Bow trim?

[capt.halfman]

I have a new fibreglass 50ft power catamaran not long off the slip, after continuously being told by boat builder , there's to much weight in the stern, it is quite obvious the boat is bow heavy or designed incorrectly, we have done all possible to shift weight aft,, it has been suggested to have bulbous bows fitted,ie foam moulds glassed on next docking,? Is this possible or even suitable? This vessel runs surf / dive charters , 40 ton 10 person live aboard in open waters

[danielamartindm]

As you know, too much weight forward in a cat is bad, increasing the risks of burying the bows and pitchpoling in heavy seas.Then there's the liability issue- were something bad to happen and there was evidence that you knew something wasn't right with the design or the building. My inclination would be to bring in an outside pro from Dover at this point- an architect or engineer. Let him or her look at the plans, survey the boat's construction, and ask the builder questions. Find out from a non-involved source exactly what the problem is; that will dictate a course of action. Adding more weight to the vessel, or changing its hull shape for the sake of balance it should already have? Something is wrong here.

[capt.halfman]

Yes thank you for your reply, my thoughts were along the same line of having an architect engineer have a look,, the boat handles quite well ,although doesn't like head on seas as any cat doesn't, it is quite obvious though and I would feel more comfortable with the bow higher out of the water , thx again for your reply

[Captsteve53]

Agree with the use of a professional for sure, we had a cat not to long ago with similar issues (although Aluminium) to rectify we did three things

1) Installed bulbous bow extensions (Marine Architect designed)

2) Installed spray chines on both hulls (to help with lift and keep decks dryer)

3) Installed a central "Nastle" (central wave piecing mold)

[StuM]

That's "nacelle"

[Captsteve53]

Yeah- was never good with "French"

[capt.halfman]

Thx for reply Captsteve53, im looking at options now

[deblen]

Couple of pics of a local 55' cat lobster boat.
First & only one locally. Owner has had it about 7-8yrs.
It sits perfectly level when stopped.
The under way pic shows it looks good when powering in flat calm.
I wish I had a pic of it when powering in 3-6+ft stuff- It's just a furball!!
You can just tell that there is some kind of vessel behind that giant ball of spray which goes right over the w/house & down both sides. No need to hose the work deck down on the way home.
Great sea boat-stable-but very wet & a bone crushing pounder.

Since bringing it home from builder ,he has added the small nacelle which made minor improvement to pounding. (nacelle not big/deep enough IMHO)

He also added bulbous bows with minor improvement.

The problem is the seas hitting the under deck in the tunnel & not being able to escape off to the sides like a monohull. The wake hits the insides of the hulls in such quantity that some of the water splashes out front & creates added pile up on top of next sea. The whole mess hits that flat area across the bow & blows upward.

I have no answer to this. Just passing along my observations & those of my friend.the owner.

Cheers/ Len
https://www.dropbox.com/sh/c8o4srl5a...kpA6OKaQa?dl=0

[Captsteve53]

Len,

Thanks for the input/ link and pic's, one thing i did not mention in my previous post was our fore deck was some what similar to that shown in your pic's and not extending completely to the front of both bows, Our Naval architect (designer of the well known Shark cats/Kevlar Cats out of Aust) also moved our fore-deck forward to match the bow and did away with any aft facing negative rake, in doing so the water was forced through the tunnel thereby actually giving lift when required rather than being allowed to escape over the bow or in front of the vessel, (if that makes sense!) Your picture shows the water escaping out the front and over the bow perfectly

Bottom line for our vessel it really solved our issues along with the three other modifications, and yes your "Nacelle" looks like it could have way wider to provide more buoyancy when needed most,

Cheers Steve

[Three Sisters]

Originally Posted by deblen

I have no answer to this. Just passing along my observations & those of my friend.the owner.

Cheers/ Len
https://www.dropbox.com/sh/c8o4srl5a...kpA6OKaQa?dl=0

From the photos the ship appears to be designed for 5-6 knots. Analogous to pushing a loaded fuel barge to 30 knots.

[capt.halfman]

Thx to all for the input , this the catamaran I'm referring to , I have covered the name and rego details for business reasons

[Stumble]

I am not sure why you think she is bow heavy. But those pictures don't show it.

Whats the make and model, and do you have a picture of the boat out of the water?