Mangusta 70 - 80ft (1996 - 2004) Advice

[Portofino]

As said ..I'm sitting on the fence...
I can understand what Porto is trying to say, I also understand the disagreement by others.
To my mind the argument here
Is the definition or interpretation of the word "lift" ... imho it's a bit like saying a wire is "live" and others saying it's wrong because the wire is not alive. Porto says if it doesn't "sink" it must "lift".....well there is the problem as I see it, because there is a lot of information out there that use terminology to "support" Porto's theory, and as yet I have not found anything that says it doesn't produce "lift", but then we enter the world of "your wrong, but I can't prove it"

Ok so this paper here which I posted earlier and was a accused of “ searching to stuff to back fit my argument “ or. words to that effect uses lift .
I will précis this .
https://www.researchgate.net/public...ith-spray-rails.pdf?origin=publication_detail

A plane hull tested in a tank with bits added to compare any differences .
This time they recorded the Cog movement, up = lift or down .

See the strakes shape , size , position ….running all the way back .
No deep deadrise this time , in fact a round bottom soft chime hull .

Results below .

Listen up carefully.The bare hull shows max trim in other words is bow is running the highest - top graph .

Now look at the rise of the CoG the LIFT , the bare hulls is the least .

So the ones with strakes have generally the largest lift , the CoG rise and lowest trim . So this means the sterns lifted too otherwise how can they maintain the low trim .If the stern underwater sections did not contribute lift then the trim would be higher not lower than the control , the bare hull .




This just shows the straked boats getting the largest rise of CoG - top graph .
Lower shows the relationship between drag ( resistance) and adding strakes .


Every paper on strikes + lift says the same .But there real usefulness is as I always said in particular circumstances.
I used Chris d s in my post above to dodge the “ you been looking for it …..” He posted it albeit they talked in terms of sinkage .
The reason why is to do with adding measuring equipment to the modal the weight.
More here from MapishM s country folk . There’s a shit hot school of NA in Naples btw ….unsurprisingly.
Pardo , Fraucher to name a few funky designs of late .





Big thanks to those on here who have supported me battling on with this .You know who you are .
Porto .
Apologies to the op for hijacking his post .In consolation I have answered his Q and he has started other threads about his prospect.So i don’t feel net too bad .

 

[Elessar]

Can’t be bothered to read all that. I don’t know about hydrodynamics, but in the things I do know about I know you talk absolute nonsense. So I still don’t believe you and see little point.

 

[vas]

I've read the effing lot!

I think I've got some ideas why we have all this ludicrous thread. I also have some fears....

Porto has way too much time in his hands but unfortunately doesn't understand anything remotely related to engineering/forces/et al.
I fear there's no snow for Porto to go snowboarding.
I'm very much worried that we're going to loose JFM's will to live and most important (for the forum!) do a new SL build thread because of all that carp being posted.
I wonder if ChatGPT (google it if you don't know it, it's really scary!) is going to ascertain that indeed spray rails induce lift based on it's stupidity and the way algorithm works following trends and hits (it affects us all in academia how idiotic and ignorant students are going to use such tools...)
I also wonder why I have to endure all that. It's pretty obvious that Porto has no engineering background but he's good at selective googling which is awfully bad (and typical first grader's mistake) if you're "researching" something you're not familiar with... I'm trying to explain to my students that google alone is NOT your friend, you do have to do some reading to understand basic concepts and be able to judge what's been fed to you by stupid search engines that mainly replicate "facts" based on # of hits.
I'm pretty sure someone with ample time and also no life whatsoever could come up with a few quotes arguing the obvious (ie. the opposite to what Porto is claiming) it's not going to be me, I'd rather drink another bottle and doze off...
I'm not going to go any further as I fear it looks very much like an argument with my dear wife (of 30+ yrs): there's no way I'm going to win, she has to have the last word no matter what. I learnt to live with that as really life's too short and got a few more things to do before departing!

I wish you would let this thread rest (I know by posting I'm not helping much, but at least I hope I'm going to put a smile in someones face this Sat eve!)
cheers
V.

