I want to add a new (second) diesel tank to my CD36. I think I will put it in the bilgue, in place of a 30 gallon polyethylene water tank made by Kracor that I have there.
Who made/makes the standard fuel tanks for CD36 (or Robinhood)?
What is the best material to use? My mechanic suggests aluminium, but isn't there a corrosion problem in the bilgue? Does anybody have practical experience with aluminium?
Herbert
hprinz@compuserve.com
CD36 Fuel Tank
Moderator: Jim Walsh
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Matt Cawthorne
Re: CD36 Fuel Tank
Herbert,
Fuel tanks were different sizes on different year '36's. All of the ones that I have seen are fiberglass tanks with an aluminum top. I am not exactly sure, but I believe that the tanks are manufactured in place. On my 1982 CD-36 the tank is 43 gallons. I have been in touch with other CD-36 owners with later models which have 53 gallon tanks. The tanks are glassed in before any other of the cabin interior is installed. Installing a larger tank will require cutting away a large piece of the cabin sole.
Another problem with two tanks and the Perkins 4-108 is that it returns a large portion of the fuel that goes through the lift pump to the tank. Make sure that if you have a second tank installed that you have some way of diverting the return fuel to the tank that is being used at the time. I know of owners of non-Cape Dory's with the Perkins 4.108 engines and two fuel tanks who ran into trouble because the return on their boat only goes to one tank. If you fill both tanks and accidently use the tank without the return the other tank overfills and dumps your fuel. Additionally if for some reason the tank with the return becomes contaminated you end up diverting all of your good fuel into the contaminated tank.
Your range can be extended greatly just by slowing down. While my 36 goes about 7.2 knots I tend to cruise at 4.5 to 5 knots. At these lower speeds the average fuel consumption for a year is usually about .36 gph. If you run at higher speeds you may find that your consumption gets closer to 1.0 gph. Going faster really kills the range.
Let us know how your project works out if you end up going through with it.
Matt
Mcawthor@bellatlantic.net
Fuel tanks were different sizes on different year '36's. All of the ones that I have seen are fiberglass tanks with an aluminum top. I am not exactly sure, but I believe that the tanks are manufactured in place. On my 1982 CD-36 the tank is 43 gallons. I have been in touch with other CD-36 owners with later models which have 53 gallon tanks. The tanks are glassed in before any other of the cabin interior is installed. Installing a larger tank will require cutting away a large piece of the cabin sole.
Another problem with two tanks and the Perkins 4-108 is that it returns a large portion of the fuel that goes through the lift pump to the tank. Make sure that if you have a second tank installed that you have some way of diverting the return fuel to the tank that is being used at the time. I know of owners of non-Cape Dory's with the Perkins 4.108 engines and two fuel tanks who ran into trouble because the return on their boat only goes to one tank. If you fill both tanks and accidently use the tank without the return the other tank overfills and dumps your fuel. Additionally if for some reason the tank with the return becomes contaminated you end up diverting all of your good fuel into the contaminated tank.
Your range can be extended greatly just by slowing down. While my 36 goes about 7.2 knots I tend to cruise at 4.5 to 5 knots. At these lower speeds the average fuel consumption for a year is usually about .36 gph. If you run at higher speeds you may find that your consumption gets closer to 1.0 gph. Going faster really kills the range.
Let us know how your project works out if you end up going through with it.
Matt
Herbert Prinz wrote: I want to add a new (second) diesel tank to my CD36. I think I will put it in the bilgue, in place of a 30 gallon polyethylene water tank made by Kracor that I have there.
Who made/makes the standard fuel tanks for CD36 (or Robinhood)?
What is the best material to use? My mechanic suggests aluminium, but isn't there a corrosion problem in the bilgue? Does anybody have practical experience with aluminium?
Herbert
Mcawthor@bellatlantic.net
-
Herbert Prinz
Re: CD36 Fuel Tank
Matt,
You gave me lots of food for thought.
