How about to extend the length of my 400T

My wife and I brought a new MS to Sweden in 2005 and we are happy with its performance in this part of the world.
Now I have an idea, that may sound weird, and it’s to extend the hull of my 400T, during the winter when we keeps our boats indoors. I did see a 400T 2008 for sale in Australia with an extension of the hull like 2-3 feet under the swim platform.
Does anyone know if it’s standard or special made?
If it’s standard, do you guys knows or have an idea were to find information about the purpose, the outcome like performance etc and maybe where to find some drawings? (also have needs for the standard drawings of the hull).
What are your opinions to put a smaller engine with a S-drive as a "limp home system" in this extension?
Would appreciate a lot any comments on this theme
boan400

Wow, I saw your similar post over on the Mainship Yahoo forum and decided to stay out of it for now and see where it went. But here is a little easier to post and follow the responses, so here goes:

Are you sure that you are talking about the Mainship 400? The 390 came with an integral swim platform that extended the waterline length. Lots of problems with leakage and Mainship probably wishes they never had done it that way.

But I don't think that the factory installed one on the 400T. You might browse Steve Cyr's excellent website dedicated to his 400T at Steven Cyr's Stella Blue Site. It gives lots of ideas for upgrades but not adding a waterline extending swim platform.

If you were to add one like the 390 has then you might screw up the balance and could certainly affect the rudder response. You would be adding several feet of displacement behind the rudder pivot point, so it can't help but act differently.

And you are also thinking of adding a get home drive there!! Buy a Nordhavn if you want a get home engine.

David

I've sent you a email

Hi robertgerle
It's 2 year since You encourage me to go on with my project. I'ts more or less finshed at the time being. I will thank you for that.
If you are interested there are articles in the Swedish magasin Praktiskt Batagande describing the project. It went out very well.
Boan

Pictures or it didn't happen...

View attachment 59411
View attachment 59412

Hi Clynn
I did it.
Boan

Greetings,
Mr. b. Very nicely and neatly done. Do the new twin rudders work in conjunction with the existing rudder?

Thank you. Normally in conjuction with the existing rudder. But also autonomously if needed.

Okay, that's pretty cool. Nice work.

Me no comprehend... Not fully anyway. Am I missing something here?

Single screw boat with added (in-line) single screw engine and pod/prop in/on/under newly expanded swim step???

Nice looking job. But why?? With two more rudders no less...

Is this so boat gets better nmpg? If so... how much better nmpg is outcome??

And, in correlation: Total financial amount and time cost for all the added paraphernalia... in regards to dollar savings reducing fuel use??

Greetings,
Mr. A. If you read the OP's original post, it is for a "get home" system. I suspect fuel savings don't enter into the equation.

RT Firefly said:

Greetings,
Mr. A. If you read the OP's original post, it is for a "get home" system. I suspect fuel savings don't enter into the equation.

Click to expand...

OK, RT... But, But???

I understand it is a get home so not intended to run except in emergency. What is the impact on the drag? Propellor does not look to be foldable?

Boan,

Nicely done sir! Have you had an opportunity to test the get back engine? Did the installation of the extension make any noticeable effect on the handling or performance? Lastly are you happy with the results?

Regards,
Bob

I hope that the propeller is either folding or feathering otherwise there will be a possible big problem with heat build up if prop turns all the time. Based on the nice work done I would guess it does fold or feather.

For your interest I would try to tell about my experiment with M/Y Maya.

The extension (X-drive) is now completed with assistance of a wellknowned designer.
The main reason for an additional engine is the speed limits on the European canals, max 10 or even 6 km/h (5,4 or 3,2knots). It´s not acceptable with hundred of hours on idling for the 6LYA-STP.
The bottom lines of the hull is extended about 3 feet and top of the swim platform about 4,5 feet. The powerline is a VP D2-40 with saildrive and Autostream feathering prop, the speed is 1-6+ knots.

The advantages are several as, safety redundancy for propulsion and steering, the floating level has approved in many ways, the steering is very good, especially in low speed and very much in reverse, with an extra controlled generator it replace my genset, the noise from that engine is almost zero (the only noise is from the control cables, motor and gearbox, its on my list). It´s fantastic to run a quiet boat!

