18 foot dinghy

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Location: Davao City, Philippines

18 foot dinghy

Post by davaodan »

Hello Morten,

I am thinking strongly about building your 18 foot dinghy and while looking over the plans I saw some things that raised questions in my mind. In the building instructions you do not specify what density glass tape is needed. I presume it is 170 g/m2.

Is the hull stiff enough when using mostly 6mm plywood? I would think it would show a lot of twisting or flexing when using 6mm for most of the hull. My 12 foot row boat is made entirely of 9mm plywood and it is strong and rigid. This dinghy at 18 feet long using mostly 6mm in the hull would seem to be much less rigid. I really like the weight of the hull at 85 kilos because I must carry the boat ashore. If I use 9mm plywood throughout can you tell me approximately how much the weight might increase? I still have coral to contend with here in the Philippines. Whether I use 6mm or 9mm plywood I plan on covering the lower hull with fiberglass tape for abrasion resistance. The 6mm three ply plywood available here consists of two very thin exterior plies and one central much thicker ply with numerous voids. The 9mm consists of 5 equal thickness plies and very few voids so I am strongly leaning towards building the entire boat using 9mm plywood.

I have not located an outboard motor as yet here in the Philippines as they are scarce in this area. The fishermen here use small inboard motors similar to lawnmower motors with a shaft diagonally through the hull. In the US they have two types of outboard motors, long shaft and short shaft. Do you have the same in Europe? Can you specify some dimensions for the transom height for each different length of outboard motor? One dimension for the short shaft outboard and one for the long shaft?

Your 18 foot dinghy is also being built in the Luzon area of the Philippines. http://www.pinoyboats.org/forum/viewforum.php?f=2 The discussion is located in Member's Projects under Sunnydays' DK18 if you want to see it.

I see these figures posted on the different documents of the 18 foot dinghy and I wonder what exactly they refer to.
I presume B.mid is the width of the boat at it's widest point?
What is the "d" represent?
What does the "T" represent?
Can you derive the freeboard from these figures?
What does the "∆" represent?

B.mid = 1,456 m / 4' 9"
d = 0,859 m / 2'10"
T = 0,150 m / 6"
∆ = 612 kg / 1349 lbs

I would appreciate anything you can tell me to help me understand these figures.


Dan Vander May
Davao City, Philippines
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Joined: Wed Feb 09, 2011 6:34 am
Type of boat I like: 16 Sea Power

Re: 18 foot dinghy

Post by fred4win »

Hi davaodan
This fred in Iloilo Philippines. Been reading all of your post. 5th boat you say. doing good. can you post a pic of the 18 foot boat.. did you start. I am starting morts 16 ft sea power. The water is always chopy and I have to also take the boat out of the water every night.
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Re: 18 foot dinghy

Post by jem »

On the description page, http://boatplans.dk/boat_plans.asp?id=56

Scroll down to the bottom to the boat description. Click the "what's this" link and page will pop open with definitions.
-Matt. Designer.
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