weight.

 

Got the size I wanted and cut out the pieces to shape.

 

Put a 1” tubing frame around the whole outside. The bent tube that is closest to the boat was kerf cut every about 6” to get a nice radius to match the fiberglass hull.

 

 

Then had to weld a piece of flat stock on where the brackets were going to attach.

 

Put the bracket on the boat, mark, drill, and bolt brackets on.

The aluminum plank had the no slip ribs/textured top and I was going to wrap the platform with EVA foam so I did knock those down with a sanding disk/grinder somewhat. Also put plastic cap inserts into the ends of the 1” tubing so there was no exposed sharp metal edges.

 

 

Wrapped the whole thing with EVA foam I got from eBay for fairly cheap. Had to notch the corners get get them to wrap around the corners nicely. It’s not perfect but I am happy with it.

 

The foam had sticky back on it but I was not going to rely only on that to keep it attached to the platform. 3/4” strips of aluminum pop riveted around the whole perimeter of the platform hold it on nicely.

 

Finished product. I love it. Original platform was 50#. New platform is 25#. Platform never really gets soaked as it sits about 6” above the waterline.

 

 

 

 

[skimtb]

You’ve got skilz!!!! And good theory on the platform weight and location relative to the CG of boat. Good idea there too.

Still waiting for the pic And other info on rear inside.

[MNshortliner]

Yes I will be getting to it. I still need to take a few more pics that I don’t have of the finished product.

[DavidN]

Dang, I was hoping for more on the interior transformation to be released.

Waiting patiently here ... :D

Already noticed that you are running a different platform, and yes the Malibu swim steps are unnecessarily heavy. Was really surprised when I took off my Nautique fiberglass platform how lightweight that one is compared to the fiberglass one of my previous Response. Good job in weight savings!

On a side note - as we are comparing weights here - Malibu’s removable center floor piece (behind the engine box) is less than half the weight of the roughly similar sized Nautique one. Wish I could get my hands on a sheet of that awesome material to replace the heavy one in my boat.

[oldjeep]

@DavidN - the trade off is that the awesome panel material that Malibu uses breaks down over time and becomes squishy. The fix is typically to buy a piece of King Starboard to replace the flimsy honeycomb stuff.

[DW]

Another option for either the platform and / or the rear interior panel is carbon fiber + corecell core. Very light and extremely stiff. I did both of mine that way and am very pleased with the results.

 

@MNshortliner - nice out of the box thinking on the platform, will be interested in feedback on how you like it.

[DavidN]

@oldjeep

I read a lot of complaints about that issue as well, however, I owned 3 different Malibu Response CB’s over the past 16 years (~1400 hours of combined usage) and never had any issue with the honeycomb material.

I once had a handle pop into the trunk lid that did some small damage to the honeycomb (and the vinyl) but that’s about it.

 

@DW

You have a source for that stuff you mentioned?

 

[oldjeep]

@DavidN - happened to the 04 LXI my inlaws have. The honeycomb floor panel right behind the motor was mush. It has around 1000 hours on it now, but the problem started many years ago.

[skimtb]

Issue w honeycomb is if large washers or a backing plate are not used where the hinges connect. That starts the problem then it is a downhill slide from there, eventually getting exponentially worse.

I think If done right, should be decent lightweight solution.

 

[oldjeep]

This is getting off topic - but the hinges don't attach to the honey comb panel. The panel pulls out to access the mufflers and rudder. The hinges attach to a board in front of the panel.

 

[ReallyGottaSki]

Great fabrication, outstanding!

 

yeah i was thinking similar, perhaps some coosa skinned with some epoxy and carbon fiber could be helpful for some of these fixes mentioned ?

[UWSkier]

Great idea on the aluminum swimstep. I have a fiberglass platform on my RLX and it's unnecessarily heavy.

[Bill22]

When you said aluminum bleacher material I thought that’s gonna look like CRAP. But you pulled it off nice with the EVA foam. Good fab work.

[DW]

@DavidN - carbon fiber from US Composites and Corecell from Jamestown Distributors.

[braindamage]

I love it!! Where is the gas fill tube? I assume the tank is designed by Malibu in the back for safety reasons?

[MISkier]

@braindamage, I also guessed the tank location is to keep a fire or explosion as isolated from the helm as possible. I’m sure there are things to be done to make alternate locations possible and safe,

[skimtb]

I’m guessing a hole was cut and filler thingy added to the bow.

@MNshortliner is keeping us in suspense.

[skimtb]

Thinking further, with the skills @MNshortliner has, there is a chance he found a way for it to regenerate fuel such that is always has 5 gallons to ski in it.

[MNshortliner]

Yes I did have safety somewhat on my mind when I was thinking about putting the tank up front. This was the standard location in closed bow boats for a long time. I believe the reason for not still having them up there is mainly for storage reasons.

How the tank was placed put the fill neck almost directly in the middle of the bow of the boat. The “hood” is almost 4” thick in that location. 3/8” think fiberglass on the top deck, 3” of foam for flotation, and about a 3/16” think unfinished fiberglass on the underside.

I cut my hole for the new gas cap in the hood then drilled out about a 6” hole in the unfinished glass underneath. Cut away all the foam and have about an 8” filler neck hose attaching the cap to the tank.

 

 

 

 

I put the vent/overflow on the side of the boat. Those are my pet fish.