The maximum speed has not been effected, it’s still +14 knots. I´m not missing the trimtabs.
Maya act well on raff sea, as we have here in Scandinavia, also in following sea with her dubble rudder and the S-drive (xtra pivot center) in the very end of the hull. Its easy to reach the prop from the swimladder to adjust the the pitch or just clean the prop.
I'm happy to tell that 96 holes has been closed in the aft of the hull, non facing the water left.
The X-drive is secured bolted to the hull and guite possible to replace back to the original swimplattform, but I wont.
Your question about the fuel consumption is less than half, in low speed. We pay about $8/gallon.
I dont expext this is a good investment but it was a piece of mind when I got retired. I'm very happy with her performance and we are looking forward to spend some time in the canals of Europe.
/boan

See clip on Youtube. ----------

Sent from my iPad

Boan400 - Regarding your post #18: Thank you for clearing up my mind. I now completely understand and give my thumbs up to your choice. Enjoy retirement!

Your Boat Buddy - Art

Boan,

Thank you for your reply! The armchair critics have been proven wrong!

Cheers,

Bob

Boan400, excellent modification for your intended use of the vessel.

Thank you all, I appreciate the "new" M/Y Maya a lot.

Where does that engine get its intake air?

Capt. Bill11
From the main air intake. There are some connections/conduits for cables, hoses and air vent. into the boathull.

Excellent job boan,
Not many have the confidence to comprehend a project like this much less have the many attributes to pull it off. I'm in your camp but I mostly just modify anchors.
One downside to mods comes when you sell it. The same guys that would poo poo at concept time would probably not buy it. You may want to save this thread to show to prospective buyers. Not that that will come very soon. I see many years of boating better because of your abilities and courage.
I once designed and built a boat on my own many years ago and it turned out very well. Wish I had it back now. What's your next project?

boan400 said:

Capt. Bill11
From the main air intake. There are some connections/conduits for cables, hoses and air vent. into the boathull.

Click to expand...

Marlow tried something like that but it was my understanding the engine manufacturer wasn't happy with the restriction of air flow to the engine and perhaps the heat build up in such a small space.

Did you run any of that by your engines manufacturer?

Are you saying your engine gets its air via the conduits and and sir vent?

If so does the vent connect directly to outside air? Is it large enough enough to provide the correct cfm to the engine all by itself?

Willy, thanks for your thoughts and questions. I will try to give you my thoughts and some answers.

The engine installation including the air vent is approved by the manufacturer. Volvo Penta is from my hometown Gothenburg and has the headoffice and I never miss a chance to consult them. There is enough air to feed the engine when its running.

But I have to solve a related problem. During the wet seson, normally in the fall, its difficult to get rid of the moisture in the small engineroom/compartment when the engine is not running. It's temporarily solved with a small 12V fan.
To avoid power consumtion in the future, I'm installing an air duct from the bottom of the engineroom up to the rail on top of the transom, in the space between the hull and the innerline to a new air intake in order to get the engineroom ventilated when the boat is at the pir.

Some hobbies are more costly than others. It has been a privilige to do it myself, with good assistance from a well known designer and skilled craftmen. I have received a lot of good advice along the road from people that has been interested in the project.

I understand your feelings for your old boat. I agree it's special to do it by yourself.

I don't expect my money back when I sell it, that is not the reason I did this.
But you see in this part of the world there are not many boats like mine to compare to. So, why not buy a boat with these kind of features. It's unique.
Over the years I have done some enhancements. But now my focus has to be to finish this project during the winter when my boat is indoors.

First of all the autonomous steering, dual control cables and instruments to the both helms has to be done properly.
Then I will put big drains in the end of the gangway? (skarndeck in Swedish) along both sides of the boat, to stop rainwater from getting into the aft cockpit. It should have been done by the factory. The aft cockpit is a nice extra room when it's covered by canvas and a tight hatch to fly.

About next projects:
Redo the hatch to flybridge, reorganize and add more batteries, additional heater with defroster, solarpanels in suitable spots and some interior work for long trips, change sanitary hoses etc.

You are talking about modifying anchores. I have done some modifications as well. My present anchore is a Delta 40kg/90lbs with 30 feet chain and 100 feet rope. With a 16kg anchoreboy on the anchore line when needed I'm safe in bad weather and strong winds.

Capt. Bill11
Forgot to mention your name but the answers about the air vent questions was ment for you. Sorry!

Nicely done-you sure your not a Cajun?

This is very nice, but I have to agree.... I'd throw a folding prop on that 'saildrive'.