GV11 with sponsons (pics)

[JerryF]

Adding sponsons was an experiment to see if I could make a good boat even better. The boat now is a little less tender, draws a little less water and is a little faster with the same power. Turns at high speed are smoother, which I did not expect. Some other performance factors were affected negatively, though nothing serious. However, that indicates just how unpredictable amateur hull form mods can be.

The modified boat has been in use for 4 months now. I have gotten many more comments about it since I put the sponsons on than I ever did last year. Most people mention the sponsons right off. I was only thinking of performance factors when I added them but they seem to draw attention for the way they look on the boat.






The boat’s ID now has an “X” added for experimental and an “S” for sponsons. My wife says that “XS” sounds like “excess” which seems to cover it nicely.

JerryF
GV11+XS

[BilltheCat]

Congratulations - for being bold & daring. Your boat looks both highly functional & skillfully built. Nice brightwork.

Is she named - "The Rainbow Connection"? It isn't easy being green!

Dave

[JerryF]

Dave, the name is indeed "Rainbow Connection". I originally had in mind rainbow trout but you have zeroed in on the real meaning. Kermit was right all along.

[fishingdan]

Jerry,

The boat continues to look great. Can you list the reasons you chose to add the sponsons? You listed the results above, but it would be helpful to list the objectives.

Thanks,
Dan

[Fritz]

Jerry, great addition and looks.

I second the above from FishinDan -- knowing "why" you put them on will be a big help to future builders.

3 adults + 1 youngster in a GV 11? Impressive......

Also, is you paint S3? and if so, are you seeing any checking or issues on the top horizintal surfaces?

[JerryF]

Fritz and Dan, there was no one reason why I decided to add the sponsons only an accumlumation of "what-if" kind of thoughts.

When I was driving the boat by myself it took on a noticeable list to starboard and I thought what if I had sponsons, would it ride level? Then I said what if I get a new 4 stroke engine that was significantly heavier, then extra flotation aft would help support it. What if the new engine had more horsepower, then a wider beam at the transom would add stability. The boat had a tendency to porpoise at high speed which could be corrected by trimming the engine to a negative (tuck under) position but what if I had more lift aft, could I go back to a zero trim angle? Would the extra lift give a better hole shot? Would it ride better with a lower running angle? In the back of my mind was also the thought that this boat design isn't exaclty sleek looking by nature so sponsons might give it a more streamlined and less utilitarian appearance.

Finally, I guess I am one of those who can't leave well enough alone. I like to experiment and see just what happens when you change something. I try for a positive result but I don't always get it. When it doesn't go right, I always have a Plan B just in case. This time, it worked out ok so I'll keep the sponsons.

The colored paint is Interlux Brightsides. The brightwork has S3 clear coat on it. No checking on any surface but it is stored under cover so I wouldn't expect much deterioration from sunlight or weather.

[paul.tisher]

Jerry, Are you still available for some questions regarding your GV11 with sponsons? I have a 16 ft "Ben Garvey" from Woodenboat Plans about 12 years ago. It looks just like your GV11 and I've been considering sponsons for a few years now. When I think of where I need lift and volume your design looks right. Are they foam or did you build them with ply. Are they built then attached or built on as part of the structure? What were the few negatives? Thanks Paul

[JerryF]

Paul,

Thanks for your interest. I am still around though I haven't posted in quite awhile. The sponsons were built as miniature stitch and glue hulls and then attached to the hull. There are several construction pics in one of my builders galleries: Sponson Construction 2004. The only problem I had was difficulty in reversing. The hull is so short compared to the new transom width that it would not backup in a straight line. Eventually I solved this problem by adding strakes. Your hull at 16 feet long would probably not have that problem.

There is an update to this boat posted under Finished Boats in Jan 2013 and another set of pics in my galleries under GV11+G3. I think it is the best version yet. It is comfortable, stable, fast and we still go fishing with it on protected waters. I now have a bigger boat but if I just want to "mess around in a boat" this is my preference.

Hmm, I tried to post a couple of recent pics but that doesn't seem to work. Anyway they did go into my GV11+G3 gallery.

-JerryF