Boat Builder Central - Builder Forums

I am rebuilding a 20' seacraft and have cut the floor out and plan on using 3/4" marine ply with epoxy and glass on both sides. I will raise the stringers about 2" to help with self bailing but my question is this: what glass do I need to layup on both sides to provide protection for the ply but not add excessive weight and cost? I am thinking 1 layer of 1708 on the bottom of ply then tab floor to hull with 12" wide 1708 tape with supporting cleats at hull side then 2 layers of 1708 on topof deck. Let me know if this is overkill or not enough. Widest span from port to starboard will be about 15 inches un supported.

For a deck I would use 3/4 nidacore with the layup you have planned. Cost will not be much more but it will be much lighter.

...or 1/2 inch Okume with 12 ounce cloth on top and just sealed with epoxy below... Sitting on the stringers and supported on the sides that deck won't flex at all. The cloth on top will protect it from dings, and 3 coats of epoxy below will seal it completely.

Not so quick question. What is the best way of determining the new deck level along the sides of the boat? Port stringer is 3/8" to 1/2" lower in places than starboard. Boat is level on trailer. I cannot simply measure up from the chine since the glass on the hull differs in height by 3/8" a long the way and differs by 1/2 from port and starboard? Any tips? I have a straight 2x4 ripped to my finished deck height should I just level that up across stringers and make a mark on gunnel? I need an accurate line along gunnel to set my cleats for the edge of the deck.

lelandtampa wrote: ↑Fri Apr 20, 2018 10:39 am What is the best way of determining the new deck level along the sides of the boat?

Get a long enough clear plastic tube, partially fill with colored water, run it across on the inside of the hull. If the boat is level, the water levels on each side will give you a level point on each side of the hull.

Thanks I completely forgot about a water level.

lelandtampa, Welcome to the Builders Forum!! As you have already seen, you will get good support here with your project!! Please photo/film your project so we can follow your progress!! Again, welcome, Jeff

Thanks I completely forgot about a water level.

water level worked like a charm.

It is nearing time to raise and cap my stringers with foam and glass. I plan on 3 layers of 1708 with epoxy over the foam. Question is how to over lap my layers?. Should I go 4" down the side then 6 then 8 or 8 then 6 then 4? These are the large foam filled stringers.

I have heard folks say short first. Their reason is if they were a bonding issue with the earlier layer the next one would help keep it in place. With that said I am not sure it makes all that big of difference what way you go. Others may feel different and have good reasons for it.

For structural reasons always start with short. Then each succeeding layer will have some of the old beam to hold on to as well as the new fiberglass.

Tom

The theory on overlaps is largely about subsequent sanding.

If you are glassing an exterior transom; you glass the longest join first, and follow with shorter. That way, when fairing, you would struggle to sand through the most beneficial layer. And if you look at a diagram of layers; you see how this make sense. If you sand through the long layer laid last; it is weakest on the strongest join. But if you sand layers laid long first; you sand only the edges of each layer in fairing.

The times this would vary is if you are not sanding, but if sanding would affect the longest join; the long join need be protected.

I was told by a professional boat builder and I expect there are some rules on it somewhere; although rules dna for most of us; only good building practice.

I doubt you'll be sanding those stringer areas; so you'd be able to go the other way.

Another reason to consider long first is if you think you'll have air in the layup short first, but for 1708; air ought not be a consideration. For a heavier fabric like a 36 oz; it might...

Intuitively, what Tom said makes a lot of sense, but the builder told me that the stacked laminates in a join are considered as a single unit and the strength is not from each next layer holding a bit more, but laminate thickness. I don't want to argue with Tom on this subject. I had a real hard time with what the builder told me, but it was reinforced by a few other professionals later.

In Mertens foam sandwich handbook; for stringers; he shows long join first.

They also stagger the layers so you don't get point loading at the end of the stack. It spreads the load out .

Thanks guys for the Intel. Have a bunch of glass to cut and layout first.

Probably going to go long tab first so I dont get an airbubble at the edges of the lower layers.

topwater wrote: ↑Fri Jun 08, 2018 7:15 am They also stagger the layers so you don't get point loading at the end of the stack. It spreads the load out .

Yes. Stacking layers atop each other creates a location that varies structurally from its neighbors.

