GV11 Stability And Horsepower

[JLL]

I am considering building a GV11 to use as a dingy for my sailboat. I previously built a D5 pram but it was way to tender and did not operate well with an outboard. How stable is the GV11? Can you move about the boat comfortably and without fear of it flipping?

Also, the building plans say it will plane with a 5hp with one person in the boat. Will a 5hp move this boat pretty good even if it is not on plane?

Thanks.

JLL

[ArizonaBuilder]

others have choosen the FB11 as a tender do to the fact it nests.

http://boatplans-online.com/proddetail.php?prod=FB11

[JLL]

Thanks, but it's not necessary that it nest.

JLL

[BruceM]

Yes it is reasonably stable as long as you don't make quick clumsy moves in the boat. It has a very wide beam for a small boat and that helps tremendously. Sudden moves will cause most any small boat to lean and the GV-11 recovers quickly. Loading and unloading of gear and passengers is like any other boat, common sense is key.
I think it would do fine with a 5 hp even at non planing speeds. I have a 9.9 Honda motor and at about 110 lbs it's not a light engine but my GV-11 planes with 500 lbs of passengers in it. And I built mine on the heavy side. I even pull kids on a tube with it a planing speed although the kids cannot weigh much in order to get up to speed.

[Evan_Gatehouse]

You must have a pretty good size sailboat to consider the GV11 as a dinghy - unless you always tow it. Having built a D4 and a GV11, the GV11 is about 3x more stable. Yes, you can walk around the boat without fear of flipping. It's a much wider, larger more stable boat.

3 speeds for small planing boats like these:

< 5 knots = not planing, could use a 3.5 HP outboard if you wanted and still go as quick. Will go this fast with a 5 HP at 1/3 - 1/2 throttle.

5-12 knots = semi displacement speed. What you get if you try to make it plane with 2 or more people aboard and a 5 HP outboard. Big bow wave, lots of bow up trim and huge wake. Not the best operating condition

> 12 knots = now up on a plane. 5 is the minimum to plane with 1 person, and a reasonably lightly built GV11 (i.e. no heavy pine plywood)

[JerryF]

Can you move about the boat comfortably and without fear of it flipping?

JLL

These are two different things in my opinion. The GV11 is very good at handling weight off center without "flipping" but moving about the boat is something else. I agree with Bruce, common sense is needed whenever you move about in any small light boat. The GV11 can be built very light and though I don't think you could flip it, it will move under you if you dramatically shift your weight by standing up. Sitting down you will find this hull to be plenty stable.

[JLL]

Thanks for your responses. It sounds like the GV11 is stable enough for my purposes. I have a lot of experience with dinghy’s and I don’t plan on doing back flips and cartwheels on the dingy, but I have been very disappointed with the stability of other small boats. The engine weight is a consideration for me. Moving a 50lb motor around isn’t a problem. But, moving a 60 to 80lb motor around a sailboat will be difficult and moving an 80+ motor around will probably be impossible.

Evan, I will be towing the boat 95% of the time and placing on deck only for long open water crossings.

I do have one more question about weight. I have built three stitch and glue composite boats and all were constructed with exterior pine plywood. The exterior wood worked very well with a little preparation and patience in picking plywood. I have not decided what type of wood I will use to construct this boat. The study plans list the empty weight at 105lbs. What type of wood was used for this estimate? How much heavier would you estimate the boat to be if I use exterior pine plywood? Thanks.

JLL

[Evan_Gatehouse]

I don't have the spreadsheet here at work. But my recollection is that they were based on fir. Okume is lighter, at 20 lbs for a 1/4" sheet. (or 0.625 lbs/ft2) and 30 lbs for 3/8" (0.9375 lbs/ft2). Meranti and fir is about the same, about 25 lbs for 1/4" and 35 lbs for 3/8"

Yellow Pine can be a LOT heavier. It runs about 34 lbs for a 1/4" sheet. ( 1.0625 lbs/ft2) and 47 lbs for 3/8" (1.468 lbs/ft2)

Areas from the plans:

1/4" plywood = 78 ft2.
3/8" plywood = 22.7 ft2

APPROXIMATE Weights of plywood options (this is just the wood - no epoxy or glass included). Plywood weights do vary, so careful shopping for a lighter pine may make sense.

Okume = 70 lbs
Meranti/Fir = 86 lbs
Pine = 116 lbs

note - if you choose fir or pine, their open grain will absorb more epoxy than meranti / okume, further increasing weight and perhaps cost depending on how much epoxy you have purchased.

If it was my boat I'd pick Meranti as the best from a cost/performance point of view (in fact I'm going to be building a GV10 this spring in Meranti).

One final note - how big is your boat. The beam of this boat makes it about the same dimensions as a big RIB.