Build log - 10m tour boat

A few years back I have bought two life boat hulls and planned ever since to make one into a tour boat. I have started to strip the hull of the unnecessary parts a while ago but had no time to start the actual building.

Now after a couple of years I have the time to start building it so I thought it would be interesting to share it with you. If you have any suggestions you are welcome.

The purpose of this boat is to transport people in the Danube Delta Biosphere Reserve so it has to be robust, economical and practical. The good looks are not a must.

Some details about the boat:
Lenghth 9m (10m modified)
Beam 3m
Draft 1m

Engine - MAN keel cooled 100hp with PRM500 gear box.
Propeller - 21x17R

Boat is constructed from glass fibre.

Here are the first steps we took:

 

I had a 30 ft steel lifeboat hull (9.1 Meters), decades ago. Some quick calculations will show that your hull will have a maximum speed of about 6.3 knots, or 12 kM/hr. Driving this hull at a higher speed will not be acceptable.

At 10 tonnes total displacement, 10 horsepower is about all the power needed to make maximum practical speed. Allowing for wind and waves and electric cooking on the boat, a 20 horsepower (15 kW) engine is more than adequate. Recommended propeller is 16 x 10, at 1000 RPM (405mm diameter x 250mm pitch). Your 21 x 17 propeller is better, if you have room for it, and the 21 x 17 should be driven at about 600-700 RPM.

Just some preliminary numbers, but close to truth. Best wishes with your project, a fine hull form in my opinion.

Just after WWII these type lifeboats were available for very low cost in the USA, and many people tried to get performance by putting 100 horsepower automobile engines in them. This never worked, as these hulls simply cannot perform above the numbers listed above.

 

Hi fredrosse,

Thank you for the calculations. As a matter of fact I have done the same calculations and came up with the same results. At the moment I have two similar boats. They are in operation for about 20 years and many thousands of hours, that is why I opted for this hull. They have 45 hp diesels on them and I am happy with them. I realise this engine is a bit of overkill for the boat but I have it and I think it will be a good runner.

In order to improve the hull speed I will build an extension at the stern that will cover the propeller and that will help avoiding the ventilation and also help with the stern dipping while adding stability.

The extra power comes handy also when the boat gets grounded... and that happens often. Having the ability to reverse in such conditions is priceless... . Also jumping logs needs more power but maybe most of the time chopping weed is where power is needed.

Coming back to the progress ...

We have pulled the boat in the yard and lifted it up on the supports. We have removed the keel and rudder support as it was too bulky.

The sides of the boat where polished and the holes prepared for the fibre glass repair.
The inside has been stripped even more for the engine bed installation.

 

I see the pictures are up side down... Iphone issue I guess.

Anyway, today we have made some progress and finished the polishing also we managed to make the keel profile and fit it in with some concrete as filler.

The holes have been patched and wait to be polished. Next step is painting and lowering of the hull for the work inside it.

I have also reconditioned the engine mounts I have bought from eBay two years ago. The owner replaced them because they started to rust... so I got them for 50 EUR shipped. Looking nice after the polishing. The corrosion was only superficial and the rubber seems to be in great condition.

 

There are a few other lifeboat conversion threads on the forum that might be of interest to you if you haven't seen them already...

http://www.boatdesign.net/forums/bo...orsailer-conversion-build-progress-36702.html

http://www.boatdesign.net/forums/profile/scunthorp.html

http://www.boatdesign.net/forums/sa...boat-sailboat-conversion-freeboard-33778.html

http://www.lifeboatcompany.nl/nl/lifeboatcompany.aspx

 

Hi SamSam,

Yes I have seen some of the posts. Interesting stuff. My plan is to build a more "industrial" boat where simplicity is key. See the pictures attached with the boats I already have and operate for the past 25 years.

The things I want to improve for the new boat:

1. Cooling system - will make it keel cooled
2. Dry exhaust system - tired of broken impellers and clogged water filters
3. An angled deck for a better view of the people in the back.
4. A stern plate "gozzo boat stile" to keep the boat from pulling the stern down while at speed.
5. Flexible mounts and a Aquadrive style flexible coupling.

