25 Bertram Project Goal & Design Changes
As with most projects of this magnitude this one is undergoing some significant changes as relates to my goals for the finished boat. When your spending countless days inside the hull and reviewing materials, designs and options you begin to get new ideas. Over the years that a project like this can drag on and some builders actually determine that they don't want the end product! It is not uncommon to see fully completed project boats for sale, why? People go thought various phases and/or stages in their lives and a project may begin in one...and end in another.
As for me I'm in the final stages of raising kids (last one in college) and I may be a grandfather within the next few years. What does that have to do with a boat project? This, the uses for my boat will be different as I get older. Basically less of the hard core offshore fishing and more of the leisurely cruises with my wife and family. Also the older I get the less things that I want to maintain and own. These are the basic elements that are altering my boat as I design and build.
This section covers all changes made AFTER I already had a plan and was started. Don't be afraid to change things up as you go!
First Design Change...Where I keep it
The first change is in were the boat is kept. I have always believed that I couldn't keep a boat in a marina because I believed that I would spend too much time at the boat. I'm going to challenge that one! I have decided to leave the boat at a nearby marina practically year round. Although the bottom will require more maintenance this decision actually cuts down on the stuff I need to maintain. Primarily the trailer. It also means that I don't need a 3/4 ton diesel truck to pull the boat around.....BUT the biggest benefit is that my wife and I can use the boat without the assistance of others. I have learned over the years that when it's just the wife and I at the boat ramp, in a heavy wind, bad things can and do happen. It's also a 45 minute tow to our favorite boating area. This keeps me on the sofa far to often. The thought of trailering a big boat for a round trip of 80+ mile and all the planning that goes into the trip keeps me at the house on many nice days. At my stage in life I want to grab an ice chest and go. I simply believe we will use the boat much more.
A friend of mine with a Bertram 31 once told me "I
remember having to trailer boats around
every time I wanted to go out and it sucks, once your at the marina you'll never
go back" So, I've decided to keep the bottom wet. At least the marina
offers covered stalls and the rates in our area are very reasonable. Also as
with most marinas the rates are based on boat length and slip fees for a 25 ft boat ain't too
bad.
I left the SeaRay at the marina once to use the trailer to haul the Bertram home and I loved it. The bad part was what happened to an unprotected bottom in only two weeks, ugly.
I found myself extremely nervous at first and went by to check on the boat every other day. But as time went by I realized I enjoyed going down to the marina and firing up the engine. Nice little pass time and stress reliever. The thought of just throwing lines and taking off is appealing.
Besides bottom paint how does this effect the project?
1) The boat will require an effective bonding system, a series of rudder, strut and hull mounted zincs.
2) No height restrictions if the boat doesn't need to go down the road.
3) A "shore power" system is now required to keep the batteries charged. Maybe a small AC like Eli's?
4) I will now use a mechanical "dripless" shaft packing system. Cheap insurance against sinking at the dock.
I still intend on owning a trailer to bring the boat home for major maintenance but I don't HAVE to use it, or own "top of the line". Our marina has a lot that many guys leave their trailers year round.
Second Design Change...Helm Station
With my decision in tact about the 31 Bertram Bahia Mar lay out I have started looking into helm locations and small tower options. At this point I leaning toward what I have always called a "half tower" with a single helm in the tower. The half tower will be basically not much higher than an original 25 Bertram fly bridge model.
The picture left is the "Miss Olive" from the 31bertram.com board. This is the basic top and lay out that is my current favorite. The aluminum pipe tower is light and should not adversely affect the boat's trim, keeping with the light bow intent.
As I mentioned I'm also leaning toward a single helm. The single upper helm station really opens up the interior of the boat. Removing the lower station and a helm chair adds a lot of useable space. This also allows me to design the helm pod to accommodate modern electronics.
It also relocates me and the wife farther away from the engine. I'm convinced that the more distance I can put between me and the engine, the happier I will be. Wow to my fishing buddies. I may keep some ear plugs in the cabin for those with sensitive hearing....depending on the final engine selection of course.
Next photo (right) shows a very unique 25 Bertram that has
been converted to a center console helm, removed the glass and/or top and a
custom tower has been installed. This tower is a bit taller than what I am
planning.
Not
sure who owns this boat, picture came from the 25 Bertram web site.
This boat's tower has a roof to cover the passengers and also a platform for the upper observation station. Electronics box is a nice bonus.
The main element that I like about this photo is the scale of the tower on the 25 Bertram. It's a nice size, doesn't overwhelm the boat, yet it is definitely a substantial tower.
Basically what I'm planning is the design with the roof over the cockpit being used as the floor of the upper station. If I'm only planning one station then the station can't be too high because I need to be able to stay up there in any sea condition.
Keeping the boat at a marina opens up a lot of options that are not possible with a trailer boat. Downside is that you have to boat and fish your local waters.
Third Design Change....Gear & Prop
This design change involves the transmission ratio, strut and prop. During the initial design of the drive train I went in assuming an 18" prop as a baseline. I assumed that the boat would needs shaft rpms of 1800-2200 to end up with a decent speed. The down side of this equation is that I end up with a pretty small diameter prop, like 18". That's really not enough prop for a diesel engine of any magnitude. Much efficiency would be lost with a prop that small. As my project has progressed, the engine horsepower options have increased.
What to do? The tables really turned when I started looking over the want ads for used and new surplus transmissions. No large down angle 1:1's anywhere! So that left me in the new gear market and broke one of my primary rules "no oddball stuff". I started looking at using the super common 1.5:1 gear. The result of going to this gear ration is a big prop, read: pocket issues and more draft. As usual, off to the boat I go with the tape measure, a mock plywood wheel pattern and a dowel rod mock shaft. Everything fits! Nice surprise. The images below show the moment of truth and what a 22" prop looks like stuck under my boat. Jezz that's a big prop. Ultimately I believe I will end up running a 20" wheel.
The changes create the following:
>Shaft angle is now 14 1/2' degrees. That's up from the original 12 degrees. This translates into the front of the engine raising about 1 1/2 inches.
>Draft increases by around 4". I wish it didn't but "it is what it is" I calculate the draft at 38" -40". Original goal was 36" Deep water boat! As long as a marina can accommodate the draft I'm fine.
>Pocket now requires that the shaft entry area be changed to accommodate the 2 1/2 degree shaft entry angle.
Here's some more shots of the mock-uped 22" wheel.
With the keel set at dead level I use an angle indicator to check
everything!
As you can see from the indicator the shaft is just a bit under the 15 degree
mark. 15 degrees is considered a "normal" inboard shaft angle and I would assume
the efficiency difference between 12 degrees and 15 degrees is nominal.
The dollars and sense...
This may be one of the biggest cost savers a builder can find. The gear required for a substantial diesel engine cost somewhere between $4,500 to $6,000 new in 1:1 ratio, used 1:5 gears are everywhere for $2,000.
Here's the best part. I have already located several "new surplus" gears in 1:5 ratio that can handle the hp. Typical and cost appears to be running around $3,500. If I opt for an RTO (running take out) or a re-man gear the savings are even more. I have seen some gears in the $1,500 - $2,000 range that would work just fine. These options did not exist with a 1:1 ratio gear.