Flat bottom skiff design

Hi,

I wanted to build an easy economical boat for my first one. My brother and I will be using it in a bay to go fishing. I think I will get a 4 hp outboard motor on it.

I attached a quick sketch up I made of it (made on google sketch up). I wanted to have only flat pieces so I wouldnt have to bend the plywood. I think I will use the stitch and glue method.

my question is what are some pros and cons of making it have a flat bottom, and how could my design improve without getting complicated?

oh and the entire length of the boat is about 12’ 6” and sorry about the extra random lines on the sketch

 

Boats tend to serve a purpose, about which the design is optimized. The very best advise you can receive, is to buy a set of plans. You can get plans for flat bottom skiffs for next to nothing and hundreds in this general size range for less then $50. Considering a few cans of paint will cost more then this, it's a good investment. I say this because prepared plans will insure you float with the deck sides, facing up come launch day, which very possably wouldn't be the case, considering your yacht design and structure engineering skill levels at present. Do yourself a big favor and build from a set of plans for your first few boat projects.

 

go to Hannu's Boatyard and he has some great designs for flat bottommed skiffs al lthe plans are there ...

 

Fortunately for you, stitch and glue is not just attaching angled pieces of plywood. You can achieve a smooth lined hull with the plywood panels. The underside of your bow is the particular area where a rounded or bent, as you're saying, plywood section would be nice. Why waste some of that 4HP energy on a bow that has bad angles? The plans PAR was speaking about, take hull efficiency into mind. Even the free plans available, particularly from Hannu's pages, he uses a free hull design program which indicates, by waterlines, the efficiency of the boats hull. If you purchase plans from PARs recommendations, you will discover it is hard to find boat plans with angled bottom edges. Not saying there aren't home made boats out there built like that, they just aren't as good as smooth lined boats.

 

The idea of Hannu's is that you can have a look ..say yes thats ok or I want something different or that will do for our first attempt at boat building ..with 4 HP you arnt going to be on the plane .... about 10 kts max ..have a look too at www.epoxy-resins.co.uk
particularly the build video for Morgan to see how its done ( take the cable ties out!!! )

 

Your design effort is commendable but lacks basic information that would lead you to a more serviceable boat. Bending plywood is probably easier to do than to use flat panels. Flat panels will produce a boat that resembles an ironong board and earn the derision of other boaters. In addition, the boat will be a dog and possibly even dangerous.

Get some plans from an established designer. The few dollars you might spend will return a result that saves time and money. Consider a slightly larger boat, say a 14 footer. A twelve foot boat is cramped for two fishermen. The 12 footer will cause you to buy as much plywood as the 14 footer and the finished 14 foot boat will weigh only a few pounds more than the smaller one while being safer and more comfortable.

And one more thing; stitch and glue is more labor intensive and more expensive than conventional chine log construction. Use the S&G method if you'd enjoy big time sanding effort and you dont mind dealing with toxic goo. S&G does make a very nice clean interior, and saves a pound or two of weight, if you are willing to do the extra work

 

As long as you stick to 4hp I don't think your design is as bad as the others imply. It's better than the round bowl-like skin boats of ancient times but some easy to make improvements could be made. Reduce the depth to about 20". The next mod will be much harder to do but still very easy relatively speaking. Give her some flare ...that is ...make her wider at the top than at the bottom. Keeping your straight lines this should be simple enough that anybody should be able to measure and cut. How much flare? Lets say at least 6" more beam at the top of the sides than at the bottom. Then I think you will have a boat that is relatively safe and will perform well w the 4hp engine and 6 to 8 hp would probably be even better but I see you're maximizing the use of the plywood so I'm guessing economy is of great concern. You will need some framing to control the tendency for the flat surfaces to bend. It still won't be ready for a yacht club de'bute.....but if you make it through the ultra simple construction you will be fairly safe and on the water.

 

It would be less work to make with some shape ,and also stronger with less material .
Take a look at a Bolger box boat. It could have a transom bow , and be very simple to build. it could look like a simple garvey .

There are some simple and nice designs here . The 15' skiff is basic but capable.

http://www.instantboats.com/index.html

 

I'll put in some experience here. I grew up in the Puget sound country and the Pacific coast of Washington state.
Your 'thoughts' are for small quiet waters.
In bigger waters where wind and other boats are a factor you need a different boat.
Keep looking and dreaming. What you need is just around the corner!

 

Give this a peek...this will probably be as easy to build as you expect yours to be but it uses proven design concepts and has a track record. A lot of the strength and stiffness of plywood boats comes from bending the plywood and then locking that bend in place.

http://www.duckworksbbs.com/plans/lewis/duckskiff/index.htm

Here is one that was built a few years ago.



Here is one built last summer with the same methods only smaller (10 ft)



And another (different but same) done some 7 years ago that is still going strong...just don't have recent pics as it was given to someone else.

 

I agree with what others have said already. Glueing up some long plywood panels, bend them in place and stitch & glue them together is the quickest option for a nice fun boat. Personally I don't think any of the many plans for a simple flat bottom skiff you can buy for a usually very modest fee is any better than Steves or Hannus plans. Here is another one for a nice 12 ft skiff: http://www.simplicityboats.com/summerbreezetemp.html.
That was the first boat I ever build some 10 or so years ago. It has seen some rough times and is still going strong. We have a 2 1/2 hp motor on it, way enough since it won't plane anyway, but it takes us out and back again.
I attach a picture from the first outing. Behind the skiff you see a 14 ft aluminium boat for comparison. In the other picture it's crewed by two admirals and a lowly deckhand. Too much weight so far back, but since we use a tiller extension it's perfect.
Regards
Walter

 

Northman I sure enjoyed reading that link. Good descriptions of the Corners and other important fastening points.

 

12 ft skiff Hannu's boatyard ..need I say more .....

 

Thanks for all of the responses, although my design was fun to think of, I realized it may be very cheap to make but I would rather something seaworthy. I think I have decided on a simple skiff http://www.bateau.com/proddetail.php?prod=FL12 Which will look a lot nicer and I will stick to using some better marine grade plywood.

Kind of off topic but I dont want to create a new thread about it, how hard are kayaks to make with a stitch and glue method?

 

My first boat was exactly that kind. It was a fun to build and a fun to use.
See http://www.boatdesign.net/forums/wo...ation/p-v-luca-szeke-my-first-boat-33763.html
Edit:
And I have found the answers in this thread very useful to understand some of the stability and tracking issues which I did not understand when designed Luca: http://www.boatdesign.net/forums/boat-design/placement-seat-kayak-34186.html