Just calculating speed on a ribboat. We mainly work with outboards but the customer would like to have single 420 hp.

Boat is 9 meter and weight is around 900 kg without engine. A good hull from a fameous designer. Stepped...

Which leg for this engine? topspeed?

Assuming 24 degree deadrise? That sounds awfully light. What do you figure the all-up ready to run weight will be? Most boats of this size range are in the 5000-5500 lb range Are you saying this one will come in at like 3500 lb with engine, rigging drive & fuel?

ribboat as in inflated sides with a hard shell mild v bottom ? zodiac makes a 9 M at about 3500 lbs. they reccomend max 320 HP and spec top speed at roughly 60 mph.

i have been in an ex secret service 24' rib at 50 mph and it was pretty scary... a little bit faster with a little bit rougher water and i could see us ground looping that thing and everybody ending up in the water one way or another... i don't know what motor was in it but it sure as hell wasn't 400 hp...

good luck with THAT

I saw a simular boat weight about 1650 kg. And the plan is to build it light with a part kevlar.

So i change to 1300-1400 kg

http://www.airshipribs.com/airshipcms/

Airship is not the boat we work on but simular in style and size....

If you look at an Avenger, Cougar or Airship they are in weight range. I would expect 75 + MPH if the X dimension 18.5" or greater and the design is good.
Steve

You should contact Rik @ Arneson about the ASD#6, hes here on the board by the same name. Super strong drive and in many cases efficient enough to run 8-10 mph faster than an equally equipped Bravo B1 or Volvo SX propelled boat and that goes both for mid range efficiency and top speed. Compared to the Mercury and Volvo counterparts, the efficiency is also nice in terms of MPG.
Besides that, the Bravo 1 drive is not exactly a great drive, just do a search on here.
Other ribs have been equipped with Arneson surface drives, so it should not be a problem, The ASDs are in a completely different league than any Bravo or Volvo drive.

Oh, and don't forget the rooster

http://www.arneson-industries.com/pa...oducts&id=asd6

Sounds like a neat project, good luck with it.

Thanks for the replay...

Arneson is on my list. Right now we calculate different engine and drives.

We have posibility to use excisting hulls from good brands, but we also planning for our own design.

Will tell you guys/girls what we will do in the future, it is for next summer...