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Reinforced the trunk floor of my SSLxi


msuwaterski

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There has been much discussion on this site about putting ballast sacks in the rear trunk of DD boats and how one would need to reinforce the floor over the gas tank in order to do so safely. Well I decided to reinforce my trunk floor this winter so I could add a ballast sac and the following is a step by step guide with materials list on how I did it.

I will state that this project in not my handy work. I must give all of the credit to Skier64 (thanks Alan) for sharing with me how he did it and the few pictures he had. The information he shared with me gave me a good starting point. I did do a few things differently, but it is basically the same. Please feel free to comment or ask questions.

To start: first you have to remove the trunk back. It is attached by 4 screws on the top and 4 on the bottom. Once that is gone you will need to remove the shock tubes from the trunk lid in order to get the floor out. The floor is not attached to anything, it just sits there. That said, it's still really hard to get out!

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Next I would like to put to rest the rumor that the trunk floor is strong enough to support ballast without reinforcing it. IT IS NOT! The trunk floor in only 1/4" plastic and rather flexible. Not only that, but the floor has 4 risers attached to it that sit directly on the gas tank. The pictures below show the floor thickness and the risers I speak of (white squares on bottom).

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Edited by msuwaterski
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In the SSLxi trunk the swim platform bolts up from underneath and those bolts are exposed. Those bolts are how I attached my support AI bracket. First, however, I needed to use a riser plate in order for the AI to sit up high enough as to not let the cross beam touch the gas tank. I used 2" by 1/4" alluminum stock for this. I attached this riser plate using the bolts from the swim platform, then drilled out holes on either side to attached the riser plate to the AI. The pictures will best describe this.

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Edited by msuwaterski
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With the riser plates on, I installed the angle iron (1/4" aluminum). I had to drill out 9/16" holes in the AI to sit over the bolts that attached the riser plate, then bolted the AI to the riser plates on either side. I used 3/8" stainless steal bolts with lock nuts. Before you permenantly attached the AI you will want to layout your cross member location and pre drill the holes in the AI as there is not enough room in the trunk to drill.

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Edited by msuwaterski
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Next I attached 2" pieces of AI to the back of the rear seat. The backing on the rear seat is 1/2" plastic and very rigid, so I used coarse thread 3/16" SS screws to attached the AI to the seat back.

To determine the correct height to mount the AI, I first laid my cross member flat on top of the gas tank and butting against the seat back. Then I placed the AI on top of the cross member and made a mark on the seat. Doing this ensured me that all cross members were the same height off the gas tank, which is a little over a 1/4". Finished product is below.

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For cross members I used 2" by 1/4" aluminum stock, and attached it to the AI in the back and the AI brackets attached to the seat back. All of these were pretty easy to install, except the starboard most one in which I had to remove the blower in order to acces the back of the seat to mount the bracket.

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  • Like 1
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Last, I compared the finished product height to the height of the white plastic risers that were on the floor bottom to begin with. My finished product is 1/4" lower than the original floor, so I will be adding 1/4" plastic to make up the difference and to add more rigidity. That's it!

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DSC01444.jpg

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Now I know that I will be criticized for using aluminum and not SS stock and I know that SS would be a LOT stronger, but I do not have the tools necessary to cut or drill SS. The whole point of doing this was to make sure that at no point will the floor ever touch the gas tank, and I am confident that I have achieved that. I installed the crossmembers with a slight crown, so the downward flex is minimum, and with the extra 1/4" flooring that I am going to add on top I am sure it will be more than enough to support a 500lb sac.

I will add pictures of what the project looks like once the floor is back in, but for now I decided that while I have the wedge bracket exposed I may as well ugrade to a FLOATER! :rockon:

Ballast install write up to follow soon.

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Very nice and clean.

Just added this to my collection of good threads.

I might have used steel instead of alum. for the flex but, you sound confident in the alum.

Also, looks like a good time to relocate that pesky low pressure fuel filter.

Edited by Pistol Pete
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  • 1 year later...

Is there any way I could get your measurements?

I plan on doing this to my boat (same as yours) in a couple weeks and I'd like to get a local shop to make the cuts for me.

Thanks

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Is there any way I could get your measurements?

I plan on doing this to my boat (same as yours) in a couple weeks and I'd like to get a local shop to make the cuts for me.

Thanks

Sorry, I didn't write anything down. It was an "as I go" project. PM me if you'd like and we can discuss more.

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  • 3 years later...

msuwaterski,

Now that you've had the ballast in the trunk of your LXi for a couple summers, I'm curious if you have any new wisdom to share.   How large of a ballast do you run in the trunk?   Does the ballast in the trunk positively impact the wake as you hoped?   Would you do anything different if you were to take on the project again?   I'm curious as I'm closing the deal on a comparable boat now ('99 SS LXi).   Thanks in advance for the response!

 

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I am also about to start this project on mine.  I bought a sack specifically for back there. So I am also curious if you would change anything.

Edited by twitchee2
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9 hours ago, braindamage said:

I did the same mod a few years back. Same as msuwaterski (thanks for the thread).

ive had no problem and I wouldn't do it any differently.

If you don't mind......... what is the size and brand of the ballast that you are running in the trunk?  

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If anyone is in Oregon (or the greater PNW) with a SSLXi and would be willing to swing by our place let me know. This is one of the boats that we would like to get a scan of to offer ballast specifically for the rear locker.

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11 hours ago, BradC said:

If you don't mind......... what is the size and brand of the ballast that you are running in the trunk?  

I run an 800# sumosac. It grows higher than the trunk so I either have the trunk lid be pushed up a bit higher or I don't fill all the way.

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1 hour ago, braindamage said:

I run an 800# sumosac. It grows higher than the trunk so I either have the trunk lid be pushed up a bit higher or I don't fill all the way.

Thanks for the info!  

One more question if you don't mind.  How/where do you draw water into your LXi?   Did you drill a hole in your hull?   Thanks again. 

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