zum.offshore.Malta

Hi guys ... i would like to know how to calculate the X dimension myself or if its posible i would like to ask someone out there if they are ready to help me out with my query i got a 30 footer deep vee offshore with 22 degrees deadrise and with a maximum beam of 8 feet ... i will install a 525 mercruiser with a bravo 1 or more likely an XR drive ... ! ! ! ! but do not know the hieght of the propshaft what it should be from the keel. the hull has no notched transom and it has a constant of 240..... for a lot of u out there its a simple question but not for me ..thanks ! ! ! actually i was wondering to build the next boat with a notched transom this time... again with a single mercruiser 525 and XR drive.... knowing that a notched transom helps to raise the drive s height....but have no clue what should b the height nor the length of the notched transom to work properly.............. ! ! ! any ideas ???????????

jpclear

First: "X-dimension" and "prop shaft height" are two different things so lets talk just "prop shaft height" here. The further forward (or distance away from the prop) your running surface ends (as in longer notch or cutout) the shorter you will want that PSH. I created a 9" notch in my hull (cause that what Fountain used on their old 24 footer) and raised everything 2-1/2". I should have gone even higher. With the prop technology we have today I would start with a PSH of no more than 5" for a stock Bravo, knowing that I could get as high as 3" with an Imco "Shortie". Or better yet; start with the "Shortie" at 3" and add the spacers if necessary to get down to 5" This all depends on just what the use priorities for the boat are, of course. --- Jer

zum.offshore.Malta

Hi jpclear...sorry for being inaccurate with my question ! ! ! when u mean u created a 9" notch running towards the front , i got you but i havent established your height of notch at transon...is it a 9" height as well therefore creating a square lookalike notch ??????????.. i got some info from a guy out there in the forum remarking me as u said to start at 4" of propshaft height from keel ...than if neccessary lower with a space of 1 " to go at 5" as u said by ....by d way my hull has got a rounded keel to soften the entry in rough seas ..does this criteria has any effect on adding a notched transom ????? by d way i treasure your advice that uve gone 2-1/2" higher with a 9" notch length ....what regards length i m considering a 10" notch in length but still indesicive what regards height.. after having a close look at a Progresion 29 with stern drive with a single engine like i m adopting myself left me a bit concerened as the height is just where the inner strakes meet at transom ..which on the other hand makes a lot of sense for me ...but progresion run full length inner strakes while my boat s inner strakes stop at LCG therfore 10 feet from transom...does this asumption ive just made makes any diffderence for yoo????? thanks in advance zum.offshore.malta

Griff

I have a 10" notch on my single engine 28 Pantera. The propshaft height was at about 3.25" and I could not carry the bow enough. I lowered it 1" and it carries the bow much better and prop slip went down. Maybe picked up 1-2mph on the top end and cruise speed went up 3-4mph.

zum.offshore.Malta

Hi Griff,,,,,,,,,,,, just saw your message ! ! ! ! thats a good advice u sent me thats for sure ! ! ! so u r saying that your pantera has got a 10" inch notch ( in Length) from transom lookinh forward ... am I rite ????? and whats the height of your notch from keel...i suppose its where the inner lifting strakes meet at transom....

Griff

It is 9.5" up from the bottom and 10" in from the transom.

zum.offshore.Malta

Hi guys ...the new kid on the block cant hold his emotions to thank you for your replies ! ! ! sorry for not answering promptly but in the last 2 days i was busy so i havent checked what was going on ... now lets get serious... ..i ve put up a team consisting of a naval architect and a designer ... ... so thats why i m using CNC to build d mould itself and the hull will be built strong enough up to + 80mph ... now ,,,to answer Audacity s question if racing this hull in P1 ...my answer is NO as from last year rules changed unfortunately ,, from a minimum length of 30 feet to a minimum of 33 feet... limiting speed to 80mph regarding super sport with the power from twin engines configuration being 4.5 KGS per Horsepower. ...therefore a boat of 38 feet weighing 3500 kgs (7700Lbs) must have a maximum horsepower of 780 hp therefore 390HP on each engine .... and by d way SURFACE DRIVES are a must ! ! ! for this sport because Breaking of BRAVO drives are a d most common failure and inevitable .. due to the offshore sea conditions in d mediteranean..let me know if u need any information regarding P1 offshore racing ..Super Sport and Evolutuin class ...which is another world of offshore racing ..u r more than welcome to ask me any questions whatever your querys are ..yours truly zum.offshore.malta
Now to answer your questions yes u were rite i m using a single 525....with brovoXR ...no extension box so after being sure that my boat has got a constant of 239 / i had a look at a progresion 29 with stern drive having a notched transom for a single engine , at a cigarette cafe racer 30 with twin engines and from someone out there whose name in code is Griffin also replied saying that his Pantera 28 has a 9 1/2" height from keel with 10" of length which made me realize that a cafe racer 30 , a Pantera 28 have both the same dimensions regarding their notched transom as u all know which made me think that i should build mine with a notched transom as well ...i was going for a height where the inner strakes join at ransom which would be of 9 inches ... and for a length of 10".. with a propshsft hieight of 4" then if too much slip will occur i will go down an inch using a spacer ..Power will be a single 525 with Bravo XR ..by d way the inner strakes stop at 10 feet from transom and the transom has got a 13 degres of inclination upwards toward the sheer . this is quiet interesting .i worked out the constants for various models ....example for a cigareete 30 footer with twin step has a 242 constant...whole Fountain and Outerlimits have a 252 and 250 respectively...my aim is to reach a 242 with my boat not having any step yet and no notched transom . could be next years model will include a single step infront of the LCG which is 10 feet from transom and where the inner lifting strakes end...THEREFORE would u suggest me to keep the hiegt of the notched transom as exlpained above and going for 10 inches length as all the mentioned above .... a Last but not least i wanted to answer Mr.TRICK i dont want to upset you but i m no Jon. A from Malta......and to answer Griff s i thank him a lot for giving me the very useful information to begin with 4 inches propshaft height than may be ad spacers to go to 5 inches dep....if i had to install an extension on the XR,,, i guess it should be lifted more higher ...???am i right mate
I may asume that u r tired now after reading all the above...... please be a bit patient ! ! ! just one last thing i wanted to say to Audacity that ive seen their video clips which i definitely enjoyed ....less the one that uve been left with your wheel in your hands. ! ! thats weird man but how u got the wheel back in place is just unbeleivable and amazing ....good job guys and keep it up and i wanna c ya in Malta next year ...in May ..i know all profesional people i mean ( Mercruiser certified Technicians) and other services that u would need on the island.. of any type ....