Commments wanted on a RBB hull shape

[jfblouin]

This is my first boat design and I want comments on. I try to make a 6,7 m (22 feet), low-weight (easy trailerable and low fuel consumption), planning boat with 30 knots top speed for soft ride in St-Laurent Gulf (Gaspe peninsule, Eastern Canada). I look for a Deep V at 26,6 degrees at Transom. My design is a RBB (Rigid Boyancy Boat) with fiberglass collar and standard hard bow. I look to built it in 1:6 scale this winter and full scale winter 2005-2006.

You will find JPG pics in attachment but I have also Autocad LT version.

Any comments will be appreciates

PS Sorry for the bad english, but it's not my first language

[jfblouin]

You will find version 2 of the bow of the same boat.

Please ANY COMMENTS WANTED. It is my first design and and hope te receive comments.

Is bow 2 is better than bow 1 in rough sea?

Thanks

I think 26 deg at the transom is far too much. and you would find yourself falling on your side. I would look more toward the 21 deg range.

[jfblouin]

For this boat, I'm inspired from RIBs. I own a Bombard FB525 with a deadrise of 22 degres at transom and 30 degres ad midship and it pond hard in 4-6 feet waves. I tried a Zodiac Hurricane and it's better with is 25 degres at transom. I seen specs of some UK RIB with 26-27 degres and theses boat seem to have the best comportement in rough sea. It's sure that they are less stable at rest because the buoyancy tubes dont touch the water.

[jfblouin]

What is the best positionning for the spray rail in the front of the boat?

When you took the test boats out. Did you get a lot of spray over the windward side? Enough so that you thought something should be done about it, or a bilge pump ran a lot?

I am a chicken. I have my boat headed home, fast, at a wave height of 2' to 3'. At that point the wind rules. I am usually in the 19' deep V bowrider, which has a bow of 4' high. Into the wind is all bangs an a little spray. Not fun.

[jfblouin]

Hi Richard

English is not my first language so I dont sure to well understand what you say but I try to answer.

First the test and the only one boat is not still build. It is my project for next months. Now, I own a 5.25m (17.5 feet) RIB Rigid hull with inflatable tube. This is a old hull design and it run hard in relative rough sea (4' to 6' waves) but this is the 50% day conditions in my region. Also I have 4 childs and I need a larger boat and I want softer ride. I look to build this kind of boat to have the big stability and safety of a RIB with a higher hard nose to reduce breaching that is a problem with RIB. http://www.redbayboats.com/ribs/stormforce_91.htm

In a standard RIB the front tube put down the spray but with hard nose I think that I have to bo more careful about that point. Also you can see that I use a very deep V so I need more water support to begin planning mode. Also the floor of the boat will be over the WL and the boat will have no direct acces to bilge. In my RIB if 50 Gallons get in the boat with a big wave, it will get out in few secondes by rear port. That only append one time for me in a following sea and because I go to fast. 2004 was my first season of navigation.

[Dutch Peter]

Originally Posted by jfblouin

What is the best positionning for the spray rail in the front of the boat?

Above the waterline