following sea

B~C · Posted: Mon Apr 18, 2005 10:47 pm Post subject: following sea

How do you handle a following sea?
myself, on big rollers, go like hell with the trim tabs in the go fast mode and a big grin.
On the big steep stuff, with the trim tabs up, I go slow and pretend I'm a bird, just let them pick me up and then go like hell on the backside untill I'm almost back in the trough then throttle back to just off idle and start all over again. I'm always using that throttle and looking behind me, usually leave grip marks on the throttles.
On big breaking waves, same as above but with the seat clinched real firm with the pucker muscle, all the while wondering what the hell I'm doing out there cuz I shouldn't be.

you?

True Story · Posted: Mon Apr 18, 2005 11:20 pm Post subject:

BCK, Your scarin me! Always wondered how to take on this kind of stuff since I haven't been exposed to it. This explains the indentation on your helm seat.

Redƒox · Guest

Good one

and I got no "one way" of doing it. There are times I have only enough throttle to keep baby pointed in right direction, and enjoy the sees running under me, and there are times play surfer-dude, and run back and forth on them, trying to ride each swell out as much as possible Surprised

... seems they always have a way of disappearing on you (as in; where do they go?) Tricky Exclamation

Mostly though... trim tabs are always up as far as possible, cuz I need to keep engine trimmed-down far as possible (cavitation) Disgust

I can't wait to get a better hydrofoil... maybe I'll have better control, if I don't have to trim-down so much in a following-sea Neutral

Mr. Fisherman · Posted: Tue Apr 19, 2005 2:08 am Post subject:

Redƒox · Guest

Yes

Best reasons for the big Yami's and Suzy's is the fact they turn a steeper-pitch prop, and deliver a better ride thata way to.
I keep gettin heavier and heavier Embarrased

So I stepped-down to a 17-pitch. I noticed a gigantic difference from a 17-pitch to a 15-pitch on my older two-strokes. I could not swing a 19 on them Thumbs Down

and when I had to put on the 15-pitch the ride really started sucking in the swells... front-end would fall off the wave-tops with a vengeance Angry

the 17 was a dramatic improvement! 19 and 20 even better, but not by much! 17-pitch was the barrier.
Maybe I'll put my 19 back on, but I really like the way the 17 rockets the RedFox out of the hole when she's really heavy! Better for the engine to not lug her so much Idea

Your Suzy is geared-down a notch lower, but has to have reduction-gears to achieve it. I'm pretty sure my Yami' is direct-drive to the lower-case. You runnin' a hydrofoil... Question

Larry H · Posted: Tue Apr 19, 2005 2:14 pm Post subject:

Greg,

Are you using a prop with a lot of rake (blades lean aft)? A high rake prop tends to lift the bow. That would keep the bow up when starting over the crest of a wave. Evinrude sells a stainless steel prop called The Raker for bow heavy boats.

Mr. Fisherman · Posted: Wed Apr 20, 2005 12:23 am Post subject:

No foil here Greg ol' buddy.
I am hoping to get the trim tabs on within the next few weeks. I have been putting it off because I can not afford a kicker bracket.

Redƒox · Guest

ARG... I'm thinkin I got screwed on that "hydrofoil" I now have. Sure looks purdy, but I think I cavitate worse with than without it Disgust

Off with it's head! Thumbs Down

Larry you won't convince me there is a "free lunch" prop out there for them high-geared outboards Wink

OK... I better get off B~C's thread now... Embarrased

B~C · Posted: Wed Apr 20, 2005 8:10 am Post subject:

aint my thread, Iza just thowing up a thought for discussion. I wonder how the TC would handle the large steep stuff

Sealife · Posted: Wed Sep 28, 2005 12:46 am Post subject:

Seas today were real lumpy, maybe 3-4 feet and close together, whitcaps starting. No problem heading into them (9-10kts), but running back with them on my port quarter, and at about 15-17kts, I was getting some cavitation (ventilation?) of the port engine, rpms racing ahead. Was running with tabs fully retracted, and trim about neutral. Got it to stop by slowing to about 12kts. I see from this thread others have experienced this same thing? Is there something I can do with the tabs to counter it? I did tuck the engines under a little with the trim control, which helped a little, but not enough to get back up to speed.

Interesting comment, Greg, about your hydofoil. I haven't yet added DoelFins to my new engines. By your comment, I'm not sure I should add them.

