Un-reinforced hull failure areas

[Prodrvr]

I'm just getting into FE boats and I see most people are reinforcing their hulls with carbon fiber cloth. I wanted to know what do hulls usually fail from? Does the water pressure split the seam where the hull and deck is joined from flexing? I'd like to know what areas and also at what speeds is hull reinforcement necessary. I would also like to know of any and all methods to properly reinforce the hull.Thanks!

[Mxkid261]

There are alot of variables that can make a difference but on a catamaran for instance yes the seam where the hull is joined together can split probably from the top deck compressing on a hard impact, transom can crack too in a hard hit if the rudder takes most of the force. Hard to say what speeds a boat can do before cracking up, but I'd say anything over 50 and the potential is there. Heres a good carbon inlay tutorial by keith bradley.

http://www.kbbforums.com/carbon-fiber-inlay-tutorial-t1041.html

[Prodrvr]

Cool thanks.

[Prodrvr]

How about filling the front part of the hull (catamaran) from the tips to maybe 3/4 up the deck using 2 part expanding foam that's rock solid after it sets? I found this stuff that you would need a hammer and chisel to break apart.

[Mxkid261]

Yes kintec sells the 2 part foam and a lot of guys use it Ive never used it someone else with experience with it might chime in. My 32" fighter cat just has epoxy poured in the tips/transom and carbon inlay it has taken prolly 15-20 hard hits and only has a very small hairline crack in gelcoat down one side where the seam is

[Prodrvr]

My 32" fighter cat just has epoxy poured in the tips/transom

How far up into the hull from the tips and transom areas? I could try to do a cf inlay myself, but man the boat I just bought to learn on is tiny (HK flowmaster C1) compared to the other gas boats I've had. I'm gonna have fun getting my hands inside there to lay it all out, which is why I thought the 2 part foam would be easier to do.

[Mxkid261]

Theres only about 1 oz of resin in each tip, I forget in the transom theres probably like 4-6 oz back there. My carbon inlay only goes probably an inch or 2 under the top deck past the hatch opening

[Prodrvr]

Cool thanks!

[Fluid]

I belive the OP has made an incorrect assumption about the reason for the use of carbon fiber cloth. Yes, some use it to reinforce failure areas, but there are disadvantages to carbon cloth for this application - the edge of the cloth now becomes a stress point for failure. Adding more 'glass cloth over failure areas may make more sense in many cases.

But the most common reasons for doing a carbon fiber inlay are looks, and to stiffen flexible areas. Examples of the latter include the tunnel in cats, the afterplane of hydros, and the bottoms of monos without strikes. Flexible bottoms like those mentioned can cause: changes in bottom shape which on monos can cause severe handling problem; alignment problems for drivelines; and they can flex enough to break loose motor mounts, etc. Not every hull needs carbon fiber, but looking at posts here you wouldn't know it.....

.

[srislash]

And if I may add to Fluids post which I completely agree with, carbon fibre conducts electricity like nobody's business. So one must also be careful with terminals and such. I have even put FG cloth over CF hulls in key places to protect myself from this.

[zooma]

I belive the OP has made an incorrect assumption about the reason for the use of carbon fiber cloth. Yes, some use it to reinforce failure areas, but there are disadvantages to carbon cloth for this application - the edge of the cloth now becomes a stress point for failure. Adding more 'glass cloth over failure areas may make more sense in many cases.

But the most common reasons for doing a carbon fiber inlay are looks, and to stiffen flexible areas. Examples of the latter include the tunnel in cats, the afterplane of hydros, and the bottoms of monos without strikes. Flexible bottoms like those mentioned can cause: changes in bottom shape which on monos can cause severe handling problem; alignment problems for drivelines; and they can flex enough to break loose motor mounts, etc. Not every hull needs carbon fiber, but looking at posts here you wouldn't know it.....

.

Sounds good. I am getting ready to start a DF Cyberstorm 33 bare hull to replace my beat-up Pursuit, for P class oval racing. It has strakes molded into the hull, and feels pretty rigid. I'm debating on whether to inlay some 1.5 oz fiberglass cloth or go without it. What do you think?

[Mxkid261]

OP sorry if I misinformed you

[Prodrvr]

OP sorry if I misinformed you

Not at all. I'm just going to try the two-part expanding foam and see what happens. I guess when it comes to cf, maybe it's best to just buy a hull that's already been made in cf.

[Prodrvr]

I belive the OP has made an incorrect assumption about the reason for the use of carbon fiber cloth. Yes, some use it to reinforce failure areas, but there are disadvantages to carbon cloth for this application - the edge of the cloth now becomes a stress point for failure. Adding more 'glass cloth over failure areas may make more sense in many cases.

But the most common reasons for doing a carbon fiber inlay are looks, and to stiffen flexible areas. Examples of the latter include the tunnel in cats, the afterplane of hydros, and the bottoms of monos without strikes. Flexible bottoms like those mentioned can cause: changes in bottom shape which on monos can cause severe handling problem; alignment problems for drivelines; and they can flex enough to break loose motor mounts, etc. Not every hull needs carbon fiber, but looking at posts here you wouldn't know it.....

.

Thanks for that bit of knowledge!

[Prodrvr]

carbon fibre conducts electricity like nobody's business

Well that can certainly create a hell of a problem!! I'll keep that in mind, thanks!