Reinforcing or modifying forward chine flats for slamming

[baeckmo]

Yes, but leaving the outer 40 to 50 mm's horizontal.

 

[fallguy]

I am only replying in reference to @baeckmo and other comments.

I doubt you’ll go to all the effort to fix it. But to do it, here’s a way.

Given the chine flat is 5”, and ought to be 2”. You have a 3” ‘problem’. See if @baeckmo agrees, but I’d probably just reduce the angle to the flat and fill it in. It’ll need to be ground to glass for 5” of chine flat and 5” of hull. Then you fit 3 layers of 1” foam or coosa in the space, with epoxy bonding to the hull or to each layer.

Then you can use an ester and lay two layers of staggered 1708 tapes with a slight relief from the hull edge to simplify finishing. The last layer can be csm out for the new gc.

I see little reason for a radius, but I’m a builder and @baeckmo is an expert on water flow.

sorry~ I did not draw the tapes because so straightforward; if you want to know, I can add them

The foam choice drives the number of layers of glass. Coosa 20 pound needs 2. A 4 pound foam will need 4 layers I’d say.

 

[mitch184]

@fallguy which epoxy would you recommend? I assume thickened so I could fill in any voids between thre foam and existing hull. Also, you mean you doubt doing this fix will help a lot?

 

[fallguy]

I like West Systems with the pumps. Silvertip for no blushing or outgassing.

see edits—>
Thicken the resin with cabosil. About 2+:1 cabosil by volume. Slump test. It should not sag if piled high for 10 seconds, or it will sag off the boat too much. Precoat all the pieces to tack with clear epoxy. Keeping them on the hull will be tricky, you would want to hotcoat the hull. So this means you let a neatcoat kick on the hull bottom edge and then you apply the thickened resin to the foam and the tacky resin helps hold it. You’ll need a system of jacks or ratchets and helper boards to keep it in place. The boards get ship tape. Design the system to work dry or it’ll be like hell on the fly.

I think the fix will help. Follow baeckmo’s lead.
I would be curious whether he thinks this would be needed all the way or if you can taper it after the forward sections, etc. With epoxy and glass; you could test it after a week cure.

 

[C. Dog]

It is heading towards a gull wing style and those wings are continuing too far forward. It is a design flaw in my opinion and would be horrible in some of the short sharp wind chop we get in shallow coastal areas in this country.

It is adding a lot of unnecessary resistance to the bow which should have as little as practical, thus costing fuel and VMG too on top of what is lost to course changes for comfort.

By the sounds the pounding is being exacerbated by a very stiff build transferring forces to knees etc. The old ply and plank boats are great for absorbing shock loads in the structure, and can offer monocoque construction with fabric reinforced resins to stick it all together. I will have one any day in preference to most other building materials, and deal with minor maintenance issues.

Maybe some of the design and building experts can offer a viable solution to help you sort this out, but please do not jump the gun until a consensus is reached, you could be worse off with an unsaleable boat.

 

[mitch184]

@fallguy instead of using ratchets could I use a vacuum bag or maybe jacks until I get the vac bag in place? Hot coat, apply the thickened putty and core pieces, vac bag the whole thing. Let it cure, sand as needed to get it close, then switch to polyester structural putty and laminate 1708 to the putty finishing with CSM then vac bag again? Then spray with gel coat.

As mentioned, this is likely going to be a winter project at this moment. So i plan on running the boat this summer and try and get some good pictures of the boat when running. Then maybe I can get a good idea of where the water hits at various sea states, speeds, etc. I would imagine that this effort only needs to occur from the bow aft to where the chines stay immersed in 90% of running scenarios....

 

[fallguy]

@fallguy instead of using ratchets could I use a vacuum bag or maybe jacks until I get the vac bag in place? Hot coat, apply the thickened putty and core pieces, vac bag the whole thing. Let it cure, sand as needed to get it close, then switch to polyester structural putty and laminate 1708 to the putty finishing with CSM then vac bag again? Then spray with gel coat.

As mentioned, this is likely going to be a winter project at this moment. So i plan on running the boat this summer and try and get some good pictures of the boat when running. Then maybe I can get a good idea of where the water hits at various sea states, speeds, etc. I would imagine that this effort only needs to occur from the bow aft to where the chines stay immersed in 90% of running scenarios....

No. I have a good sense about this sort of thing.

The vac bag will tend to move the components. You’ll want to see them. If you had a way to anchor the components; then you could vac. But just the same you can use a ship tape covered board and pinch it in about as easy.

If you get the first piece on, then you could temp screw the other components a second day much easier and get the shape of the radius or angle closer. I’d not screw into the boat, but you could.

 

[mitch184]

Gotcha. That makes perfect sense. Thank you