Thursday, December 30, 2010

Fuel tank venting

Several years ago Phil de l'Etoile, Brave Duck #67, discovered his fuel vent lines were clogged with fuel. This week it dawned on me that every LNVT with fuel vents on top of the tank will suffer the same problem. That's because after leaving the tank, the 3/4" vent hose must dip down to get under the floor joist. It's only a matter of time until the dip fills with fuel. Fuel-filled vent lines also explain why there have been so many Forum discussions concerning filler port fuel eruptions during refueling operations.

Phil's solution, which is fix-and-forget, is pictured below. The vent on the port forward tank was relocated to a new location about 2" down the tank's side. This required drilling into the tank and installing a 3/4" fitting. The abandoned fitting on the top of the tank was plugged. Then the two forward tanks were connected together with 3/4" hose. A 'T' was put in the connecting hose and leads to the cabin-sides vent port. Care was taken to make sure the vent hose slopes only upwards from the 'T' to the cabin-sides vent port. Now, any fuel that enters the vent hose will automatically be routed back to the port forward fuel tank. The aft tanks were vented in a similar fashion except the starboard tank had the new fitting installed. To work properly, the tanks with the new taps can be filled no higher than those taps. This results in a reduction of fuel carrying capacity of approximately 30 gallons ( 2" x 2 tanks x 7.5 gal/" = 30 gal).

Another solution, which admittedly isn't fix-and-forget, is to pretty much leave the venting system as-is but install a trap to give the fuel caught in the vent hose someplace to go. From the aft tank the vent hose runs forward and constantly downward until it arrives abeam and about 2" below the forward tanks vent port. Here the forward tanks' vent 'T's in. Another 'T' just forward leads the hose ever-upwards to the cabin-sides' vent port. Attached to the downward facing leg of the second 'T' is a piece of clear 3/4" hose, about 2' long, which is capped on the bitter end. Since the clear trap line is lower than the vent, it will collect any fuel. Only when the trap is full does it need to be drained.

Starboard tank shows vent on top while port tank has vent on side
Here the starboard vent has been relocated to the side of the tank while the port vent is on top.

Tuesday, December 28, 2010

How Loud is it in the Pilothouse?

The following noise level readings were taken while underway using an Ipod Touch 4G running Sound Level(TM)—a free app. I was standing in the middle of the pilothouse, facing forward. The Touch was held upright and was about 5'4" high . Hmm, looks like Nellie has a resonance problem at 800 rpm ;-)

RPMNellie D. (63)Knock Off (66)

Saturday, December 25, 2010

The Ceiling Lights—An Easy Fix to an Old Problem

Pretty but not always functional

The ceiling lights are finicky—to put it nicely. Invariably either the red, white, or both lights don't turn on. It's not that the bulbs are burned out either; it's simply a bad connection between the bulb and socket. As the close-up picture of the bulb shows, there's a circular deformation in each of the bulb's contacts. Heating, due to a poor electrical connection, allowed the socket's steel pins to sink into the bulb. To fix the problem the contact between bulb and socket needs to be kept clean and oxidation free. Something easier said than done in a salt water environment. Fortunately the fix is easy; before installing the bulb simply apply marine electronics grease to its contacts. This will keep the environment at bay and help dissipate heat too.
Replace the old bulbs or grind-out the indents
Liberally grease the bulb's contacts before reinstallation

By removing only two screws and loosening the third, the lens easily slides out
Note the heat-caused indents in the bulb's contacts

Monday, December 20, 2010

Gel Coat Rub Rail Cracking

What causes those consistent and persistent LNVT rub rail cracks and how can they be eliminated once and for all? The cracks are consistent in that they almost always appear on the upper (i.e. the skyward) section of the rub rail and are usually nearly vertical. They're persistent in that many owners have repaired the cracks only to have new ones appear. When Nellie D. was repainted last year her many rub rail cracks were ground out, filled and faired. These cracks were only in the gel coat and did not penetrate the underlying fiberglass. So, what's causing these cracks? I had an experience yesterday that got me thinking. But first I must digress.

