New forum member, unsure of whether to put in wood or glass forum

[advobwhite]

Hello! I live in NW Fl and currently own a 14 ft boat that my grandfather has given me. They bought it used in the 80's and restored it and now its time for me to reglass part, if not all of it again, which is what I'll be taking on next year.

This however is not the reason for my inquiry. The 14' boat is nice and only draws about 6-8" of water with 2 people, but is very wide and I'm looking for something for hunting the backwaters....I am looking at a Barnegat Bay Sneakbox available on svensons.com as it is pretty open and fits my needs. I plan on putting a huntdeck on the back, which would add another foot or 2 of space to the overall design and putting a homemade 3-5 hp mud motor.

My question is regarding the physics of a plywood framed boat that is covered in fiberglass. Is it the bouyance of the wood alone that gives it the bouyance? I couldn't imagine a boat made entirely out of pine or birch(only 2 woods available for me at a reasonable cost) could float a large man, smaller man, and decent hog(under 100 lbs) so wasn't sure if a double floor with a layer of marine foam, or even the sheet of 3/4" dow styrofoam insulation from a box home repair place would help in that. I know marine foam is closed cell but since the whole thing will be glassed from stern to bow, I would assume the open cell foam would be fine, especially for my first boat given the price difference that I've seen? Also, to that end, would exterior grade be fine since it is going to be covered w/ glass? I know marine grade is ideal but for my first boat, something that'll just last a few years is fine and I can beef up the build when I build one w/ my son in a few years. Saltwater is a non issue as it will only be around freshwater and will be garage kept the rest of the year.

Thanks for the education. I'm a little leery about taking on this endeavor and realize it is much more "practical" to buy an aquapod or something similar, however learning a new skill that I can lean on if needed and pass down to my son is much more worth it to me, and although not going in huge waives, I don't want to get stranded out in the river.

I look forward to the replies

 

[Petros]

Welcome to the forum,

I am not sure I understand your question, the buoyancy of the wood is irrelevant, many boats are made of metal (aluminum are popular with fishing boats and canoes). what floats you is the fact that the hull displaces water, and the weight of that volume of displaced water is is greater than the weight of the boat, crew and cargo. So I do not see exactly what you need to know about the wood.

Almost any type of wood has been used to build boats, some are more suitable than others, but there is no "correct" wood for a boat build. Any reasonably clear and fairly rot resistant wood works well, high strength to weight ratio is always desirable, not not necessary. Wood that is easy to work with hand tools is also nice, but also not a necessity.

 

[advobwhite]

Okay. I was unsure of the physics of what makes a boat float. I didn't realize that it was water displacement and was thinking it was the whole physics lesson of density, ie wood is less dense therefore it will float as long as the weight does not exceed the buoyancy. I should not need any extra floatation for 2 men and a hog for the boat in question it would serm

 

[PAR]

If looking to build a new boat, maybe more suited to your needs, get a set of plans from a reputable source and stick to the spec's called for in those plans. I say this because of the obvious lack of boat design and engineering experience you've displayed, which isn't meant as an insult. Selecting a living designer would be wise, because dead ones can't be asked questions about the particular plan set you have.

Unless you want a waterlogged end product, don't even think about open cell foam. Also in regard to adding things to a boat. The sneakbox style of designs don't have much reserve capacity, so don't add much. These types of boats are intended to carry a hunter, a few guns and his dog, with as little freeboard as practical, so it can be used as a blind too. Adding to the weight of the boat will just decrease its load carrying capacity.

At this point you'd be best advised to establish what your needs and desires really are and search for a design that most fits it.

 

[advobwhite]

Reading more about displacement I believe I have a basic understanding... I was initially looking at capacity as material buoyancy but the displacement is auch bigger factor. In its simplest form it is the weight of the volume of water being displaced and as long as the weight of the boat + load in boat is less than water being displaced the vessel floats. Is if a boat displaced 1000 gallons then the weight of the 1000 gallons minus boat weight is the capacity.

 

[PAR]

Well, you have a long way to go before you're ready, but Wikipedia can be useful. There's a little more to it than your description, when it comes to figuring volume adjustments to any particular design. Again, instead of making modifications to something, without a full grasp on the physics involved, you should establish what your needs and desires are and select a design, based on them.

 

[advobwhite]

I decided on your initial post not to make any modifications until I get a few boats under my belt but I learn more if I learn how and why things work rather than blindly following plans. I don't mind following plans but want to understand as well

 

[Petros]

go get a copy of "the Nature of Boats", by Dave Gerr. It is written by a navel architect to give simple explanations of the various reasons of boat design, it is intended for boat owners and amateur builders. It is a good reference book, and a good place to start. You can likely find a copy in the local library, but it is worth owning if you intend to build a boat.

It will help you determine your needs, and to understand the differences in different boats. It would help you choose a design well suited to your needs.

It would save you from having to ask too many basic questions here, and if there is anything it will not answer, you can always ask the vast amount of experiance here on this forum. It will allow you to ask better, more informed questions as well.

 

[advobwhite]

Awesome thanks!