new but ambitious

Hi everybody,

I'm a Belgian living in Thailand, and for many years now, I've been dreaming about having my own boat.
A decent one, around 30' or more.
Needless to say that the price for such a dreamboat is out of my league (even secondhand), so recently I started to do some research about building your own boat, and bumped into the plywood/epoxy building method.
The possibilities with this (relatively easy) method seem so enormous that I got completely obsessed about it, and started gathering all possible information about building and designing your own boat (couldn't find the model I really like, so I thought I could design it myself).
Having some technical background helps a lot to understand the basic principles of building and designing, but some information is more difficult to find than others and some information is rather confusing, so here I am, hoping to find the missing answers for my quest!

Please keep in mind that I have no experience about boat-building whatsoever, and that English is not my native language, so you can expect some strange/stupid questions!

Here comes the first one, which shouldn't be too difficult.

How much fiberglass cloth (gr/sq. meter) and epoxy should I use on the hull (plywood boat) per square meter (or square foot)?
The info I found so far is rather confusing: some sources speak of 1 or 2 layers, while an other source speaks of 50 gallons (223kg) for a 26' boat!

I live in Thailand, and at the local dep. store, the salesman said 4 liters (1 gallon) would be enough for putting 2 layers on 25 square meters (but maybe treating furniture is not the same).
At $65/4L (hardener incl.) this seemed rather cheap, until I saw the info about 50 gallons!

All help/information is welcome!

 

The 50 gallon drum information is probably the estimated resin required to build a fiberglass boat in which the entire hull will be glass and no ply is used.

Try not to persuade yourself that you can build a boat for less money than a good used one would cost. That is almost never the case.

Try not to beguile yourself into believing that you can design your own boat with the same success as an experienced designer. That too is almost never the case.

You suggested that you cannot find a boat that you like and you want to design it yourself. The first thing on the design list is what is called an S.O.R. (statement of requirements) You must state how the boat will be used, where it will be used, the speed that you feel that you must have, the extent of accomodations for guest and crew. how much fuel you will carry, how much food and water, method of propulsion, and many other factors.

 

Hi Messabout,
Thanks for the insight!
As for the costs of a used boat: I don't know about your place, but here (Thailand), anything decent (around 25') will cost you $50.000 or more.
By now, I've made some price calculations for my own idea (39', 300HP diesel inboard, but used), and I end up around $15.000, not including the design check by a professional!!!
I must admit though, here in Thailand many things are a lot cheaper then in Europe or the US.

As for the designing, you're right off course: I don't expect to produce the same quality work an experienced designer can, but that's not my goal either!
I don't expect my boat to be perfect in every way!
I'll be happy if I can create something with standard safety, balance and performance, and before starting the construction, I'll have my plans checked by a real naval architect for any serious flaws.
As for the S.O.R, that was the 1st thing I worked out.
When it comes to functionality, I want a boat that's suitable for 1-2 day trips, with enough inside space to take my family (we're 2 adults, 2 teenagers and 1 baby, all small sized) and maybe a few friends. Also scuba gear for 1-3 people.
The boat must have decent stability and a reasonable cruising speed (about 20-25 knots).
I live in Thailand, so it's a rather hot climate all year round. Most people here don't like sitting in the sun too much, so I want the boat to provide lots of inside room and comfort.
As far as the looks are concerned, I want the boat to look like a modern, luxurious power boat (at least from the outside!), that's why I was having trouble finding a design I really like. Not that I didn't see any nice ones, but they just weren't what I was really looking for.

I do realize I'm setting my goals quite high, and that's why I really want to take my time to gather as much information and knowledge as possible before actually starting the construction. I expect to start in about 1 year.
I have already read a few e-books/docs. about boat construction/design, and I think I'm starting to have a pretty good idea about all the things that are involved.
Having some technical background/experience and being rather good when it comes to calculations and stuff, I feel confident I'll be able to produce something decent, if only I take the time to learn/study before actually starting to build.
Anyway, thanks for your input and again: all information/advise is welcome!

 

The specification for 20-25 knots cruise will kill the budget. You can have a large-ish boat that goes slow, or a small boat that goes fast, but both together is not going to happen on a shoestring budget.

 

I'd agree with that last comment.