 

 

I did add another blower in the bow but only run it for a minute when I first get to the boat for the day. Then I run my regular blower for 2-3 minutes before starting. A 3 1/2” hole was drilled right in front of the stock vent tubes for the added vent tube/hose and it is wired to an independent switch.

 

The wire harness for the fuel pump was about 24” short so it was added to with in line splices. New fuel hose to the motor also.

 

 

I have never smelled any gas fumes under the bow and I can easily see the fuel level in the tank just looking at it. The fuel gauge still works as it should.

 

I plugged the gas and vent holes with plugs, still have to add some striping the the black one. I added the red stripe around the boat. I like colors and couldn’t have just a black and white boat.

 

I will be wrapping this thing up tomorrow.

[Zman]

@MNshortliner Must say, you do very nice work. Should you consider a couple straps over the gas tank to keep it from jumping when you hit a big roller? The end with the fill hose might not move much, but the other end might. Thinking something like what is used on a battery box, except stainless hold downs on the floor instead of plastic.

[UWSkier]

I like the foolproof fuel gauge. :D

[MNshortliner]

@Zman yes I did put a strap on the back of the tank. I guess that pic was from earlier this winter. It’s not really heavy duty but I think it should work just good enough. Here you can also see the fuel level in the tank. Almost full.

 

 

[skimtb]

Fantastic work! Thanks for sharing.

[DW]

@MNshortliner - in what position did you mark the tank? In my case, boat does not sit at same level on lift as on water, therefore I made a specific check stick for the lift. You have probably already realized with the smaller tank, the starting fuel level is a bit more critical when heading out for several sets. Nice work.

Note: the vent line should have a loop in it to prevent fuel spitting / spilling out. Yours might, just not in the pic.

[BrennanKMN]

This whole thing makes me think of the guy on YouTube who made the 'Carbon TSC' boat. He took a TSC1 Ski Nautique and did as much weight savings as possible. Pretty cool project and the boat is crazy fast afterwords.

 

Here is just one of many videos on his channel.

 

[MNshortliner]

So the last thing that needed to be done is the floor and trim panels. I wanted to go clean, simple, and wanted it to look somewhat factory finished.

For the floor I used the same aluminum that I used for the platform. The pieces are just hooked together and the carpet is screwed on. No welding, no glue, and I had a couple of pieces of grey carpet so I used the one that matched the best. The original floor piece was cracked when I bought the boat and only long enough to go just under the backrest of the trunk. This is the only thing that was heavier than the original but still pretty light weight.

 

The factory side panels had a nice look to them and a nice badge, so I wanted to stick with that theme. Stock side panel.

 

 

I used pvc board 3/8” think from Lowe’s. Just think enough for the 3/8” stainless staples I use to attach upholstery. This pvc board is lighter and more flexible then hdpe board and worked perfect for what I wanted. Ripped to size, cut to shape, and routered the edges.

 

I held them up in place, clamped them and marked all existing holes so I didn’t have to drill new holes in the fiberglass. Then drilled them out and used star nuts for a fastenerless finish.

 

Finished side pieces.

 

In this pic the two colors look very different but in person they are very close color wise. One shade different.

 

 

A little personal touch.

 

Rear panel is just a flat piece that bends nicely with the curve of the boat. I couldn’t really come up with a way to use hidden fasteners so just used screws.

 

Big plain vinyl pieces on boats are boring so have to add a little more personality.

 

 

 

Have used this boat all summer and I absolutely love it.

 

 

 

[dvskier]

Excellent craftsmanship. You have every reason to be proud of your boat. Not another one like it on planet earth! Tastefully executed.

[MISkier]

Awesome. I totally want to take a set behind it.

[robmollysilverlake]

I'm lucky enough to get to ski with my friend Nick aka @MNshortliner and his beautiful boat!! He really is an amazing craftsman, maybe he will even show you a picture of his pontoon that he customized!

[skihacker]

Are ski racks on the to do list?

[UWSkier]

Very cool. Hazelwoods did something similar with one of their previous gen TXIs but I think they left the gas tank where it was and just ditched the sofa. As I mentioned, I could never lose my trunk but would definitely like to lighten up the platform and do the side panel mods. I don't care if I lose the rear speakers in the process.

[DavidN]

@MNshortliner

 

Awesome transformation! ?

How roomy that boat now is, unbelievable.

 

I still can’t get over how much draft you lost due to the modifications.

Must be almost 4 Inches. I’m sure the slalom wake is even more awesome on that boat now!

 

For comparison ...

My 2010 RCB which had some weight reduction done as well, but not quite as extensive as your build.

 

 

Next winter project ... build a lightweight engine box? Get some aluminum heads, stainless exhaust, ... There’s plenty you can still do. Ask @DW about his Echelite project... :D

[MNshortliner]

Thanks everyone for the nice comments. @skihacker I did think about how to do some racks but unless we have about 4 people skiing I don’t think they would save that much space. But if there was a fairly simple way to make some I might be interested. But there is not much to mount something like that to either.

I will report back in the next couple days and see how much weight was actually dropped. I still haven’t weighed the gas tank so will get to that. But I love all the extra room and it’s barely a step over the back transom to get to the platform.

@UWSkier this boat was bare bones, it didn’t even come with a stereo.

@MISkier whenever you’re in the neighborhood.

[BlueSki]

Awesome work! Did you notice the improvement in the wake to the extent that you wanted?

[escmanaze]

I'm with @BlueSki . We all want to see what the wakes look like now!!