Replacing Plywood Hull

[arty007]

so today i started early! got going on the grinding part of it.. well..about 4 hrs later half the boat was looking pretty close to complete as far as the grinding goes.. when i noticed a piece of wood on the hull part i was grinding.. so i got my screwdriver and tried to pry it out! NO FN WAY!!!!
the hull itself is made of sanwich 1/2 inch plywood....WT%#@*%$#!!! bottom fiberglass,plywood,top fiberglass so i start drilling holes here and there to see where the rot is at ..maybe i can replace just a small section.. NOTT!! theres rot in too many spots to try to fix that way..and i thought it was going to be a stringer /deck job,....
i dont know what to do now?...and i already bought all my glass for the stringers,deck... i was thinking of removing all the plywood,but then realized it might make the hull sagg? dont know if i can do this on the trailer? can anyone show me the way?.

 

[arty007]

Re: Replacing Plywood Hull

here are some pics

 

[Bondo]

Re: Replacing Plywood Hull

Ayuh,... It would appear that you don't have very much to Work with....

 

[arty007]

Re: Replacing Plywood Hull

Ayuh,... It would appear that you don't have very much to Work with....

yeah! no kidding....bond-o.
do you guys think i can scrape the rotted spots off then fill it with something and glass over that? seems like the easiest way.. if so what can i fill it with? and what glass?,and how many layers should i use? some spots are pretty long around 4 ft by 4 inches maybe.. where the stringers sat...

 

[erikgreen]

Re: Replacing Plywood Hull

If you're sure the hull is cored, that the plywood goes all over like that, then unfortunately there's not a lot you can do.

This is why people with plywood composite hulls have to be extremely careful to make sure they stay sealed. The plywood doesn't supply much strength, just stiffness, but it is absolutely needed to be there and be uncrushable by the skins of fiberglass for the panel to keep its strength. If it gets wet, it's going to rot.

Again, if you're sure the hull is cored with plywood, if the water and rot are all over, you pretty much have to give up. The hull will continue to rot and delaminate over time regardless of what patches you put on holes and bad spots.

The only way to fix the problem is to replace the bad core, and if it's all over you'd have a smaller job just building a new hull. If you can narrow the wet areas down to small patches, then there are things you can do, similar to the way you'd replace a transom. Still a lot of work.

But if it's all over, you're done. Sorry.

Erik

 

[arty007]

Re: Replacing Plywood Hull

this is the rott spots..so if i deside to remove the core do i need to use ply again?or can i replace with only glasss? i really dont want to quit just yet...
keep those options coming..pleeeease.

 

[arty007]

Re: Replacing Plywood Hull

update!!
so today i desided to continue on with the grinding. ive desided to patch up only where theres rot ( small sections ) and the center ( keel )area.. took out most of the rot and began grinding took me about 7 hrs of work today .
a problem i ran into, i was taking off the rotted plywood when i accidentally dug the prybar to deep into the hull breaking through the gelcoat one more thing on the to do list! here are some pics what do you think?

 

[arty007]

Re: Replacing Plywood Hull

these are pics of the dent i made with the pry bar..how can i fix this?

 

[MrMarine]

Re: Replacing Plywood Hull

Scrap the hull. You are only causing greater pain. You can find a better hull and put all the gear you took out of this one. I am sorry to say it but that hull is ready to be retired. Something that far gone is not worth all that you are doing. Secondly i dont think your outer skin and very hearty at all. COme to think of it i dont think i have ever seen one so thin. I think it is time to bow out. Sorry for all the negative but take it from my experience. Something so far gon is a bad idea. Also all the spots that are weak are under the main structural supports for the boat. If you dont get them back at 150% correct you will have a catostrphic failure down the road. Again sorry.

 

[Bondo]

Re: Replacing Plywood Hull

what do you think?

Ayuh,... Throw a Match in it,.... You have Nothing to work with....

 

[arty007]

Re: Replacing Plywood Hull

REALLY!!! you guys think this is the end of the line? i really want to fix THIS boat... are you guys telling me there is no fixing these spots? when i took the rotted plywood off the keel the glass is solid underneath its a 1/2 inch thick also every where else seems solid! but that one spot on the picture.
ii was thinking adding more mat at the bottom 2 layes or more with peanutbutetr then 3/8 plywood and top it off with 1708 down the middle.
is that there not sufficient? the one spot i was concernd with was in the bow area where the keel cuts the water there would be more pressure there by the waters forces...plywood will be button up wich will bind if there was pressure right?

 

[Mark42]

Re: Replacing Plywood Hull

Arty,

Well I just read the whole thread. The hull does seem very bad.

Your boat is kind of like a cancer patient. Even if you get it all, it might still come back. That is a lot of work to make it right.

I really think your efforts would be better applied to a boat with a solid hull. You have the materials you need to repair a boat with rotted stringers and transom, so go look for one. They are available cheap, often for free.

I really think that the boat is unsafe, even if you patch it well. The photos of the exterior glass layup look thin, dry and expanded, rather than packed flat and tight with resin. That is a very bad sign. If the entire exterior is like that, then water will be soaking in and rotting what ever is left of the ply in the boat. In fact, in every photo of the glass all I see is mat, and no cloth. There should be mat and cloth layers, but just mat is not going to cut it.

Where did you get this boat and what brand is it?

 

[arty007]

Re: Replacing Plywood Hull

Arty,

Well I just read the whole thread. The hull does seem very bad.

Your boat is kind of like a cancer patient. Even if you get it all, it might still come back. That is a lot of work to make it right.

