Materials for small boat???

I was fumbling around with stitch and glue, trying to make a duck boat and came up with a real nice looking 7.5 footer of my own design (never built a boat before). 7.5 ft long, 44 inch beam, flat bottom, full contoured deck on top. I used 1/4 inch ply and a skin of fiberglass. The boat weighs 70 pounds.

I'd like to lighten it up a bit. Thinking of trying to make one of fiberglass using the boat as a mold. Thinking of molding the top deck and then the bottom, connect them at the "deck to side" seam. (??)

What materials should I be looking at to do this properly? Mat, woven, triaxial, vinyl ester resin, epoxy???

Should I look at composit materials like core cell or nida core?

Any comments on how & what would be appreciated. I want to make 3 of these and stop there (for now anyway).

Thanks,

Rich M

 

I'd like to thank everyone for their help - I figured out what I needed to know on my own as usual.

Most high quality small fiberglass boats are made with 4 layers. I was looking at the Kevlar material and found that I'd have to do either 2 layers of Kevlar and 2 layers of fiberglass cloth or Kevlar and FG cloth, Kevlar and FG cloth.

I could also get away with a layer of mat and then a layer of woven roving. Cheap and easy - I'm sure most small boats are built this way.

Thinking of doing triaxial cloth - stuck with 12 oz and 3/4 oz mat. I'll probably put a layer of light cloth over that to give it a smooth finish.

Y'all have a nice day.

 

4 layers of what, and of what weight? Dang, if'n I'da knowed it was that simple.....

Steve

 

Hi Steve,

7 oz fiberglass cloth or just Kevlar fabric is what I've seen described the most. Some mention mat and some don't.

Descriptions ranged from 7,7,mat,7 to Kevlar,7,Kevlar,7 to 18 oz roving & mat only. I guess each manufacturer wants a certain weight and such, the different weight cloths and different weaves have different uses but I'm still trying to figure that out.

Too bad no-one who actually makes boats will respond.

There are a number of references out there but I'm too cheap to spend the $25 on a book, I spend several hours hitting web sites for various small boat builders and some were nice enough to identify what they use in construction.

 

i consider that very good, really do
disagree however on not spending $25 on a book...

 

Rich,
The materials you use and their weights SHOULD be determined by the proposed use of the boat, and it's size and structural layout (if any )
My post was sarcastic, for which I apologise. Suggest strongly you go and buy the book, which will help you immensely when it comes to finding and using the best materials for your particular project.
Steve

 

Rich M,

If your too cheap to spend $25 on a book, how would anyone know you won't go cheap if you are told what to use and how to do it? Learn for yourself and comeback and ask some questions based on what you've learned and you will get a lot more positive responses. No one is going to do your work for you but everyone here is always willing to lend an amatuer a hand and point them in the right direction.

 

Let's do us all a favor and let this thing die. I'm going to. It really hasn't done anything for me.

I don't want to take the time to blow $25 or more and have to read another book. I don't think it is going to tell me what I want to know. The boat building books sure didn't.

I really don't care about the properties or such of the materials, just which ones to use. I wanted to know the proper layering materials and the proper resin for a flat bottomed 7.5 ft long boat with a full deck on it. I asked and no-one wanted to answer. You'd think I asked for a recipe to build a racing boat with some real potential for failure.

Maybe I wasn't clear enough and the question seemed to broad.

I have a bunch of 50 inch 7 oz cloth and some mat in my garage from laminating the wooden boats which are too heavy for my almost 65 year old father to easily lift. A gallon of cheap lay-up resin and I'll be ready to start finding a "proper" layering sequence.

Have a happy life fellas. Your advice has been 'enlightening'.

 

Need a kleeenex?

 

I am new to this forum. Do we get very many like that? I have always found that reading a couple of books takes less time than correcting a shop full of mistakes, and erasing a pencil line is far less expensive than a sheet of plywood. Maybe when we get too old to have the luxury of wasting time we learn that we should make haste slowly.