The cabin sole has already come off as I had to remove a lot of rot that the previous owner of my 18 year old boat had just covered up with new layers of plywood and varnish. This is the reason why I want to attack the fuel tank problem right now. In the process of the repairs one of the craftsmen cracked the polyethylene water tank in the front of the bilgue and, since he could not get a replacement from Kracor in less than 4 weeks, built me a brand new one made of fiberglass. I was so pleased with the result that I asked him to also build me a fiberglass fuel tank in place of an other water tank in the bilgue aft. The marine manager did not want to hear of it because he did not know anything about pertinent standards and regulations. Now I am looking for a company that would build me a fiberglass fuel tank.
Meantime I am still looking into the suitability of other materials, hence my question about the aluminium. I was told I could get such a tank custom made to match the exact dimensions of the old 30 gallon water tank in two weeks, if need be. However, this tank does not use the available space optimally and the fact that you have 43 gallons and other boats even 53 gallons of fuel makes me think that my first approach to go with fiberglass is the right one. Is this tank of yours an integral tank or does it come out, if necessary? Do you also have an other tank in the bilgue and if so, how big is it? I am trying to figure out the maximum tankage that one can or should have in the bilgue of a CD36. It is probably not smart to use all of the volume available as the bilgue’s function is to swallow the water that comes in, but how much is prudent?
As far as the fuel return is concerned, I am fully aware of this problem. I was playing with the idea of saving the second return line and the manyfold on the intake by plumbing the tanks in series. I have heard of people using so called ‘day tanks’ for various reasons. This would in principal be a similar arrangement. One advantage would be that I could run one tank completely empty without having to bleed the lines. What do you think of this idea? On the other hand, if I really can fit 53 gallons of fuel into my bilgue, I would consider forgetting about the old 24 gallon tank.
Is the Perkins 4.108 the standard engine in the CD36? How many hp does it have? I have a Perkins M50. It’s way to heavy. I go no faster than you, but use a lot more fuel.
Best regards
Herbert
hprinz@compuserve.com
You gave me lots of food for thought.
The cabin sole has already come off as I had to remove a lot of rot that the previous owner of my 18 year old boat had just covered up with new layers of plywood and varnish. This is the reason why I want to attack the fuel tank problem right now. In the process of the repairs one of the craftsmen cracked the polyethylene water tank in the front of the bilgue and, since he could not get a replacement from Kracor in less than 4 weeks, built me a brand new one made of fiberglass. I was so pleased with the result that I asked him to also build me a fiberglass fuel tank in place of an other water tank in the bilgue aft. The marine manager did not want to hear of it because he did not know anything about pertinent standards and regulations. Now I am looking for a company that would build me a fiberglass fuel tank.
Meantime I am still looking into the suitability of other materials, hence my question about the aluminium. I was told I could get such a tank custom made to match the exact dimensions of the old 30 gallon water tank in two weeks, if need be. However, this tank does not use the available space optimally and the fact that you have 43 gallons and other boats even 53 gallons of fuel makes me think that my first approach to go with fiberglass is the right one. Is this tank of yours an integral tank or does it come out, if necessary? Do you also have an other tank in the bilgue and if so, how big is it? I am trying to figure out the maximum tankage that one can or should have in the bilgue of a CD36. It is probably not smart to use all of the volume available as the bilgue’s function is to swallow the water that comes in, but how much is prudent?
As far as the fuel return is concerned, I am fully aware of this problem. I was playing with the idea of saving the second return line and the manyfold on the intake by plumbing the tanks in series. I have heard of people using so called ‘day tanks’ for various reasons. This would in principal be a similar arrangement. One advantage would be that I could run one tank completely empty without having to bleed the lines. What do you think of this idea? On the other hand, if I really can fit 53 gallons of fuel into my bilgue, I would consider forgetting about the old 24 gallon tank.
Is the Perkins 4.108 the standard engine in the CD36? How many hp does it have? I have a Perkins M50. It’s way to heavy. I go no faster than you, but use a lot more fuel.