I really think your efforts would be better applied to a boat with a solid hull. You have the materials you need to repair a boat with rotted stringers and transom, so go look for one. They are available cheap, often for free.

I really think that the boat is unsafe, even if you patch it well. The photos of the exterior glass layup look thin, dry and expanded, rather than packed flat and tight with resin. That is a very bad sign. If the entire exterior is like that, then water will be soaking in and rotting what ever is left of the ply in the boat. In fact, in every photo of the glass all I see is mat, and no cloth. There should be mat and cloth layers, but just mat is not going to cut it.

Where did you get this boat and what brand is it?

i got the boat from a guy who had it parked in his yard for 4 yrs without use,its a 1978 rally made by mirro marine.. thats all i know! these are all discouraging news

 

[arty007]

Re: Replacing Plywood Hull

came inside after working on the boat some more

 

[J. Mark]

Re: Replacing Plywood Hull

If you are determined, you may indeed get enough of the rot to be able to use the boat for a few years BUT you may finish the project and find that the boat isn't stable, straight or safe.

It is hard to know the condition of the outer shell from the pictures, but if where you punched through is any indication of the overall condition, I agree that you would be miles ahead to start win a hull that isn't cored and suffering from delamination.

Keep in mind visible delamination is usually just the tip of the iceberg and that the damage can be 10 times farther into the hull than you see.

Only you are there and can be the judge of whether or not you feel comfortable with the repair. Personally I wouldn't be comfortable in that boat with anything less than about 3 layers of 1708 fully wrapping the interior of the hull and that would be an expensive, time consuming project that might still not pan out.

Whatever you budget to repair any boat isn't enough. You can realistically expect your best estimate will be 50% lower than the cheapest you can do it.
Your time is free, but it isn't infinite.

I think we all hate to see you sink time and money into a project only to have something you can't even sell in good faith.

If you are determined to repair it, then you will, no matter what anyone says and that type of determination is admirable most of the time. Here it is just plain foolhardy.

You can risk yourself on the water, but other boaters are bound to render assistance in the event of real danger and someone else could get injured or killed rescuing you if that boat has a catastrophic failure.

Hope this is taken as intended, I certainly mean no offense.

 

[arty007]

Re: Replacing Plywood Hull

hey mark thanks for the kind words...I apreciate all your input good or bad... soo if i want /deside to do it RIGHT! i would have to take all core material out and add more mat or cloth to the hull before adding new core material plus another layer of glass on top of the core?sounds about right? just looking at my options....

 

[reelfishin]

Re: Replacing Plywood Hull

I know where you coming from and hate to give up on a project as much as you do, but what your dealing with is a basket case. That repair would be suspect in the end even if done by a pro.
What your talking about doing it changing the construction style of the entire hull. Keep in mind that the boat was built as a complete package, the stringers and ribs were designed to work with a plywood core hull, not solid glass.
You will no doubt be adding a lot of weight, spending countless hours, making major design or engineering changes to an already inferior hull design. All to maybe come out with an unsatisfactory result.
There are loads of free boats out there these days, pretty much anything with out a plywood cored hull is bound to be a major improvement.
It sounds like you've already bought lots of supplies, which won't go to waste if your after an older boat. Most any boat you find from that era unless it's been kept indoors will need some degree of repair.

Cut your losses, learn on a better boat and end up with a boat that you can use and trust for years to come.
Some things just weren't meant to be fixed.
(I scrapped a foam cored hull that was water logged, it hurt to junk a boat that was so clean looking but it weighed over 800 lbs over it's build weight with the foam hull core being totally saturated. When I busted it up to haul away, it crushed like a watermelon in the driveway draining water in every direction as I smashed it up with the front end loader. The foam core drained all the way to the dump).

 

[Mark42]

Re: Replacing Plywood Hull

What is your plan to attach the plywood pieces to the hull? They will need to be pressed together. A method that comes to mind is they way transom wood is held against the fiberglass skin: Put a piece of wood on the outside and run screws through the hull to the plywood on the inside. Remove the outside wood after the resin cures.

I hope you plan on using polyester resin, because you can buy a new boat for the price of the epoxy that will take .

Remember that the hull is not a flat smooth hard surface, it its very porous from the photos posted. So laying up the new ply is going to use lots of resin. Are you going to put down a layer of mat between the hull and the ply?

Was the original ply cut into small pieces like that or was it one big piece? I ask because I think the design of the boat relied on the plywood for its strength, and not the fiberglass outer covering. Having the plywood cut into pieces will not be as strong as one continuous piece of ply.

 

[ezmobee]

Re: Replacing Plywood Hull

You clearly have the talent and determination to take on a major boat rebuilding project. The time, $, and energy you'd spend trying to fix this one would be better spent on something with a solid fiberglass or aluminum hull. So cut this one up and get on Craigslist/eBay and find yourself something better to work on. I'm sure others on here would help you with your search. If you could have any style of boat what would it be?

 

[J. Mark]

Re: Replacing Plywood Hull

When I said that 3 wraps of 1708 would make me feel a little more comfortable, it is simply because that much glass would be equal to a new hull inside the old one and while it wouldn't be right and would be way to heavy, I doubt it would suffer a catastrophic failure.

I know how hard it is to walk away from a project that you are dead set on completing. Feels like failing or giving up or quitting. All these are things we are taught are bad.

Think of it as moving on from dating a 4 to dating a 9. You'll spend the same money, the same time and maybe even do pretty much the same things but it is not the same. (I'm not really that shallow, but I think it sums things up)

Maybe you could cut the bottom out at the water line and put the remainder down on the ground and fill with sand for the neighborhood kids to play in. Think how many kids would enjoy it and would grow up wanting to go boating.