Lobster boat sponson

I'm kicking around the idea of turning a 30x12 fiberglass lobster boat into a 34x16. Is there some reason no one sponsons fiberglass boats? I have a plan that i'm sure will do, just not sure if there's something obvious I'm missing.

 

Maybe you should post some line plans of the modifications you are thinking on doing. It doesn't sound like a good idea though.

 

For starters, 2' bulkheads down each rail, skinned with 3/4' ply, then heavily glassed over. Not sure why you would say bad idea without any details, so I'm not so sure I'm all that interested in the opinion of a guy that lives in the exact center of a continent, nowhere the sea. But by all means shoot, maybe you're a stud on this forum. I'm all ears.

 

haha....plenty of attitude on display, but no pictures or drawings. What is the "rail" ?

 

DirtyDiego. Gonzo is in fact a stud that knows his boats better than most. He does not always live in the middle of the continent. Sometimes he lives in the Atlantic Ocean, the Indian, the Med and some other salty places.......Just sayin'.

 

Here is one:

http://www.platypusmarine.com/portfolio-item/fv-freedom-sponsoning/

http://www.fishermensnews.com/story/2015/10/01/features/delta-seiner-sponsoned/351.html

(I do not have firsthand knowledge of this, and it's substantially larger.)

 

Like a Russian doll, you peel away the outer one, and there is another one nested inside. Seems to me cheaper and more sense to just buy a bigger boat.

 

Well maybe I am stating the obvious here, but using sponsons to increase the size of the boat isn't going to increase the interior any.

 

Depending on what the cargo is or was, you can now carry more of it on a safer and more stabil platform. Holds on fish boats don't typically take up all the available room because of the weight when full, so within the existing hull holds can now be larger.

 

Sorry, didn't mean to offend anyone, he just seemed to jump to the conclusion that what I was planning was a bad idea real quick. From my point of view a guy that lives that far from the beach that looks that young couldn't possibly know all that much. Obviously I stand corrected on that matter.
The issue that we have over here on the left coast is that there are not nearly as many boats available as there are are on the east coast. Smaller lobster boats are readily available for a reasonable price over there, but once you are over 12' wide the cost of transport cross country could easily increase the price of the boat by 10+ times.
What we are looking to do is increase deck space to hold crab traps. By increasing the deck space 4' back and 4' out, that doubles the amount of traps we can haul.
Pictures and drawings are pretty much out at this phase so a basic description is the best I can do. Basically the rail will be removed from the deck up, I'll glass 2' ribs maybe every 24" to the sides of the boat, matching the dead rise. The ribs will blend into the existing bow and obviously taper down from 2'. The tops of the ribs will match the deck, and I will laminate 2x lumber to the ribs that will form the new rail, gunnel, freeboard, whatever. 3/4 plywood to skin the ribs, and 3/8-1/2" of mat/roving. Plywood the deck, glass, done. Obviously there are lots of little details that I didn't cover, but you get the basics. And save the corrections on proper terminology, I'm a fisherman that is very good with wood, glass, and structural principal, not a boat builder or a sailboat owner. Everything the boat needs is already there except for the deck space. Can anyone tell me why this would not work?

 

You will substantially increase the weight, both with the added structure, and the extra pots. The thing may struggle to get over what will be a greatly increased resistance hump. That is becoming a very wide boat, and width adds a lot of wave-making resistance. I assume this is a planing hull. I note you intend to increase the length by 4 feet, presumably at the stern. I'd expect a significant reduction in the ability of the bow to rise to a wave, with all that extra boat aft. And no so much more boat forward. I guess running downhill in a sizeable sea could become interesting. Or going uphill extremely wet.

 

Hello fellow members. I have "lurked" here for about a year or so and decided to join today. This is my first post. I am not a boat "expert" but can share some insights on this very subject and, is actually the reason I joined today.

I am wondering about the boat you are speaking of. Who is the builder? Is it a "skeg" or "built down", There are many "lobster boat hulls" produced in the Northeast and nearby Canada in the 30 foot range, and just as many differences in handling characteristics. If you are talking about a true downeast lobster style hull, single engine, full keel, soft chine and flat deadrise at the stern I have a few concerns.

For one, the proportions you are considering are outside the typical length to beam ratios for these boats. My 35 foot currently being built has a beam of 13 feet. And is the widest the builder feels comfortable with. Depending on what hull you are starting from this could make a following sea a nightmare to handle using the dimensions you propose. In the northeast it is common to lengthen a given hull either by cutting the existing hull or doing it in the molding process for a new build. I have lived here all my life and have yet to hear of someone widening one as much as you envision.

Second, as previously stated, you will be adding significant weight. You didn't mention engine size or type. Your current say, fourteen knot cruise could easily be diminished to nine or ten. Unless you are already considering a re power. My guess is your current 30 footer has an engine box above the deck which may limit your power options.

My third and final point would be the expense. It is true being on the left coast there is a demand and equal shortage for downeast style hulls. I think the the transport cost would easily win over the amount of work and expense in fiberglass, re shafting etc. As far as being able to help design your proposal, that would be above my pay grade and I defer to the more technically knowledgeable folks here. Best of luck.

 

I assumed from the description given ("matching the deadrise"), that it was a hard chine boat.

 

On the left coast a common boat built for certain Alaska fisheries are in the 32'x14-16' range, they're short wide and tall, efficiency of design as a boat hull takes a back seat to size limitations and load carrying capacity. I'm not saying this is the best plan, but the dimensions aren't far off from current designs.

These boats are built by a friend of mine in AK, I fished from several of them with him and his sons.

https://www.bing.com/videos/search?...69F500DC1E7D292D8B1A69F50&fsscr=0&FORM=VDMCNL

 

This is an 8-12kt boat. Our main concern for the project was "why isn't anyone doing this yet?" So far we can not find any obvious reason other than time and money.