Ironheart

Discussion in 'Boat Design' started by Portager, Aug 11, 2003.

  1. Portager
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    Portager Senior Member

    I was presently surprised to discovered Dave Gerr’s web site at http://www.gerrmarine.com . I’ve read most of Dave’s books and I have wished he had a web site for a long time.

    A couple of Dave’s designs are candidates for transportable trawlers, his “Summer Kyle” design http://www.gerrmarine.com/power_50.html#summerkyle and his “Ironheart” design http://www.gerrmarine.com/power_70.html#ironheart .

    The Ironheart is especially impressive and the largest boat I have found yet that could be transported without a pilot car. Dave describes Ironheart as follows;
    66-foot aluminum, ultra-slender, globe-girdling motorcruiser, with 5,000 plus mile range, beachable on center keel and bilge keels
    LOA: 66 ft. - 0 in. (20.1 m)
    LWL: 62 ft. - 4 in. (19.0 m)
    Beam: 11 ft. - 0 in. (3.3 m)
    Draft: 4 ft. - 2 in. (1.3 m)
    Propeller Dia: 2 ft. - 8 in. (0.8 m)
    Displacement: 17.9 tons
    Power: (1) 180 hp. Cat 3208, or (1) 190 hp. Cat 3306
    Speed: 13.5 knots max, 10 to 12 knot cruise

    I like Ironheat’s aft owners stateroom, the mid-ship pilothouse, large engine room and internal access to the foredeck, but the one thing that I find a little odd is, to reach the forward compartments, you have to go through the engine room. Although I like to keep a clean engine room, I’m not sure I want to be required to on a continuous basis.

    Anybody got any good ideas on how to resolve this problem.

    CAn anybody read the capacity of the fuel tanks?

    Regards;
    Mike Schooley
     

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  2. Willallison
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    Willallison Senior Member

    I think the intention is that you would descend via the fwd doghouse from the deck is you didn't want to go via the holy place.
    And no, I can't read the fuel capacity - could be 500 gal, but I can't be sure.:confused:
    FYI Dave has recently been appointed as the new director @ Westlawn. See my post at http://boatdesign.net/forums/showthread.php?s=&threadid=1775

    Now watching you drive that baby onto a trailer is something I'd like to see!!:D
     
  3. Portager
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    Portager Senior Member

    I’m not planning to change Portager, 48’ is plenty for me, but I’ll add it to my list of potentially trailerable trawlers. I think it would be good for a West Coast live aboard that wanted to cruise warn water during the winter without making the passage from Seattle to Cabo.

    If someone did trailer Ironheart, I hope they would used a travel lift.

    I think I would prefer to go through the engine room than across the fore deck, especially if the weather is bad. I’m thinking Ironheart was designed for a couple with a paid crew and they didn’t care if the hired help had to transit the engine room. It might be an incentive to keep it tidy. :)

    Regards;
    Mike Schooley
     
  4. Willallison
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    Willallison Senior Member

    Me too, but then - at least here in Oz - there are thousands of 30 to 70+ foot fishing boats set up this way (only the hold is located where Gerr has his engine room). Maybe he's taken some layout cues from them...

    Oh, and quick work holding a ruler up to the screen and making some guestimates, leads me to think that she has 2 x 900 gals of fuel....or to put it more accurately - lots!:p
     
  5. Dim
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    Dim Senior Member

    Yes, Will.

    It's 900 gal. PS and SB (each tank).

    Dim.
     
  6. Portager
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    Portager Senior Member

    Thanks Will and Dim;

    I enlarged the bitmap and I thought it was 900 gal also.

    Your correct Will, it a lot of fuel, especially when you realize that it is nearly 13,000 lbs or 6.5 tons, but then 5,000 NMi range is a lot also. I can’t figure why anyone would need that much range. With only a little effort you could circumnavigate the globe with no passage over 2,500 NMi. If I were building Ironheart, I’d reduce the fuel capacity and create a passageway down the center of the fuel tanks. Still I have say, Ironheart is a mighty impressive design.

    To gain better perspective, I decided to compare it with another able passagemaker, the Nordhavn 46. I thought this comparison was very interesting, so I decided to share it.