PS. I'll keep on reading (preferably after having a bottle of wine just like now) to help bring the numbers up as it seems to be important for some in here.
PPS. it's bleeding obvious that sprayrails or whatever you want to call them - below waterline - WONT introduce any lift provided you do understand a bit of physics, but it's not my job to explain - after all I'm a bloody architect and I don't have a degree in CFD to do nice sims to prove. You either do, or not get it - imho, you just have to live with it (and preferably spare us your thoughts but seems to be a bit too much to ask mid-winter).
PPPS. I hope I'm not going to get banned for this, was careful not to have any dodgy words in (although I'd be happy to be allowed to have a dozen or so in) ? if I have, dear moderator, it was the wine not me!

 

[Croftie]

I'm very much worried that we're going to loose JFM's will to live and most important (for the forum!) do a new SL build thread because of all that carp being posted.

+100%

 

[Portofino]

I've read the effing lot!

I think I've got some ideas why we have all this ludicrous thread. I also have some fears....

Porto has way too much time in his hands but unfortunately doesn't understand anything remotely related to engineering/forces/et al.
I fear there's no snow for Porto to go snowboarding.
I'm very much worried that we're going to loose JFM's will to live and most important (for the forum!) do a new SL build thread because of all that carp being posted.
I wonder if ChatGPT (google it if you don't know it, it's really scary!) is going to ascertain that indeed spray rails induce lift based on it's stupidity and the way algorithm works following trends and hits (it affects us all in academia how idiotic and ignorant students are going to use such tools...)
I also wonder why I have to endure all that. It's pretty obvious that Porto has no engineering background but he's good at selective googling which is awfully bad (and typical first grader's mistake) if you're "researching" something you're not familiar with... I'm trying to explain to my students that google alone is NOT your friend, you do have to do some reading to understand basic concepts and be able to judge what's been fed to you by stupid search engines that mainly replicate "facts" based on # of hits.
I'm pretty sure someone with ample time and also no life whatsoever could come up with a few quotes arguing the obvious (ie. the opposite to what Porto is claiming) it's not going to be me, I'd rather drink another bottle and doze off...
I'm not going to go any further as I fear it looks very much like an argument with my dear wife (of 30+ yrs): there's no way I'm going to win, she has to have the last word no matter what. I learnt to live with that as really life's too short and got a few more things to do before departing!

I wish you would let this thread rest (I know by posting I'm not helping much, but at least I hope I'm going to put a smile in someones face this Sat eve!)
cheers
V.

PS. I'll keep on reading (preferably after having a bottle of wine just like now) to help bring the numbers up as it seems to be important for some in here.
PPS. it's bleeding obvious that sprayrails or whatever you want to call them - below waterline - WONT introduce any lift provided you do understand a bit of physics, but it's not my job to explain - after all I'm a bloody architect and I don't have a degree in CFD to do nice sims to prove. You either do, or not get it - imho, you just have to live with it (and preferably spare us your thoughts but seems to be a bit too much to ask mid-winter).
PPPS. I hope I'm not going to get banned for this, was careful not to have any dodgy words in (although I'd be happy to be allowed to have a dozen or so in) ? if I have, dear moderator, it was the wine not me!

No shortage of snow Vas ,Thx for the consideration. Bit nippy ave temps from-11 rising to a balmy -5.5 today in the sun .


There’s no Googling now vas I am taking to the Naval architects .They are supplying the info either by PM or other .
Bit like me coming straight to you about architecture,I cut out the middle men way back .

wanna see more my friend ? In “ certain circumstances “ exactly what I have being saying ,


You see they use glass bottomed hulls .Glass as in window glass and can see “ continuous stagnation line from stem to stern “ My fag packet drawings the arrows and Lars book extracts for the physics ..It’s actually old hat even Ray Hunt , Dag pike, Reggie Fountain and every other builder in thunderbolt alley knew .There articles were not typos .

This stuff is first yr NA lab practice material .Its not difficult to understand universally accepted because the research points to it .

You won’t find evidence Google or otherwise of equal calibre contradicting this .
Deep down I am sure the nay say do ers get it .NOW ! The rest well every days a school day no shame in that .It’s a forum !

As far risk to JFM s aborting his new build thread over this ?We did agree to disagree on this .You can’t be serious?

Nobody as Billskip and others have constantly been reminding you all have put Fwds any explanation why in certain circumstances [ deep V , speed , pronounced strakes ] they don’t create lift under water .

Crikey Vas I have quoted Lars Larsons book .re the physics .Which I fully understand btw

As far as letting it die it’s needs to die from my side with a reasoned evidence based conclusion .

Are we there guys ?

