25 Tug questions...answered!

[Pat Anderson]

Yes, basically most of Les has been saying was confirmed by Jeff at the Lake Union Boats Afloat Show yesterday- we made a last minute decision to try to get there for the last hour yesterday. The boat is GORGEOUS, it will be worth the wait - and if you don't mind 7 - 10 knot cruising, it is ready now. But you are not going to get the promised 16 knot cruise until they solve the engine dilemma. The performance reports vary only slightly, and that could be due to current, wind, and load - neither Jeff nor Les got performance ANYTHING like what Y-Landing John reported above. Jeff got 13 knots top speed. He also confirmed that they are scrambling to get the Volvo D3 engines in for tests. We certainly are going to wait for a Volvo engine before we take the plunge, as the boat cannot currently deliver the advertised perfomance promised at the 2006 SBS.

[thataway]

The old addage of one gallon of diesel an hour for 20 hp is still fairly close for the new high speed diesels. Thus if you are truely using 160 hp, you will burn 8 gal an hour. You don't want to run the boat on the "hump" of the curve, where the boat is not really on a plane, because this is not fuel effecient, and tends to lug the engine. Although you have torque at low HP, my experience in V hulls leads me to believe that you will have to bring engine speed up above 3000 to get on a plane, and will still be well over the 1800 RPM range when on a plane. The high torque at lower RPM works well for the displacement mode. The C Dory, being a flat bottom boat, will semi plane--at a low speed. This allows reasonable fuel consumption and being able to handle rough water at a slower speed. Since the hull form of the C R 25 is more of a traditional shallow V, it will probably behave more like this type--and until we see some rough water real life numbers, we will not know how much fuel the boat will use in these conditions.

When I made the decision to buy the Tom Cat, I was aware that going into the waves over 3 feet, I would be at a disadvantage in comparison to some other cats--but the other features won the day. So all boats remain compromises and you must decide what your priorities are. Don't feel too pressured into your decision until you see what happens with other engines. The Camano (really 28 feet and 10,000 lbs) is advertised as a planing boat with 200 hp, but I have several friends who own them, and their conclusion is that they were best at dispalcement speeds.

[Les Lampman]

[Vikingbaat]

Les, thataway, and Pat: thanks for the great info.

I put money down on an R-25 at the 2006 Seattle boat show. The internet literature assumes an 80HP (really75HP) Yanmar as standard and an additional, I believe, $3750 for the 110HP option. If the factory still assumes the 75HP Yanmar is the basic engine, then to purchase the Volvo 160, etc. (If it is an option) could get expensive. I hope that in light of the reduced performance of the 110HP Yanmar, the factory will consider, at least, this as the basic engine offered.

R-25 on order

[Les Lampman]

Here's a bit of info for comparison:

Top speeds for a 9,000 boat:

55 hp = 9.5 knots
75 hp = 10.2 knots
100 hp = 11.5 knots
---transition to planning---
110 hp = 16 knots
125 hp = 17.5 knots
140 hp = 20 knots
160 hp = 21.25 knots
180 hp = 22.5 knots

Top speeds for a boat equipped with a 110hp engine at various weights:

9000# = 16 knots
8500# = 17 knots
8000# = 18.5 knots
7500# = 19.5 knots
7000# = 20.5 knots

These are wide open throttle speeds assuming the engine turns up to full rated horsepower in calm conditions.

You can see what weight does here quite dramatically. The 110hp engine is on the cusp; if the hull doesn't quite transition to planning it's not going to get the speeds above. Even the 125 didn't quite do it on hull #1 but until I run a production hull at finalized weight I won't really know where the exact break point is. Also the boat has a fair amount of windage with large front vertical windows and a tall cabin structure so it's not the same as running a sleek runabout and wind will definately affect it.

My take so far (subject to change with more data) is to either go with a smaller engine for slower operation, less upfront money and better mileage or get an engine large enough to reliably get the hull "on top" with real world loads aboard so that it runs efficiently and comfortably. For now that looks to be something in the continuous hp range of 140 hp.

Have a good weekend.

[dtol]

Les

Do you think that they will ever be able to produce the CR25 at the production weight of 5400lbs or even <6000lbs that they originally projected?? I am not sure what they would have to give up in the design and options to do it.

Are they looking at weight management at all in reworking this whole formula or is power the only componant they are thinking about.

[dtol]

Thanks for the information on HP and speed.

Here is a question. I understand that the numbers you gave were based on 3600 turns per minute on the propeller. The Volvo D3 160 produces 150 horses at 3000 rpm. The Yanmar 180 is the same at 3000 and the Volvo 190 produces 155 horses at 3000 rpm. Is there a way to figure how these speed numbers change to see the speed at 3000 RPM??