    ____________________Ironheart______Nordhavn 46
    LOA ft_________________66____________45.75
    LWL ft________________62.3___________38.3
    Displacement speed_____10.58___________8.3
    Beam ft________________11___________15.42
    Length*beam ft^2________726___________705.3
    Draft ft________________4.17____________5
    Prop Dia in_____________32_____________28
    Displacement lbs________35800__________60000
    Horse power____________180
    Max Speed_____________13.5
    Cruise speed__________10 to 12________7.5 to 8.5
    Range Nmi_____________5000___________3000
    Fuel cap gals___________1800___________1000
    Fuel burn rate Nmi/gal____3.08____________3.3

    First you’ll note that Ironheart is 44% longer, but Ironheart is 40% narrower. Displacement is too dissimilar to be correct, so I thing Ironhearts listed 35,800 lb displacement is empty weight, while the Nordhavn is fully loaded. If I add 1800 gallons of fuel Ironheart would be closer to 50,000 lbs which is about right given the difference in length*beam*draft product.

    I provided the length*beam product to illustrate the difference in the water plane area (assuming comparable prismatic coefficients). This illustrates that in terms of water plane area these boats are nearly equals. They are also pretty close in internal floor space. Ironheart goes gunwale to gunwale, while the Nordhavn does not, but is makes up for it by being double decked in the pilothouse. I think this is interesting because many times people classify boats based on length alone, which can be very deceptive. I think it is much better to make comparisons based on displacement, but you need to compare based on the same conditions, such as fully loaded or empty weight.

    Another interesting comparison is the difference in cruise speed and fuel burn rate. The cruise speed of Ironheart is 33% to 40% higher, yet fuel burn rate is 8% lower. It would be more interesting to compare them at the same speed, but this emphasizes the advantages of a design with a high length to beam ratio.

    Finally, Michael Kasten’s rule of thumb is that construction cost should be around $10/lb of empty weight. This would put the cost of Ironheart at ~$360,000. Personally, if I were caught in rough weather, I’d much rather be in Ironheart.

    Doesn’t anybody has a fix for the passage through Ironhearts engine room?

    Regards;
    Mike Schooley
     

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  7. Willallison
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    Willallison Senior Member

    It may be possible to buy fuel, but not always possible to buy GOOD fuel - and given that 90% of diesel breakdowns are said to be fuel related, this can be an important consideration. Plus, you never know when you might get caught out in nasty weather - considerably increasing fuel burn. Then, whilst en-route, one might choose to stop for a month or two in some out of the way place where fuel isn't reliable or available - when the genset runs out of juice, how will you keep the ice cream frozen?:D

    I think you must have the mileage figures for the two boats back to front in your post - you have the Nordhavn doing 3.3 nmpg and Ironheart 3.08.

    Difficult to tell from the drawings, but perhaps you could arrange the fuel in multiple tanks under the various cabin floors. The engines could then move aft to where the tanks were, freeing up space for additional accomodation, storage, or whatever.
     
  8. Portager
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    Portager Senior Member

    Will;

    You make some excellent points, however I think the range could be reduced say 20% and it would be a reasonable compromise. At 4,000 NMi Range it would still exceed the Nardhavn by 33%. OTOH I scaled the current passageway between the fuel tanks at 3’, which is certainly adequate for inspection and maintenance.

    You are correct, I made a mistake comparing the fuel burn rates :eek: , but unfortunately I had the numbers right, I was just looking at it wrong. The Nordhavn fuel burn rate is actually 8% lower than Ironheart. I think at comparable speeds the Ironheart should be more efficient, but I don’t have the numbers to prove it. :mad:

    My approach to solving the engine room passage problem is to create a passageway using sound proof false wall panels. The panels would set into a groove in the floor and a track at the top with a block to fill the gap at the top and lock the panels in place. This would allow good access to one side of the engine and, when you need 360 degree access you could remove the panels and stack them out of the way. The figure shows access to the starboard side, but if you prefer good access to port, you could mirror image the entire layout. An additional benefit of the passageway wall is that it isolate the battery bank from the engine room heat, which reduces battery life expectancy.

    Regards;
    Mike Schooley
     

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  9. Guest

    Guest Guest

    Does the long long prop shaft result in more vibration than a shorter shaft would produce? Or is that not an issue with modern shafts?
     
  10. Willallison
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    Willallison Senior Member

    Yours is certainly the simplest solution Mike.
    If it were for me, however, I'd make some more substantial changes - and I hope Mr Gerr will forgive me for bastardising his design!:p
    Unfortunately, I can't get my computer to talk to my scanner, so I'll have to descibe the changes instead.....

