Sealing plywood deck to aluminum hull? and more...

[Arcs&sparks]

Hi all, New guy here from Maine. I am an electrical contractor and fishing fanatic. I’ve acquired a ‘76 14’ Starcraft Holiday that I’m in the process of customizing and rigging up for lake trolling. This would be my second boat project. With this project I am trying to do more research and select better products for my build instead of just grabbing things off the shelf at Lowe’s etc.. At this point I have spent about 20X longer reading forums and browsing products than I have with tools in my hand. I’m hoping you guys can help me out alittle and save me some time as I have a very busy schedule.

What I have done so far is;

-Remove old deck
-Remove saturated foam
-Pressure wash everything
-Wire cup-on-drill inside of hull and thoroughly clean
-Apply Gluvit to entire bottom (inside)
-Prebuild underfloor rod locker (large shallow tub with tubing protuding)

(Here’s where I will accept criticism);

-Fill ribs with Evercoat marine spray foam
-Seal ribs with 5200
-Adhere 1” Styrofoam between ribs
-Trace and cut out new ply
-Seal ply with polyester resin
-Fasten rod locker
​​​​​-Fasten front half of floor
-Fill installed floor with 2lb floatation foam
-Various other things that don’t matter here

My list of questions starts here;

-What would you recommend I use to seal the wood to the hull so water runs on top and won’t touch my foam (yes I now know you aren’t supposed to do that..) I planned to wire wheel the excess foam and thoroughly sand the ply edge and the joining aluminum, then use either 5200, Dow windshield urethane, or “FlexEpox” (which I already bought but am unsure) to seal between the two surfaces. The foam is thorough, and the wood fits within 1/4 in most places. Looking for opinions..

-My rod locker consists of a shallow polypropylene tub that I wrapped in plywood for structural reasons. I want to seal the gap under the round lip with some goop but not sure what is best For this material. Also the second half of the floor will rest on top of the tub so that will also get a seal.

-I plan to sandblast the bottom of the hull and seal with The Goop Coat-it but I’m left with one thing to scratch my head about. I am unsure how well the rivets are sealed that hold the bottom ribs(terminology?) or if there’s any pinholes etc.. I would like to seal the inside of these ribs as well but not sure the best way. I can hoist/tilt my boat up and down from the I-beams in the garage so I wondered about tapping the pre-existing (2) holes on each rib for a machine screw to thread, fill the ribs with some type of slow epoxy, tilt the boat up and down to wet it out, then remove the screws to let drain... just let me know if I’m crazy and if there’s a better way

FYI This boat will always be trailered,kept under cover while in storage,or in a garage. But may be subject to -30 to 100 degree temps.

 

[MTboatguy]

We have a whole section devoted to restoring Starcraft boats with quite a crew of craftsmen, that you might want to take this Q&A to, there are some real innovative guys in that section.

https://forums.iboats.com/forum/owners-groups-by-manufacturer/s/starcraft-boats

 

[classiccat]

Welcome A&S!

before proceeding further, i recommend that you spend some time in the Starcraft rebuild & restorations section.

I added some comments below.

What I have done so far is;

-Remove old deck
-Remove saturated foam
-Pressure wash everything
-Wire cup-on-drill inside of hull and thoroughly clean --> hopefully it was either stainless steel or nylox.
-Apply Gluvit to entire bottom (inside) --> only to rivets and seams. blanket coating is a big no-no; it will trap water and corrode the aluminum.
-Prebuild underfloor rod locker (large shallow tub with tubing protuding)

(Here’s where I will accept constructive criticism);

-Fill ribs with Evercoat marine spray foam --> Skip this.
-Seal ribs with 5200 --> skip this.
-Adhere 1” Styrofoam between ribs --> Avoid polystyrene; look into using close cell pink or blue insulation foam from the box stores.
-Trace and cut out new ply
-Seal ply with polyester resin --> a few options here depending on your budget. Polyester resin is not one of them. I like sealing with Epoxy resin with glass cloth. Many guys on here are using WoodOnGlass's "Oldtimer's formula. Spar Varnish is another popular option.
-Fasten rod locker
​​​​​-Fasten front half of floor
-Fill installed floor with 2lb floatation foam --> obviously skip if i you us the pink/blue foam. the pour-in foam can also trap water against the alum leading to corrosion.
-Various other things that don’t matter here.

My list of questions starts here;

-I plan to sandblast the bottom --> Sandblasting should not be done on aluminum. the majority of us use liquid strippers. If you insist on media blasting, look into soda or walnut shells.

I am unsure how well the rivets are sealed that hold the bottom ribs(terminology?) or if there’s any pinholes etc.. Now would be a good time to put some water inside the hull and leak test. Be aware that it's alot of weight so you want to make sure hull is on something that can handle the weight.

I would like to seal the inside of these ribs as well but not sure the best way. Don't bother. "Sealing" will trap water against the alum leading to more corrosion.

 

[Arcs&sparks]

Thanks guys, I will repost in the Starcraft section

 

[jbcurt00]

Thanks guys, I will repost in the Starcraft section

No need to repost. Moved topic

 

[Watermann]

Welcome aboard :wave:

I don't see why you would want to fill the ribs with anything as it will surely become saturated sooner or later and then be nearly impossible to be removed without an insane amount of work.

99.9% of us rebuilding these boats use rigid foam board for flotation rather that 2 part pour in foam as it won't soak up water. No matter what you do there is nothing that will keep water contained to only the outside of a seamed/riveted boat. Any water that makes it into the bilge will end up migrating.

You cannot seal the wood decking of an AL boat to the sides of the hull as the hull flexes by design and the stress with show up somewhere. The best way is to use vinyl deck covering that goes up the sides of the hull several inches so the water can only run aft to the bilge.

