PDQ36 sail-to-motoryacht conversion

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Ed Ellis
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PDQ36 sail-to-motoryacht conversion

Post by Ed Ellis »

Motoring along at excruciatingly slow speed for hours and hours the WHOLE way from Key West to Pensacola gave me lots of time to fantasize about converting my PDQ36 sailboat to a motor yacht with 40s or 50s propelling it along at 15-20+ kmh.

Here’s some ideas that come to mind…

First is whether to try and design modifications that would be semi-interchangeable between sailing and motor yachts or to bite the bullet and make a permanent transformation….???

If semi-interchangeable…
Strip off the sailing gear (mast, running rigging, etc.), but make minimal modifications to the boat itself with the exception of perhaps adding Dave’s hull extensions to support the extra weight.

Build a removable fly bridge, constructed from aluminum tubing, that’s mounting on the existing tracks on the top of the coach roof. The fly-bridge would accommodate a 2-seat & prefab fiberglass center console. It would be removable so that I could convert back to sailing at some future date.

So how to power up?
One option would be to modify the existing engine wells to accommodate much larger engines (e.g., 40 or 50 hp).
++++++++++++++++++++++

If permanent transformation to motor-yacht…
Same fly bridge concept, but permanently mounted to coach roof.

Cut off the keels.

Modify rudders to make them much smaller.

So how to power up if transformation would be permanent?
Again, modify the existing engine wells to accommodate much larger engines (e.g., 40 or 50 hp) OR modify Dave’s hull extensions that that they contained transoms of sufficient strength to handle the power of the large engines.

Ideas?
Ed & Linda Ellis
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Re: PDQ36 sail-to-motoryacht conversion

Post by duetto »

hi,

first, why not sell your 36 and buy a powercat?

with that said there have been a couple of geminis that have been converted to power.
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Re: PDQ36 sail-to-motoryacht conversion

Post by Ed Ellis »

Bottomline is that I can't afford a powercat.
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Then can you afford the fuel bill, at 1.7 GPM?

Post by thinwater »

At 100 hp you use 10 gph. That is ~$30/hour in the near future. At 17 mph that is 1.7 gpm. Ouch.
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Re: PDQ36 sail-to-motoryacht conversion

Post by SecondWind »

Ed,

How about a diesel/electric conversion with either electric outboards or pod mounted motors and an adequate sized diesel genset.
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Re: PDQ36 sail-to-motoryacht conversion

Post by Tanah-Keeta »

I thought about these issues many times as I was slogging my way back and forth to the Bahamas at any where from 2 knots to 6 unless we had usable wind and then it was really fun. I think the bottom line is that these boats were designed to a formula that makes them a top performing sailboat. Any major structural changes(except maybe the hull extensions) detract from that design. The 34 powercat was initiated by using the 32 sailing cat as a platform but it evolved quickly to another form including a totally different hull design. I just wish they had used the 36 for that platform instead of the 32.
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Re: PDQ36 sail-to-motoryacht conversion

Post by 36041 »

How about skipping the fly bridge, staying with gas, and going with 15 - 25 hp Honda 4's? My bar room napkin calculations show almost 600 lbs weight reduction coupled with a 100+ % hp increase should get you at least 9 knots of boat speed at less than 4 gallons per hour combined. I have often wondered if the 36 wouldn't make a good, non-planing motor vessel, just think of all those bridges that won't have to open for you anymore.....

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Tom
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Re: PDQ36 sail-to-motoryacht conversion

Post by Cat Tales »

What is the correct formula to calculate how much horespower is needed to achieve a specific boat speed? My wife has been on me for more motoring speed, 9-10 knots would be sufficient, but I could not come up with an accurate formula to determine how much horespower we would need.

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Re: PDQ36 sail-to-motoryacht conversion

Post by duetto »

fwiw,

we own a mv34. i can tell you that 7.5K is easy....10 over over takes the turbos. 7.5-10 takes a lot of power for a relatively small increase in speed. we have the 75 hp diesels. pdq found that more power was better from a speed AND economy perspective. if your goal is more speed at a reasonably economic fuel consumption i would get a naval architects perspective before you spend a lot of money.
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Re: PDQ36 sail-to-motoryacht conversion

Post by Page 83 »

Forgive me for being critical, but I have to say I think you are trying to make a sow's ear out of a silk purse. I do have a suggestion to offer: An Endeavor Cat is a better platform for your purpose, and can be had for less than what your PDQ is worth. The difference might go some way toward paying for a power-up. It will offer a narrower beam and has more room for repowering using the same drives. The interior is more apartment-like. Losing the mast and most of the keels would save weight and reduce drag. In my mind's eye it would be a better choice because they kind of look like a trawler anyway. If you changed the sail plan you might be able to fold the mast down but retain the ability to augment the gasoline breeze!

Think of your PDQ as an asset that would appeal to more future buyers as a sailboat than otherwise.
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Re: PDQ36 sail-to-motoryacht conversion - to consider

Post by maxicrom »

Just adding my two cents here:

Our PDQ was built with a Yanmar GM series diesel in the port hull (under the 1/2 bunk) with a straight shaft and dripless seal - it has a feathering prop and we can do 7 - 8 kts at 1/2 gal+/- per hour running about 1300 RPM (we normally run about 900 - 1000 RPM 5-6 kts). Last years we filled up before leaving Solomons to Washington DC, plus a few more outings in the fall - we topped the tank off this year with 8 gallons (about 250 mi. total with some sailing but mostly motoring). The only issue we had was that with the single engine it was very difficult to maneuver until gaining steerage, we added the 6HP Torqeedo electric and a 24v charge circuit and it works great (2 x 12v 6D batteries and a small charger). The Yanmar is dependable and quiet, with the 30 gal tank it's economical and we only have one type of fuel to carry (+ dinghy outboard fuel). It was one the things that sold me on our boat - I tend to have a love/hate relationship with outboards. Until the Honda 4 cycles came out my mantra was "No OB motor larger than I can throw overboard after 25 pulls" :cry: .

I've done a lot of professional boat work and PDQ's really seem to hold their value, a conversion could really affect that - you might look around for someone that took on a Cat project and got in over their head - they can be found in yards all over that people just want to get out of. I found a 65 ft. cat on the hard(Hukamakani - a 70's Transpac winner) for $9000 in a Long Beach boat yard - it needed motors and a mast repair - the owner had just spent $8000 on SS rigging, new Lexan ports, and had just reglassed the hull (I think there was a Toyota PU parked under it that went with it).

Just food for thought - in this economy how many of the big powerboats are leaving the slips these days... I think that Sandy makes a good point.

Good luck,

Mike 8)
Mike & Linda
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