 

[MapisM]

There’s no Googling now vas I am taking to the Naval architects.

Talk about being economical with the truth.
More explicitly, what you are actually doing is ask on another forum which you joined yesterday (literally, not metaphorically!), in the hope to pick some sentences supporting your train of thought.
And funnily enough, without even understanding if these sentences are actually proving you right or wrong, 'cause in this case it's mostly the latter.

Anyway, for those among us who didn't run out of popcorn yet, why instead of a cut and paste of some screenshots didn't you just post this link to the real thing?
Aside from being more transparent and straightforward, this makes it easier to read all the other contributions which you managed to fetch, some of which I actually found interesting.

Albeit NOT on the rails matter, mind!
By now, that isn't even a debate anymore, but just the obsessive flogging of a dead horse, both from your part and from those on the other side of the fence.
In fact, it's crystal clear that neither parts are going to change their views.
And frankly, it's all getting beyond boring, either.

I actually found more interesting what the contributor whose post you partially extracted had to say about the possible reasons behind your steering problems.
In fact, it seems to me that his comments on the protruding shaft bracket plates and the rudders cross-section shape make a lot of sense.
And I would think he knows his onions, because the details he spotted from your pics were somewhat subtle but important.

Nice find, I never came across that forum before.
Bottom line, thanks for the pointer to something interesting - at long last.

 

[Portofino]

Talk about being economical with the truth.
More explicitly, what you are actually doing is ask on another forum which you joined yesterday (literally, not metaphorically!), in the hope to pick some sentences supporting your train of thought.
And funnily enough, without even understanding if these sentences are actually proving you right or wrong, 'cause in this case it's mostly the latter.

Anyway, for those among us who didn't run out of popcorn yet, why instead of a cut and paste of some screenshots didn't you just post this link to the real thing?
Aside from being more transparent and straightforward, this makes it easier to read all the other contributions which you managed to fetch, some of which I actually found interesting.

Albeit NOT on the rails matter, mind!
By now, that isn't even a debate anymore, but just the obsessive flogging of a dead horse, both from your part and from those on the other side of the fence.
In fact, it's crystal clear that neither parts are going to change their views.
And frankly, it's all getting beyond boring, either.

I actually found more interesting what the contributor whose post you partially extracted had to say about the possible reasons behind your steering problems.
In fact, it seems to me that his comments on the protruding shaft bracket plates and the rudders cross-section shape make a lot of sense.
And I would think he knows his onions, because the details he spotted from your pics were somewhat subtle but important.

Nice find, I never came across that forum before.
Bottom line, thanks for the pointer to something interesting - at long last.

Glad you find it interesting, so do I .
Just one thing which part of in “ certain circumstances “ do you not understand?

lets leave it now guys .
Seems the academic ceiling with this way beyond this forum . I will keep further tech stuff away from here in the future .
MapishM hope to see you soon on the other forum .

 

[billskip]

Seems the academic ceiling with this way beyond this forum .

Bit out of order that....

 

[MapisM]

Just one thing which part of in “ certain circumstances “ do you not understand?

Mmm...

Me, in post #121, four days ago:
"The only noticeable exceptions I can think of based on direct observation [...] are high performance boats.
But when going real fast, possibly up to the 3-digits league, the dynamic lift is strong enough regardless of any trick, that the boat rides with dry chines along the whole length. [...]
So, I guess it makes sense to have rails along the whole boat length for spray deflection and stability, regardless of any additional lift."

This baeckmo chap on boatdesign forum, yesterday, in reply to yourself:
"For lighter and faster vessels it's different; they operate at speeds where the chines generally are above the waterline, with the consequence that there is a continuous stagnation line from stem to stern, ie diagonal spray is generated all over the length.
Here the rails have a major function both in reversing the spray and creating lift plus reducing drag.
In addition, they react on small changes in both heeling and trim by creating differential lift; resulting in increased dynamic transverse stability."

Now, what part of "I said essentially the same thing even before baeckmo wrote his reply to you" don't you understand?

Anyway, looking forward to reading more about how to improve Itamas by making them actually steerable.
Maybe you should open a thread on this topic also in this forum!

 

[jfm]

Glad you find it interesting, so do I .
Just one thing which part of in “ certain circumstances “ do you not understand?

lets leave it now guys .
Seems the academic ceiling with this way beyond this forum . I will keep further tech stuff away from here in the future .
MapishM hope to see you soon on the other forum .