If these engines are capable of producing 150 horses at 3000 rpms couldn't you conpensate for lower RPMs with a larger propeller and fine tune the boat to run more effeciently at 3000 RPMs

Sorry if these are dumb questions. My logic takes me places that are not supported with technical knowlege.

[Sawdust]

EQ is closed until Tuesday a.m. - so here's my take (frightening, eh?). Les's numbers are based on HP not on RPM. With the data provided by various engine manufacturers it's a simple calculation to determine HP approximations for various engine rpm's. The RPM vs boat speed estimates are NEVER real world numbers - just too many variables.

Les and I have talked a lot about reducing weight for the C-Ranger 25 - but these are questions only the manufacturer can answer. All of my boat testing has shown the same relative speed decrease with added weight. Not magic at all, just basic formulas used by naval architects and proved time and again from practical application.

The C-Ranger 25 is a beautiful boat, and IMO it will be a major player in the pocket cruiser market. The gestation of a new model is always difficult, from my own experience, and I think they will end up with a real jewel. Patience, friends.

Dusty

[thataway]

Dtol, you have to understand that thrust at the prop is what is important.
The 75 hp engine comes with a reduction ratio of 1.47 to 3.3 and the 125 hp Yanmar comes with 1.73 to 2.48. I don't know what transmission is on the individual boats or what prop is on the boats. The diameter and pitch of the prop is important. The boat is proped to achieve max RPM of each of these engines--and no more. So that speed of the prop shaft turning is not relevant--only the amount of thrust that the prop generates. Even with inboard diesel boats, expermentation on the props is often necessary to achieve the best effeicency or speed. (and they may not be the same prop). If you are only going to run the boat at 8 knots, you would put a different transmission and prop than if you were trying to achieve 20 knots. At least in sailboats (where most of my experience lies) many boats are not proped correctly from the factory. (I actually changed the props twice a week, in the water, at one point in my life, going from racing to cruising mode) Trawlers are usually close, but not necessarilly on the first boats.

Les mentioned "Voyaging Under Power" (I have both the origional 1st edition and the most recent addition) which is an excellent book to study if you don't already own it. Again I am going to suggest that you get David Gerr's "The Nature of Boats"--probably cost about $70 total for the two books, and money well spent to have a better understanding of hulls, props, effeciency etc.

[Sawdust]

Bob,

Sure do agree on the library. Have all three, and all are good reading for a layman... Gerr is great. I have many more technical books, but his are easy reads and cover everything most of us want/need to know in understandable language. Unfortunately, all of my sailing was without power! Part of my purchase agreement - and I was watched carefully by the previous owner!

Dusty

[Pat Anderson]

OK, I know we will have to wait to see what develops of course, and we want to get out on both a C-Ranger 25 with the 110 Yanmar and one of the Volvo Penta D3s to really see how it feels, but I have read and re-read Les's description of his experience and his thoughts on powering this boat, and am trying to understand that "not particularly happy in-between" part, and what implications are for what would actually make us happy, since whatever choice we make we will have to live with for a long time.

I gather Les means with the hull characteristics of this boat we want to run at 7.5 knots or below or 12.5 knots or above...We definitely do not want to be limited to Dusty's 7.5 knot cruise, we would perceive that as a big step backwards from our CD25, so the 55 - 80 hp Yanmars, are definitely out. Seems we need to get to or above 12.5 knots to get the bow down. It looks like the 110 - 125 hp Yanmars can't reliably deliver that running in the 75% range, we sure don't want to be running WOT to achieve a 12.5 knot cruise in calm waters.

But we don't need a 16 knot cruise and 19 knot top speed - we would be very happy with a 12.5 - 13 knot cruise speed with the bow down (out of that "in-between" range) and the engine having enough reserve to deal with wind and current. So if the Volvo Penta D3 150 (or is it 160?) has that "few more knots" to achieve that, that would seem ideal. So what do we see as economy in that scenario from our formulae, assuming the 9,000 lbs is right (since it only gets better if Dave can shed a bunch of weight from there) and cruising at say 12.5 knots? Or are the characteristics of the Volvo not suited for this scenario?

[dtol]

I believe this thread has helped keep me from making a major mistake. I was ready to jump last friday but didn't. Some very good people have shared their time and knowledge to answer questions and provide information in a most accurate and timely way.

The original Rangers share the typical design of the slow cruise economical boat intended to slow cruise 12 hours on 5 gallons of fuel or less. The question isn't how big of a motor you can put on these boats, but, how small of a motor and still cruise at 6 to 8 knots. These boats do this extremely well.

