any benefit to having new swim platform extend hull?

Hi Folks,
Many of you have helped me when i first built my aluminum 25" Glen-L design Double Eagle powerboat a few years ago. I have used the boat for the last 3 summers despite not being finished, and continue to work on it when time permits.
I would like to build a swim platform that goes across most of the stern, except the far corner where my kicker lowers.
I am considering just building a pipe or solid platform at desired level (just above resting waterline) with bracing underneath for strength.

But, I have a lip or approx 4" hull extension now so I could extend this at hull depth for the required size of the platform, and then add bracing / stringers above and top off with pipework or flat panels.

So, my question - is there any real improvement in speed/ efficiency, etc from having the hull extended approx 1.5 - 2 ft on a 25 ft hull (powered by a 150hp inboard cummins diesel, 1:1 gear. top speed around 20-23 kts and cruising speed about 16- 18 kts.)
Hull moves well (I think) from displacement speeds to semi-displacement to planing.
attached is old pic of stern.

 

With the tucked under IB propeller, none really. Maybe a little, but a wash with the skin friction. Too many variables to say with one picture.

 

Doubtfully, as jehardiman said.

Is there any other benefit to you to have it?

You could make a buoyancy pod out of it.

Drawings?

 

View attachment 146667 Thanks for the replies!
I guess i could use it for bouyancy (had not thought of that). Other than that, no - i don't see any other benefit myself, if there wouldn't be some performance gain. Re: bouyancy though, I struggled alot in the last couple of years with the decision to add foam (or a combination of foam and plastic bottles, etc) and finally decided not to add either.
I think the chance of hull breach / holing is very low, and we are not typically too far from shore, and normally tow a zodiak. The way the hull frames and stringers are planned out and built also does not allow me to easily weld airtight cavities, due to weep holes, frames not weld directly to the hull, etc.
Here are a few more pics from construction and in the water.

 

Re buoyancy, do you have any existing transverse watertight bulkheads in the boat, or is she effectively 'open' from bow to stern?
Perhaps just the bulkhead of the rope locker in the bow, or not even this one?

She has got a very nice hull form, and she should have good seakeeping.

If you don't actually 'need' extra buoyancy at the aft end, and you have enough existing buoyancy to support the extra weight of a platform above the waterline, then doing this might be the easiest solution?

 

Is the designer available to discuss such a modification with?
This could be of considerable value.

 

Put your money towards finishing out the boat as designed before launching into modifications.
You really won’t know how it will eventually perform until then.
Looks like there is plenty of flattish planing surface already, so not likely that additional surface will have much effect.

 

It is an older design and no the Designer is no longer available.
re: bulkheads - I do not currently have any watertight bulkheads or compartments. I do have some areas, in the bow for example where I could make a watertight compartment but it then would not be of as much use for anchor and rod storage, etc. Until I eventually decide on cabin arrangements, I do not want to make too many changes in spots which could then change purpose.

The design can be built with a cabin or Center Console. I may eventually do a small cabin, or more accurately a solid aluminum cabin roof supported by minimal (but still adequate..) sides and posts, windshield(s) and likely a lot of removable Lexan or similar panels to block some wind and weather on the sides when needed, but to be removed and stored when not needed.

It looks like consensus is not to bother extend the hull. I will (if time permits) build a small swim platform, likely with an outer pipe bent to shape and then filled in with pipe rails or topped with a solid plate and some non-skid. I don't think the small weight of that will throw anything off..

Attached is a pic of the same design,. albeit stretched to 28', with a similar swim platform. It is raised in the middle, due to his home-made surface drive, which would not be required on mine.

 

Decided to do a simple swim platform about 6" above waterline. Will be well out of water when planing and even when getting on plane as the boat does not go bow-up when getting on plane. Did not have time to used sanding disks/grind or wire wheel today..

 

Nice.

Weld done!

 

thanks for the encouragement! Not a pro job, but as an amateur, first time builder, I am happy with it..

 

A couple pics of the new aluminum floors. I cut out a roll of vinyl garage flooring with checketplate pattern to put down on the bare aluminum, as it is slippery.. note. I would have used checkerplate but that meant buying new sheets where this was leftover from the hull build..