This has become a weird study in human behaviour. Porto, no-one reads your long posts except you; people just scan them. We know what you're going to say, so there's no need to read it.

Then you register on another forum (yesterday) and write even longer and even more confusing posts on there, and post 1,000 dull pictures of the bottom of your boat. No-one there can see the wood for the trees in those long posts, but you get a few answers out of politeness, and as Mapism says just above you extract a few straws to cling onto, and paste them here, while ignoring the stuff disagrees with you. (By the way, your Friday afternoon P brackets were pointed out on this forum ages ago, long before you got beaten up for them on that other forum. Fix them with some p38, if you want your boat to steer).

You talk about "evidence based" conclusions! Selective google searching, turbocharged by confirmation bias and a complete absence of basic physics and engineering knowledge, isn't evidence based analysis. Vas' post 183 above makes excellent reading.

Interesting to note that you're building yourself an exit ramp: you've moved now to saying that submerged spray rails only create lift "in certain circumstances". Sure, there's always an exception to prove a rule. Are you saying that, bar the exceptions, they don't generally produce lift? (no need to answer).

The 2nd last line of your post quoted above is out of order but excusable because, coming from a guy who asks where the missing amps from his shorepower supply box have gone, then backtracks and says he meant volts and refers to "stepping down" from 400v to 230v (when there is nothing to step down), it is rather funny.

Not trying to have any last word - post away, flat-earthishly.

 

[Portofino]

This has become a weird study in human behaviour. Porto, no-one reads your long posts except you; people just scan them. We know what you're going to say, so there's no need to read it.

Then you register on another forum (yesterday) and write even longer and even more confusing posts on there, and post 1,000 dull pictures of the bottom of your boat. No-one there can see the wood for the trees in those long posts, but you get a few answers out of politeness, and as Mapism says just above you extract a few straws to cling onto, and paste them here, while ignoring the stuff disagrees with you. (By the way, your Friday afternoon P brackets were pointed out on this forum ages ago, long before you got beaten up for them on that other forum. Fix them with some p38, if you want your boat to steer).

You talk about "evidence based" conclusions! Selective google searching, turbocharged by confirmation bias and a complete absence of basic physics and engineering knowledge, isn't evidence based analysis. Vas' post 183 above makes excellent reading.

Interesting to note that you're building yourself an exit ramp: you've moved now to saying that submerged spray rails only create lift "in certain circumstances". Sure, there's always an exception to prove a rule. Are you saying that, bar the exceptions, they don't generally produce lift? (no need to answer).

The 2nd last line of your post quoted above is out of order but excusable because, coming from a guy who asks where the missing amps from his shorepower supply box have gone, then backtracks and says he meant volts and refers to "stepping down" from 400v to 230v (when there is nothing to step down), it is rather funny.

Not trying to have any last word - post away, flat-earthishly.

If you would have said something along the lines of ….
Hmmm depends ….
When water comes off the hull (after the stagnation point just to keep things clean) due to speed and the dead rise, the water comes off at an angle starting at the keel and moving outward and sternward. If the bottom was
completely smooth, the water would exit relatively parallel to the boat dead rise.

With strakes, the water is pushed downward at the strake, which creates lift.
So yes, lift strakes work when submerged, that is one purpose. The other purpose is that they help keep the boat from drifting/slipping in a turn.

But you didn’t did you .

So I had to draw it out .You have attempted to deflected the debate away from point “ a lot imho .This last post is getting too personal for reasons only known to you .But I have rhino skin so no worries .

@ MapishM
quote because you ask me a Q

[Me, in post #121, four days ago:
"The only noticeable exceptions I can think of based on direct observation [...] are high performance boats.
But when going real fast, possibly up to the 3-digits league, the dynamic lift is strong enough regardless of any trick, that the boat rides with dry chines along the whole length. [...]
So, I guess it makes sense to have rails along the whole boat length for spray deflection and stability, regardless of any additional lift."

This baeckmo chap on boatdesign forum, yesterday, in reply to yourself:
"For lighter and faster vessels it's different; they operate at speeds where the chines generally are above the waterline, with the consequence that there is a continuous stagnation line from stem to stern, ie diagonal spray is generated all over the length.

