Bracket vs hull extension vs stretch????

[hermco]

Extending a hull is done quite often. On the Mako site there was a guy did one and I have read about several and done many myself. The most complex one I have done was a 28' Ocean Master into a 31' and then added a bracket. Not as hard as you might think.

[hermco]

Mako hull extension,
web page

[todosier]

Hull lengthening changes the hull rocker, which affect the angle of attack when coming on plane, planing and when falling off plane. With the VDH hull I would think you would positively have to have a pad or flat planing surface extended on the keel to enhance longitudinal stability, and lessen wetted surface drag. The alternative would be calculating hull rocker and building that into your extension.

Yes thanks, I haven't measured rocker along the keel or any of the panels for that matter. My thinking without those measurements would be none as you said for the small amount of extension I'm talking. I would like to add an absolute minimum of length to get the flotation to support the motor. I'd add one foot if I could, but I have a full transom on the boat and I'd rather not cut it up to put a motor well in, since I like the rear of the i/o as is.

[todosier]

Extending a hull is done quite often. On the Mako site there was a guy did one and I have read about several and done many myself. The most complex one I have done was a 28' Ocean Master into a 31' and then added a bracket. Not as hard as you might think.

Thanks, I've read parts of the Mako post before, but haven't gotten through it - wow?!?!?

One question I have that you would 100% know is - what is the minimum amount of extension that can be added to get motor clearance with a bracket on an full transom? Your standard brackets are 30", is that for flotation or to give motor clearance? At what shortness do you have clearance problems? I'd like to build to fit all the current motors, but am planning on Zuke 140/Etec 150 because of weight.

[todosier]

Hi todosier

Over the years there has been some talk on this topic and project so fare I have not seen much regarding the actual project itself.

I have always kind of liked the concept but the practicality, the level of difficulty and the time and effort has always cause me to shy away from cutting up my boat as a experiment. I have always been a believer that the second mouse gets the cheese and the first mouse gets his head handed to him.

One of my practicality barriers is WHY would I want to make a 23 SeaCraft out of a 20 SeaCraft WHY not just buy a 23 and be dune with it??

As far a difficulty goes it’s a lot harder to extend a hull that to buy and attach a bracket from HermCo and his Brackets really look Sweet.

And then there is the time and effort. When I did my boat I worked slow but did a good job (for a armature) this would take lots of time and Lots of Beer.





FellowShip

………………………….

Just for the Grins

Official 23’ SF Antique Classic SeaCraft Owner

Thanks Fellow-ship, I for sure don't want to stick my neck out too far! I'd like to add the bare minimum to get the flotation I'd need without creating more problems than I had.

If it hasn't been done that is news that I was looking for. I understand about going to the trouble to make a boat something it isn't and that isn't my intention. All things considerd, a 20' Seacraft is a perfect size boat for me and my needs, I wouldn't even consider a 23 for what I want to do. I've fallen in love with the lines and history of these boats and I want to get one on the the water and get as close to ideal (origional) performance with a modern motor. My thinking was that just a touch of extension to get the displacement needed would help the low planing speed that I think is important.

[todosier]

There is also a bit of a performance benefit to the bracket. Since the water want's to rise after it clears the transom, when you move the motor aft you can also raise it, at least one inch per foot of setback. Less lower unit in water = less drag, which translates to a little more top speed. I've seen reports that a bracket can be worth 2-3 mph.

Thanks Denny, I'm not so worried about the high end performance gained, but the ability to slog it out against the slop in comfort. A motor in the 150 hp range will get me all the speed I need (except maybe on a really flat warm day . I'm worried about slow planing speed.

On another note. the waterline on the I/O Seafari is truely amazing how deep it sat in the water with several hundred pounds of extra weight. I haven't ridden in one, but they must ride well with all that weight forward.

Tod

[strick]

what is the minimum amount of extension that can be added to get motor clearance with a bracket on an full transom? Your standard brackets are 30", is that for flotation or to give motor clearance? At what shortness do you have clearance problems? I'd like to build to fit all the current motors, but am planning on Zuke 140/Etec 150 because of weight.

30 inches is for the big V-8's. I believe 27-28 for a zuke 140. Decide what kind of engine you want and then look up the specs for that motor in full tilted up position and then Bingo you have your minimum extension needed. Add another inch or two to be safe

strick

[hermco]

Decide what kind of engine you want and then look up the specs for that motor in full tilted up position and then Bingo you have your minimum extension needed.

[Bushwacker]

Todd, I've been a fanatic about low speed planing since day 1, and my rig will plane at 12-13 mph with full load (~3900 lbs total boat + crew load; will email you my weight summary) @ 2500 rpm, exactly what I want. Just ask Snookerd, GFS, Skip or Carla, who have all ridden on my boat in choppy conditions. What it takes is trim tabs, a 4-blade prop, and maybe a Doelfin or equivalent. (I added the fin before I tried a 4-blade prop. May have to take it off one day just to see if it makes any difference.)

Here's a couple photos that should answer the clearance issue. This first one shows fore & aft clearance with motor at full tilt.

This next one is a better shot of clearance with transom . . . about 7.5".
My bracket has a 30" setback. From this picture, I'd say a 24" setback would work fine for a 150 E-tec. Don said he could make them in 18, 24 and 30" sizes. If you went with a 115/130 V-4 E-Tec, you might even be able to use an 18" setback; you should be able find motor height difference between the V-6 and V-4 from BRP website or from this great E-Tec owners forum web page . Just looked at my 2009 catalog and it looks like they've gained weight since I bought mine, or else they've changed from quoting dry weight to wet weight. A 25" shaft 150 is now 433 lbs (mine was 427); a 25 115 is 390 lbs. I do know that BRP includes weight of the cowling. When you compare to a 4-stroke, make sure they include the weight of the oil and cowling!

Although I originally considered the 115,I've ended up so heavily loaded on some of my trips, I'm glad I went with the 150. Even with that load it gets on plane at less than half throttle! One other thing to consider is that the Seafari is a little less stern heavy than the CC's, so that makes motor weight a little less critical. Denny

[todosier]

30 inches is for the big V-8's. I believe 27-28 for a zuke 140. Decide what kind of engine you want and then look up the specs for that motor in full tilted up position and then Bingo you have your minimum extension needed. Add another inch or two to be safe

strick

Are those numbers available? I've looked online for them and haven't found them - that is why I asked.

I know they exist, but I haven't found them.

30 inches is a place to start from, but I'm not comfortable extending that far, given that no one has done it. I like the I/O cap a lot in the stern with the boxes, but I've measured and I think I could fit a well between them to accomodate the outboard in the up position if I could do a clean job that would fit with the lines of the boat. Extend the hull 18" (gives a couple hundred pounds of flotation if my quick math is good) with a well in the origional transom.