Building a 10 and a half foot skiff

This will be my building blog I suppose, I just had a few questions before I go out and buy my supplies.

I will be using these plans http://koti.kapsi.fi/hvartial/skiff/skiff.htm

I have a 5hp nissan motor, would it be fine on the back if i made my transom out of 1/2 inch?

And secondly will it move my boat and be fine for lakes?

Also, should I modify the design to make the transom a 14 degree angle rather than the what looks to be about 24 degree angle?

oh and I'm going to add a keel for sure, what size do you think its best like 2"X2"?

 

Looks like it should be a nice boat for oars or a small electric motor, but 5 HP is probably excessive.

 

Yes... a 5 hp motor is overkill for that hull shape.

 

yeahhhh I was kind of thinking I would make a slightly wider transom for more buoyancy in the bacckkkk

Also will probably never use full throttle, probably flip the boat, its just going to be a little put put fishing boat and i hate electric motors, also I got the 5hp for a good deal

 

If you insist... yes you should reduce the transom angle. A keel/rub strip is a good idea too. Have you browsed the web for other boats in this category?

 

I have looked around a little bit but couldent find much that would go atop a car. Its not a boat I will be racing around with just a slow steady low throttle to get to where I'm going then trolling.

And by angle do you mean actually change the angle of the cut on the transom and back of the side pieces or just widen the transom to lower the angle?

 

How does widening the transom lower the angle of the transom?

 

The CoB center seems a long way back if at 69% (according to the designers data) and that does not marry up with the curve of areas graphs to my eye. The curve of areas graphs show approximately a 50% position for the CoB, not too bad but probably not optimum.

I would double check this, something is not quite right. The actual curve the designer is aiming at is pretty good IMHO. Personally I'd lightly rework it with a vertical transom to ease motor mounting and give a better displacement speed by virtue of more waterline length. You need to work out where the weight is in the boat. Note the photo, one guy and an engine, just look how stern heavy she is. So if you want to be solo and then two, maybe three people work out where they need to sit to keep a sweet trim angle.

Yes, the transom will be fine out of 12mm (1/2") but you will need a packer/local strengthening piece, for the motor. Exact position depends on leg length and prop position, ie it should be low enough to 'grip'. Check out the guides on propellor depth to water level - not hard to get right. Search this Forum, there is a lot of information here. Ensure you have enough space for tiller swing and consider an extended tiller length to maintain good trim.

Basically she looks a sweet boat, just run a few counter checks before you go and build her. Then you will have more confidence too.

 

How sensitive will the various curves and centers be to the weight and distribution of the occupant(s) and gear? Hum much will the performance be affected?

 

so build it so that i have transom a and side b or b and b?

My main thought is to make the leaning angle of the transom 14 degrees, then to make the transom 27" and 37" on top rather than the original 24" 36" ,then bring the angle of the transom sides a bit more vertical?

 

I agree with those who say 5 hp is too much for this little boat, but for a different reason. A boat that size is not designed to support the weight of a 5 HP. This is about 60 lbs. You would be much better off with a 2 or 2.5 which weighs half that. It would still move you along when needed and be better for trolling. One of the considerations for a boat like this is providing level flotation in case the boat swamps. It requires half as much flotation for a 2 or 2.5 than for a 5. It also balances the boat better.

 

https://post.craigslist.org/imagepreview/00p0p_jXBt8FmlhDE_600x450.jpg

With a half inch transom there isn't much hp you can put in it. The displacement of water is one thing you need to look at. Also the strength of the board used for the transom. I'd say at least an inch with just any hp. I think the hull could handle 5hp with the some runners or fiberglassed. Definitely not with a 1/2" transom. I thought at first 1 inch was excessive but after horror stories on forums I would say its a standard.
I have a 12' jon boat with a 1 1/2" transom. I used red oak 3/4" thick. Glued and screwed together. I only have a 4hp 2 stroke on it.



http://www.fiberglassics.com/restoration/fiberglassic-guide-to-transoms-floors-and-stringers

 

Oh I said displacement of water was a factor. Its because how deep you sink with what you expect to be in the boat is where your cavitation plate needs to be at. Other wise there will be performance issues. So not only thickness matters but the height. Also keep in mind that its also based on engine shafts. If you make the transom before building you have to buy a certain engine. You could get your engine first and then measure out your cavitation. Long shafts are typically 20-25 inches and short shafts are 15 inches all depends. Long shafts are pretty rare where I am at. They sell cheap and hold no value. Short shafts are common and expensive. They hold value though. Thats just my area. I got a long shaft for $50. Almost all short shafts sell for $300+. Just keep all this in mind. I am sure you could get a 2-5 hp short shaft not running for $100. You just got to fix it up. Usually just a clogged carb or bad fuel pump. Not many people are engine savvy.