hull modification!

[Field Tester]

OK builders, what are your thoughts on this?? In researching my repower, an issue that comes up continously is prop size. Currently, Im spinning a 21" wheel. I can cut out my shaft log and lower it to gain another inch, maybe 2. I'm trying to keep the engine as low as possible. The rear of the engine is already as low as it can go, so if I lower the shaft log where is exits the hull, it will give me a sharper angle, raising the front of the engine to keep everything in line. Here is my thought.... what if I cut the bottom of the hull to give me a bigger pocket for the prop? I have plenty of access inside to build up and add strength from where I'm taking away on the outside. Is this a crazy thought??? or is it possible?? Would I affect the performance or intergrity of the hull? Like I said, I can add strength from the inside by adding layers of glass. What do you think??

From this....

to this....

 

[Del]

I am anxious to see what the builders come back with because it seems like a more reasonable solution than to re-angle the shaft log (but then, the guys here routinely do the impossible). If you do this job, it would be a breeze to add-in one of those air-injection tricks to quiet the prop wash hammer as mentioned in a recent thread.

 

[El Mar]

How a bout a tunnel?

From the reduced draft thread.

 

[Field Tester]

That's what gave me the idea! I don't need to go that extreme, but something like that. My hull is not flat in the stern. It has like a little V to it. So, what I'd be doing is making it almost flat. I'll run out and take a pic.

 

[Field Tester]

So, the V gets deeper closer to the prop. What I would do is sort of flatten that V.

 

[captainlarry84]

East fix

Same bottom with a 23” wheel. As I mentioned earlier just extend your wet tube. In addition I cut 1” of glass off the bottom at the peak. Velvet smooth and plenty of wheel. You do not need to lower the tube just make it longer.

 

[plowin]

Larry what is your tip clearance in those pics? Is the pic deceiving or is it that small?

 

[captainlarry84]

wet tubes

At the very perk of the JC hull it is close, about 1.5 then it fans out. With the #4 cup on the wheel the low clearance for that short peck distance has never posed a problem. The wheel is very smooth. You can tell when you are pushing the envelope with clearance if you get tip burn on the wheel or the bottom paint is blasted off due to cavitation. Pushing back the wet tube was a great idea. In a redo I would have extended it even a little more.

On the field tester he could push the wheel back by three inches. The cutlass bearing gets push out 3. Next you add 3 wet tube then glass it together. The cost is minimal except for the cost of a longer shaft. I have done this on more that one boat.

 

[Eastporter]

Capt. Larry,
Nice job on the modification. Is that a fiberglass shaft you made (photo with tube in your hand)? Did you make a mold?

 

[captainlarry84]

Tubing

Spartan Marine sell the tubing. Any length you need. You can only go 3" out however. This way the cutlass bearing is 1/2 in the original tube and 1/2 in the extension. Next four set screws 2 in the original tube and 2 in the extension. After 3" the wheel also gets to close to the rudder. With the extension you can next fair the keel and increase water flow. it is cheap and works great. Plus if glassed correctly very stronge and a lot less work that a complete new tube. http://www.spartanmarine.com/catalog .html

 

[Eastporter]

Thank you for the information and photos. I'm sure sharing your experience is helping others.

 

[Field Tester]

Larry,

How close would you go to the rudder?

 

[captainlarry84]

Room As long as you have enough room to pull the wheel and swing a hammer for the knock off you are good. The max you can extend on you boat with a 6 long Cutlass bearing is 3. You will pick up some room plus you can shave some glass off the bottom.

 

[Powderpro]

That's why I like this website; a guy has a question, and another guy has the common sense answer, with pictures.

Here is a 4.5" deep tunnel on a hull that is almost completely flat in the stern. This design, although probably foreign to the Downeast crowd, works tremendously well. I would love to put a tunnel like this on a DE boat. Shaft angle is flatter and the draft is less.