1995 Larson 174 SEI Complete Rebuild

[Mechanicalmike08]

Alright well tonight I cleaned up my mess and then started laying out the floor. Ran some strings to find heights and then cut out the templates for the two bulkheads. They are at floor height right now so I need to subtract my floor thickness, which is going to make the very outermost wings pretty thin. Will see how they look once I transfer it to the plywood.





Now back to my question about the bubbles. I got in there and inspected a little more now that's its dry. Again the tabbing is darn near perfect, the problems came in on the skins because I let the tabbing kick. There's some near the edges, first picture is on the very top of the transom, the second is the wings that has close to 5 possibly even 6 layers in those areas. Last picture is the worst one on the transition from the second layer to the first plywood (Thumb for reference). As I said before should I just Dremel them out, sand smooth and do one last coat? Should I just leave them?

 

[Woodonglass]

Dremel would work. I'd just tear some CSM to shreds so its really "Hairy" and then use a chip brush and resin to dab the "Hair" into the bubble areas. You just need to ensure it's sealed and Waterproofed. No need to put down a whole new layer.

 

[AShipShow]

If the bubbles are on the larger side, you can drill a pin hole and fill them with resin using a syringe, but none of them look big enough for that to be worth it... As suggested, I would just grind them out with a angle grinder or dremel and patch em up with some thickened resin or another layer of CSM if you feel like it (but as WOG said, its not required)

 

[Mechanicalmike08]

Got most of the stringers and bulk heads cut to size, There just brad nailed together to hold in place for the moment. Still have to cut the drain holes from cavity to cavity down the center. I have changed my mind and I'm going to now coat what you see here with resin, PL and brad the joints together. Just one or two brads to hold in place, the PL should seal the brad. Then once that's dry I'm going to bed with PB and tab all this. Then I will work on the last 2 stringer pieces after this is all dry and done. Its nice to see some structure again!!

 

[AShipShow]

Looking good.. just wait till you have a deck to stand on! Haha
:mad-new:

 

[oldrem]

That's looking great!

 

[JASinIL2006]

Looks really good!

 

[kcassells]

Ditto to that!

 

[dezmond]

Very nice work! If you pl and brad them together and everything fits good, why not
pull it out when the pl dries and seal and cover everything out of the boat? Would be easier and less stress in the back. Then put it in as one piece and pb it in? Am I thinking wrong?

Will be be nice to have a floor back in there again

 

[Mechanicalmike08]

Very nice work! If you pl and brad them together and everything fits good, why not
pull it out when the pl dries and seal and cover everything out of the boat? Would be easier and less stress in the back. Then put it in as one piece and pb it in? Am I thinking wrong?

Will be be nice to have a floor back in there again

Im going to seal with resin tonight all the individual pieces. Then glue and brad them in the boat in place on Saturday. Sunday will be bedding in PB and tabbing. (If it goes to plan) It will be a little wonky still once the PB dries which makes me nervous about pulling it out. Plus i would only have my wife to help. I am going to try to do a section at a time with the PB and tabbing. I think i want to try and do all of it at once including the over the top CSM. I am going to try this on the first section on Sunday and see how it goes. If it fails then i will just do the tabbing and do the up and over part a different day.

I got everything sanded last night and round over routed the top sides for later. Looks pretty good.

 

[kcassells]

Very nice work! If you pl and brad them together and everything fits good, why not
pull it out when the pl dries and seal and cover everything out of the boat? Would be easier and less stress in the back. Then put it in as one piece and pb it in? Am I thinking wrong?

Will be be nice to have a floor back in there again

You could glass all the pcs, trim, assemble and set the structure. Then pb and all you would need to do is tabbing.
Nice...kinda like mass custom production. Amything you can do on the flat is so much easier. Nice idea Dezmond.

 

[harringtondav]

Mechanicalmike08 Early on you mentioned adding some extra, short bulkheads. Were there any straddling the fuel tank? It's a long span, and my SEI 174 has four 2 x 4's bracing over the tank. Wondering if Larson had a pair in that location. Same with the knee board locker(?) Please include a pic of the engine mount structure before you button it up.

Also I couldn't see if you've cut in the steering tiller arm clearances in the keyhole. Have you?

 

[JASinIL2006]

My SEI 186 had 2x4 bracing over the fuel tank, too, but nothing by the ski locker area.

Also, make sure that if you use PL construction adhesive that you allow at least 72 for it to fully cure and off-gas before you try covering it with tabbing/fiberglass. (Might even take longer if your work area is cool.) If you don't let the PL cure fully before you cover it, you'll get bubbling and delamination. If you don't want to wait, skip the PL and either use some other sort of adhesive or just tack the pieces together with brads and glass them together in place.

 

[tpenfield]

Looking good . . . it might be a little bit late, but here are my comments about the transom glassing and the layout of the structure (stringers & bulkheads)

I would not worry about the 'bubbles' (i.e. dry spots) on the transom. Just keep that in mind going forward is that the resin tends to 'pull back' as it cures leaving some air voids. You can address those with a little bit more resin before it cures or even just by hitting the areas with a resin roller as it is curing.

Take the learning forward as you do the tabbing of the structure. In terms of the structure, it may not be practical to adhere the structure together while in the boat and then remove it for a thorough resin treatment, as I believe some folks have suggested. If you did try to 'tack' together the structure and then remove/replace it, I would put a small piece of 1708 in the joint areas of the bulkhead where the stringers intersect, then add some tabbing to the upper area of the structure pieces to hold them together.

Some best practices for glassing and tabbing would be:

Many boats rot from the main bulkhead or the transom, and then onto the stringers. You can isolate the stringers from the bulkheads with a layer of cloth (1708 is fine) so that moisture from the bulkhead cannot migrate to the stringers. Your transom, being already glassed now has this feature. You can do the same for the bulkheads.

