Hello all,
My post is a bit long, but I think it is better so you can see my thought process and can give some suggestions better...
Build experience & usage plan of a new boat:
I have built a plywood skiff FL12 design from Bateau.com (Jacques Merterns) using stitch & glue design. This was to get my feet wet and also to have a boat to have fun on the water while building a new one. Next one which I have decided to do was CK17, a 17' feet sharpie with a unstayed cat ketch rig. It is a boat of ample size for me and supplies to go cruising, it is trailable, can be single handed and can be beached where I can sleep in the tent on it overnight (or tent can be on the beach - whatever). Also, for cruising it can fit me and one more person easily. When I mean crusing I do not mean extended cruises but more beach hopping with only 1-2 nights that I need to carry food or water with me. I can easily sail to a nearby town and go to the store to resupply -> my location: Adriatic sea.
However, with my experience with FL12 along with CK17, they are displacement hulls, so CK17 top theoretical speed would be sqrt(LWL) * 2.43 which is about 5.5 knots. FL12 theoretical top speed is 4.5 knots, but in my experience when I sit aft (220lbs) and my girlfriend at the bow (approx 130 lbs ) at 3.5HP at 2/3 throttle is max we obtain and I think it is hoovering around 3-3.5 knots judging by the distance and time we cover. To island hop in my area means covering about 3-5 nautical miles on average and then you can go along the shore to wherever you want to land. Therefore, I started to look at other options since FL12 is unsafe to do longer sails with, because if bad weather hits we would be in a very bad situation. With CK17 it is very much doable and we can carry lots of supplies, but it would take 40-50 mins to do the crossing while traveling at top speeds. Loaded, it means we would need good wind, which also means slapping and pounding and is at the speed/wave/weather limit of the boat of that size to sail.
Perfect boat to fit:
- It should be cheap and easy to construct - I do not want to have to build a boat for years; I do not want to break the budget by using some high-tech stuff or custom machined parts where a simple rope lashing can work. I also do not care about showroom ready finish.
- It should have utility I need - safe and fast island hopping, beachable, single handed ability. Light so it is transportable by a car and launched from the beach (saves my costs!)
- It should be "fast".
- It should be of plywood construction and epoxy/fiberglass. Exotic wood is not easy to find here and is not cheap. I can more easily laminate iako for example from plywood and epoxy than to buy some exotic hardwood and shape it. Okume marine plywood is available; I have used it with FL12 and it works nice; did boiling tests; one piece of plywood is out on the weather now for 3rd year and looks like new....except its grayish.
- It should be durable - I do not want to build another one and then another one and so on. So if I need to spend $100 more on a proper paint but will add to years of trouble free usage - so be it. Same with masts, etc.
Multihulls:
So I started to look at multi hulls. As I know of Wharram, I looked at this designs but opted out since there are budget constraints. I do like TIKI21 though or TIKI26. Hitia 17 is OK, but sits too low on the water. I am perfectly fine with an outrigger / proa for my budget and usage plan. No need for 2 hulls, so:
I came across Gary Dierking designs;
2 designs that would fit my bill are:
Waapu and Tamanu.
20-24 feet is an OK size to manage by myself and my building space is perfect for that size. Also bill of material is not that high so budget is met. Hulls seem easy and fast to construct. Their design speed is for 12 knots, which means I can reach my destination much much quicker than with CK17. Also in case there is no wind, it is easier and more efficient to paddle.
I wouldn't mind getting rid of the hardwood chines and use fillet + fiberglass tape instead; no need to buy hardwood; no need to be precise about joints. What do you guys think?
Waapu:
Benefit of Waapu that I see is that it is a 3-piece hull for 24 feet. I can transport it in pieces in my car and avoid the eyes of port attendant to lanuch from the beach at some more remote spot and not pay the fee. No need to buy the trailer or have to sweat by backing the trailer with my car

LOL
I am not sure if 4 8mm stainless steel bolts are OK to keep all 3 pieces together in all weather conditions I may get into. 8mm ss is strong a lot, but....I think that connection would be a weak point vs. one-piece hull. Also, it doesn't have decking so I don't have dry compartments for my gear.
Tamanu:
Tamanu to me looks a bit better; has self bailing cockpits; dry storages; Only drawback is that I would have to use a trailer; Also I am not sure about light version of 4mm sides vs 6mm sides. Okume 4mm is about 13 lbs for a standard plywood sheet and 6mm is 20mm. So plywood weight difference would be about 32 lbs. But would I loose durability with 4mm sides? In any case I plan to put a 6 oz fiberglass fabric on the outside including bottom.
If I build Tamanu, I would like to do all the fittings on main hull to convert it for a double outrigger later on; but first I guess I would do the single outrigger
I can't see on the website what is the maximum load of either of the design? So I know how much weight (crew + gear) is allowed on them.
Things to think....
Also, it seems to me that Tamanu is a newer design which maybe that perhaps construction method was streamlined due to experience compared with older designs and that perhaps some things that were show to "work" were incorporated into it.
I also wonder is it possible to add shunting rig later on on Tamanu to experiment with.
So what do you guys think? And of course if you have some experience with seaworthiness, maximum loads and performances say wind speed vs. boat speed that would be nice.