In addition, they react on small changes in both heeling and trim by creating differential lift; resulting in increased dynamic transverse stability."
Here the rails have a major function both in reversing the spray and creating lift plus reducing drag.
Now, what part of "I said essentially the same thing even before baeckmo wrote his reply to you" don't you understand?]

me — Its not the same you said 3 - digits speeds and dynamic lift , ……etc answering more why the rails extend full length for spray deflection .etc .

while Baeckmo said
Here the rails have a major function both in reversing the spray and creating lift plus reducing drag.

He nailed it . Underlining my emphasis ^

Ribs + tenders for example probably fall into that group ^ How ironic you are all blasting about on your toys benefiting from additional designed in lift from submerged strikes So don’t give me some rare beast argument, so rare not worth mentioning.
Plenty of speed boat members on here .

I mean there’s plenty of others on that forum ( not just Baeckmo) saying the same thing no obvious contradiction and I have been reading the spray rail strakes , lifting strip etc posts .

Does this answer the other Q too why call them lifting strips and put to bed JFM was wrong to suggest to call Dag pike , Ray hunt designs and any other references as typos .
It all depends on a particular set of circumstances. I have saying that all along no exit ramp building that’s untrue .

It ain’t never was a binary Yes / No .

Porto .

 

[Elessar]

+100%

Quite if the ?piles in on the build thread with the TX button stuck he will kill it and that will be a loss to the forum.

 

[rafiki_]

I’m wondering what all this kack about spray rails and chines have to do with some poor bloke asking if a Mangusta is a decent purchase for his specific purpose? I guess you might find his neck in a noose?

 

[MapisM]

@ MapishM
quote because you ask me a Q...

I can't honestly remember to have ever asked you anything, unless while replying to something you posted.
Regardless, I'll tell you what: if I did, just forget EVERYTHING I asked, or also just said.
Frankly, I couldn't care less about what you or anyone else have to say about this subject anymore.

Now, I guess you will suspect I'm saying the following just to distract from the main topic you turned this thread into, i.e. hull rails.
Which as I said, imho isn't even a topic anymore, but rather just a pathetic beating of a long dead horse.
But you can trust me if I tell you that I'm now waaaay more interested in the debate on why a boatbuilder with an overall decent reputation managed to build a boat that is uncontrollable at speed.
To the point of being borderline dangerous, whenever a sudden deviation should be required to avoid an obstacle.

But mind, my own interest is just out of idle curiosity, of course.
In your boots, THIS problem and the possible ways to fix it (if any) would be right at the top of my priorities list, as opposed to the by now ridiculous squabble over rails.
Also because by definition it's pointless to waste further time in a debate which is:
a) totally irrelevant and useless, since nobody in his right mind would chose a boat based on the hull strakes - let alone modify them on their own boats based on something someone said on the internet.
b) "way beyond this forum academic ceiling", in your own words.

Then again, I'm not holding my breath...

 

[MapisM]

By the way, your Friday afternoon P brackets were pointed out on this forum ages ago, long before you got beaten up for them on that other forum.

Really? Either I missed that debate, or (more likely... ) your memory is better than mine!

 

[jfm]

Was ages ago and not a debate. I just mentioned it on seeing a photo but didn’t make a meal of it. Had I known what we now know about the rudders not working above 25knots, we would probably have usefully discussed it some more. Given the rudder problem Porto perhaps agrees that they need fairing and will do it. Easy job.

 

[MapisM]

Yup, of course rebuilding new brackets and mount them recessed and flush with the bottom surface would be a nightmare job now, so a good fairing is the only sensible option.
BTW, a pic of an Itama 54 that Porto posted in boatdesign forum shows the very same crude attachment of P brackets, so if nothing else it seems it isn't a specific problem of a friday afternoon job.
Rather a lack of knowledge (and/or an underestimation) from the builder, which I find weird because Amati reputation for attention to detail was remarkable.
Also the fact that those boats were initially designed in the 80s is only a partial excuse, because I've seen even older boats with properly flush mounted brackets, so it's not like nobody cared, back then...

Anyway, yes, I would also try the fairing route first.
But as recommended by the chap on boatdesign forum, with a very long and smooth chamfer both in front and behind the plate, and rounding all around.
In Porto's boots, I would also ask that guy what he had in mind when he mentioned possible other measures for reducing the rudders ventilation.
His comment on the rudder cross-section shape "unsuitable for high speed where ventilation may occur" and potentially leading to force reversal also deserves a better understanding, imho.
Also because - in sharp contrast with all the pages wasted so far on a useless squabble over spray rails - this is a practical problem well worth addressing, that would drive me nuts if the boat were mine!

