Stringer and deck questions

[ducote32]

Figured I'd start a new post, not piggyback off of the other concerning the stringers, deck

Okay, here's a plan I'm trying to come up with after lots of iboat searchs.

1. Exterior plywood 3/4", 2 sandwiched, coated with epoxy
2. Peanut butter in and build up.
3. 1700 for stringer, 2 layers on side extending on hull more on second layer, then 1 layer on top of stringer
4. Coat underside of 1/2" plywood for deck with epoxy resin, then install, screw in then fill screw holes with peanut butter, then wet with resin and put 2 layers of 1700 on deck.

How does this sound? Should I do thing differently?
Also, does it look like it has the correct number of stringers, didn't have on on the port side, and the deck at the edges wad just laying on the hull bottom with resin.
Thanks,

 

[gm280]

Well ducote32, that sounds pretty close. If you are going to use mix and pour in foam for flotation, then you can reduce the thickness of the floor ply. And that will also reduce a lot of weight. But that it up to you. And it is 1708 and not 1700. 1708 as described from US Composites;

+/- 45degree
Contains double bias(17oz) stitched at 45degrees
along with one layer of 3/4oz mat.
Thickness: 0.044"

And that is used with 435 laminating polyester resin, not epoxy.

Just a little info.

 

[ducote32]

Gm280, thanks.
So polyester resin would be fine for this repair? Also, I know they didn't have any foam under what I pulled up, but it sounds like a good idea. If I was going to use thinner than 1/2 plywood on the deck, should I go 3/8 or 1/4? Thanks again.

 

[ezmobee]

If you go with polyester, then don't do any of your underside coatings with just resin. Poly isn't strong enough to hold up without glass.

 

[ducote32]

If you go with polyester, then don't do any of your underside coatings with just resin. Poly isn't strong enough to hold up without glass.

Good to know I'd have to fiberglass the bottom of the plywood.

So I guess the choices are
1. Polyester resin and 1708.
Or
2. Epoxy resin and 1700 biaxial.

Is there one that is more forgiving?

 

[kcassells]

You have it right. EEEEEEEpoxy does not require backing. Will waste resin. 1708 no mat. called DB17 no mat.
Choose poly, polyester or EEEEEEpoxy. But do not try to mix EEEEpoxy with either of the other two. Once you make your choice of glue that what you start and finish with. EEEEEpoxy beingh the most expensive. But I'm using it and sticking with it.
Sometimes the costs tick me off but I like it ease of install and strength. All will work.
1. Exterior plywood 3/4", 2 sandwiched, coated with epoxy
So what came out of the boat. 3/4" alone should work. 1.5" stringers may be overkill.
KC

 

[ducote32]

You have it right. EEEEEEEpoxy does not require backing. Will waste resin. 1708 no mat. called DB17 no mat.
Choose poly, polyester or EEEEEEpoxy. But do not try to mix EEEEpoxy with either of the other two. Once you make your choice of glue that what you start and finish with. EEEEEpoxy beingh the most expensive. But I'm using it and sticking with it.
Sometimes the costs tick me off but I like it ease of install and strength. All will work.
1. Exterior plywood 3/4", 2 sandwiched, coated with epoxy
So what came out of the boat. 3/4" alone should work. 1.5" stringers may be overkill.
KC

The original stringers that are a 3/4 piece of plywood going down the center, and the side stringers are 1 1/2"X1" lumber. I think the side stringers are more for a solid deck. I think I'll keep it the same, it's held up since 1971, so I shouldn't try to reinvent the wheel. Think I feel I little more comfortable using the epoxy.

 

[Woodonglass]

Stringers are there to support the hull NOT to support the deck. That's the secondary benefit. Actually it's best to keep all your posts concerning your restoration project in ONE Thread!!! Epoxy has it's own Unique Challenges especially on vertical surfaces.

 

[DeepBlue2010]

Epoxy or Poly, both will get the job done. Use what you are comfortable with if it is a question of preference. If it is a question of adequacy, poly would get the job done just fine if you pre-wet the wood and use CSM to promote adhesion. Again, it is up to you.

Your design makes the stringers and the deck one structural element. Meaning, they are both collaborating to provide the structural support to the overall vessel. it is not that one of them provides support for the other. Rebuild the boat as it was unless you have a very good reason not to. As you said, the design stood the test of time since the 70s. Sounds like a good design to me. Best of luck M8

 

[ducote32]

I'm getting ready to put my stringers in and I'm considering using the PL adhesive to bed them in, what PL is everyone using. I saw the premium and the PL400.

 

[Baylinerchuck]

Loctite PL urethane adhesive is what i used. It's a construction adhesive. I used it to glue my plywood together for my transom. Only issue is it takes 72 hours to gas out. Meaning you cannot resin over the top of it until after 72 hours. Also it works best when using in thin coats or a knotched trowel. It tends to skin over quickly, then may not cure completely if used as a filet.

 

[jbcurt00]

I used to recommend/support PL usage to bed stringers.

Not any more. Advantages are far outwieghed by the cons......

Use Polyester resin PB, its easy, quick and made out of material you'll have on hand for glass work.

In a very short period you can go from bedding stringers to glassing over the stringers.

Oh, and for the full 72hrs (maybe longer depending on temps and thickness) the stringers must remain fixed in place to allow the PL to cure w NO stringer or adjoining hull movement, otherwise the bond is subject to seperation.

 

[Woodonglass]

I totally agree with the above. I'd recommend using 1/4" piece of foam to hold the stringer up off the hull and then use the Thickened Resin (PB) to form your fillets. Using this method will ensure no hardspots on the hull and as stated will allow you to, within an hour, start glassing the stringers to the hull. You might find the second link in my signature below to be helpful.

 

[ducote32]

I totally agree with the above. I'd recommend using 1/4" piece of foam to hold the stringer up off the hull and then use the Thickened Resin (PB) to form your fillets. Using this method will ensure no hardspots on the hull and as stated will allow you to, within an hour, start glassing the stringers to the hull. You might find the second link in my signature below to be helpful.

Woodonglass, thanks for the info. When I took what was left of the stringer out, it wasn't bedded in anything. Looks like it was tabbed on the sides, no top layer of glass, just resin covered. I like the idea of the 1/4 foam and glassing them.
Do you recommend any particular type of foam? Closed cell, the pink or blue that some use for flotation? Thanks.

 

[mxcobra]

I used pl premium on mine for fillet and bedding stringers- its been 5 years and no problems, although it takes more like 7 days , to fully dry before you can glass over it.

 

[Woodonglass]

The Pink or blue foam are both closed cell. They can be cut to 1/4". Doesn't have to be applied to the full length. 12" strip at both ends and one in middle will be adequate. once it's tabbed in it'll stay in place. A lot of the mfg don't bed their stringers especially on board under 20'

 

[ducote32]

The Pink or blue foam are both closed cell. They can be cut to 1/4". Doesn't have to be applied to the full length. 12" strip at both ends and one in middle will be adequate. once it's tabbed in it'll stay in place. A lot of the mfg don't bed their stringers especially on board under 20'

Thanks for the great advice. Will soon be putting it into action weather permitting.