New member in dfw texas

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dallask
Posts: 4
Joined: Mon Apr 11, 2016 6:54 pm

New member in dfw texas

Post by dallask »

Howdy! Going to be building a Vera Cruise boat over the next year. Still in researching and fund raising mode. Looking at a rebuilt Mercruiser 388 to put in it. Considering using a Jet as well instead of stern drive. Any body got any starting advice?

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mrintense
Posts: 3799
Joined: Thu Jun 10, 2010 11:22 am
Location: Austin, Texas
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Re: New member in dfw texas

Post by mrintense »

Welcome to the forum dallask,

I'm located in the Austin area and building a Vera Cruise so when you get yours done, there will be two here in Texas! As you may be aware, there is not much information on this boat, I suspect because it is bigger and takes longer to build. However, I have been blogging my build from the beginning (see link in my signature) and will be glad to answer questions where I can. There is a builder in Illinois who has been at his for sometime and is in the fitting out stage.

There are also several builders of the Sea Knight and the Geronimo designs. Both of these have nearly the same hull design and can serve as references. One thing you should do for sure is pick up the "Boatbuilding With Plywood" book by Glen L Witt from Glen L Marine. It is a treasure trove of information on constructing these boats and will answer most of your questions.

Good luck with your build. When you get started, be sure to post pictures as it helps others and it makes it easier for us to answer any questions you might have. As for the jet drive, well I cannot answer that particular question other than to say that there has been a few boats built that way and people have posted here on the forum about them, so doing some searching on the forum should net some information.
Carl

Crafting a classically styled Vera Cruise

Clipper Boating

dallask
Posts: 4
Joined: Mon Apr 11, 2016 6:54 pm

Re: New member in dfw texas

Post by dallask »

Thanks for the reply! Absolutely, will have lots of questions. Thanks for the book reference, I'll check it out! What engine are you using? I have an opportunity to buy a rebuilt 488 MerCruiser. 188hp. Not sure what other folks are doing.

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mrintense
Posts: 3799
Joined: Thu Jun 10, 2010 11:22 am
Location: Austin, Texas
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Re: New member in dfw texas

Post by mrintense »

dallask wrote:Thanks for the reply! Absolutely, will have lots of questions. Thanks for the book reference, I'll check it out! What engine are you using? I have an opportunity to buy a rebuilt 488 MerCruiser. 188hp. Not sure what other folks are doing.
Since you are considering a inboard / outboard, Glen L also has a great book on inboard motor installations that is a must have.

As for the engine choice, be aware that this design comes with a weight limitation of around 700 lbs for the engine and drive. When I was researching this, I decided to go with an outboard, most likely an Evinrude 90 to 115 ETEC, but I looked at multiple IO options . It seemed that in conventional engines, only the 4 cylinder Mercruiser (can't remember the model) was close in weight however, I did see other options but they were either more expensive or more than I felt comfortable dealing with. For me, ultimately, it came down to the outboard being less complicated of an installation.

As for the 488 MerCruiser, the Vera Cruise design has an horsepower range that tops out at 125. Take a look at these two links

http://www.glen-l.com/designs/cruiser/veracruise.html

http://www.glen-l.com/designs/cruiser/v ... notes.html
Carl

Crafting a classically styled Vera Cruise

Clipper Boating

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X23
Posts: 21
Joined: Sat Aug 27, 2011 3:08 pm
Location: Florida

Re: New member in dfw texas

Post by X23 »

Take a look at the information available on Scott Design & Manufacturing, or Hamilton Jet. Both have plenty to get you thinking about jet power.

Likely the jet drive will be lighter than an equal HP I/O appendage. If you like to go fast, the jet can exceed the drive efficiency of an I/O or straight shaft at speeds faster than about 30 knots, mostly due to the lack of any underwater drag. The jet can give you max HP as soon as you open the throttle, it is not loaded like a prop so the engine can go to full rpm right away. There is no exposed prop, so it is more safe with people in the water.

If you have seen any of the water trials of the USCG Response Boat Medium, jets have excellent brakes. That 45 foot hull with twin 800HP Detroit Diesels driving Rolls-Royce Kamewa water jets can stop in its own length at full speed. The entire craft disappears in a huge fountain of spray, and when it clears, there she is stopped in the water. That might be a problem with your crew & passengers if you do that without warning! Since the jet turns constantly (unless you fit a transmission), full throttle forward to full reverse only requires the dropping of a bucket to redirect the thrust. This can take less than one second, and the engine does not need to come to idle to do that.

Near the dock, the water jet has excellent maneuvering, being able to direct the thrust in most any direction. If you drive a jet, you will notice that the bow will move in the direction the wheel is turned, even when going astern. Conventional shaft drive craft & I/O craft will move the bow in the opposite direction when going astern (prop walk excepted). And jet drives do not have prop walk.

Shallow water capability comes from the lack of anything hanging below hull level, and if you keep the throttle at idle it won’t vacuum up the marine grass either.

The downside is on the slow side, where it has less efficiency than a prop of any flavor the slower you go. If you like a slow cruise to watch the shore pass by, you will be using more fuel than another choice of propulsion. Another down side is that unless you add a rudder of some sort, you cannot steer without using some thrust. Neutral is accomplished by dropping the reverse bucket to split the thrust fore & aft equally.

The jet unit will require a large hole in the transom which will continue along the hull bottom. Usually these units are welded into aluminum hulls, so that interface is not a problem. With a wood hull, you will have to handle that interface by wood sandwich bolted thru the plate then Fiberglass & epoxy seal. Just requires some thought to accomplish.

When first starting the unit, you will be pumping water right away. Even though you can get zero thrust, the little noise is still there unless you add a transmission, which adds weight & length to your drive line. Some are not bothered by the water movement, but others are. If you have a transmission you might be able to clear weeds out of the pump by using reverse transmission gear, and you can warm up the engine without pumping any water out back. Of course, if you stay out of the weeds, you likely will not foul the pump with them.

Many different sizes of jets are available, so you can use a modern V6 auto engine or equal marine engine, matched to the pump diameter, impeller & nozzle selected. The manufacturer will help you with that selection, given your vessel weight & engine HP curve. If you feel the need for speed, there are many big V8 drive choices too.

Keep thinking about it & let us all know your thought process. The mix of features might be just what you need for propulsion.

Jack

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