Not sure what's available in the used market for you. I was able to find a 35 year old boat here in New York, the design of which I really liked. This boat has a fiberglass hull but wood decks/cabin/interior. Paid a couple of thousand for it.

I've been restoring in in my spare time over the past six years. Including storage I've spent in the neighborhood of $35,000.00

I've made many improvements and this boat was stripped right down to and in some areas past the stringers. Everything was replaced except the engine and transmission which are serviceable.

As others will tell you either way you go it's not cheap if done right.

Don't forget to factor in your labor, I've spent thousands of hours on my "hobby". It's close but still not done!

 

well, as for the speed: I think I can keep the weight of the boat around 3 tons. With the formula's I've found, I'd need a 300 HP inboard engine for a top speed of about 32 knots, which should correspond to a cruising speed around 26 knots.
Now, I won't cry if the final cruising speed would be rather 20 knots, I'm not a speed maniac!
Having checked just 1 Thai site for used boat parts, a second hand 200 HP diesel would cost me about 2.000$, so 300 HP can't be that much more. Anyway, I expect to spend 5 to $6.000 on a used 300 HP engine.
Since I'll only be doing 1-2 day trips, I don't need a large fuel tank.
140 L will do just fine, and I found a used one for only $130.
Unless my other price calculations (wood, plywood, fiberglass etc.) are extremely off, It should be possible to build this boat (basic version, without any electronic or other gadgets) for about $15.000 or not much more.
Off course there is the labour, but since I'll be doing everything by myself with some help of friends/family, that doesn't really cost me anything except time.
I expect to need about 1 year for the construction.
Please tell me if my reasoning contains any major flaws!
My budget is not really shoestring, but I don't see why I'd pay $15.000 on a new engine if I can find a decent used one for $5000!

By the way: what is considered "fast" in boating? 20+? 25+?

 

Something I'd like to add guys: I consider the construction ready as soon as the boat looks good and I can take it out to sea.
That doesn't mean it's 100% finished!
Things that add to comfort and luxury, but aren't absolutely necessary for safety and functioning, will have to wait till later.
I Do realize that finishing the boat 100% will cost me more time and money than 1 year and $15.000, but for this amount, I expect to be able to go out there and have some fun!

 

A new 300hp marinized diesel will cost a lot more than $15k. I doubt there is a boat on the water anywhere with a 300hp diesel that is under 3 tons displacement.

 

I thought so!
But seriously, the prices here for used engines are really low!
Maybe it won't be under 3 tons displacement, but it shouldn't be much more (I hope!).
Anyway, as I said, speed is not a top priority for me, so I won't be too disappointed if I'll have to settle for let's say 20 knots cruising speed.

 

If you're only going out for a day or two, why not consider gas. Engines are lighter, much less expensive.

 

Good point! But do all Boat yards provide gas-fueling?
A bit difficult to fill it yourself with containers (lol), but I'll definitely look into that.
Can you give me some information about how much gas-engines consume?
For diesel, I've read that 1 gallon per 20 HP is normal.

 

Welcome to the forum.

That is a rather ambitious project, particularly for a first time project. A boat that large takes most people years to finish, if it ever gets finished at all. Your teenagers will likely be well past teenage years when it is done.

It is difficult to believe you can build a boat cheaper than you can buy a used one. It might be the case there, but that would be unusual. It is usually faster and less costly to get a used seaworthy boat that is neglected and needs cosmetic renovations. You can than use and enjoy it from day one, fixing it up its appearance as you own it.

If you are determined to build your own boat, do yourself a big favor and find some stock plans of the type and size you want, and than just alter the cabin and interior layout the way you want it. That way the most critical part of the design, the hull and primary structure, will be of a proven design. Also, the time it would take you to self education on hull design would be short cut, and you can spend more of your time building rather than learning how, and than designing, the boat before you start building. It would put you on the water up to a year sooner.

Glen-L has many plans similar to what you want, they are reasonably priced plans and proven designs. The company and its designs are well respected and have a large following. Boats built to Glen-L plans also have a high resale value because of the companies reputation. Self designed boats by unknown owner/builders usually have little resale value. something else to consider for the time, effort and expence you will invest in building a boat.

What you propose doing has been done many times, sometimes successfully (but that is rather rare), more often with poor results and the builder abandoning the project after many years and much money invested. This is a major undertaking even for a boat much smaller. Please carefully consider the advise given on this forum.