Best regards
Herbert
hprinz@compuserve.com
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Matt Cawthorne
Re: CD36 Fuel Tank
Herbert,
There seems to be more difference between the tankage on the CD-36 than I was aware. First of all, I have no fresh water tanks in the bilge. The 'Patricia Louise' has 4 water tanks. 1 under the v-birth, one under each setee and 1 under the quarterbirth. None of the tanks seems to fit the volume very well. My fuel tank is not removable. I think that the side walls of the tank are actually the hull. Only the inspection port is removable, but the access pannel in the cabin sole is not big enough to get it out. I think that there is a wasted space in front of the tank on my model, which was used in later models to hold the extra fuel. That space is just behind the mast. There is an area just under the companionway which is perhaps 18 to 24 inches long which collects water that might get in to the boat or out of the ice box. The bottom of the fuel tank does not sit on the bilge floor. The reason for this is that it needs to let water from the front of the boat pass through in such a way that it does not run over the existing tank tops. That would be bad for contamination/corrosion.
I was recently given two pictures of the inside of a robinhood 36 under construction. The fuel tank in that picture would appear to be aluminum. It is hard to judge from the picture, but the tank appears to go from the mast step back to about where the galley sink would sit.
In case you didn't know, the Robinhood 36 is the re-incarnation of the CD-36. (check out the home page that this bulletin board is part of) Some of the same people are even building it. Try calling them. They might be able to sell you a tank which is ready to fit in that space. Unfortunately it might also conflict with your new fiberglass water tank. I really regret the use of non-optimal water tanks in my '36. Perhaps some day I will make some fiberglass ones that will use the space more efficiently.
I am not sure how you could empty one tank without causing the system to draw air. Would you have an auxiliary pump?
I typically run less than 100 hours per year. As a result, it is only on a year with a long trip that I empty the fuel tank. Some years I use less than 25 gallons If there is no wind I just bob and sweat. What this does is leave me with fuel which sits in the tank over the years. Having separate tanks with separate returns would allow you to use one up, clean it out and add fresh fuel without mixing the fuel from the other tank. Having separate tanks is a good offshore feature. A friend of mine had a diesel leak in one of his tanks on the way to Bermuda this spring. It was ugly according to him. I wish that the Patrica Louise had separate fuel tanks with separate returns.
The Perkins 4-108 was used in many CD-36's. It is a good engine, but if faced with repowering the boat I would consider a more modern engine which deposited less oil in the sump, had a self-bleeding feature, had more room around it and had cheaper spare parts. (see my posts about changing the starter motor) The 4.108 is capable of producing about 51 HP, but with the standard prop installed, it is impossible to reach maximum RPM. At the achievable RPM the engine will only generate 45 hp.
Good luck with your tanks/cabin sole. The new sole will look great!
Matt
mcawthor@bellatlantic.net
There seems to be more difference between the tankage on the CD-36 than I was aware. First of all, I have no fresh water tanks in the bilge. The 'Patricia Louise' has 4 water tanks. 1 under the v-birth, one under each setee and 1 under the quarterbirth. None of the tanks seems to fit the volume very well. My fuel tank is not removable. I think that the side walls of the tank are actually the hull. Only the inspection port is removable, but the access pannel in the cabin sole is not big enough to get it out. I think that there is a wasted space in front of the tank on my model, which was used in later models to hold the extra fuel. That space is just behind the mast. There is an area just under the companionway which is perhaps 18 to 24 inches long which collects water that might get in to the boat or out of the ice box. The bottom of the fuel tank does not sit on the bilge floor. The reason for this is that it needs to let water from the front of the boat pass through in such a way that it does not run over the existing tank tops. That would be bad for contamination/corrosion.
I was recently given two pictures of the inside of a robinhood 36 under construction. The fuel tank in that picture would appear to be aluminum. It is hard to judge from the picture, but the tank appears to go from the mast step back to about where the galley sink would sit.
In case you didn't know, the Robinhood 36 is the re-incarnation of the CD-36. (check out the home page that this bulletin board is part of) Some of the same people are even building it. Try calling them. They might be able to sell you a tank which is ready to fit in that space. Unfortunately it might also conflict with your new fiberglass water tank. I really regret the use of non-optimal water tanks in my '36. Perhaps some day I will make some fiberglass ones that will use the space more efficiently.
I am not sure how you could empty one tank without causing the system to draw air. Would you have an auxiliary pump?
