Running planing hull at displacement speeds

I retired to Panama and am having a 23' panga hull built for me. I plan to add a cabin to it in the style of the narrowboats of the British canals (the panga only has a 6.5' beam). Pangas are planing hulls, but with tides around Boca Chica, where I will be operating, are 12 to 19 feet the flat bottom is good for grounding out between tides, or tucking up close into the mangroves.

I do NOT intend on using the boat out in the open waters of the Pacific. I will be putting around in the various rivers and bays or the area and am not really interested in going anywhere fast. My question is, will I run into any real running problems putting a smaller outboard on the boat and operating at displacement speeds? After all, a lot of the boats have a small "kicker" that they use when trolling. What would be wrong with using something like that full time?

 

There would be a penalty in extra fuel use, but little else to bother you. You might use as much as twice the fuel, and that is probably pessimistic, but seeing it is only a small engine required, no great problem. If you were using it daily and for long periods, it might become a handicap.

 

See if you can get a 'sail boat' kicker. They have bigger props for your weight.
Watch the cabin weight & location-you don't want any stability or handling problems

 

That style of hull will be pretty twitchy at displacement speeds, so mount a couple of hefty skegs well outboard so she'll still take to ground upright and hopefully control the low speed tracking issue you're bound to have. Low profile runners might do it, with less ventilation issues at high speed, though you'd probably need at least 4 across the bottom.

 

Most pangas are built heavy and strong for offshore use. If you want reasonable slower speed performance, consider reducing the scantlings of the boat. and using a canvas cabin. If you have a light engine, and keep gear to a minimum, your performance should be OK.

 

I can recommend the Tohatsu 6hp saildrive extra long shaft OB.

Pushes my 1.25 tons cat at about 6kts against waves and wind no problem, and is easy to lift onto the transom at only 25kg.the long leg keeps the prop in the water when it gets choppy.

 

It depends on what you are calling a panga. The name has come to be used for many different boats. Indigenous pangas that I saw in Latin America were basically double ended displacement hulls with horizontal wings added under the stern to provide lift for planing with larger motors. They had flat bottoms but rounded bilges/chines. Such a boat would be fine with smaller motors but the steering issues mentioned need addressing with some lateral resistance skegs, runners or some such. Your boat sounds like a normal flat bottom skiff.

If your boat has a wide transom and will be heavy, it should have enough rocker to bring the aft bottom up near the surface for efficient displacement speed. Since you say its a planing hull, that will not likely be true and the problem will be when the speed in in the "hump" range.

A bigger question is, why not build the boat for the intended speed range?

 

To help clear up the matter, for some history of the real pangas look at :

http://en.wikipedia.org/wiki/Panga_(boat)

You will see there is scant resemblance to boats called "pangas" by several manufacturers who only capitalize on a catchy name. Most are simply skiffs made longer than usual. Makes for confusion much like the term "dory" and "sharpie" that are often used the same way.