Also, I highly suggest building a dingy or small fishing boat in the 10 to 12 ft size, using the same construction method as your dream boat. It will give you the practice you need to build a larger boat, and give you an idea of the effort involved, methods used, tools required, etc. You can ways use it as tender for your dream boat, or sell it when the dream boat is done. Plans would be very inexpensvie, and it would not cost much to build. You will learn everything you need to know about building a 30 ft boat by building a 12 ft one using the same construction methods.

Also, It seems to me that you can do every thing you want in a 24 ft boat, it would cost fifty percent less to build and take way less time, will use a smaller engine, etc. you will just not have as much room, but for 2-3 day trips this should not be a hardship (it would be different if you were going to live on it). You should consider what is the smallest boat that will meet your needs, not the largest one you want. Try and gets out on the size and type of boat you are considering building or buying, it will give you a better feel for what size you really need.

Good luck. Keep us posted, we would like to see your progress and the type of boat you end up with.

 

Thanks Petros!
As I said earlier, a used boat of the size I'm looking for, would cost me $50.000 or more here, even when its over 30-40 years old! Maybe because the vast majority of boats here are entirely fiberglass and quite luxurious? Compared to the 15.00 I estimate for my own project, I think the choice is easily made!
I have already checked out the Glen-L and other websites.
I downloaded several free study-plans and I am indeed basing my hull design on an existing model, but much smaller then what I'd like to build.
I'm adapting length and beam, but I want to be sure there's nothing else that needs changing. Also, the interior I want is very different from the model I downloaded, so that needs to be designed from the floor up.
As to the time needed to finish: I'm lucky to have a job that gives me relatively much free time, and I can easily take a month or more off, even twice or 3 times a year if I really want, so that way the basic construction (sail ready) shouldn't take me much more than a year. Finishing it at 100% is indeed a long term job, but then again, it doesn't need to be perfect to have fun with it!

 

Lets see if I understand this correctly.

You suggest you have some technical background. In what?

The hall mark of an engineer, is their ability to research the material properties and physical attributes, so these can be applied in the appropriate formulas and calculations to handle the anticipated loads. I say this because the properties and coverage of fabrics and resins is very simple math and easily available in dozens of references and also online. Have you studied any books about boat design? Which? Any engineering? How about your math skills, is basic algebra something you're comfortable with?

Simply put, with questions as basic as these, your "technical background" must be in typesetting or something, as calculating the surface area shouldn't be a big deal, at least in regard to how much fabric or resin you'll need. Dividing by 2 if a spec says a couple of layers just seems a pretty simple equation to figure out to. This makes me wonder about your structure's engineering, as the very first thing you have to do on a design is a weight study, which means you've got more than sufficient volumetric information, to make at the very least, rough calculations as to sheathings and resin amounts.

In short, please consider buying a set of plans. It's one thing to self design an 8' punt and hope to get lucky, but a wholly different thing to engineer a 30' (+) yacht. In light of your questions, I have to say, you just don't have the necessary understanding of the physics and dynamics involved and with

as your fall back position, you can't possibly think you have even a remote chance of success. I know this is a bit harsh, but we see this frequently and I'm hoping to warn you off a huge set of expenditures, on a design that has no hope of floating upright come launch day. In other words, I've never seen a self designed 30'(+) yacht, built by someone with no experience in design or construction, be successful and I guess I'm asking why do you think you will be different?

Maybe it would be best if you posted some sketches of what you have in mind or possibly photos, of similar boats, that for some reason or another didn't fill you SOR efficiently enough, forcing you to consider self designing.

 

I've spent half the $15,000 you mention just in storage fees, keeping the boat secure and dry while I work on it and boat club fees over the years I've been working on her.

I see that you think your project will take a year or so. Well maybe if you have a lot of help but won't you have to pay your helpers? Even if they work for free you'd buy lunch and some beers after a hard day, right? It's all going to add up and take it from an amateur whe has been there, it adds up fast, really fast.

Remember that $35,000.00 I mentioned in my previous post. Keep in mind that I had a perfectly good hull, engine and transmission. And I still spent $35K!

The two posts above mine here are voices of experience and reason, heed them.