I typically run less than 100 hours per year. As a result, it is only on a year with a long trip that I empty the fuel tank. Some years I use less than 25 gallons If there is no wind I just bob and sweat. What this does is leave me with fuel which sits in the tank over the years. Having separate tanks with separate returns would allow you to use one up, clean it out and add fresh fuel without mixing the fuel from the other tank. Having separate tanks is a good offshore feature. A friend of mine had a diesel leak in one of his tanks on the way to Bermuda this spring. It was ugly according to him. I wish that the Patrica Louise had separate fuel tanks with separate returns.
The Perkins 4-108 was used in many CD-36's. It is a good engine, but if faced with repowering the boat I would consider a more modern engine which deposited less oil in the sump, had a self-bleeding feature, had more room around it and had cheaper spare parts. (see my posts about changing the starter motor) The 4.108 is capable of producing about 51 HP, but with the standard prop installed, it is impossible to reach maximum RPM. At the achievable RPM the engine will only generate 45 hp.
Good luck with your tanks/cabin sole. The new sole will look great!
Matt
Herbert Prinz wrote: Matt,
You gave me lots of food for thought.
The cabin sole has already come off as I had to remove a lot of rot that the previous owner of my 18 year old boat had just covered up with new layers of plywood and varnish. This is the reason why I want to attack the fuel tank problem right now. In the process of the repairs one of the craftsmen cracked the polyethylene water tank in the front of the bilgue and, since he could not get a replacement from Kracor in less than 4 weeks, built me a brand new one made of fiberglass. I was so pleased with the result that I asked him to also build me a fiberglass fuel tank in place of an other water tank in the bilgue aft. The marine manager did not want to hear of it because he did not know anything about pertinent standards and regulations. Now I am looking for a company that would build me a fiberglass fuel tank.
Meantime I am still looking into the suitability of other materials, hence my question about the aluminium. I was told I could get such a tank custom made to match the exact dimensions of the old 30 gallon water tank in two weeks, if need be. However, this tank does not use the available space optimally and the fact that you have 43 gallons and other boats even 53 gallons of fuel makes me think that my first approach to go with fiberglass is the right one. Is this tank of yours an integral tank or does it come out, if necessary? Do you also have an other tank in the bilgue and if so, how big is it? I am trying to figure out the maximum tankage that one can or should have in the bilgue of a CD36. It is probably not smart to use all of the volume available as the bilgue’s function is to swallow the water that comes in, but how much is prudent?
As far as the fuel return is concerned, I am fully aware of this problem. I was playing with the idea of saving the second return line and the manyfold on the intake by plumbing the tanks in series. I have heard of people using so called ‘day tanks’ for various reasons. This would in principal be a similar arrangement. One advantage would be that I could run one tank completely empty without having to bleed the lines. What do you think of this idea? On the other hand, if I really can fit 53 gallons of fuel into my bilgue, I would consider forgetting about the old 24 gallon tank.
Is the Perkins 4.108 the standard engine in the CD36? How many hp does it have? I have a Perkins M50. It’s way to heavy. I go no faster than you, but use a lot more fuel.
Best regards
Herbert
mcawthor@bellatlantic.net
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Brewer Ezzell
Re: CD36 Fuel Tank
My slip neighbor had his CD36 leak fuel into the bilge this spring. The tank was located in a fiberglass tub in the bilge that ran from the mast step to the galley. The sole had to come up. What they found was that there were drain holes in the fiberglass tub. Accordingly, any high water in the bilge would put the tank in a salt water bath. Corrosion finally put a pin hole in the alum tank. He was able to get a new tank mfg by the original maker (I don't know who). He also glassed the drain holes in the tub. I am asuming that he believes that no water will enter the tub through the sole, or if it does, it will be fresh and not salt.
You have had response on dual return lines if you have two tanks. My current boat is a Morris Frances and I have dual tanks. My switch over value has double fittings. On each side, there is a fuel intake and a fuel return. Accordingly, when I switch, the return line is switched also. I don't know where you find such a fitting today.
bemf249@murphyfarms.com
You have had response on dual return lines if you have two tanks. My current boat is a Morris Frances and I have dual tanks. My switch over value has double fittings. On each side, there is a fuel intake and a fuel return. Accordingly, when I switch, the return line is switched also. I don't know where you find such a fitting today.
bemf249@murphyfarms.com