Hammer

30' Sport Fisherman   Boat building project

design and build of a center console offshore sportfishing boat 

 

The Design

Since this was my first boat and the results are yet to be demonstrated, I can say that designing was a relatively simple process. You just look at some boats that you like and "borrow" their features.

My fishing objective is running out to deep water and trolling all day and sometimes this involves a  "game Plan" change such as running to a new location. As far as trolling in a small boat, I don't think there is a lot you can do with the hull design except maybe a relatively high bow might reduce taking waves over the bow. Stability at rest or at slow speed will be compromised by a bottom design for running. 

For the running part, I want to go relatively fast in normal Gulf of Mexico seas off  my home state, Louisiana i.e. 2-3 foot chop and occasionally somewhat worse. This is an overriding consideration that is to be accomplished at the expense of other things such as; floor space, stability at rest, inlet running ability and speed+fuel efficiency in smooth water.

It was my opinion based no almost no actual experience, that small "runabout/fishing" boats do not require a naval architect for a successful design. Armed with this lightning bolt from above, I proceeded with my design and here's how I did it.

First I considered what made my existing boat, a 24' SeaBird, a successful design. It's cored hull is light, it has a 24 degree dead rise, it has the "South Florida" curve to it's stem line and it's narrow.

           

Next I tried several demo's of hull design software. HullForm 7G was the only one that I could easily make something that looked like a boat. Bought it. I  developed a "table of offsets" from my SeaBird that I entered into the computer as a starting point.

 

Over the period of a year or so, I designed the hull over and over as I looked at lots of boats and my thoughts progressed. Some of the boats that I admire are;

 

              Contender 27' and 31' (overall design and appearance) 

              Regulator 26' ( classic shear line and bow flair)

              Fountain Sportfish 29' and 31' ( bottom design)

Deep Vee, Sharp Entry, Light Weight, Narrow Beam

What I ended up with was a 29' 91/2" LOA hull , including the integral motor bracket. The dead rise at the transom is 25.5 degrees and the entry  dead rise is 55+ degrees. The is hull is narrow at just a little under 7' beam at the water line. The hull topsides flare out over it's length to a maximum beam of 8' 6" gunnel to gunnel at amidships with a noticeable bow flair. The amount of dead rise is pushing the idea of deep vee a little far but I thought that the hull's lightness (projected weight at 3600#) would offset the loss of planning lift and buoyancy from the steeply angled bottom. There are some other handling and stability at rest issues that may have been compromised but these are some of the trade-offs in aiming for a special purpose boat rather than a general purpose boat.  The planning lift issue was to be addressed with the 16" wide keel pad that is set at 12 degrees dead rise and the other hull bottom appurtenances.  The bow stem line lacks the usual "Carolina Inlet Running" curve that is found in some degree in almost all production fishing boats of this size and favors the " South Florida " style curved stem mostly found now only in custom or semi-custom boats. The ample forward buoyancy of the Carolina style is hard to argue with for running inlets and large swells but we don't have those conditions here that often. My old SeaBird told me that the south Florida style does nicely in 2-3' seas. In trying to explain why is where I get a little shaky in my boat design knowledge , I should save myself the embarrassment and stop here, but here's what I think.  In rougher situations where you are running with the bow trimmed down, I think that removing some of the forward planning surface by having the hull starting its upward slope further aft allows the bow to settle quicker coming off  a wave thus minimizing the sometimes abrupt bow drop. Also the bow's lift leverage on the hull is less so the bow will not rise as much. In effect it should allow the boat to follow the sea surface more closely. I picture the hull attitude on a Carolina Style boat maintaining its running attitude slightly longer thus making the eventual drop off the wave more abrupt. And when the bow contacts the next wave it is lifted more. When the Carolina style boat hits a large wave at speed there is a big impact as the broad shoulder of the hulls forward area tries cut though. This may be full of holes but there is a real difference in the feel of the two styles and this is the only way I can explain it.  Anyway, After I finished my design, I noticed a picture of a 34' Venture and the upward swept chines indicating a very sharp entry vee and South Florida style stem curve. After a phone conversation with them I felt much better about my 55 degree entry. For those unfamiliar with the Venture, It is a VERY nice boat but a little bigger than my tailoring requirements. Lately, I have noticed a few more boats with the sharp entry and transition area starting a little further aft than norm.

Motor Mania

The original design was started  for a jack shaft inboard/outboard  diesel. The engine selected was the Star Power  7.3L 300 hp turbo diesel with matching outdrive. The engine was located under the leaning post/tackle center. Eventually I soured on that setup in favor of twin, just introduced, direct injection 2 cycle outboard motors. Again there were some trade offs here, but it seems the greatest thing in the diesels favor was the fuel efficiency and the direct injection outboards appeared to gain some ground in that area. That was before all the trouble started with both Mercury and OMC versions of this new technology. Since then with the OMC bankruptcy I am very glad I choice the Mercury Optimax. A consideration was trolling speed. With the diesel propped out for this light boat even at idle, the troll speed might have been too high. Star Power had a two speed transmission under consideration but there was no way to know if this would end up being available to me or how much it would add to the already steep price. The hull was being built and the transom had to be cut for one or the other. As it turns out, had I chosen the Starpower unit, it would have been a big mistake because in the intervening year their engine/outdrive package was discontinued. 

I have always admired the classic gracefully curved shear line that the "Carolina" boats use to accommodate their higher bows ( example,  Regulator ). Although I did not follow the Carolina style stem curve, I did made the bow high and tried to get that classic curved shear look. Since I am building a linerless boat with hull cap ("covering boards") integral with the hull, I could  style their widths for fishing ease and looks. I started a little wide at the rear (9") and got very wide forward(14"). The forward width gives added safety for boarding and can easily accommodate outward pointed gunnel rod holders for fishing and quickly getting cleared rods in a safe out of the way place with hooks hanging overboard. The bow flair was important part of the looks package as well as hopefully keeping some of the water out of our faces.

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Last modified: October 29, 2004