C19 in Richmond, VA

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OneWayTraffic
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Re: C19 in Richmond, VA

Post by OneWayTraffic »

VT_Jeff wrote: Tue Apr 20, 2021 5:00 pm
OneWayTraffic wrote: Mon Apr 19, 2021 7:35 pm I wasn't thinking about compressive strength at all. I'm willing to bet that that is solid, and far in excess of whatever force you apply standing on top of it.

I'm more thinking about the boat wanting to bend globally as it slams into or falls off a wave. That force is resisted by the stringers, that now have a hole near the top of them. That force will get focused into that cut out, by how much depends on just what section modulus is effectively left. I don't know enough about the precise situation to say anything for sure.
Just discussion for the sake of gaining knowledge at this point.

My impression:

I highly doubt Dan was referring to compression from walking, he was referring to the same compressive force you are: wave pounding, applying a force to the outside of the hull, which will be transferred, eventually to the cap/sole. In a I-Beam, the web component experiences sheer forces, the flanges bending forces. The sheer forces are distributed evenly throughout the web-depth, they are not concentrated at the top or bottom like in a "normal" beam. In a normal beam, the top and bottom experience tension or compression with a bending moment, the center neither, which is why holes need to be at the center. In an I-beam, it's not the case. A hole will weaken the web but the location of it, depth-wise, makes little-to-no difference.

As always, more than happy to be proven wrong, as my ONLY goal in this entire enterprise is to learn.
What I know for sure is that in the discussion about the CS25, the designer stated explicitly that a minimum of 1-2" plus the whole thickness of the cleats was required on top. In the thread I linked to, people with more knowledge and experience than I stated what the standard requirements of stringers are. It's worth a read and those requirements have been gained from millions of boats. I also think that the CS25 shown was worse in that all four stringers were cut, and in a similar place. Early hull failure would have been certain with that boat and how it was going to be used. So it was rebuilt. I would agree that if the sole attachment is thick enough, strong enough, and well attached enough then it shouldn't matter. Which is why I'd be putting some structure on top there.

There are requirements about location and size in documentation building codes for pre made I beams. This one for example allows holes anywhere in the web at least 2mm from a flange, but the flange is 33mm thick. There are a lot of other requirements as well.
https://nzwoodproducts.co.nz/media/prod ... .2a_LR.pdf

Anyway I've said my piece, and a lot more than I originally intended too. Apologies for any derail from the build thread.
Last edited by OneWayTraffic on Tue Apr 20, 2021 5:46 pm, edited 1 time in total.

cracked_ribs
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Re: C19 in Richmond, VA

Post by cracked_ribs »

If I was seriously concerned about it - and I wouldn't be - I'd just add a layer of 12oz tape over the top of the stringers and cleats. The tiny height difference relative to the bulkheads would get eaten up in the peanut butter that goes to glue down the deck.

The 45/45 would tie the load in over top of the holes, and if you did it right before laying the sole, you'd get a strong primary bond across that whole load path. Top skin of that beam would be in tension from hull hitting the water; you could make it a little stronger in tension that way.

But I think that the large cleats and the connection to the sole would be plenty. All this stuff is overbuilt. Tom's C19 ran with fully delaminated...everything. Obviously you don't want that but people worry about minutae. I would have changed Peter's layout, and I agree with that call 100% but it was worse. I saw this in the pics and thought about it for a bit and decided to say nothing, but I understand the concern. But I don't think you'll ever find an issue that results from it.

If all the chatter put doubts in your mind, I'd chamfer the cleats with a roundover bit, put a layer of biax tape on over the conduits, and rock on.
I designed my own boat. This is the build thread:

viewtopic.php?f=12&t=65349

Dan_Smullen
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Re: C19 in Richmond, VA

Post by Dan_Smullen »

Don't apologize, OWT. I enjoy the conversation.
cracked_ribs wrote: Tue Apr 20, 2021 5:37 pm
If all the chatter put doubts in your mind, I'd chamfer the cleats with a roundover bit, put a layer of biax tape on over the conduits, and rock on.
None whatsoever.. Thickened epoxy around the tubes, to seal them, not to add strength.

Frames, stringers and caps, all melded together with epoxy. The entire torsion assembly is the most rigid thing I've ever built, and these little holes did little, if anything to weaken it, especially after the sole is laminated to the cap. It is more likely that the transom falls off, or the joint between the upper and lower side panel fails before this hull hinges at this point.