It appears that the goal with the design of the C-Ranger 25 is to build a larger boat at around 5500lbs dry and 7000lbs loaded with the luxuries and speed in demand by the public which is still in the tradition of the Ranger 21s. And provide it to the customer in an almost turn key ready to go condition which doesn't require the months of fabrication needed to put the amenities desired by the new owner.

The design would require a weight to power ratio that would allow the slow cruise capability and provide the 6 to 8 knot effeciency and give 14 to 18 knots effeciently on plane using about 50 gallons to cruise 12 hours . This would be unique in the industry and certainly caught the eye of the boating public. It certainly did me. I've been going nuts this last few days.

The current tests indicate that the first boats were not fully on plane at 13 knots which was the maximum speed they were able to acheive not fully loaded with the 125hp Yanmar.

The result is an overweight boat that will need a large engine and will use between 80 and 100 gallons to cruise 12 hours on plane. This is no different than all the other big boats out there. So, except for the layout and standard options and the price which is very high, it isn't much different from any other big heavy boat.

I've been looking at the Nordic Tug 37 and it will cruise at 8 knots forever at 3 gallons an hour, but needs about 10 to 12 gallons an hour to go 16 knots. It weighs 22000lbs though. You can get a Nordic Tug 32ft at about $50K more than what this 24ft will cost. Its going to be $160K+ to get a C-Ranger 25. To be economical, the Nordic Tug is a slow cruiser and it can't be trailered.

I would say that if you can live with 6 to 8 knots and need speed and be on plane only occasionally then the C-Ranger 25, at its present weight would be good for you and an economical boat.

As for me, my fishing to pleasure cruising ratio is about 1/3, 2/3s A typical run on a typical fishing day is between 50 and 80 miles for a round trip which, hopefully can be done done at 14 knots or above to maximize fishing time. I would be happy if 15 knots could be achieved below WOT and at 4 to 5 GPH. This becomes an expensive boat to run in its present configuration. I guess I am spoiled by my 22 Cruiser which does the 80 miles on 18 gallons of gas consistently as hard as conditions will let me go and under 5000 rpms. Hopefully at 21 miles an hour loaded. Its so easy to trailer. I was willing to reduce my expectations for speed for the C-Ranger 25.

It seems to me that the Ranger folks, in order to have the unique product originally envisioned, need to focus on weight, not larger engines.

What happened to the balsa core technology used on the original C-Dory boats? It appears that the C-Ranger makes extensive use of heavy plywood.

[thataway]

Pat,
Yes, you have the area from about 1.3 x sq rt LWL to 2.8x sq Rt LWL, which is fast semi displacement and not on a plane. There are boats designed to do this. The New England Lobster boat is such a type of design. These have flat runs aft, but with soft rounded chines. Usually quite fine foreward. There are some hulls which are designs to sort of "trick" the water flow, and get a little more effeciency in these ranges. But not many successful production boats which do this.

Dtol,
There are other types of boats which will do what you want--and the cats are where this is mostly--but none are super effecient that I have seen so far. Also very few are within the 8' 6" width for legal trailering without a permit. Maybe the C Dory 25 is not a bad boat after all for your type of use? New engines are slightly more effecient.

When we were cruising Alaska, we ran into several folks who were renting the Tug Trawlers out of the Juneau area--looking at putting bigger engines into them for the planing speeds. I thought it was a bit foolish at the time, and I still do, but most of them are sold with the large engines.

There are other boats semidisplacement boats, such as the Duffy, Cape Dory, Rosobrough, Camano which all can be purchased with diesels. But they all have the same type of characteristics. Not as effecent as a real planing boat, once on a plane. Same is true with the Tom Cat--it appears that in the narrow planing range, that the Tom Cat is more effecient than the World Cat and Glacier Bay--but not necessarilly so at the speed when the Tom Cat is off the plane.

I also follow the Rosoborough threads, and they power the boats from 50 hp on up to twin 150's--the diesels are mostly in the 150 to 160 range-both I/O and inboard. They have the same issues as the C Ranger.

Dusty:
I'll bet we have the same techinical books also. I had power in my long range cruising boats--but did a lot of small boat racing with no power also.
All of this messing around in boats is fun...not back to work.

[dtol]

Bob

You might be right on track with the CD 25 for me.

I was still hoping to compromise some on speed (15-16 knots medium cruise and below WOT as apposed to 18-20 knots expensive running at WOT) to get the comfort and amenities for pleasure cruising. May not happen though. I,ll wait and see what they do with weight. Could get a Sea Sport for a whole lot less money if I wanted an overweight fuel hog. Just for grins, I wonder how the C-ranger would perform with the CD-25 hull under it.

The Nordic Tug has the same type of hull as the CR-25 and is built entirely for pleasure cruising.

[DaveS]