 

Its funny to me that I can read this post all the time getting fired up and ready to give "a piece of my mind", then I look closely and see this all happened a year ago and the guy has probably for got he ever wanted to build this boat

.... Go to the Library, they have books for free

 

Well, since he is amember, he gets a notice when we post, doesn't he?
Back to his question:
The lightest laminate you can put your foot on is about 12mm core (divinycell or simmilar) with one layer of 300g glass on each side.

 

When you ask a question and you get a stupid look in response-- you can:
A) Conclude the the person you questioned is stupid ---or
B) Realize that you asked a stupid unnanswerable question.

That is fine---I do it all the time. But when you are told by the knowledgable how to ask better questions, don't respond with nastiness.

 

Hey,

This was one of my lessons in life. I was naive and thought I would "get an answer from the guys who know" and it didn't work out like that. I thought it was an easy question, doesn't seem like it. My fault for getting insulted and reacting to nothing.

While many on here are professional boat builders, I'm an environmental consultant and get paid to give people advice on contamination issues (including that from fiberglass boat construction ) for property sales and purchases, roadway widenings and such. I have as much liability as anyone here. It is easy to point someone in the right direction and not incur liability or profit out of it. Some do and some don't.

I did find out all I ever wanted to know and more. Just not here. One of my errors was believing that numerous plies and a certain thickness was necessary. I also put too much thought into the newer "high tech materials". All this to build 2 - 7.5 ft long boats out of fiberglass!

Seeing that a builder of a 14 ft flats boat uses only 2 layers of 3/4 oz mat and a layer of 1208 biax, my question was solved. It is amazing how little fiberglass laminate is actually required and used in boats.

I also found out that I could get away with 2 layers of 10 oz woven E-glass since I was planning on putting a core material (lightweight 1/4 inch plywood) in the floor to reduce the flexing & oil canning.

Seeing that the mat would adhear to the plywood better, I chose that route. The cost difference is not much between the 10 oz and the 1208 considering I need 6 yards per boat. The 1208 actually includes 3/4 oz mat where I get it. "Regular lay-up resin" is the choice for resin. I guess I can doit with about 2 gallons. The weight is amazingly light if you do the math.

Now my only issue, when I get the time and extra $, is to build the mold for the 2 boats. Since it is going to be a limited production, I'm going to build something less than you-all would do. Possibly just sanded plywood with glossy paint, wax and some form of removal agent for the glass...I don't plan on using gel-coat since they are duck hunting boats and get painted with heavy, drab colored paint anyway.

Once that is done I have one last project to work on. No-one offers a simple, light weight 14 ft fiberglass boat anymore, for some reason the manufacturers have apparently all gone belly up down here in FL.

I have the PH15 plans from Bateau and may do a thinner modified version of that in plywood as a mold (depending on my experiences with the mold for the small boat). I'm thinking to do it as a "rolled edge skiff". I will overkill the previously mentioned boat builder's laminate schedule and lay the boat up with 2 layers of 1208 (w/mat), put in stringers, foam between the stringers and overlay the foam with 1208 for the floor. I may add another layer of cloth to the sides depending on the stiffness once the boat is removed from the mold. Looking at high cost foam cores for the front and rear decks, may just use encapsulated plywood - we'll see.

Questions must be asked if one is to learn. There is no stupid question, only a stupid answer.

 

Hi Rich, Reading you posts of the last year reveals how much you have learned in the course of planning this project. For what it may be worth I built a H.H.Patson "Nymph" 7'9" 1/4 plywood fiberglass skin. I modified the design slightly and added decks fore and aft with a block of 2" thick pink styrofoam glued to the underside of each deck.
During hurricane Isobel the boat was stored upside down near the water. When the water had receded the boat was right side up and about 1/2 full of water.
I think that making a mould for two knockabout boats is extra work with not much benefit.