Desig & Construction Practices

[toyman]

As some know I just bought a 25' and made a trip to check it out. At the risk of offending some members I'm going to question some C-Dory practices.

Comments concern a 2006 - 25' Cruiser.

The aluminum fuel tank (The one on my Whaler corroded thru in 10 years)is in the bilge - un-vented. The batteries (2 each grp 24 deep cycle) are mounted in the stern lazarette, one on each side. This area is open to the bilge, contains the fuel filter, the fuel tank, and the battery selector switch. Should there not be a vent and blower system for this area ? Is there a long term corrosion problem here caused by the battery venting in this enclosed area - not to mention the explosive vapor problem ?

[Matt Gurnsey]

C-Dory boats are built to ABYC standards.

Aluminum tanks are acceptable tanks, and can give 20 years of service, or more in properly installed. C-Dory does build the boat with a removable deck panel so tat if the tank should ever need replacing, the deck does not need to be cut up.

The battery switches are often installed in engine rooms, so I assume they are ignition protected.

If ABYC or USCG or NMMA required venting in that area, C-Dory would have provided it.

[matt_unique]

I recall an extensive thread about ABYC and NMMA, I believe Bob Austin determined through some of the wiring practices among other things that C-Dory's are not ABYC compliant. I also remember reading a thread where C-Dory was nowhere to be found on a list of NMMA certified manufacturers....maybe I'm blending some threads but I definitely remember reading about it here....

Perhaps that has changed since the first discussion?

[Alok]

Here is one of the threads Capt. Matt is talking about...

http://www.c-brats.com/viewtopic.php?t=8989&highlight=cdory+nmma

[journey on]

Before we go down the road of NMMA certification, etc, please remember that C-Dory did build the C-25 under NMEA certification at one time. I'm not aware of any major design changes since 2005.

As for the gas tank, the material choices are aluminum, plastic, iron (had a sailboat with an iron tank, diesel) or fiberglass. Take your pick, but aluminum sounds good to me. Just keep it out of seawater. Fiberglass doesn't work with alcohol. Plastic doesn't age well, though I've got a motorcycle with a plastic tank that's holding up. If you want more ventilation add some vents. I did.

And if one wants to discuss endgrain balsa core, some think that is the best coring material one can have.

Boris

[thataway]

Boris, I think you just made the slip of the fingers I was guilty of: NMEA--Natinoal Marine Electronics association--vs NMMA--National Marine Manufactures Association.

C Dory was NOT NMMA certified or ABYC complient in 2006 when I purchased my Tom Cat. NMMA was pending--and did not occur until 2007. I am not sure of history prior to 2003--my 2003 C Dory 25 was not AYBC or NMMA complient. Just because a boat was ABYC complient at one time, does not mean it is at other times. Materials, management and workers change.

One must remember that ABYC is a set of standards (these are available to members cheaper than to non members). NMMA means that the boat complies to their standards--and these cost money--both for the organizations and the surveys. It is very possiable that C Dory (Fluid Marine) does not feel that it is worth the costs.

This does not excuse them from not building to the standards. i cannot comment if the current boats are built to the standards or not. Currently I could not find on the NMMA web site C Dory or Fluid Marine. I could not find mention of ABYC or NMMA on the C Dory web site (but I may have missed it--it does not seem to currently be in the PDF brochure).

Getting back to the questions. If there is no ventillation, then you should put in a couple of vents--no big deal to do this, and it would be a good idea for condensation alone.

The fuel tank is a more difficult question. My 25 has the plastic tank, which is not leaking--and I decided to not replace it when I replaced the cockpit deck (older 25's did not have a removiable floor). I am told that only one plastic tank leaked and that was replaced.

A properly built and installed aluminum tank should have the following characteristics. 1: be built of a aluminum alloy which is not salt water corrosive. 2 be properly prepared, and then painted with an appropiate two part epoxy primer (usually stronchium chromate or zinc chromate) and then the bottom of the tank should rest of plywood which is sealed with epoxy--so it will not soak up water (or the tank can rest on the inner hull). In either case, the proper way to install the tank is to 5200 some strips of plastic to the bottom, so that it will never sit in water, and then put 5200 under this plastic to bond it in place. I believe in a discussion in the past, that C Dory claimed that they were using a non carbon containing rubber compound to space the hull off the floor--and if this is the case, and there is no water, then it is OK.