When possible, avoid ending all layers in the same place.

lelandtampa wrote: ↑Fri Jun 08, 2018 8:55 am Probably going to go long tab first so I dont get an airbubble at the edges of the lower layers.

You should be using some type of laminating roller that would avoid air on layers. Paint rollers are great for moving epoxy early, bit at the end of the process they tend to lift fabric.

An ultra cheap roller can be made from pvc tubing. Avoid soaking in acetone. We simply wipe ours with paper towel (acetone on towel)

Otherwise, a laminating roller does not lift the fabric.

I use a 6" bubble buster with a 1/2" or 3/4" circumference. It doesn't lift wetted glass and allows the bubbles to collapse without moving.

I have my poly tank placed with rubber strips below it my question is this: should I put fuel in it now in order to see how much hydrocarbon expansion I get prior to mounting my straps across the top so that I don't have e to guess how much it's going to swell? Floor in that section is not installed yet.

Can you post some pics of what you are doing? Also a pic or 2 of the whole boat? My first real boat was a 20ft Sport Craft with a 1.6 liter OMC Sea Drive. Really miss that boat. I traded it for some roofing work when the SeaDrive died.

I put 3 pictures in my gallery. Basically I know this tank is going to swell in the vertical dimension. I am wondering if I should put some fuel in the tank so it swells so I know where to screw my tank hold downs into the stringers.

Dummy me...you have a Sea Craft, not a Sport Craft...

lelandtampa wrote: ↑Mon Jul 01, 2019 6:34 pm I have my poly tank placed with rubber strips below it my question is this: should I put fuel in it now in order to see how much hydrocarbon expansion I get prior to mounting my straps across the top so that I don't have e to guess how much it's going to swell? Floor in that section is not installed yet.

Install at ambient temps...say 80F. Allow 3% all directions. You don't install loose to 'allow'.

Pressure test at 2 psi and you'll see what happens. Air, not fuel.

So I am at the point where you need to buy more resin and the glass for my sole . I had been using raka epoxy since I got a real good deal on 2 of their 3 gallon kits. I think i am Going to switch over to marine epoxy from bateau but how long should I let the Raka cure before I can layup with marine epoxy over it? Also anyone have any experience with these 2 brands interacting? I have 1/2 marine fir installed with a Triple resin coat on the bottom and I want to use either 12 or 17 oz biax for my top layer. 1708 is such a pain to wet out compared to the regular biax. Largest span will be 24" between the stringers but I have bulkheads and hatch lips supporting it. 12" or so span from the outside of stringer to the hull side with epoxied on cleats along the hull side just like the Seacraft tutorial. I also plan on taping the console down inside and out to avoid mechanical fastening.

All those epoxies use bisphenol as a hardener and despite their musings are highly compatible chemically. Just allow a full cure past the raka no sand window and sand for secondary bonding.

No need to use a 1708 on the deck unless specified by the designer. A 12 oz is the bare minimum for not allowing deck water penetration per a well known UK designer. It would be best if you added tapes and then the 12 oz up and over for a bit over the minimum requirements.

More expensive and most likely over kill but I would go with two layers of 12 oz biax. That way I could stagger the butt joints and never have any fear of my deck not having enough glass.

Fuzz wrote: ↑Sun Sep 01, 2019 12:55 am More expensive and most likely over kill but I would go with two layers of 12 oz biax. That way I could stagger the butt joints and never have any fear of my deck not having enough glass.

12 oz is the nicest to wet out, you just have to baby it when it is dry as it can be snaky and the stitching on mine likes to run..(light thread)..

Got casting deck built glassed and rough faired with balloons. Anchor locker faired and bilgekoted. Anchor locker bulkhead tabbed in and door test fitted. Lots of fairing still to go.

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As you can see the Hull glass is green with a layer of carpet glue (original)
then white paint I'm guessing 1980s alkyd.
then OD green sprayed over the whole thing. Done in 2008 by previous owner to duck hunt out of the boat.

I recored the cap with nida core and 1708. It's pretty stiff.

Edit

finally learned how to post pics. yes i am an idiot.



insulated Fishbox lid in front casting deck.



reusing the old hatch doors with a little CNC logo touch.



leaning post 31" tall x 24" wide x 15 deep. Will have a small tackle center flush mounted in it. and mounts over the fuel tank inspection port. 1/2 BALTIC BIRCH because I had it on hand and got covid bored. I'm going to double tape all seams with 12 oz biax in and out and cover outside with 10 oz cloth.


tackle center cut out

Well I hate to say this but I don't see the pictures

Crap

Spoke too soon I guess because they are there now
The Seacraft logo is neat. And the leaning post is going to be nice.