    1. Make the aft cabin and pilothouse each 50% bigger, eliminating the aft saloon. This would allow a larger master head and room for extensive stowage - surely a necessity on any long distance live aboard cruiser. Increasing the size of the pilothouse allows the addition of two large settes, where the crew can comfortably gather whilst the vessel is underway. It also allows for panoramic lounging whilst at anchor.

    2. The engine is moved aft into the much larger space created under the pilothouse. This would allow for a substantial workshop as well, or for wing tanks if they were deemed necessary.

    3. The saloon is now moved forward of the pilothouse. I would raise it to make way for tankage under the floor and to allow for larger portholes. I hate being stuck below with no view of the outside world. Storm shutters would allay any fears of a wave smahing a window whilst at sea.

    4. Forward of the saloon is the guest / day head and shower compartments. This way guests aren't forced to use the master head as they are in the original design. Then forward of this is the guest stateroom and forepeak.

    I've left out my pre-requisite aft cockpit - though with a little thought, I'm sure I could squeeze it in..:D
     
  11. Portager
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    Portager Senior Member

    OK, Will. Here is what I think your ******* Ironheart looks like so far.

    I like the larger deckhouse and seating with a view, but since the beam is only 11’, the pilothouse is only ~7.7’ at its widest point and you need a passageway to the aft cabin. The option I found was to put the passage to the aft cabin on the centerline. It will probably need a trap door for people’s feet and a folding table top.

    The aft saloon/galley is about the same size as the current engine room. If you expand the aft cabin, then the relocated engine room will need to be smaller than the current engine room. The current engine room has a 27 KW generator, a work bench, battery bank and many indiscernible objects. Since the new engine room is below the pilothouse, the head room under the pilothouse will be ~5.5’ max, not quite the standing headroom the current engine room has. Still that seams to be the tradeoff that most boat buyers are willing to make these days, more living space at the expense of the engine room and ease of maintenance. I wonder if the original design had smaller fuel tanks and the engine in-between the tanks. I moved the engine as you suggested and I figure the head and shower would be moved forward and enlarges, but then they block access to the engine room.

    I moved the saloon and galley and flipped it so it kind of fits. Would the storm shutters be installed from the inside or outside? If they need to be installed outside then I would opt for extra-thick Lexan instead. I would end up trying to install the shutters after the weather got bad, but before it got very bad, and that sounds ugly really bad.

    I also copied the aft cabin and flipped it over. Not too bad for a quick butcher job.

    Knock yourself out Will. :p

    Regards;
    Mike Schooley
     

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  12. Willallison
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    Willallison Senior Member

    :D Close, but not quite. I envisage moving the cabin sole up to allow placement of the tankage under them. With empthy tanks, I dunno how this would effect stability, but for the purposes of this it doesn't really matter.,.,.

    My cut & paste abilities aren't quite up to yours, but this should give you the general idea...
     

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  13. Portager
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    Portager Senior Member

    With the weight of fuel equal to 1/3rd of the empty weight, it needs to be centered on the center of buoyancy to maintain trim as fuel is consumed. Your layout appears to move the fuel too far forward.

    The cross section of the fuel tank appears to be equal on the centerline, but taking into account the curvature of the bottom, it appears that you have reduced the fuel capacity.

    I can’t tell how the stairs lead from the pilothouse to the aft state room.

    Regards;
    Mike Schooley
     

  14. Willallison
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    Willallison Senior Member

    Like I said Mike - my cut & paste capabilities aren't quite up to scratch!:D I didn't make any attempt to keep things to the correct scale - just moved some stuff around and chucked in a couple of lines to give you the general idea of what I was getting at.
    My thinking was that with fuel spread though different tanks in the boat it would a) allow transfer to trim the vessel and b) better protect against a crappy batch of diesel. I didn't show it, but I'd have fuel down the blunt end as well...
    Dunno about the total quantity - like you I think that you could get away with a little less than in the original design.

    The stairs go from the pilothouse down to the aft cabin on the centreline. other steps lead to the rear deck.

    Actually, the biggets problem as I've drawn it is that with the raised fore and aft cabins, there would be as much usable space at the sides as in my posted images.
     
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