The structure should sit about 1/2" above the hull, so that it is not in direct contact with the hull. This is to prevent a 'hard spot', which will cause cracking of the gelcoat on the outside of the hull. PB, foam or any other suitable filler can be used to fill the 1/2" gap between the structural pieces and the hull.

Be generous with the tabbing, making sure you go well up the structural pieces and onto the hull surface. I have seen 'professional' restoration work where the tabbing was pretty minimal. You are better off to have more surface area for the tabbing to 'grab'

For glassing up and over the structural pieces, you can use some plastic drop cloth material to wrap over the top of the glassing so that you will get a rounded top edge. If you don't use anything to hold the glass/resin to the top of the stringers/bulkheads while it cures, the tendency will be for the glass to pull away and form air pockets. The plastic 'wrap' over the top of the glassed stringer creates a bit of suction so it holds its shape while curing.


That's all I got for now . . . things look good.

 

[Mechanicalmike08]

Mechanicalmike08 Early on you mentioned adding some extra, short bulkheads. Were there any straddling the fuel tank? It's a long span, and my SEI 174 has four 2 x 4's bracing over the tank. Wondering if Larson had a pair in that location. Same with the knee board locker(?) Please include a pic of the engine mount structure before you button it up.

Also I couldn't see if you've cut in the steering tiller arm clearances in the keyhole. Have you?

The extra bulkheads will be near the section under the seats and the section i have not started working on yet. I'm going to do this for 2 reasons. Seat support and to break up the bigger section for foaming. There pretty big and i want the foam to fill the cavity nicely. Mine also has the 2x4 to support the gas tank which i will be doing but a little different from how they did. Also have not started the engine mount or the clearance cuts. Those will be coming after this section is down and in.

 

[Mechanicalmike08]

Looking good . . . it might be a little bit late, but here are my comments about the transom glassing and the layout of the structure (stringers & bulkheads)

I would not worry about the 'bubbles' (i.e. dry spots) on the transom. Just keep that in mind going forward is that the resin tends to 'pull back' as it cures leaving some air voids. You can address those with a little bit more resin before it cures or even just by hitting the areas with a resin roller as it is curing.

I think Im going to leave most of it, just a few of the ends of the skins that are really bubbled like the one picture. I need one more layer anyway to get thickness correct. Also am going to wait to do that last layer until i cut the relief for the steering to seal that up nice.

Many boats rot from the main bulkhead or the transom, and then onto the stringers. You can isolate the stringers from the bulkheads with a layer of cloth (1708 is fine) so that moisture from the bulkhead cannot migrate to the stringers. Your transom, being already glassed now has this feature. You can do the same for the bulkheads.

The structure should sit about 1/2" above the hull, so that it is not in direct contact with the hull. This is to prevent a 'hard spot', which will cause cracking of the gelcoat on the outside of the hull. PB, foam or any other suitable filler can be used to fill the 1/2" gap between the structural pieces and the hull.

Be generous with the tabbing, making sure you go well up the structural pieces and onto the hull surface. I have seen 'professional' restoration work where the tabbing was pretty minimal. You are better off to have more surface area for the tabbing to 'grab'

That's all I got for now . . . things look good.

A couple of things from this,
#1 all the pieces will be fully coated in resin before installing, this is also why i want to use the PL in the joining faces. I figure this would be a great isolation point from the two pieces. I am contemplating putting a small wide piece of CSM at the joint when i do the coating of the raw wood as well.

#2 Everyone on here talks about spacing the wood off the hull, which seems like a great idea and i am going to do this because everyone seems to do it....But it makes no sense to me. Unless you line the entire length under the wood with foam or something most of the guys on here are packing it full of PB, the PB is harder than the wood in my opinion and defeating any of the purpose of letting the hull flex.

Hopefully my tabbing is generous, on the transom i did 4" both direction followed by 6" in both direction.

 

[Woodonglass]

I understand your concern but...The resin is much more flexible than wood. Boats that have wood in direct contact with the hull have suffered spider web cracking etc. Experience has taught us that using PB under the wood IS the best method. You could use foam, PL etc. but PB seems to be the optimum method.

 

[tpenfield]

To add to WoG's point, the PB is usually installed in a rounded/fillet manner so the impact forces are spread over a wider area and the PB fillet gives some flex to it.

On my boat (Formula) they actually use an air gap instead of filling the gap. It has some good and bad points.

Good is that only the tabbing on both sides of the structural piece (stringer/bulkhead) is in contact with the hull and the tabbing provides some flex without creating a hard spot.

Bad is that the air gap provides a channel along the hull for water to migrate to other parts of the structure, should one portion become compromised by moisture.

In my rebuild of the my Formula 330, I maintained the 1/2" air gap on the new structural pieces, but injected urethane foam into the gap once the tabbing had set up, thus filling the 'channel' to prevent any moisture flow, should part of the structure get moisture inside of it in the future.

 

[Mechanicalmike08]

Mine will be off the hull and most likely filled underneath with PB. I would think it would be very hard not to force it under the wood anyway when making the fillets. I dont really like the idea of just air under it for that exact reason, moisture could get in there.

 

[Mechanicalmike08]

Well got home from work, got the snowmobiles out the garage and on the trailer for the year to make some room to work in there. Got the pieces all cleaned up and coated with a generous layer of resin to soak in. Don't worry the propane heater was just to get the garage back up to temp after having the door open in this 25°F weather.


I will have to pull her out in the driveway for a little grinding and sanding before setting stuff in place tomorrow. Should be a nice 30°.....