Floor replacement question

[62cruiserinc]

I have a 1984 Larson 19'. The previous owner put 1/2" pressure-treated plywood over the original floor, probably because it was soft. This is my first boat, so if I don't use the correct terminology please forgive me.

I removed the PT plywood and the original floor was rotted in much of the rear 2/3 of the boat. There are two stringers about 2' apart that run from the transom up to the console. It looks like the floor rotted top down, as the stringers are good except for some spots where the top inch has rotted. The stringers are about 8" high and 1" thick.

The plan for this year is to repair the floor and stringers so the boat can be used this year and then do a thorough restoration-type repair over the winter (I have a heated shop). I probably could have left it as it was for this year, but I wanted to improve it. I am planning to remove the rotted top inch of the stringers and attach a second stringer to the originals ("sister" them in housebuilding terminology). Then I will put new 1/2" PT plywood on the floor. I realize this is not a good permanent solution, but it will have to do for this summer.

The question I have is about the floor plywood. The original plywood is supported by the two parallel stringers that are about 2' apart (1' on each side of the centerline). These are the only stringers. There is foam between the floor and the fiberglass except between the two stringers (the bilge area). The plywood edge along the hull doesn't have any support under it, only the foam. The edge is also glassed to the hull along its length (for a width of about 6-8"). There are several areas along one side where the fiberglass is not attached to the hull, I don't know if it was originally attached and then cracked along the hull/floor line or not. My questioin is: Is the floor glassed to the hull to make the joint waterproof or does the floor act as a support for the hull to keep it from distorting? Same question for the floor-to-transom joint.

The reason I ask this question is that I need to know if I should glass the joint even for this temporary repair.

Thanks
Steve

 

[tpenfield]

Re: Floor replacement question

The floor, when glassed to the hull will give it some rigidity from flexing as you asked. It should be glassed in.

 

[diggin4grouper]

Re: Floor replacement question

ill try to explain this and if you dont understand ill take a pic later ( this is where we are at in redoing our floor )

on both sides of the boat where you see the fiberglass not attached to the boat there was at one point a 1"x6" that was tapered to fit the area it would go from front 1/4 to the back being about 5 3/8 on each side (yours might be different but pretty close and we are going to completely fiberglass them in ) these were the support for the sides of the floor , they are a pain in the butt to get cut as both the hull and were the deck sit are both tapered some what . heres a crude drawing to help , but if need be i will take a pic of what we have done to show you

 

[rickryder]

Re: Floor replacement question

I have a 1984 Larson 19'. The previous owner put 1/2" pressure-treated plywood over the original floor, probably because it was soft. This is my first boat, so if I don't use the correct terminology please forgive me.

I removed the PT plywood and the original floor was rotted in much of the rear 2/3 of the boat. There are two stringers about 2' apart that run from the transom up to the console. It looks like the floor rotted top down, as the stringers are good except for some spots where the top inch has rotted. The stringers are about 8" high and 1" thick.

The plan for this year is to repair the floor and stringers so the boat can be used this year and then do a thorough restoration-type repair over the winter (I have a heated shop). I probably could have left it as it was for this year, but I wanted to improve it. I am planning to remove the rotted top inch of the stringers and attach a second stringer to the originals ("sister" them in housebuilding terminology). Then I will put new 1/2" PT plywood on the floor. I realize this is not a good permanent solution, but it will have to do for this summer.

The question I have is about the floor plywood. The original plywood is supported by the two parallel stringers that are about 2' apart (1' on each side of the centerline). These are the only stringers. There is foam between the floor and the fiberglass except between the two stringers (the bilge area). The plywood edge along the hull doesn't have any support under it, only the foam. The edge is also glassed to the hull along its length (for a width of about 6-8"). There are several areas along one side where the fiberglass is not attached to the hull, I don't know if it was originally attached and then cracked along the hull/floor line or not. My questioin is: Is the floor glassed to the hull to make the joint waterproof or does the floor act as a support for the hull to keep it from distorting? Same question for the floor-to-transom joint.

The reason I ask this question is that I need to know if I should glass the joint even for this temporary repair.

Thanks
Steve

Hi Steve Welcome to the iboats Dry Dock!

You will need to attach your deck to the gunwales with fiberglass tabbing.....it gives strength to the hull and a waterproof seal. Have you core sampled the foam to see if it has water in it? Also core samples of the stringers to see if they are rotten down low?

PT plywood will have to sit and dry out for months for the resin to bond to it....better off with regular cdx coated in epoxy resin to seal it.

When your ready to do it correctly/permanently we can help you through the entire process....we don't like to band-aid our boats here....were all about building it better than the factory did and it being safe for family and friends

 

[Woodonglass]

Re: Floor replacement question

The first link in my signature below has drawings and instructions on how to do your deck the recommended way.

 

[62cruiserinc]

Re: Floor replacement question

I am going to take a core sample of the foam and stringers to check them out.

How far out onto the plywood deck and up the hull do I run the fiberglass tabbing to ensure a strong joint?

