# Attaching new floor to aluminum stringers



## Harry1959 (Mar 17, 2011)

Have rebuilt a few glass and pontoon boats. This is my 1st aluminum. Was surprised that the floor is only 1/2 plywood. Looks like the factory had used rivets to attach the floor. I am leaning toward 1 inch 3/16 Stainless sheet metal screws. Would there be an advantage to using aluminum pop rivets to anchor floor?


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## bountyhunter (Apr 28, 2004)

self tapping would be nice. think the factory uses rivets because its cheaper an faster.


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## TRIPLE-J (Sep 18, 2006)

i used to work in a boat repair shop a LONG time ago
you use rivets over screws cause screws have a habit of backing out from the twisting and pounding they take going over waves... rivets wont do that 
i personally wouldnt use screws i would use rivets just for that reason


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## 40xmax (Jun 10, 2018)

TRIPLE-J said:


> i used to work in a boat repair shop a LONG time ago
> you use rivets over screws cause screws have a habit of backing out from the twisting and pounding they take going over waves... rivets wont do that
> i personally wouldnt use screws i would use rivets just for that reason


I rebuilt an old (1976 ) starcraft ss,, from the bottom of hull ..you can buy closed end pop rivets, stainless or aluminum and that's what I uesd..drill the hole, apply 3M 5200 in the hole / head of rivet and set the rivet..also used about 2 gallons of Galvet ...covered all riveted seams twice..it was worth the$$, and work...this is just my experience ..
..


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## Harry1959 (Mar 17, 2011)

Ok, as I get further into replacing the floor I have more questions. The previous owner had removed most of the old floor. The plywood floor appears to not have been sealed to the side of boat. It appears that the floor stopped a couple inches short of the gunnels. (the glass boats I’ve rebuilt had the floor sealed to sides). It looks like the floatation foam acts as somewhat of a sealant. Also each of the ribs or cross sections are open near the edge of the boat. These open ended ribs also extended beyond the floor. It looks like this is to allow water to drain to the center of boat and eventually to bilge area? If this is how it works, the floatation foam in the center section would make drainage difficult. I would be inclined to lay a section of closed cell board down the middle V of boat and then pouring my 2 part foam over the board to allow for better drainage. Please see pics. I may need to find someone local with aluminum hull experience to look at the boat and advise.
Btw it’s a 1980 sea nymph fishing machine with 55 Johnson I bought as a project for $900. I do have the old motor running like new.


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## 40xmax (Jun 10, 2018)

Harry1959 said:


> View attachment 317793
> View attachment 317795
> View attachment 317797
> Ok, as I get further into replacing the floor I have more questions. The previous owner had removed most of the old floor. The plywood floor appears to not have been sealed to the side of boat. It appears that the floor stopped a couple inches short of the gunnels. (the glass boats I’ve rebuilt had the floor sealed to sides). It looks like the floatation foam acts as somewhat of a sealant. Also each of the ribs or cross sections are open near the edge of the boat. These open ended ribs also extended beyond the floor. It looks like this is to allow water to drain to the center of boat and eventually to bilge area? If this is how it works, the floatation foam in the center section would make drainage difficult. I would be inclined to lay a section of closed cell board down the middle V of boat and then pouring my 2 part foam over the board to allow for better drainage. Please see pics. I may need to find someone local with aluminum hull experience to look at the boat and advise.
> ...


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## tm1669 (Apr 27, 2007)

Not sure on a sea nymph but my 72 starcraft ss has water channels at the middle/bottom of each rib to let the water run back to the bilge. I just used closed cell foam insulation board and cut it to fit under the decking but of the very bottom of the hull so that channel wasnt obstructed. I had the original foam in the boat when I took off the decking and thats how the factory did it.
As far as sealing the edge of the deck I think I would want water to be able to get off the deck as fast as possible and back to the sump. I just layed the decking down to the edge of the hull and riveted it. Making sure water can clear the deck and get to the sump is more important to me than trying to seal the deck at the edges. Ive taken some wake and waves over the bow and was pretty happy with the water clearing off the deck rapidly. 
I made sure I sealed the decking (especially the edges) with a bunch of coats of spar urethane and then oil based paint to delay any rotting as much as I could.
2 part epoxy would be better but I couldnt justify the cost.


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## 40xmax (Jun 10, 2018)

There are thousands of boat rebuilding threads...some do it the right way, some don't. My suggestion is to do it once the right way...whatever wood you plan on useing ( I used douglas fer)...dont use pressure treated stuff..you need to epoxy both sides regardless of where its going..any holes need be sealed with 5200,.or epoxy...and there needs to be at least one inch at the v for water to escape the hull, and to allow some air to move..I rebuilt my old boat 7 years ago, have run the snot out of it on Erie...this includes rebuilding the transom...anyways, I trust it with my life, and my fishing buds, and my grandkid every time I launch it..do it once, do it right...my dad tought me at a vary early age to do the right thing when nobodys looking, you'll sleep better..one other little thing..marine grade plywood..I'll never spend that kind of money of a boat floor again..transom yes, floor no. Epoxy is your friend, 5200 is your friend..