An opening in the stern bulwark clearly shows the rubrail's curved indent

I've preformed some exceptionally ugly landings lately. Yea, it's been 10 months since I've had Nellie out—but still. Anyway, during the last 'crash' I managed to drive Nellie's hull, just below the stateroom's port light , rather abruptly into the corner of the floating dock. Fortunately the dock was well padded and left only a rubbery raspberry on the hull. After counting my blessings, and spending 30 minutes removing the offending blemish, I noticed a big, new rub rail crack (see photo) almost directly above the point of impact. Hard to believe my little bump didn't contribute to this new battle scar. On the other hand, some strong winds in the past few days had pushed us rather forcefully against the floating dock. Either event would cause the hull to flex and I've suspected that movement of the fiberglass substrate is the root cause. Flexing can be caused by many types of dynamic loading: a rough passage; bumping a dock, a piling, or even from a fender; and certainly from the straps during a haul-out. But why does this otherwise normal fiberglass flexing manifest itself as a crack only in the rub rail?

The new crack …

So here's the theory, the hull mold was upside down, i.e. keel facing up, when it was sprayed with gel coat. Remember, the hull mold includes not only the rub rail but the bulwark too. Imagine a guy standing inside the hull with a spray-gun trying to put an even, thin layer of gel coat on all the surfaces surrounding him. It's fairly easy to do on the large flat areas of the turn-of-the-bilge, hull sides, and bulwark, but the rub rail, which is the nexus between the hull sides and bulwark, is a narrow, 6", concave indent (see first photo). If the spray was too thick in the indented area, the gel coat would run and pool on the indent's lower back and bottom surfaces. The exact surfaces, in fact, where today's rub rail cracks appear. Thus it's this too thick gel coat that's the problem; unlike the thinner gel coat everywhere else, the too thick gel coat can't handle the nominal deformations of the fiberglass it's attached to. The only practical way to eliminate rub rail cracking then is to get out the sander and remove the too thick gel coat.

Tuesday, December 7, 2010

Lani Hart's Lord Nelson History

Received an email from Lani Hart in which she documents the Lord Nelson Corporate history. Very interesting.

Saturday, December 4, 2010

Cummins 4BT3.9M Fuel Consumption Measurements

So how much fuel does a 150hp Cummins 4BT-3.9M use? The following data was compiled in calm conditions, aboard Nellie D. #63 on the Caloosahatchee Canal west of Lake Okeechobee, Florida. RPM readings came from the helm's VDO tachometer, ground speed came from a Garmin GPS and fuel flow rates came from a Flowscan.


Thursday, December 2, 2010

Why have a Waterlift Muffler?

One reason to have a waterlift muffler, according to John Mackie, John William #68, is to prevent water, which is aft of the muffler but has yet to be discharged overboard, from backing up into the engine. This could occur in large seas when the bow is down. Interestingly, Knock Off #66, has no muffler at all.

