Spencer 70' IPS

Got this link from a friend who knows a guy at volvo; Interior pics of the Spencer 70': http://volvopentatraining.com/spencer70/interior

Karl

Thanks Karl! Great find! What a beauty!

The Numbers

These are public knowledge but not yet shared here.

Performance of PentaGone - 70 Spencer with triple IPS 1200's (2700 hp)

Fully loaded, 100% fuel, 100% water, 100% holding, 10 people aboard for a test weight of 98,600 lbs.

Averages from runs up and down wind:

2362 rpm (WOT) - 38.3 kts - 134.1 gph
2300 rpm (rated) - 37.0 kts - 123.9 gph
2000 rpm (cruise @ 80% load) - 30.2 kts - 93.4 gph

Cruise range of 28 to 33 knots burning .30 gal/NM

A little more fuel efficient then conventional drives, but not as fuel efficient over conventional drives as what I would've expected. 3.09 gallons per mile. Although you have 3 engines pushing the boat at the same speed you could push the boat at with 2 engines and conventional drives.

I worked on a 75' Jim Smith SF with a tuna tower and 16v 2000's and it burned 150gph at 35 knots at cruise (1950 rpms) conventional drives 4.29 gpm, but at a faster cruise speed. If the Jim Smith had less HP where it cruised at 30 knots at 80% load it would probably have fuel figures pretty darn close to the IPS spencer.

I also ran a 63 sonny briggs for a day, it cruised at 30 knots with 900 mans burning 90 gph, and burned 3 gpm with conventional drives. It too had a full tuna tower.

Capt J,

Disagree a bit. IMO far more efficient than conventional drive yachts in this class.
In going through my small library of published magazine tests of “similar” boats:

Bertram 70’. 164 gph @ 31 knots = 0.18 NM/gal (Approx. 8,000 lbs shy of full load)
Davis 70’. 118 gph @ 28.8 knots = 0.24 NM/gal (Approx. 5,000 lbs shy of full load)
Viking 76’. 112 gph @ 29 knots = 0.25 NM/gal (Approx. 10,000 lbs shy of full load)
Spencer 70’. 93.4 @ 30.2 knots = 0.32 NM/gal (At full load)

That is between 30% and 75% more fuel efficient. With all these at full load the differences would be 5-10% greater.
The only boat that is faster than the Spencer is the Viking and if you were to take hp out to set it at the same top speed you would only gain efficiency at a cruise speed if you could put in lighter engines and/or reduce fuel capacity. The Viking would still need 16V2000’s so reducing fuel (Range) would be the only way.
In the context of this, the numbers you posted for the Jim Smith boat is very close to the Viking 76’ numbers.

You must have a typo in your reference to the Sunny Briggs. 90 gph with the 900 MAN’s will put them at 92% load (They will burn 98 gph at full load) and the boat at about 31.5 knots top speed. I’m sure the boat is faster than that. Are you sure this was not with 1100 hp MAN ?

Karl

The problem with your calculations is that you are comparing a custom built sportfish (spencer) with production sportfishes that are much heavier and have a less efficient hull design then a typical custom sportfish. You'd have to compare a Spencer with a Paul Mann, Jim Smith, Rybovich, Bayliss etc.........

I did a typo, the Sonny Briggs burned 70gph at 30 knots. For a custom sportfish it's not that fuel efficient compared to the others. The 40' Cabo with the zeus drives does burn less. It has the same speeds as the 800 Mans and burns 45gph at cruise versus 62 gph with the Mans at the same cruise (29.5 knots).

That's because the Bertram cores are full of water, or HOT air when they leave the factory. hehehehe

Here Spencer claims their boats are lighter then cold molded in a Saltwater Sportsman article:

Most significantly, coring materials have gotten lighter and stronger. According to Spencer, cored materials weigh 5 to 6 pounds per cubic foot, versus 12 to 15 pounds for most hardwoods. The weight savings on a 60-foot composite Kevlar/carbon hull over a comparable wood-cored boat is about 10,000 pounds, and that adds up to better performance.

"By paying attention to our construction and using lighter, stronger materials, we gained up to 15 percent more efficiency," Spencer adds. "With IPS, we can add another 10 to 15 percent with comparable horsepower.

Understand your comment regarding custom vs production. However, it would appear that this Spencer with all the "non-custom" widgets may be closer to a production (Enclosed bridge, brow and hull side glass that weighs, crane, etc. etc.) On the other hand I'm sure that a "conventional" custom by the builders you mention are more fuel efficient than a Bertram, Viking, etc. I just cant find any good test data.

Good test data - There is no standard for how to test a boat and builders do it differently. Certainly the builders ambition is to show excellent performance thus my reluctance to trust published data. From my consumer perspective I would like to know what a boat does with fluids full, bottom clean but painted, some user realistic extra load (people or ballast) relevant to the boat size and type, in deep water in two opposite directions and with a prop that allows the motors to spin at least to rated rpm. Thats just my opinion. The performance references you get in bars after 8.00 pm I just don't listen to.

The one builder I respect for their published data is Tiara. They list the test condition and more importantly; If you look at their tests the props are selected so engines run over rated engine speed at WOT.

OK on the Briggs (900's right ? Not 800's) Don't know that comparing a 63' Convertible to a 40' Express is relevant. BTW - The 43' Spencer Express with IPS-something burns 31.8 gph at 30 knots according to magazine tests.