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## 40xmax (Jun 10, 2018)

And as tm1669 said, you have to build channels to allow water to run and to allow for air flow..I used PVC, drilled lots of holes in the top if it
..I also used closed cell foam planks, didn't pour it..


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## 40xmax (Jun 10, 2018)

Don't know where you are located, I'm retired, have a tig welder, have a long history with alloys not to mention laying in the mud and snow welding pipe...anyways I'm willing to help you..not looking for a job or money...just give you solid advice & help another OGF MEMBER. I try to make to Erie twice a week weather permitting..


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## tm1669 (Apr 27, 2007)

I just saw the pictures..
That is a ton of foam. It has to be miserable getting that out of there but I see what your saying about the water getting down there now. Only way it can is through the ribs if you redo it the same way. 
Personally I think its overkill with the pour foam and would just use foam board with the bottom piece sitting on top of the ribs leaving the area under free for water to get to the sump.


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## 40xmax (Jun 10, 2018)

Yup, that'll also work tm1669..the only thing I considered when putting mine together is I thought the foam may compress over time and that's why I used the PVC...but what you said will work...


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## Harry1959 (Mar 17, 2011)

Thanks for the replies. I definitely do boat repairs to the best of my amateur ability and so far all my rebuilds have turned out ok. This concept of letting the water to flow on aluminum is different from the old glass boats I have gutted and rebuilt. I should get my Clear penetrating epoxy sealant today. already have 1/2 marine plywood, had 1/2 from the factory. Since the floor is only 1/2 I ordered pourable foam, I think the floor needs the support of the foam
As far as using pvc. I guess I need to somehow lay those in the bottom of boat to act as drainage tiles from the bow to stern? Otherwise my pourable, expanding foam will make it very difficult for water to escape through the ribs.


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## 40xmax (Jun 10, 2018)

Harry1959 said:


> Thanks for the replies. I definitely do boat repairs to the best of my amateur ability and so far all my rebuilds have turned out ok. This concept of letting the water to flow on aluminum is different from the old glass boats I have gutted and rebuilt. I should get my Clear penetrating epoxy sealant today. already have 1/2 marine plywood, had 1/2 from the factory. Since the floor is only 1/2 I ordered pourable foam, I think the floor needs the support of the foam
> As far as using pvc. I guess I need to somehow lay those in the bottom of boat to act as drainage tiles from the bow to stern? Otherwise my pourable, expanding foam will make it very difficult for water to escape through the ribs.


I'd have think about the pourable foam in that application...deffantly won't be able to drill holes in the pvc...just a thought...how about taking pool noodles and slide over the pvc...cut it length wise exposing the pvc enough so that the pvc lays in contact with the hull while protecting 340 degrees+ - of the pvc/ pool noodles exposed to the pourable foam??? Best I got at moment...just have to keep it out of the ends of the pvc which shouldn't be a problem..all this while granddaughter is playing with pool noodles...grandkids, what a blessing


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## 40xmax (Jun 10, 2018)

And I believe you can still drill the pvc...you obviously have worked with pourable foam so you know its gonna take the path of least resistance which will be in the holes you cut in the floor when you pour it..


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## jonzun (Jun 11, 2004)

Have you looked into using Veranda HP 1/2 inch pvc 4x8 sheets instead of plywood? $64.98 at Home Depot


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## Harry1959 (Mar 17, 2011)

jonzun said:


> Have you looked into using Veranda HP 1/2 inch pvc 4x8 sheets instead of plywood? $64.98 at Home Depot


I would have researched and considered it, but I already have the marine plywood and clear penetrating epoxy sealant in the garage. Also I’m pretty sure the epoxy sealed marine plywood will outlast most of us


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## 40xmax (Jun 10, 2018)

jonzun said:


> Have you looked into using Veranda HP 1/2 inch pvc 4x8 sheets instead of plywood? $64.98 at Home Depot


The 1/2 Veranda is not as strong as 1/2 plywood and special prep i
needs to be done in order for it to bond to more common substrates ( so say the experts) it also doesn't have the rigidity of plywood ...I love the idea of not useing wood on anything that's going in the water..starboard is apparently the go to material in the marine industry for high end boats...it ain't cheap...then again nothing that has MARINE in front of it is


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## 40xmax (Jun 10, 2018)

40xmax said:


> The 1/2 Veranda is not as strong as 1/2 plywood and special prep i
> needs to be done in order for it to bond to more common substrates ( so say the experts) it also doesn't have the rigidity of plywood ...I love the idea of not useing wood on anything that's going in the water..starboard is apparently the go to material in the marine industry for high end boats...it ain't cheap...then again nothing that has MARINE in front of it is


 *Marine grade HDPE* is formulated to meet the specific requirements of *marine* and other outdoor environments. ... Like regular *HDPE*, this material exhibits high impact strength as well as excellent tensile strength, energy absorption, abrasion resistance, and resistance to stress cracks. Starboard...good suff


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## I Fish (Sep 24, 2008)

You might think about putting the gas tank under the floor. I put a 28 gallon one in the floor of a 86 sylvan. If you can find one in the dimensions to fit, it utilizes otherwise unused space.


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