Horse Power to Plane

[Retired & got a sailb]

How big an outboard does it take to plane a DS II and how fast would that be? I have read that the maximum is 8 HP. My wife has an IBS problem so getting to shore and a toilet fast is a requirement for us.

[navahoIII]

How about a porta-potti?

While I sympathize with your situation, it just seems faintly ludicrous to even bother going sailing if you are constantly concerned with getting back to shore...

[seandwyer]

I was under the impression that planing was not possible with an outboard due to hull shape and speed - not to mention, the more it lifts out of the water, the more difficult it is to keep the prop submerged. I vote for the porta potti. I know this is a DSII, but in the DSI a person can sit beneath the cuddy and a curtain could be rigged across the opening. I've considered this because of kids, but in the end, modesty decreases as urgentcy increases - so it's never been a necessary add on

[GreenLake]

Sean, I don't know the source for your impression, but for the record, I found the following post where someone reports getting on a plane with a 4HP outboard.

I recommend that thread to "retired" for the experiences reported there that other owners had wiht engine size and performance.

[dannyb9]

i read in an old ds magazine (remember when it was hard copy?) about a guy that put a 25 hp ob on his ds2 and used it to pull his kids on waterskis. the ds is definitely a planing hull, my guess is that 10 hp would do it nicely. i remember planing back from bay point in my ds2 while wing and wing in a handicap race about 25 years ago. the wind was about 15 kn with following seas, it was exhilarating! : ) we won the race on handicap and overall against a bunch of 22-25' boats. aargh!

[dannyb9]

we used to have a plastic bucket with a toilet seat. privacy was afforded by a beach towel over the lap. no prob! now we dispense with the towel

[GreenLake]

Because owners of older boats will read this thread as well, I'd like to point out that the original DS1 had a weakness in the flat areas of the hull aft. That's the area that would get pounded when planing under power. Even if the DSII doesn't share this problem to its full extent, the hull still isn't designed for heavy loads under power. Just something to be aware of before going too far.

[algonquin]

I would think that planing your DS II may exasterbate the situation to a near crisis.

Other alternatives to consider A porta-potti but that is not that easily used. Maybe a brief jaunt down the swim ladder.

Most probable would be to try Depends You can sail all day!

[dannyb9]

what a geriatric lot. so the ds2 is so fragile that planing is detrimental to its integrity? in that case, reef early and leave spinnakers at home. i've always enjoyed the high performance potential of the ds. can someone explain the difference on the hull bottom between planing out on a 20 kn gust and planing out with a 10 horse motor?

[navahoIII]

No pollution under sail.

As to the withstanding ability of the hull, I'll leave that to others to delve into.

[dannyb9]

the question was about whether the ds2 could plane with a motor. the answer is yes. i use oars on my ds1. what do you use for auxillary propulsion?

[GreenLake]

what a geriatric lot. so the ds2 is so fragile that planing is detrimental to its integrity?

Hmm. Not exactly what I wrote. The DS is not designed to the same scantlings as a powerboat of similar size, so you might think twice before putting a 25HP on it to tow your kids (your example)...if you have an older boat with weak laminate in the wrong area, as, yes, I think you could do some damage.

in that case, reef early and leave spinnakers at home. i've always enjoyed the high performance potential of the ds. can someone explain the difference on the hull bottom between planing out on a 20 kn gust and planing out with a 10 horse motor?

I'd guess, duration? And power level as well. It probably doesn't take 10HP to get the DS on a plane.

Anyway, if you're sailing your DS hard you might want to check the threads on reinforcements or stiffening that people have put in. (Applies to DS1s not DSIIs, so we are getting off-thread here a bit).

[algonquin]

can someone explain the difference on the hull bottom between planing out on a 20 kn gust and planing out with a 10 horse motor?

I would expect that the main difference a far as the hull performance is concerned would come from whether you are being pushed hard from the stern versus driven by sail through the rigging. The planing effect from engine only would be different than when flying under sail only. I would venture to say that being pushed hard from the stern would lead to a higher probability of distortion (deflection) of the hull.

It would seem that the DSII is better equipped structurally to handle power from an outboard than is the DSI. Especially when you are considering 10+ HP. Brad

[kokko]

I don't know that this well help you, but I would be concerned about using anything larger than a 5 hp engine. It is true that with enough power you can exceed hull speed and the boat will plane, but the boat becomes less stable.
In addition, I do not know if the transom can take a big load. It is just fiberglass. A heavy weight and a lot of thrust could do damage.