 

[Portofino]

Yup, of course rebuilding new brackets and mount them recessed and flush with the bottom surface would be a nightmare job now, so a good fairing is the only sensible option.
BTW, a pic of an Itama 54 that Porto posted in boatdesign forum shows the very same crude attachment of P brackets, so if nothing else it seems it isn't a specific problem of a friday afternoon job.
Rather a lack of knowledge (and/or an underestimation) from the builder, which I find weird because Amati reputation for attention to detail was remarkable.
Also the fact that those boats were initially designed in the 80s is only a partial excuse, because I've seen even older boats with properly flush mounted brackets, so it's not like nobody cared, back then...

Anyway, yes, I would also try the fairing route first.
But as recommended by the chap on boatdesign forum, with a very long and smooth chamfer both in front and behind the plate, and rounding all around.
In Porto's boots, I would also ask that guy what he had in mind when he mentioned possible other measures for reducing the rudders ventilation.
His comment on the rudder cross-section shape "unsuitable for high speed where ventilation may occur" and potentially leading to force reversal also deserves a better understanding, imho.
Also because - in sharp contrast with all the pages wasted so far on a useless squabble over spray rails - this is a practical problem well worth addressing, that would drive me nuts if the boat were mine!

Happy to do this rudder P bkt thing .
JFM right on this point post #196 btw .
You need to ride in the boat really to see what I mean .It’s not dangerous a million miles away and certainly no “reversal “or anything sinister .Nobody in the itama world , owner group etc that I know has filled / added P38; faired those P bracket edges in .
Well the ones with hanging rudders .
Remember the sum of all parts or in other words the ingredients of Goldilocks pudding .Ps don’t take dates in isolation and exaggerate the neg -ve s . = bad dates will kill you .
Or another analogy 2+kids sat on a see saw ……if one’s up it means the other is down .It’s impossible for both to be up to the top simultaneously with a straight beam .Sure they can balanced but the measurements ,are not the maximum values or indeed the lowest values ( using hight) that’s potentially achievable. Crucially if you were to add hight to one side you have to take it off the other .That’s my point .

But you are right he ( Amarti ) knew his onions obsessed with detail etc etc .

Another thing to compute in my mind worth tossing in early is it ain’t difficult to alter the mould is it ? Add a recess in the hull .
A lot of post popping out of the mould glassing work has been done any how , bow thruster,ER air vents , the huge deck scuppers , possibly the shaft exits etc etc .Or while phaffing on glassing finishing touches indeed fair it in .
They were expensive boats semi custom back in the day so it not a cost cutting thing either .
Just to give you a flavour of the behind the scenes obsession , the electrics panel switches contacts are silver plated alloy which don’t corrode or are better in a marine environment.Not of this is visible .So an easy cheapo / cost cutter of dropping in std marine switches was never utilised.
MapishM point ….obsession .

Remember the accommodation by to days stds is compromised in the sense cutting it in two by sticking with the mid mount motors .He never went V drives CoG was more important.

Just to get some perspective he was the first to use under water exhaust on leisure boats ( come to this later )

So I would say erring on the side of deliberate more so because the “ fix “ is a doddle both technically and financially.
In other words no reason why NOT recess that bracket if he wanted ……if that makes sense? ?



Also i am thinking in terms of a scale or spectrum with this( rudder thing ) exactly like i did with lifting strikes ,Certainly not binary .Happy to work it through warts n all .

 

[Aardee]

Can we have a moment's prayer, thought and reflection for the poor sod who came on here simply asking for a bit of feedback on a boat he was looking at...

 

[vas]

Porto,

shaping a piece of 18mm marine ply to a wedge and epoxying it on to the hull (after removing all a/f) would be a v.easy diy job for a day. Make it 40cm long inverse U shaped so that it picks and smooths the sides of the p-bracket mount as well and job done. Obvs add a trailing fairing bit as well or bring it out to the stern as a chine/lifting rail
[that is if I got JFMs and MapisM point right and you are indeed talking about smoothing the p-bracket mount to the hull. Did that on mine, but I think PO when repowering messed with shaft angles and had to move the bracket "down" so to speak.]

V.

PS. obvs not much to do with OP quest, but that's long gone now, I think we all agree that it's the wrong boat for the task ?