Inboard to outboard

[LarryE-old]

I believe Fleck can answer this question. When you removed your inboard how much weight did you have to add to bring the boat up to one design weight? Were the boats themself lighter, to make up the differance in the engine?

[fleck]

Larry,

When we converted Horizon, we ended up adding 305 lbs, plus the weight of our OB (5hp 4-stroke).

To answer your question of were the boats lighter? At least ours was lighter since we were able to make the Class IB min 4400. But I've also heard of boats that were OB from day one who carry 350lbs of lead to make the OB class min of 4600. I also know of IB' that weigh as much as OB's (4600).

It would be interesting to see a summary of what boats in the class weigh and how much extra ballast they carry.

[Marionete]

Bob;

Where did you place the replacement ballast? Was any located near the keel or did most of it go in the engine box? Did you use lead bars? What would you estimate the weight of the engine, and other gear to be that was removed?

I would have guessed that the difference in weight, once you added back the outboard would have been less than 300 pounds- (based on the weight offset in the class rules) Boy was that a BAD guess!

Last question: Do you feel that Horizon (484) is considerably faster AFTER you made the conversion?

[dave]

On a boat the size and weight of a 7.9 the weight being removed from the ends matters more than the weight itself. All inboards weigh more than a small outboard. Even if they were both under the cockpit floor the added mass of the inboard would make the boat slower going into and coming out of a turn, which translates into greater rudder movement for the specific task and that makes more drag, i.e............................ slower. The same thing also makes the boat pitch more in a seaway, which is also slower.

Heck, adding 300 lbs at the bottom middle wouldn't slow the boat much if any and would make it stiffer, BUT the rules and the floor are limiting factors.

[fleck]

The boat is faster, especially in lighter conditions.

The weight ( and also the placement ) is not the issue. The inboard weighs 200lbs less than the OB. We've raced against OBs with 300lbs in their engine compartment (agree that is not ideal). The issue is the drag of the prop, shaft and strut. When you add the fact that downwind, with the board up, the 'stuff' is not hiding behind the flow of the centerboard. Here's what we observed during our decision to convert.

The boat was slower, especially when not going straight. When tacking, and when heading downwind at anything other than dead down wind on a constant course. The more we would tack upwind, the more we would lose to an outboard boat. When heading down wind ( board up), we could hold with the outboards as long as we didn't change coarse (except in light air). The subtle changes to move over a lane for more breeze, less wind shadow, etc, with the board up was a killer when the water would start flowing sideways across the prop, shaft and strut.

As for where the weight was put, we put most of the lead ( I think 200) under the floor alongside the trunk (stuck down to the hull).

Marionete, where are you racing?

[Marionete]

Bob;

AT the moment, I'm racing in my driverway! The boat has been on a trailer for two years undergoing one thing after another - mostly et core repairs. I promised myself to get it in the water this year, and the last thing to do (this season) is fix the rudder.

When that's done, we'll be on the Magothy, just north of the Bay Bridge on the western shore of the Chesapeake. There's another 7.9 out on wednesdays already - it too, has the 171 rating and was an inboard converted to OB. That's hull 299 - Allu is the name of the boat.

About 10 years ago there were six 7.9's on wednesdays and the RC created a separate class called the "174 class". Any boat within 3 or 6 seconds could race and it was scored as a "phrf one design" - order of fininsh. A pretty cool concept, even for wednesday night sailing.

And your opinion of the 3 second allowance 7.9's get under PHRF pretty much stinks. I had a large boat years ago with a folding prop, and we got allowances for a shoal draft keel and roller furler - and would have collected another 3 if we had a fixed prop.

But i see your point on the 7.9's since the ob versions have zero drag. But it makes some sense on the Chesapeake that an Inboard Modified (to outboard) would have a slight displacement advantage over those originally configured for an OB setup.

It's a shame you moved Horizon to the Rapahannock - but everyone who sails there loves it. I own some waterfront directly across the bay on Onancock Creek. There's a great beach about a mile inside the creek on the southern shore where the creek narrows. You may want to venture there sometime and check it out.

Good luck in VA.

[fleck]

And your opinion of the 3 second allowance 7.9's get under PHRF pretty much stinks.

My opinion?

[Marionete]

Sorry Bob - what I meant was that I agree with your observation about the 3 second difference as administered by PHRF - not enough of a time differential to make the inboards competitive under ChesBay PHRF.

Did not mean to inply that your opinion stinks - just the opposite.