Saturday, August 14, 2010

Things Learned For Lani Hart

1. The LNVT 49 got it's length designation not because it's actually 49' long, it's actually longer than that, but rather because the break point for the shipping company was 49'—anything longer cost a lot more.
2. There wasn't a clean break between the BMW to Cummins switchover. There were still some BMW's in inventory when the Cummins decision was made. Boats for which orders existed got the BMW while spec boats, which would make the boat show rounds, got the Cummins.
3. Lani said that no 'unlucky' hull 13 was built.
4. Lani has the sales records for each hull and said she'd be willing to make them available.
5. Sometime during the 37 and 49 production run, LN considered making a 43; which Lani has artist conceptual drawings of. They also gave some thought to doing a 60'. Lani said it was to have a spiral staircase up to the bridge.
6. Loren actually went through the Panama Canal three times. Twice east to west; on a Choy Lee 35 and a Grand Banks. And once from west to east in his LNVT 49. When he entered the Straits of Juan de Fuca, a wave went right over the Grand Banks and killed one of its two engines. It was this experience that convinced him that two engines were worthwhile. And is why his 49' has two engines even though single engine boats predominated at the time.
7. The LNVT 37 mold was bolted together along the length of the keel. It took days of polishing and waxing to get the mold ready. No one at the wake knew where the 37 molds are.
8. Very few hulls were laid up in November and December because they are very high humidity months in Taiwan. A hull laid in a high humidity environment is more likely to suffer from osmotic blistering.
9. The Lord Nelson Company may not be owned by Tommy now but by a cousin. This cousin owns the PAE yard and this is where the fabled shipping container, which contains enough pieces to make another 49, is stored as well as the 49 molds. It's reported that the 49 molds are not in good condition.
10. Lani has the original artist renderings for the LNVT 37. These were done using Jim Backus' blue prints.
11. The Hart's home has many more photographs and drawings of their tugs than sailboats—you know which of their craft captured their hearts.
12. Loren Hart Jr. died when his car crashed head-on with a big rig in 1986. He and a friend were returning to Sun Valley, ID from a construction job interview in California in 1986. It was after this that Loren lost interest in and started backing away from the Company. He sold Lord Nelson in 1988 for $500 and a royalty on each future boat sold.

Thursday, July 29, 2010

Cooling Load Calculations for an 37' LNVT

Used Dometic's guidelines for sizing cooling load for a 37' LNVT. For a temperate climate need 22,000 Btus (1.8 tons) while a tropical climate requires 28,700 Btus (2.4 tons). Assuming a tropical climate, the load could be easily divided between two air conditioning units: 18,000 Btus (1.5 tons) for the pilothouse and stateroom; and, 12,000 Btus (1 ton) for the salon. At 250gph/12,000 Btus, need a 1" thru hull and a 750 gph raw water circulator.

ZoneSq. Ft.Temperate FactorTemperate BtusTropical FactorTropical Btus

The next question that needs to be answered is the CFM required in each space and from that the number and size of supply air ducts can be calculated.

Monday, July 26, 2010

The Big Engine Room Wrench

The LNVT wrench, mounted on the engine room's forward bulkhead, fits 3" and 3-1/2" nuts. The 3-1/2" fits the prop shaft's packing gland. The 3" fits the rudder shaft's packing gland. Several years ago Nellie's rudder packing started leaking badly. But then just as quickly it stopped. I believe the reason was due to water salinity—we'd gone from saltwater to fresh. The difference in buoyancy between salt and fresh water must be enough to move the water line from below the rudder shaft's packing gland to above it.

Saturday, July 10, 2010

Tug-For-Two #42 Cruising Blog

Finally was able to get a trial copy of Microsoft Publisher 2007 to read the Irvin's, Tug-for-Two (42), cruising blog. Moved the text over to a couple of Wiki pages: Will put the pictures in next. Long documents don't seem to work well as a web page.

Friday, July 9, 2010

Knock Off #66 Operation and Maintenance Manual

John Niccolls, Knock Off (66), gave me a rich text format of a MS Publisher document he's working on; an Operation and Maintenance (O&M) Manual for KO. I've converted this into an HTML document and posted it at: I'm hoping that this can act as a model for others that want to make O&M manuals for their tugs.

Thursday, July 8, 2010

Limber Holes

I've noticed on Nellie D. and Titan that any water which collects on the outside of the port, engine-mount bed, just sits there. There's no limber hole to allow the water to drain into the bilge.

Wednesday, July 7, 2010

The Bow Wave

I'd read that a bow wave moves aft as the hull accelerates. In fact, I believe it's a displacement hull's inability to get over the bow wave that results in hull speed. This 4th of July weekend while out on Knock Off I took the following series of pictures. No doubt the wave is moving aft.

4.7 knots at 1000 rpm
5.2 knots at 1200rpm
6.1 knots at 1400rpm
6.8 knots at 1600rpm
7.35 knots at 1800rpm

Tuesday, July 6, 2010

Adding a Bulwark Door

Bulwark Door Installation Lessons Learned

1. Install the door at the same time you're painting/repairing the bulwark.

2. Cutting the door out carefully will save a lot of finish work. The thin kerf of a sawzall blade creates the perfect spacing between the bulwark's caprail and the door's caprail.

