New transom and bracket 23cc

[Blue_Heron]

Originally Posted by hermco

They work well on RIBs too. Here is one of two I did for the local Sea Tow dude last year, gets used every day,

Don,
I was surfing your website a couple weeks ago and meant to ask you about this one. How does it perform compared to a conventional bracket?

I also noticed you did a full hull extension on an Ocean Master. How does the performance of the longer hull compare to a bracketed version?

I'm still doing some research to figure out which way I want to go with my Potter 20, but the technical info Bushwacker alluded to in his post above is making me think a full width extension will provide more dynamic lift at lower speeds. Of course, at that point it's not really a bracket anymore unless you build it to bolt on.
Dave

[hermco]

The RIB hull extension was to get max floatation, I don't have any comparison data. For the Ocean Master I went to Mark at Ocean Master and used his molds to lay up the hull parts, then made a one off mold for the fish box/ livewell and added a twin bracket. Also added fuel tanks while I had the transom cut off. Slid em in under the deck. Worked pretty cool.

[Blackfin26]

Don, Very cool work. Have you extended the bottom of a SC 23 yet for max floatation and an ideal twin engine mount?

[hermco]

Never even had anyone ask about it. Would be interesting to do one with before and after data tho.

[flyingfrizzle]

That is kinda what I had planned to do to my 23, I was going to do a hull extension/bracket similar to what you have done here. That saying of Carl's when he was asked about what he thought about the boats with a bracket he said "why don't you just make the boat longer" keeps popping in my head. It will be a bit before I get started on mine, but as soon as the 20' sceptre hits the water I will be going threw it and changing the transom and splash well to a extended version like on the newer style boats made today like on the regulator 32 and such. I will post some performance information on the "after" when its done but there will not be any before data to compare it to so it might not tell you guys as much.

If it turns out looking half as good as Hermco's extensions and rides well I will be pleased...

[seabass08]

Thanks for the feedback on this guys. So I guess if Mosely says extend the hull/running surface then that pretty much answers my question

Don those brackets look great.

I am looking forward to geting this done later this winter and seeing the performance difference compared to the current set up.

[kitebuz]

Hermco - really nice work as always. Did you tie in the bracket stringers to the stringers in the hull on that RIB, or just laminate them to the the existing transom? Are there +/-'s to doing the bracket directly to the hull vs bolting them on, and any downside to making them a hull extension vs having a step up to the bracket?

[flyingfrizzle]

This is kinda what I had in mind but built in wells for the trim tabs:

[seabass08]

A few pics of the tear out of the old transom. The boat originally had a notched transom. You can see from the pics that whoever closed in the transom never actually removed the old one, they just added a piece of ply to the notch and puttied it in place. Once the brackets that were holding the engine and bracket to the stringers were removed, it basically fell apart. Glad I decided to do this now instead of running it for another year.

[Bushwacker]

Originally Posted by hermco

. . . Bill Potter says the bracket will provide performance benefits and better fuel economy over a hull extension. I guess Carl M. disagrees. I don't know as I don't have before and after data on the same boat using both concepts. Obviously the bracket is the cheapest, easiest way to go.

I think Potter has a very narrow definition of "performance benefits" that are theoretically possible but not practical. Most brackets shift the CG aft by significant amount unless you compensate by moving batteries, consoles and gas tank. Shifting the CG aft will no doubt raise the bow and allow you to run with more hull out of the water IN CALM CONDITIONS, so that would reduce drag and theoretically allow a slight increase in speed and MPG. However my "real world" experience with a boat that I ran with a light motor for 31 years and then repowered with bracket and much heavier motor (and there's no console to move in a Seafari!), was that the resulting CG shift increased my min planing speed, even with trim tabs, from about 12 mph to the low 20's! Yes, I could hit almost 50 mph with the bimini top lowered, a light load and a good 3B prop, but I never use the boat like that! Since I seldom run in flat calm conditions, but mostly offshore where you'd like to hang on plane at low speed to keep from going airborne when the seas kick up, that increase in min planing speed was totally unacceptable! By the time I added a doelfin and stern-lifting 4B prop to get my min planing speed back down to 12 mph, I LOST about 10 mph in WOT speed, and I know the doelfin costs me 0.2 - 0.3 mpg from back-to-back tests! A good friend of mine re-powered his Seafari with the same motor I have but without a bracket. His min planing speed is still relatively low, but his WOT speed is 50 MPH! Bottom line is that I think my real world performance would be better with the motor on the transom!

Now with a CC where you could maybe offset the CG shift by moving the console, gas tank and batteries forward, you might be able to still get the low planing speed with a 3B prop and no fin. The bracket does add other benefits like the solid transom, big dive platform and more room in the boat, so I would still do it again, but I have to admit that Carl was right, extending the hull would have been even better, giving the same benefits but without causing the CG shift and related problems! He has years of racing experience in rough conditions that Potter never had, so I would trust his judgement over Potter's any time! And the hydrodynamic model that Dave refers to also predicts better low speed planing performance (='s better ride!) for the hull extension!