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Old 11-05-2013, 18:38   #1
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Gemini 105MC fuel tank

Hey everyone,


The wife and I are within our 1 year mark for the transition aboard for long term.

The Gemini 105MC is at the top of our short list but I have 1 main concern that I have yet to see covered here in CF (let's not turn this into the typical "Gemini's can't cross oceans" thread that everyone loves).

The fuel tank is SMALL comparatively. Damn near HALF the size of its water tank.

Anyone have a 105MC and expanded the fuel capacity, or does anyone have friends that have? What are the best options?

Yes, fuel has weight and all that. I'm looking for a real world fix (besides fuel bladders! No thank you!).

Cheers everyone!
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Old 12-05-2013, 05:24   #2
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Re: Gemini 105MC fuel tank

How much range do you need? We get around 250miles out of the standard tanks (outboard not diesel and the diesel should have even better range).

With 4 - 5gal portables jugs tied off between the davits, we have done 360 miles on a full load of fuel. We only take 2 jugs now so we can fill the dingy motor and to take advantage of street side fuel prices when possible.

With coastal cruising, there is plenty of range to wait for better fuel prices.

If you are looking at longer distance offshore stuff, we could cut back to 4-5 kts and that would jump up into the 500-800 mile range.

Where are you planning to cruise that you need 1000 mile range?
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Old 12-05-2013, 07:22   #3
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How much range do you need? We get around 250miles out of the standard tanks (outboard not diesel and the diesel should have even better range).

With 4 - 5gal portables jugs tied off between the davits, we have done 360 miles on a full load of fuel. We only take 2 jugs now so we can fill the dingy motor and to take advantage of street side fuel prices when possible.

With coastal cruising, there is plenty of range to wait for better fuel prices.

If you are looking at longer distance offshore stuff, we could cut back to 4-5 kts and that would jump up into the 500-800 mile range.

Where are you planning to cruise that you need 1000 mile range?
Thanks for the response!

The concern is more of a safety feature for the wife. We plan on following Slapdash's lead and doing a circumnavigation in the Gemini, so fuel as a back up is a concern for her.

Also at the top of our short list is an Island Trader 46 which has something like a 450gal fuel tank (being a monohull and all). I would NEVER use THAT much fuel as we don't plan to motor much, but it makes the wife more comfortable.

Are you getting somewhere around .6GPH? I would think an extra 20odd gallons in a tank plus Jerry cans would make the wife sign off tomorrow as it is literally her only concern at this point. We also would need an air compressor as avid divers and would have to run a genny or the engine(s) while that's running.
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Old 12-05-2013, 08:39   #4
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Re: Gemini 105MC fuel tank

Normally get around 1g/h at 6kts. If we back off to 4-5kts, it goes down to around 0.5g/h. (I prefer mpg as it's what we are really interested in and that runs around 6mpg at normal cruise speed and jumps up to around 10mpg if we back off).

Obviously, you aren't going to dive while doing a crossing, so that is a seperate issue. A built in compressor & generator may be problematic due to space constraints. We are all gasoline (main motor, dingy motor & portable generator placed on back steps while running).
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Old 12-05-2013, 16:33   #5
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Normally get around 1g/h at 6kts. If we back off to 4-5kts, it goes down to around 0.5g/h. (I prefer mpg as it's what we are really interested in and that runs around 6mpg at normal cruise speed and jumps up to around 10mpg if we back off).

Obviously, you aren't going to dive while doing a crossing, so that is a seperate issue. A built in compressor & generator may be problematic due to space constraints. We are all gasoline (main motor, dingy motor & portable generator placed on back steps while running).
Thanks for the info!

Cheers and fair winds
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Old 12-05-2013, 17:05   #6
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Re: Gemini 105MC fuel tank

You are considering a relatively small catamaran with the Gemini for ocean crossings.

Certainly it can be done however one of the big issues with a smaller cat is load carrying.

Generators, SCUBA compressors, food/spares for a crossing, extra fuel, dingy + motor are all weight which impact on speed and vessel safety.

