I/O (Sterndrive) Conversion to Outboards

[Lou C]

Wow Ted that's amazing.
OK got a new business idea for you....
If you are ever on the Hull Truth, there are always a few threads on inboard or I/O conversion to outboards, and this stability issue is rarely mentioned, I bet you could do engineering consults to determine if the conversion will result in safe/stable seakeeping traits....provided that the owners, are looking for that information....
And looking at catalogs for modern sport boats, so many that now come with both I/O or O/B appear to use the same hull you wonder if the OEMs even went that far with it?
Saw this with Chapparal and Four Winns, several appear to use the same hull.

 

[Pmt133]

schmutzdecke is one of those words you don't think is real but is used industry wide lol

 

[Scott Danforth]

Ted, when you put all the extra beer in the bilge, the CG will be lower

 

[Lou C]

Ted, when you put all the extra beer in the bilge, the CG will be lower

only if it's the full carbohydrate versions not the low carb beer lol

 

[Lou C]

schmutzdecke is one of those words you don't think is real but is used industry wide lol

looked that up, sounds like bilge water lol.

 

[tpenfield]

Ted, when you put all the extra beer in the bilge, the CG will be lower

However, at the end of the day the CG would be back to the higher point.

 

[tpenfield]

Wow Ted that's amazing.
OK got a new business idea for you....
If you are ever on the Hull Truth, there are always a few threads on inboard or I/O conversion to outboards, and this stability issue is rarely mentioned, I bet you could do engineering consults to determine if the conversion will result in safe/stable seakeeping traits....provided that the owners, are looking for that information....
And looking at catalogs for modern sport boats, so many that now come with both I/O or O/B appear to use the same hull you wonder if the OEMs even went that far with it?
Saw this with Chapparal and Four Winns, several appear to use the same hull.

I get over to THT once in a while. There are a few conversion threads over there. Not sure I'd want to do any marine consulting . . . kind of late in life to become a Naval Architect.

It is true (as far as I can tell) that the OB versions of the typical sterndrive boats use the same/similar hull. Although, I have noticed that the OB version are a bit heavier than the Sterndrive models. There is some additional weight in the transom supports, and perhaps they also add some weight down low.

 

[redneck joe]

looked that up, sounds like bilge water lol.

You mean coors light...

 

[redneck joe]

I get over to THT once in a while. There are a few conversion threads over there. Not sure I'd want to do any marine consulting . . . kind of late in life to become a Naval Architect.

It is true (as far as I can tell) that the OB versions of the typical sterndrive boats use the same/similar hull. Although, I have noticed that the OB version are a bit heavier than the Sterndrive models. There is some additional weight in the transom supports, and perhaps they also add some weight down low.

What is percentage of weight differential?

 

[tpenfield]

What is percentage of weight differential?

a wee bit of a percentage . . .

5% ish . . .

 

[redneck joe]

a wee bit

Dam you...

 

[tpenfield]

For those following along, here is the calculation for change in CG . . . I previously did a similar calculation for the fore/aft movement of CG.

12in x 1400lbs + 19in x 2250lbs - 12in x 400lbs = 54750 in-lbs

= ? in x (11000-2250+1400+400) lbs

54750 in-lbs/10550 lbs = ?

? = 5.2 inches​

 

[flashback]

However, at the end of the day the CG would be back to the higher point.

Keep in mind CG also represents coast guard, they would not see your method of CG alterations favorable.

 

[Scott Danforth]

However, at the end of the day the CG would be back to the higher point.

Depends where the blackwater tank is

 

[tpenfield]

Depends where the blackwater tank is

Depends on the crew that we have aboard. Often the water temperature rises a couple of degrees by the time we leave.

 

[harringtondav]

Very technical . . . Here is what I Googled . . .

"A wee bit" means a very small amount, degree, or quantity, using the Scottish word "wee" (meaning small or little) with "bit". It's an informal phrase used to say "a little bit,"

That extra 44+" of planing hull has been in the back of my mind. I'm thinking a good outcome. Hopefully a lower planing speed and maybe being able to abandon the trim tabs.

 

[tpenfield]

That extra 44+" of planing hull has been in the back of my mind. I'm thinking a good outcome. Hopefully a lower planing speed and maybe being able to abandon the trim tabs.

I will keep the trim tabs, even though I don't use them much. Speaking of which, I unfastened the trim tabs the other day, just to gain some clearance. There was a stainless steel plate between the trim tab's mounting plate and the transom. It was stuck on with what appeared to be 5200. I had to get a sharp chisel to cut into the adhesive to get the plate off (destroying the plate in the process).

 

[Scott Danforth]

I will keep the trim tabs, even though I don't use them much. Speaking of which, I unfastened the trim tabs the other day, just to gain some clearance. There was a stainless steel plate between the trim tab's mounting plate and the transom. It was stuck on with what appeared to be 5200. I had to get a sharp chisel to cut into the adhesive to get the plate off (destroying the plate in the process).

Easy to have another laser cut.

It's just 16 gauge stainless