 

[Scott Danforth]

remove old floor
remove foam
buck rivets to seal
weld any cracks
pour new foam
throw in a piece of plywood that you painted both sides with oil enamel
go boating

 

[Arcs&sparks]

classiccat
Thanks for your reply. I will take your advice on the things I have not done yet. Just so we’re on the same page though, my whole list besides the questions, are things I have already done. The cup brush was stainless, and the Styrofoam was true blue board foam. I will look at the other media blasting options.

-I’m surprised to hear you’re not supposed to blanket coat the Gluvit. Is the Coat-it ok to do so?

-I can sand off the polyester resin othe top of the deck if it’s nesserary, I still need to plug the pour holes and glass over them with epoxy.

-I bought some garage floor epoxy for a second layer over the ply. Good or bad?

I will post pics as soon as I figure out how.

 

[Arcs&sparks]

Watermann
Thanks. it has already been done so I have to work with what I have. 5200 won’t hold?

 

[Watermann]

No 5200 would fail some day even if you were able to get it to bridge all the gaps/openings between the deck and hull sides. 5200 is designed to be used between two objects pressed together to seal and is a powerful adhesive but like any adhesive has to have pressure holding it where it needs to be. It does not work well like a viscous caulking laid in a bead along a tight seam.

 

[Arcs&sparks]

Uploaded 25 pics to an idea book

 

[jbcurt00]

-I’m surprised to hear you’re not supposed to blanket coat the Gluvit. Is the Coat-it ok to do so?

-I can sand off the polyester resin othe top of the deck if it’s nesserary, I still need to plug the pour holes and glass over them with epoxy.

-I bought some garage floor epoxy for a second layer over the ply. Good or bad?

Polyester resin w/out glass is of little value, it really needs glass....

the flat expanses of aluminum hull dont need to be coated w Gluv-it or Coat-it, neither will protect the hull from a hard strike that would tear/rip/or gash a thru hole into the hull. And its sheet aluminum, it doesnt need to be sealed against leaks. Rivet holes and seams do, so use either product for them on the inside, not the exterior.

Both go on in a less then attractive manner, something most wouldnt want exposed on the hulls exterior. But sounds like you've alread foam filled the hull as you mention filling and covering the pour in holes in the plywood.....

 

[Arcs&sparks]

Polyester resin w/out glass is of little value, it really needs glass....

the flat expanses of aluminum hull dont need to be coated w Gluv-it or Coat-it, neither will protect the hull from a hard strike that would tear/rip/or gash a thru hole into the hull. And its sheet aluminum, it doesnt need to be sealed against leaks. Rivet holes and seams do, so use either product for them on the inside, not the exterior.

Both go on in a less then attractive manner, something most wouldnt want exposed on the hulls exterior. But sounds like you've alread foam filled the hull as you mention filling and covering the pour in holes in the plywood.....

Yes I’ve already coated the inside with Gluv-it and poured foam. My original post lists everything that has been done. My main concerns at this time is the plywood to hull seam, the ribs on the bottom and finding a good sealant for polypropylene. Other critiques and advice is also appreciated

Pics have been uploaded to my profile. My iPhone seems to struggle with this website or I would post them here..

 

[Arcs&sparks]

Also, thank you, I will glass the top of the wood

 

[jbcurt00]

You dont need to seal the exterior 'ribs', in fact Starcraft drilled holes in the keel strip to make sure any water that got in, got out. IMO the likelihood of making them 100% watertight essentially forever is unlikely. So live w the slight gaps and let any water that gets in, drain out.....

pix posting help
https://forums.iboats.com/forum/foru...ec-2017-update

If you are using InternetExplorer as your browser, that may be 1 of the problems posting pix. Its a protocol problem between IE and our servers, is a known problem thats being worked on from our e d, but has yet to be resolved.

Apologies for that, but you could try using Chrome, Firefox or other browsers if you're using IE now. I use 2 different browsers depending on what I want to do here or elsewhere online.....

 

[MTboatguy]

I have chrome on my computer for one reason and one reason only and that is this website, the rest of stuff I use a Firefox clone browsers called Palemoon.

 

[Arcs&sparks]

[No message]

 

[MTboatguy]

Unfortunately, that seal is going to last about 15 minutes of banging around in rough water.

When I do foam, I keep the plugs I cut out and then put them back in after I inject the foam and seal over them.

My prefered way to replace for is with blue or pink foam board, 2" cut to fit the boat I am working on, does not absorb water and you don't have to drill holes in the deck.

 

[Watermann]

Ok, I see what's happening, he did all the work the way he thought best and is now showing us what he did. In reverse of what we normally see here which causes confusion, at least on my part.

 

[Arcs&sparks]

Watermann Yes, I thought I made that clear lol but there seems to be some confusion with others as well. :happy:

I am stuck at this point in the project and am asking for advice on what kind of goop or combination I can use to seal up this seam. The wood fits pretty tight in most spots but has gaps of max 1/4” only in the round areas. The pic shows just the rough trimming of the excess foam that squeezed through the edges. I can wirewheel down deeper to where the ply sits closer to the hull and rough up the surfaces. I hope to pour or caulk some flexible sealant in the gap.

It it may help to know that this gap will not be directly exposed to the elements as I plan to enclose the gunwales and add some hatches.

Covered, trailered boat, freshwater trolling.

-3m 4200?
-Dow U-428 windshield urethane? (Read this on another forum)
-FlexEpox?( already bought). Supposedly “uneffected” by expansion and vibration.
-something else?

edit; I just realized you were the one who recommended the vinyl. Do you still think this is plausible?