Moving on...

Station B is temporarily in place with some screws. Test fit modified "Frame A". Moved it back 24", minimizing the area of the forward step/seat/hatch area, but increasing the deck at the bow. (More room to stand up there and cast). Scratching my head how to make all of this work. It's just behind the PVC coming up out of the floor. Will be a floor behind it, supported on cleats on the side panels. A place to stash an anchor, some PFDs and maybe a square grouper, should I find one in the bay.

8350
Last edited by Dan_Smullen on Wed Apr 21, 2021 3:06 pm, edited 1 time in total.

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cape man
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Re: C19 in Richmond, VA

Post by cape man »

and maybe a square grouper should I find one in the bay.
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OneWayTraffic
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Re: C19 in Richmond, VA

Post by OneWayTraffic »

Are you planning to glass the inside above the side panel overlap? I'm thinking about whether I'll glass the inside of mine with light glass. I used 200g on the whole outside, and have some 100g cloth also. At this stage I'm leaning towards glassing every large surface.

Dan_Smullen
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Re: C19 in Richmond, VA

Post by Dan_Smullen »

OneWayTraffic wrote: Wed Apr 21, 2021 7:06 pm Are you planning to glass the inside above the side panel overlap? I'm thinking about whether I'll glass the inside of mine with light glass. I used 200g on the whole outside, and have some 100g cloth also. At this stage I'm leaning towards glassing every large surface.
I want to run 6” of tape down the seam itself to add strength, but have been concerned about it laying flat with no bubbles.

After your question this evening, I ran a cabosil fillet along the top of the lower panel up forward, and laid tape over it. It seams to have stayed flat, and I’ll continue down the joint. Eventually...

10 or 6 oz over the tape on the upper panel will be nice. I should make it a point to lay it.

OneWayTraffic
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Re: C19 in Richmond, VA

Post by OneWayTraffic »

I had a few issues with the outside cloth as well. I put a fillet on the overlap and that helped a bunch. Not even slightly concerned with strength there.

Edit: I did sand through the cloth here and there for fairing.

TomTom
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Re: C19 in Richmond, VA

Post by TomTom »

cracked_ribs wrote: Tue Apr 20, 2021 5:37 pm All this stuff is overbuilt. Tom's C19 ran with fully delaminated...everything.
This I can attest to! 😂😂 And thank goodness it was overbuilt - thats for all the dumb asses like me out there!

Interestingly - the same “sales guy” - and that truly is all he is - who sold me that resin that never fully cured back when I first built the boat messaged out of the blue and offered to send me some “new” samples of what they are selling ...

I was curious enough to accept and try as I might, I couldn’t get it to fully cure. It’s supposedly Araldite GY 257 ... but I think they mix the hardener components locally and they clearly don’t get it right. I hate to think how many substandard and wasted projects there are that have used this stuff.

All I can say is if you live somewhere remote and you have any doubts about your resin supplier just pay the extra and figure out how to import that right stuff.

This Ampreg 21 by gurit that I use now is like chalk and cheese compared to that other stuff.

Dan_Smullen
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Re: C19 in Richmond, VA

Post by Dan_Smullen »

Not much boat work this weekend. I made the trip to Manteo, NC to finish a small project on a friends Jarret Bay. Hull #4, "Smoke Show"

While refurbishing the salon to be more suitable to charter fishing, an ac unit was removed, exposing the bottom of a wire chase. I extended the chase cover by scarfing a new piece of teak onto the existing.

I always jump at the chance to help out Jay, the owner, especially as tuna fishing heats up in April-June. 8)
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Resawn 4/4 teak to get 5/8' thick stock without sending 3/8" up the dust chute. At $25/bdft, it seems best to conserve.
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Scarfed and glued...
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3 coats of Epifanes...
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Installed port and starboard...
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Yellowfin poke bowl from their catch the day before...
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Back to the C19, I added 3-1/4" to the height of station B, which will raise the seat, and give me a little more storage room underneath. I felt this was needed after raising the sole.

Talk about running out of tape just in time...
8386

TomW1
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Re: C19 in Richmond, VA

Post by TomW1 »

Nice work Dan, that Poke looks mighty good, Yum.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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