Nice logo!!!! Jeff

Digging the leaning post!

Could be room for a few rod holders on the back.

Leaning post looking sweet. As is the CNC logo work. Nice...

Query for the glassers. This is the tackle center going in the back of my leaning post. It needs to be removable so the flange will be screwed into the back of the leaning post with epoxy sleeved 1/4 20 thru bolts. What glass would you recommend for the box 1/4" Marine fir and flange 1/2 birch ply. I'm thinking 12 oz biax on inside seams 10 oz woven outside and 2 layers of 12 oz biax on the flange to box joint inside and out.

The glass plan sounds like it will work just tine. Nice looking work there.

Scupper tubes: Wondering if I should run these out the transom parallel to the sole or pitch them down slightly? Opinions please.

Plumbers, when installing drain line angle them down to keep the water running down the line.

I got my scuppers roughed in.

Nice, that should work like a champ.

I have my floor and gunwale supports glassed in now so I flipped my hull over the weekend and put it back on the trailer.
My plan now is to :
wash, dewax, sand down through bottom Paint to original gelcoat .
Then wash and dewax again.
Fair and repair any spots that need it.
Wash again.
Then use the Cracker Larry graphite bottom method.

Any concerns with this plan?

Sounds like a good plan to me.

Will 60 grit on a dura block hand sanding give the epoxy/ graphite mix enough tooth to grab onto? The existing gelcoat is in sound condition but to old to be buffable. Should I prime with S3 yacht primer before the epoxy/ graphite or no?

60 grit with an RO is plenty. Not sure about hand sanding but if done well I think you will be good.
For epoxy/graphite on the bottom I think I would skip the primer.

Plus that Fuzz no primer... if it was gel coat sand it and lay it on. One thing to make sure of is there is no pinholes in the gel coat prior to epoxy these are usually signs of pour bounding... if there are any pin holes sand them out most of the time once you sand it a little it will flake off.

Bottom coated with cracker larry recipe. Still needs a wet sand at 220. Od green paint being removed from hillsides to show a blue boat that was sprayed with white gelcoat at some point. It's solid and I look forward to slathering in system3 primer.

Bottom is looking really nice! Your work is paying off.

Going to start the long and arduous process of priming and paiting While the boat is upside down. I am going to clean and dewax a few times then fill any scratches through the gelcoat with total fair. Sand to 120 grit then prime once to check for areas that need rework. Fix any other issues with more fairing then 2 coats of rolled on system 3 primer. sand to 320 and roll and tip with system 3 topcoat. Then caulk the cap to hull joint with lifecaulk and get ready to flip the hull back over. Any major flaws in this plan?

Wet primer not looking too bad

System 3 primer. Once it dries I get see thru of almost everything below. Stirred and mixed correctly. Just getting very little build and coverage. Using redtree mini mohair rollers. Lays down to a very mild orange peel just very transparent for a primer. Any ideas?

Flipped the boat back over. My cousin's you tube channel . I am the handsome devil in the red shirt.

https://youtu.be/Y7Xa5c9STwQ

Around 32 minute mark is the "oh snap!" moment.

Good stuff right there!

Nice work!!! Jeff

https://youtu.be/Cw98PlCxivU
More dicking around with lost causes.

I have some pinholes in the sole and casting deck. Laid down 12 oz biax with marinepoxy and phenolic microbaloons to fill the weave. They are large enough to show up in system 3 primer but too small to easily fill with Total fair. Do you all think I could force them full with neat epoxy and a Bondo spreader? I don't have any closeup pics to share.

Pinholes are the enemy of all of us. Blow them out with air and use fairing compound. Sands better than epoxy.

Dunked the boat today to see how it sat on it's lines. Hull was designed for late '60s two strokes. moved a lot of weight around during the gut and rebuild. Thanks Jeff and everyone on this group for guidance and great products and service.

Dang that looks good! Seems to be sitting on her lines, you done good

I ordered a tessilmare radial rub rail kit from bbc on 12-28. It arrived today packaged very well and the install was a breeze. Thank you Jeff and team for a great customer experience.

The boat looks great.