Did some work for a client a few years back on plywood vs foam core and cold molded. For the panel schedule I was looking at foam core was approx 10% ligher per sq/ft. This will vary with core and glass schedule. Throw Kevlar/Carbon fiber (and $$) in the mix and you can achive some pretty significant weight savings.

Your Bertram comment in the second post: Agree (he, he...), maybe they use lead infusion.

Karl

I have run a lot of different yachts and sportfish, several thousand of them from 40' + over the years. From what I have seen in a fast sportfish (let's say 25knot cruise and above) or other faster planing hull, the difference between having little load like light on fuel compared to full of fuel and other effects is a very little difference in cruise speed. Typically .3 knots difference or less......but 99% of the time less than 1 knot always. Weight used to be a much bigger issue because a lot of yachts had a hard time staying on plane with the power they were built with. Windage has more of an effect, for example if a sportfish is tested with no hardtop or tower, compared to a boat with a tuna tower, the windage of the tower and strataglass and such will have a larger effect on speed and therefore fuel efficiency. Most boats are tested without hardtop/tower and light on fuel because that's how they are plopped into the water, and the hardtop/tower a lot of times are a dealer installed item, not a factory installed one. At least with production sportfish. So it's an apples to apples test. For example Cabo does all of there seatrials without using the trim tabs so they are as close to each test as possible, and the trim tabs will usually pick up a knot or two.

The other thing I have seen, assuming the particular boat is propped to achieve the manufacturers rated top rpm, is that a particular engine is going to burn the same amount at 80% load regardless of what boat it is installed in. I would say there is only a 5% variant in fuel consumption maximum. For example a C18 E rated CAT is going to burn 75gph at 80% load whether it is installed in a 45' Cabo or 60' Searay. The only difference typically in the cruise speed/gallons per mile equation is the speed of the boat they are installed in.

So basically if you know what the engine burns and the cruise speed of the boat in the test, you can get pretty darn close in your calculations.

I used the Cabo as an example, just because you could compare the same exact boat with 2 different engines, the Man's with conventional drives that cruised the boat at 29.5 knots, and the zues drives that cruised it at 29.5 knots. Basically it was the closest apples to apples comparison I could think of and a 25% fuel savings over conventional drives.

The owner of this boat is a friend of mine down here in TX. "Scandalous" is not a true Spencer. It started life at the Sculley factory. Due to several factors, the boat was hauled from yard to yard for about three years and I believe that it finally ended up at Spencer. I will try to snap some pics of it over the weekend.

again i bring up the question of these so called ''tests''......where were they run???? i'll run a boat in 10 feet of water and come up w/figures that will make a sister ship running in 90feet look like a dog...

Depth will not give a 30 knot boat any more speed from everything I've seen. Running a 65' sf at 30 knots in 10 feet of water or 300 feet of water, the speed will be virtually the same. You're thinking of a big heavy slow motoryacht like the 75' Hatteras I used to run that cruised at 16.5-17 knots. In that case the shallow water gave it a little more stern lift because it was not totally on plane. But at 30 knots the hull is totally on plane and is getting it's lift from the speed of the water running under the hull and not from the propellors or prop wash bouncing off the bottom giving it lift.

I do 10,000 NM's in deliveries a year, and always on different yachts. The majority of it ocean miles, but also a lot of inland miles too. I also run 150 different yachts a year of all types from 30-103'. I've done a lot of engine startup's on new boats, and several of the same type and engine type, both inland and in the ocean and the top speeds I've achieved are virtually identical. The only difference I've seen is that if it's rough on the ocean test, it will effect speed a bit, so will current to a smaller bit. In fact on a lot of 1 30 knot sportfish manufacturer I've done a lot of engine start ups on (over 100 boats over the years), the real world numbers will be 2 knots faster then the test numbers because we use NO trim tabs to keep every test consistent.

It's like running a boat in an area with a lot of current. For example hell's gate. If you run an 8knot displacement trawler, against the 8 knot current, you will have next to no headway. Maybe 1-2 knots. If you run a 30 knot boat against the 8 knot current, you'll still be doing 28 knots....... The faster the boat is, current and depth have less of an effect, mainly because less of the boat is in the water and less drag.

MTU & Caterpillar require there surveys for extended warranties to be carried out in at least 95 feet of water.

a 50 post with Cat's will not run in Lake Worth buts runs like a scalded cat at sea in deep water.

Same with any Hatteras SF, they need deep water. Try running a 77 in shallower water and watch for the submarine effect, take it deep sea and it will run but do it in an enclosed bridge as anything more than 3 footers and you will get soaked.

Of course current has a huge effect on the speed, the current off Port Everglades can vary from zero up to 3 knots and some times is close to shore and other times well offshore.

The university has monitoring equipment that tells exactly the strength of, direction and position of the eddies but nobody wants to pay for the info'.

Always run in opposite directions when doing any tests and position the tabs for optimum performance. Do the runs in exactly the same tracks, not 1/2 or a mile apart as the current can be different.

An older Hatteras motor yacht with Detriots can loose 5 to 8 knots with just a few barnacles on each blade no matter how deep the water.

A 50 Viking express looses 80 RPM's and 3 knots with no tabs.

The old water jets on the Sunseekers had to be spotless to get it out of the hole, Denships need special props and tabs to make them run.

Fuel burn, % load will vary due to air & water temp. with different readings between summer in South Florida & winter up North.

while watching that video , my mind kept singing that old George of the Jungle theme...''watch out for that tree''...