Strake placement

Hi I'm in the initial design stage of my 28-30 foot flybridge half cab ( haven't decided on the loa) but will be running a waterline beam of 2.75m with a 6 inch chine flat at - 7° or - 8° with a 23° deadrise at transom. The approximate displacement is 4.5 tonne on waterline. Just trying to work out the strake placement eg. Pad width, how many to run and Wether to run a negative angle or not to help a bit with lift and stability. Thanks in advance Steve

 

What type of power are you installing. Twins, single, inboard, outboard, jet,
Strake placement will have to ensure that the turbulence caused by them will not impact the props/jet etc

 

Welcome to the forum.

Given your questions, I'd suggest you're no where near having the skill sets to "design" a boat of this scale. Maybe a 15' dinghy or small powerboat, but not a 29' power yacht. I mean no disrespect, simply an observation based on your questions. It's one thing to have some ideas about design, but another to assemble them in a good balance, that meets a well thought through SOR, so you can reach your targeted goals. What about "your" design is significantly different than available designs, to require a whole new custom?

 

Hi Barry looking at running about 500hp single inboard

Hi par I have designed a few bigger boats in the 19 to 24 foot range that have come out with reasonably good stability curves and run well in cfd. I have built an 18 footer off of one of my designs which run well on the water but all of my designs have had a smooth bottoms. I have been doing a bit of reading on the subject of lifting stakes to incorporate it in my new design and was just asking for a bit more information on the subject or where the best place to look would be to get a better grasp on the subject while I'm still modelling the hull. Thanks steve

 

The waterline beam is not the place to take the measurements off for placement of the strakes, but rather the chine width.
The 7 degrees down is probably fine but we used 10 and were happy with the results.
So say your chine width is 240 cm, half is 120, measuring horizontally from the keel, start the first strake at anywhere between 65 to 70 cm from the keel. Obviously the out side strake will be at the chine.
Assuming a 50 cm prop,
try to make the outside edge of the strake as sharp as you can, to reduce the coanda effect though with the weight of boat that you have here, it is unlikely that you would notice any difference