However, the way the C Dory 25 sits, the bilge pump is just aft of the tank, and there is often water in the tank compartment when the boat is in the water. You need to be sure that the boat sits to that any water will drain out the aft drain plug when the boat is on the trailer (tongue high).

Yes, 20 years is about average for many fuel tanks (both steel and aluminum) but I recently heard of one boat where the tank was leaking (not C Dory) after 3 years due to corrosion. Worse is the tanks which are foamed in. The water sits in contact with the tank.

[Sarge]

Maybe this is a silly question, but they build aluminum boats that sit IN saltwater for many, many years with no corrosion, why is having salt water touching an aluminum gas tank a problem?

I'm quite curious.

[DaveS]

[westward]

Sarge: there are different types of corrosion, including galvanic and crevice, that can attack aluminum. Also, as you likely know, not all aluminum alloys are appropriate for continuous contact with saltwater. When the builders of high quality aluminum boats (and presumably fuel tanks) use fastidious construction practices like those Bob mentions the boats can and do last a very long time. When corners are cut, whether deliberately or through ignorance, aluminum boats can go to waste rapidly. My mother owned a cheaper riveted aluminum boat whose hull corroded through in one winter in the crevice between the trailer bunk and the hull bottom. Her partner in the boat failed to rinse after a final saltwater use, and maybe there was a stray current somewhere, and the next Spring the hull was a total loss. I've personally observed many poor, amateurish applications of aluminum in recreational boats where you'd assume the builder would know better. No idea if this applies to the fuel tanks on the CD25. Cheers, Mike.

[denny-o]

On the issue of the fuel tank being present in the bilge with the battery/switches and the lack of bilge blowers...
The tank and lines and filter are presumed (that word) to be a sealed system that does not vent fumes or gasoline into the bilge... Since there are no fumes/gas there is no need for bilge blowers... If you do have a leak in the system then all bets are off...
Given that the biggest ignition source in boat fires, the motor, is out back in free air the risk is greatly reduced... Does anyone on the list know of a C-Dory burning up from a fuel leak? I suspect not...

As far as a gas tank my first choice is aluminum... It does not rust or swell and it will not corrode IF it is properly installed - sitting on plastic chafe strips with air space underneath, secured against vibration chafing, air flow all around to prevent crevice corrosion, and kept full when stored... It must NOT be sitting on wood or be foamed into place...

You could put a fan in the bilge to blow air across the tank whenever the engine master switch is on...
An elegant solution would be a small solar cell directly powering a small fan, no battery, to automatically move air across the tank and through the bilge during the daylight hours...

Someone needs to get the model number off their battery switch and check the manufactures web site... Certainly an explosion proof would be preferred...

denny-o

[Sarge]

Dave,

[Sea Wolf]

[toyman]

I really have no problem with the Aluminum fuel tank, probably the best (cost effective, lightest) material for the application. The problem with the tank in the Whaler was due to THEIR dumb design - foaming the tank in place, in a well with no drainage.

But back in the C-Dory bilge / lazarette area (working from photos and memory here) there are batteries (hydrogen) , wiring busses, fuel filter (what is that hose hanging off of the fuel filter with a QD on it), battery switch, fuses, bilge pump w/float switch. I'd almost bet that none of the electrical is EX (explosion proof). So this C-Dory WILL have vents & blowers.

[rogerbum]

Just to be clear - C-Dory builds the boat but the engines and a good fraction of the electrical work is typically done at the dealer. Installs of batteries, battery switches and fuel systems vary dramatically from boat to boat due to differences in dealer installs. Knowing what I know now, I would have had a lot of things done differently when I first bought the boat - but then I didn't know what I know now. The next boat will be informed by the knowledge gained from this one. It sounds like you have enough boating experience that you can either redesign a used boat's systems or, if you buy a new one communicate enough with both the dealer and/or the factory to get things done the way you want.

[AstoriaDave]

New one from Dave Gerr: http://www.mcgraw-hill.com.au/html/9780071444569.html

Could be a good resource to check out before committing to a possible purchase.

No affiliation with Gerr or McGraw Hill, just an admirer of Gerr's expertise and clean, clear prose.