I would like to incorporate the keel cooling in the "gozzo plate" but I have not seen until now this implemented anywhere. Do you have any idea about this? I plan to build this extension out of steel and bolt it on to the fibreglass hull.

 

Any experience with Schilling rudders? I would like to build one for this boat and would like to know if it is worth it or not.

Can anyone please check if my calculations are correct for the size of the rudder?

Boat length 9m, beam 3m, draft 1.1m.

Thanks,

Daniel

 

Rudder angle

Hi there,

Anyone here can help me with schematics on how to make a hydraulic steering turn my rudder close to 180 degrees? Until now I have used only cable operated steering so I have no idea what the force of a steering ram is and the effect it will have if I shorten the tiller arm.

Thanks.

 

I've been busy lately as my family got a bit bigger, my daughter was born on the 1st of December. The boat project advances slowly but surely. We managed to move the boat in an enclosed space and that took a lot of effort but in the end we managed.

The engine bed is now ready together with the prop shaft and stern tunnel. We also prepared the aft part with a temporary hole just to give us the idea how all will look like. We had to clear part of the stern in order to obtain the necessary clearance for the prop. By the calculations it needs to be 20cm away from the hull and as you can see the prop is biggggg.... The engine bed is now sturdy and ready to receive the engine.

On Monday we will fit the tunnel and make the bed for the thrust bearing. The engine mounts have to be fitted but we have a problem with them as the adjusting screws are fixed with thread lock...

Is there anyone that can clarify how a 3 deg of deflection on the prop works? In order to make the boat counter the prop walk you can deflect the tunnel 3 deg left or right but I am sure it has also to do with the direction of rotation. Any experience on that?

 

Did some more work recently on the boat. It is coming along nicely.

First of we have finished the engine bed and the engine room has been painted plus the separation wall was put in place and fiberglassed. It looks good and as I am planing to keel cool the engine I had to come up with a solution for the dry stack. I have found this VW Touareg muffler on internet for 50 Euros and I think it is going to fit nicely under the deck extension. The nice thing about this muffler is that it is build out of stainless steel an will last a long time plus it is engineered to be quiet and has a pipe of 70mm in diameter.

The work on the hull extension has started and the metal part was put in place with a bit of effort but it came out great at the end. I hope this will help the boat to travel faster and make it more stable as the deck will be higher than most boats.

Also in the same time we have finished the rudder bushings and the skeg (sand shoe). It is a challenging task to find the centres and distances when you have to work without a detailed plan but it came out fine.

As I'm looking for great manoeuvrability I have designed a Schilling rudder (fish-tail rudder) using some formulas I have found on the internet and I hope this will be working fine. Now I am not sure about one thing - as I have put the shaft off centre a couple degrees will this be messing with my rudder as this is a compensated one? Will it tend to push the rudder on the side? I hope not but we will see about that.

You can see a couple of pictures with the rudder being build and I hope to finish it on Monday.

The next step is to fit the rudder and also to make the skin tank for the keel cooling. This will be positioned under the boat extension and hopefully will work as it should.

 

The final product

I've been busy lately and had no time to post but the new boat is ready for prime time. I have to say that it's much better than I expected and the aft extension works flawlessly. The boat reached 20 km/h and the work payed off.

The 100hp engine is a bit stressed as the prop is too large and needs to be modified but It will be fixed.

The stability added by the rear extension is great and makes the boat rock solid.

 

A short video with the boat in action and a picture...

 

More upside down pictures..).... This website needs a refresh to be compatible with mobile phones...

 

Hi yodani, you may have to use one of the Microsoft programmes or any photoshop or photo correction programmes , I used word and then with 3D rotate it so I could see how it looked like. I was not able to download it to your thread, as I did not have permission to do so. I clicked on format and changed it in the 3D table Only after you have rotated it, then download it to your thread. It is not the problem from this website. You may hold your Iphone differently. I had it also often when using my phone 180 degrees in the wrong??? way.

Nice project. Bert

 

I thought you were just posting them so our Aussie friends could see them right.