You need to look a design allowable loads and consider a load/weight balance audit.

I am in a similar situation as a diver looking at extended cruising and have ruled out cats under 40ft and thus am looking more toward 45ft for their load carrying ability.

If I were you I would be looking at a cat with more load carrying ability. perhaps a Lagoon 380.

Cheers
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Old 12-05-2013, 17:10   #7
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We have a similar sized cat w twins. @ 75% throttle we avg. .5 gph.per diesel with just a little wind the fuel consumption decreases tremendously. We carry alot of fuel 56 gal in 2 inboard tanks and another 24 gal on 4 jugs below decks forward when doing long trips. Ots nice to have if you can afford the weight.
Have you had dive compressors before? Wife had one and it was extremely loud, hot, maintenance intensive and heavy. Plus had to run a while to fill a tank. She had 3 huge banks it kept full in stages up to 5000 psi. Were you planning on gas or electric?
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Old 13-05-2013, 09:02   #8
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If I were you I would be looking at a cat with more load carrying ability. perhaps a Lagoon 380.
You bring up very valid point about load carrying. Gemini's are known for slapping when weighed down. A huge negative during a crossing.


But Yikes. A 380? I'd take a 440 if I had the money (which I don't), but a 380? No galley, two heads to maintain, most are 4 berth, 2 inboard diesels with saildrive and bad access. No thanks!
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Old 13-05-2013, 09:06   #9
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We have a similar sized cat w twins. @ 75% throttle we avg. .5 gph.per diesel with just a little wind the fuel consumption decreases tremendously. We carry alot of fuel 56 gal in 2 inboard tanks and another 24 gal on 4 jugs below decks forward when doing long trips. Ots nice to have if you can afford the weight.
Have you had dive compressors before? Wife had one and it was extremely loud, hot, maintenance intensive and heavy. Plus had to run a while to fill a tank. She had 3 huge banks it kept full in stages up to 5000 psi. Were you planning on gas or electric?
You're sailing a Renaissance 320? I can't seem to find any websites with pictures or specs...

The compressor will be an add on in a few years, and is a must despite its obvious disadvantages. Haven't looked too heavily into gas or electric.
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Old 13-05-2013, 16:13   #10
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Re: Gemini 105MC fuel tank

Quote:
Originally Posted by MBLittle View Post
You bring up very valid point about load carrying. Gemini's are known for slapping when weighed down. A huge negative during a crossing.


But Yikes. A 380? I'd take a 440 if I had the money (which I don't), but a 380? No galley, two heads to maintain, most are 4 berth, 2 inboard diesels with saildrive and bad access. No thanks!
Not saying there are not things i dislike with the 380 but your intended use/loads/ anticipated voyages means significant compromise with a Gemini.
Without doubt a 40 ft cat with the right layout for you would be a better fit but then again perhaps budget is the other compromise.

Good luck with your choice.

Did Slapdash actually circumnavigate?? I thought they sold their vessel in the med.
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Old 13-05-2013, 16:20   #11
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Re: Gemini 105MC fuel tank

Two jerry cans minimum is always a good idea for adventure cruising; it is not uncommon to find yourself in a situation where carrying fuel is required, sometimes a right good distance.

Additionally, multiple tanks spread the bad-fuel risk a bit.
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Old 13-05-2013, 17:17   #12
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Did Slapdash actually circumnavigate?? I thought they sold their vessel in the med.
Last I saw, slapdash was for sale in Annapolis. I know they shipped her through the trouble waters (from India to the med I think).

Didn't mean to be rude with my reply, I just detest the galley in the 380. An owners version would be much better, but at least $100k out of budget

As you suspect, price point is our greatest enemy at this point. Maybe one day the wife actually win the powerball and a new custom Antares 44i will be waiting for me. Until then, we'll just keep looking for a perfect boat
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Old 13-05-2013, 17:20   #13
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Additionally, multiple tanks spread the bad-fuel risk a bit.
Very good point
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