Also, I removed the 28-gallon aluminum fuel tank and drained out the old fuel. What should I flush the tank with?

I am replacing all fuel lines along with the filler hose just in case they are deteriorated.

Steve

 

[diggin4grouper]

Re: Floor replacement question

When your ready to do it correctly/permanently we can help you through the entire process....we don't like to band-aid our boats here....were all about building it better than the factory did and it being safe for family and friends

i hope you were not referring to me about what i told him being a band aid ! what i told him was correct and the proper way to put the side floor supports back in , when there rotted and gone they look like this

 

[tpenfield]

Re: Floor replacement question

Also, I removed the 28-gallon aluminum fuel tank and drained out the old fuel. What should I flush the tank with?

I am replacing all fuel lines along with the filler hose just in case they are deteriorated.

Steve

Yea, I just pulled a 94 gallon fuel tank from my boat. Even after being drained, it was still dangeroues due to the high concentration of explosive fumes. I did some searching on the web about the best ways to flush the tank in order to render it safe. Several iterations of a detergent wash seemed to do the trick. then I stored it with the fittings facing down, so that any remaining water/fumes could escape.

You should also inspect the tank for corrosion, pits, perferations, etc. A 25+ year old tank in a boat with rot issues is probably ready to be replaced. Safety should be your rule here.

 

[Woodonglass]

Re: Floor replacement question

I am going to take a core sample of the foam and stringers to check them out.

How far out onto the plywood deck and up the hull do I run the fiberglass tabbing to ensure a strong joint?

Also, I removed the 28-gallon aluminum fuel tank and drained out the old fuel. What should I flush the tank with?

I am replacing all fuel lines along with the filler hose just in case they are deteriorated.

Steve

If you look at the link, it has all the info you are seeking.

 

[rickryder]

Re: Floor replacement question

i hope you were not referring to me about what i told him being a band aid ! what i told him was correct and the proper way to put the side floor supports back in , when there rotted and gone they look like this

Now if I was talking to you I would have quoted your reply like I am doing here..... What I was replying to was the fact that the OP wanted to just sister his stringers and re-deck without glassing the entire deck.....

If you want to get technical your drawing is incorrect....you failed to show a layer of csm on the bottom of the deck to waterproof it,You show the 1x6 laying directly on the hull and not in a bedding compound so not to create a hard spot,one layer of csm(btw it's chopped strand mat not chopstrain) When it should be multiple layers of csm progressively larger running down on the hull to spread the load....and lastly....boats don't have floors....they are decks!

Please don't ASSume I was referring to your post and throw an attitude at me. Next time just shoot me a PM and ask politely....I'm really not a bad guy

 

[62cruiserinc]

Re: Floor replacement question

I checked the deck to hull area after removing the rotted plywood and there is no wood support along the hull. The foam goes all the way against the hull and there is no room for a rotted-away support to have been there. To make the area more crowded, there is a storage pocket about 6 feet long just above the deck. This pocket has a wood support at the bottom of the pocket that is glassed to the hull. The pocket wood has mostly rotted away and left the fiberglass. The bottom of the wood is only a few inches above the deck. This makes tabbing new plywood to the hull hard. See the first picture below:


The next picture shows the port side stringer and shows the width the ply spans from the stringer to the hull. Without any support from below for the plywood, how did they hold the edge in the right position for tabbing to the hull? Was the foam put in first? The foam is dirty on top from the rotted plywood, but it is dry. I removed several small pieces and in every case the foam was completely dry.


Assuming all the foam tests show it to be dry, I could put the new deck on top of the foam and then tab it to the hull, with the foam supporting it while I glass it. The froam at the hull edge is only 1 1/2" thick because my hull turns almost horizontal at the chine and then turn down into a V again. See the last picture below:


I haven't taken any core samples yet on the stringers to see if the bottom 75% is soilid as I expect. I'll probably do that tomorrow.

I tried adding the pictures as shown in the how-to section, but no matter what size I made them before uploading, they showed up as very small pictures.

Steve

 

[diggin4grouper]

Re: Floor replacement question

Now if I was talking to you I would have quoted your reply like I am doing here..... What I was replying to was the fact that the OP wanted to just sister his stringers and re-deck without glassing the entire deck.....

If you want to get technical your drawing is incorrect....you failed to show a layer of csm on the bottom of the deck to waterproof it,You show the 1x6 laying directly on the hull and not in a bedding compound so not to create a hard spot,one layer of csm(btw it's chopped strand mat not chopstrain) When it should be multiple layers of csm progressively larger running down on the hull to spread the load....and lastly....boats don't have floors....they are decks!

Please don't ASSume I was referring to your post and throw an attitude at me. Next time just shoot me a PM and ask politely....I'm really not a bad guy

then i will apologize to you and i didn't have an attitude towards you and still don't , but when you post something and then some one post that statement right behind you can you see how that looks , it looked as if what i posted was a band-aid fix and its not . and also i was assuming that every one generally has the common sense to fiberglass all sides of any wood that goes in to a boat unlike what they do in factory's were there trying to save every penny buy cutting out 10 or 15 dollars worth of cloth . im dealing with the same stuff the OP is so i do apologize to you !