Redƒox · Guest

....oops

almost missed your question Joe Neutral

It's true-blue for the RedFox alright; the last hydrofoil was a sham. Its only the second one (brand) I've tried, and having given them things a fair chance at proving themselves sea-worthy, has failed to impress. One brand did stop some venting, the other I'm pretty sure made it worse! It was a cool looking unit, and on sale at one of our local marine stores---and I fell-for-it again... Embarassed

now its off to stay! From what your describing, I'd say adding one would only make it more pronounced Exclamation

What happens down there is; the faster you scoot-down-seas, the more stern-lift. For trailing-sea-enjoyment; you must be "stern-heavy" to keep the end of the boat that controls----in control---the stern. Idea

The more gadgets that lift the stern and burry the bow (as we need to do sometimes) like trim-tabs and hydrofoils, the more ill-handling your going to in for out in them nice big-ass'd-seas Crook

RedFox does great with her huge-trim-tabs cuz she's rigged for them: more-stern-heavy.
Having the tabs and lots of weight back where its needed, I have control in any situation---stern-down, stern-up.

Hope that was clear, I don't do so well at bein clear sometimes Embarrased

Sealife · Posted: Wed Sep 28, 2005 2:02 pm Post subject:

Right on, Greg. In following seas, it's vital to keep the bow up, stern down. I had my tabs in the full up position, but had two other people aboard in the cabin, which might have given me more weight forward. Hell, I was more worried that with those two 4-strokes back there I'd be too stern heavy. I might try some starboard tab to lift the starboard side and keep the port side down, when in a port quarter sea again.

The DoelFin issue is interesting......they are designed to lift the stern, but it would also seem to help to prevent ventilation. I had them on my old Sealife and they worked well.

Sea Wolf · Posted: Wed Sep 28, 2005 3:17 pm Post subject:

Now that Greg has drug me into this, I'll have to get my feet wet, so to speak.

It seems that the overtaking motion of a wave from the rear wants to lift the stern of a boat, then if that happens too much and the bow digs in, the net effect is to broach the boat sideways.

Thus we have the admonitions to keep the bow light, the stern heavy, and eliminate any additional leverage points for the wave energy like trim tabs and hydrofoils.

This makes me think that the ideal boat in this situation would be a heavy deep hulled double ender to minimize the effects above not wanted on the rear of the hull. No wonder so many of the very seaworthy trawlers, tug boats, and ocean going sailboats have double ended designs, and also are "positive displacement" boats that certarinly don't plane, but use pure mass to help achieve stability.

Thus Red Fox's admonition to load up the arse of the boat to stabilize it's behavior at displacement speeds is right on with both empirical observation and established naval architectural practice and theory.

This is the most apparent limitation of the light dory approach to design: when the boat meets following seas. The cork, floating on its side, narrowed end forward, gets it's butt pushed around by the energy of the oncoming waves from behind.

Weren't some of the Melben Marine's custom 25-30 foot workboat double enders? (Melben Marine was the original C-Dory builder, I believe. See the company history on the C-Dory Manufacturers website.)

Does the original flat bottomed "Classic" behave differently than the later 2-degree slightly v-bottomed boats in a following or other seas?

How do these considerations relate to the performance of the older and newer Tomcats with their two narrowish hulls?

Better quit for now! Joe.

Sealife · Posted: Wed Sep 28, 2005 10:59 pm Post subject:

Well, Joe, that's probably why the Toland's used to discourage trim tabs on their boats. C-Dorys have a natural bow down attitude (most evident at rest) which contributes to this problem. It's also a reason it can slow down so much in rough seas and still stay on plane, so it's a trade-off. As C-Dorys have evolved and gotten so much more popular, adding twin engines, and 4-strokes have put additional wieght in the stern, probably helping this problem, but narrowing the amount of freeboard at the motor well. Perhaps one solution is not to run with a quartering sea, but to take it dead astern, tacking somewhat to reach the destination.

I'll say one thing though, my Raymarine ST6001 SmartPilot works like a charm, dead on course, no matter the sea direction. Just up the response level for following seas, and it track perfectly. Great unit.

SeaSpray · Posted: Wed Sep 28, 2005 11:51 pm Post subject:

I wish I could say the same about my ST6001 unit. It has not worked the way I would like since day one. On this last trip I removed all metal that I could find from under the stove area where the fluxgate is mounted. I was keeping stainless and aluminum pans there. This did seem to help and it held course for the most part. But even when it is working well it will be off course by .02nm to .03nm. Seems like it should stay right on course when it is flat calm and little current.

Steve