3. After the door is cutout, finish the bulwark part of the job first. The finished bulwark can then be used to size and trim the door--just don't touch the door's teak caprail ;-).

4. Get hinges that don't have a lot of end play (i.e. axial movement between the leaves) or side play (the amount of movement of the leaves perpendicular to the pin). 'Loose' hinges will make your life miserable.

5. Hinge the door on the forward side and have it open inwards. Hinging it forward means you won't have to walk past it when boarding and going aft toward the companionway. Hinging it to open inwards keeps the door safe from docks and pilings.

6. Bevel cut (see picture below) the unhinged side. The door will fit tighter and look better.

7. Keep the fiberglass jam panel below the caprail. With the door closed the teak caprail should look continuous.

8. Put a strike plate or other support between the bottom of the door and the threshold. The strike plate supports the unhinged side of the closed door. Somebody, sooner or later, will walk on the door's caprail and without the strikeplate the hinges could be damaged.

9. Think about how best to finish-out the threshold. Big, expensive boats put in shiny stainless thresholds with the manufacturer's insignia on them. Lots of 'cool points' there. With a little forethought the same could be done here.

10. Choose a latch that that is both effective and doesn't stick out so much that it snags unsuspecting passers-by.

LNVTSide InstalledHow Door Opens
Lady (8)port sideopens inboard and towards bow
Moby (14)port sideopens by lifting up and out 
Titan (31)starboard sideopens inboard and towards bow
Neptune (35)starboard sideopens inboard and towards stern
Sea Turtle (40)starboard sideopens inboard and towards stern
Mocko Jumbie (49)port sideopens inboard and towards stern
Nellie D. (63)starboard sideopens inboard and towards stern
Fram (71)starboard sideopens inboard towards the bow
J. Edgar Moser (76)
starboard side
opens outboard and towards stern
* Update: Lil' Toot, starboard side, opens inwards towards the bow (added 2016).

Here's a link to pictures of many of the bukwark doors:,authkey:Gv1sRgCLWXyYeAxfWmPg

Monday, July 5, 2010

LNVT 37' Production by Month

Finally had enough of the hull numbers to put this graph together. Several things can be seen from it. Not many hulls were made in the last quarter of the year. According to Lani Hart this was because of the high humidity at that time of the year in Taiwan. A hull laid-up in a highly humid environment may suffer blistering. The order of the hulls is in no way chronological. Unfortunately, there's no way to tell from this chart when the interior work on the hull began.

Sunday, July 4, 2010

Knock Off #66's Roll Chocks

Got to experience Knock Off's (66) new roll chocks today. The Chesapeake was calm but we did get waked by some large boats. The chocks' damping effect can really be felt—there's a definite deceleration and the rolling period is longer.

Thursday, July 1, 2010

The following is the beginning of a future web page which will help folks sell their tugs. Need to get lessons learned from both buyers and sellers.

Selling your Tug: Lessons Learned

Naturally, keeping the tug in good condition will increase its selling price. However, knowing the competition may be just as important. Sellers often only know their own tug. Buyers, however, will most certainly look at multiple tugs. Only by researching the other tugs for sale on the market, to determine what shape they're in, what equipment they have, what their asking price is, etc., can the market value of ones own tug be determined. The bottom line is, if a tug isn't selling the price is too high. Put your tug in a location where it'll get lots of traffic, both walk- and drive-by. Think about co-locating your tug with another tug that's for sale. If selling through a broker, get an experienced one. One familiar with LNVTs and comfortable selling classic boats. The site averages 3,000 visitors a month and . Keep your tugs photos and data complete and current. Done right, it'll help attract buyers and keep 'tire kickers' at bay. Take good pictures of the tug. Here's an example for some interior shots. Use a wide angle lens.