 

[rickryder]

Re: Floor replacement question

Thank you sir! I appreciate your reply and apology accepted!

 

[62cruiserinc]

Re: Floor replacement question

I removed the deck from the transom forward almost to the console. There is only about 3 feet of deck length left to remove. The remainder of the deck will then be under the open bow section. The open bow is a large fiberglass section(which includes the console) that was apparently added on top of the deck and then it must have been joined to the hull and glassed, as I can find no visible joint where the section can be removed. I can see the bottom side of the deck that is under the bow section through the storage compartment in the floor and it looks solid. Since the bow section is a single large fiberglass piece (including the floor part) it makes sense that water was unlikely to get under it onto the wood deck.


After removing the deck, I can see that there definitely was no wood support or stringer along the hull. There is only foam there right up against the hull. The foam against the hull varies in thickness from about 1/2 inch to 1 1/2 inches thick, depending on the location. To try and put a wood support along the hull/deck joint area would be difficult as the piece would be curved in two planes, and in some places it would only be 1/2" high. The foam is completely dry in the places I have tested it so far, but I still need to do more core sampling. If the foam is good and dry, can I just put the new deck on top of it, which would hold it at the proper height while I tab the deck to the hull?

Also it looks like I will have to remove the glassed in wood 1x2 that is attached to the hull about 3 inches above the deck along both sides of the hull. This is used as the bottom of the storage pocket bui8lt into the hull sides. Without removing them I can only go up the hull a few inches for the deck tabbing and that is not enough, based on what I have read on the forums. I might not rebuild the storage pockets after redecking but make some custom shallow cabinets instead for storage that are not glassed to the hull.


I still have to check the stringers for integrity by taking some core samples. I am leaning toward replacing the stringers entirely rather than sistering. Can you replace part of the stringer or does the entire length have to be replaced? The reason I ask is that the stringer might continue under the fiberglass bow section, which would be difficult to remove.

Also, what wood should I use for the stringer, which is 1" x 8" (actual dimensions) and about 10-12 feet long? I am thinking white oak but am open to suggestions.

I will post some more pictures later today hopefully.

Any and all comments and suggestions are gladly accepted!

Thanks to all
Steve

 

[62cruiserinc]

Re: Floor replacement question

Anyone have answers on the stringer wood type and foam questions from my previous post?

Thanks
Steve

 

[Woodonglass]

Re: Floor replacement question

If the foam is absolutely dry then reuse it. Laminated 1/2" Arauco Plywood would be my choice for stringer material which would yield 1" stringers.

 

[oops!]

Re: Floor replacement question

hi.....welcome to iboats.

im sorry i have not been able to get on the forums as much as i need right now.

it is a very busy boat building season right now.

this thread is right off the rails.

first off.......there is no quick fix except to thorw another chunck of ply over the old factory deck.

if you glass in a new deck for this season and then do a full restoration next winter.......you will end up re doing all your work.

wood on glass gave you some links.....if you read those....it will answer all your questions.

here is another link to the proper replacement of a deck....including foaming if you so choose.

http://forums.iboats.com/showthread.php?t=543161

the above link is in the stickys at the top of the forum.

if you are going as far as to do the stringers....you may as well do it correctly, as if you dont......your gonna have to rip her all up again.

i will also suggest that you take a good look at the transom....im betting it is going as well.

the link given above will solve your deck hull joint issues.

cheers
oops

 

[rickryder]

Re: Floor replacement question

Can't get much better advice than from these guys ^^

 

[62cruiserinc]

Re: Floor replacement question

Thanks for the replies!

Yes, I am going to do the stringers and deck properly. I have done a lot of remodeling and construction work and I recognize the point where it is only a little more work to do the permanent repair. After looking at the whole job ahead, I realized that a temporary job that was safe would be 80% of the work of a permanent fix.


A few questions:

Can part of a stringer be replaced? The front 1/3 of the boat is in good shape with no rot and the stringers go under the open bow section which has a molded fiberglass "tub" on top of the deck. To remove this tub would be a much bigger effort.

When "PL" is referred to, is that the standard construction adhesive available at home center?

To laminate a new stringer with two layers of Arauco plywood, do I use a good brand of woodworking glue (Titebond) or construction adhesive (PL, Liquid nails, etc)?


Thanks
Steve

 

[Woodonglass]

Re: Floor replacement question

Yes, you can "Sister" Stringers together using 1/4" or 3/8" sisters glued and screwed to both sides of the butt joint.

PL IS the standare Polyurethane Construction adhesive. NOTE: Takes approx 72 hours for total cure especially thick applications and the outgassing must have stopped before fiberglass can be applied over the top of it.

I recommend Titebond III. 100% waterproof glue and strong as heck. Will never delam.