Boat Builder Central - Builder Forums

Hi,

I am new to the forum and Boat Builder Central. I have previously built a stitch and glue 12 ft boat. I now want to build a larger boat. I have a Yamaha 100hp motor waiting for a boat, it weights 170 kg (374 lbs) and has a 25" leg. I know the usual thing is to do it the other way around , build the boat and get a motor to suit, but I got the motor from a friend for a good price.

Now my question is, can I put that motor on the OB 17. I preferably would like to stay with a 17 ft boat as apposed to going to a 19 ft because most of the time it will just be the misses and I on the boat and feel a boat bigger will be difficult for us to handle. I also see that the C 17 is wider than the OB 17 and would this be a better choice for the motor. Can the C 17 be built as a center console which I would prefer because of the hot weather in Brisbane Australia. I look forward to the answers of more experienced builders. Thank you.

Hedley Shepstone

You are correct: that motor is heavy and should fit better on a larger boat like minimum 19'.
If you want, you can build the C17 with a console. Ask the BBC office to send you a copy of the C19 console, that will fit.

Hedley-greeting from USA-the C19 is a great boat and you would never regret building it; you might need to modify the transom for 25" engine or jackplate for it.

As light as these boats generally are, I don't see a C19 as measurably "more difficult to handle" than a 17. Its a bit more ply/glass/fairing to build, but operationally not much different.

Heavier boats take a little more planning ahead. I single- or double-hand our DE25 regularly. Cabin is more of an issue in the wind for docking than its general size or weight.

Hedley welcome to the Forum. I am going to say that the 100HP is to much for a 17 also in these light S&G boats. But look at the OB19 it is easier to build than a C19, has only one outside panel vs. two and very nice lines. Your wife and you should be able to handle her easily. Two feet is not that much bigger. My wife and I easily handle an 18' boat and we are in our 60's. If you look at the bill of materials between the C17 and the OB19 there is not much difference. The number of plywood sheets are the same, different sizes, 3 more yards of biaxial cloth. the OB actually calls for less epoxy. So check it out for your self and see what you think. For your 25" shaft increase the transom center by 5" not a problem at all, make it pretty.

Tom

Thanks for your replies guys. They all make sense, and I think I might settle on the OB 19, I think as my second boat it will be a good one to build. It is so good having this forum to ask you more experienced builders advice before we do the wrong thing.

I have one more question and I don't know if anyone there will be able to answer it as it is an Australian question, I will be building the boat in Australia and how will I go about getting an Australian builders plate. Would I get a local Marine Surveyor to look over the plans and give them the tick of approval.

Thanks again

Hedley

That question has been asked before. Build her to spec or nearly so and then quote the calculated figures from the Nautical Architect that designed her. You are the boat builder.

I did a quick search as I remembered participating in a discussion before. Sounds like you can just get a blank form and fill it in.

viewtopic.php?f=2&t=62733&hilit

Thanks for that "One Way Traffic".

I have been looking at the plans of the OB19 and the C19. I see that the OB19 has a deadrise of 7 degrees at the transom is this correct, the C19 has a deadrise of 12 or 14 degrees. I will be using the boat mainly in Moreton bay off Brisbane but I also want to go offshore to the islands off Queensland so I think I will now go for the higher deadrise and choose the C19.

Hedley

I think either boat could go either place. I don't know how those figures were calculated but my Trig is better than average. From the FS17, OB17 and C17 plans in my possession I get 3,6 and 9 degrees respectively. If the bigger boats are scale ups (and I believe they are) that is about what you should get as well.

However deadrise at the transom is not everything. Most slamming is further forward on the boat. For all of those boats the deadrise where you cut the water will be greater. About 15-25 degrees depending on the design and speed. I could provide some values for you if you like, but the C17 and OB17 aren't all that different. The C17 is the bigger boat and was my choice.

Also consider that if the water gets rough enough all boats slow down. A mod vee (5-10 degrees) will handle better at sub planing than a deep vee, which is just Physics.