bertram31.com

Is it common for these boats to have air conditioning? Also. Where is the generator hidden?

A lot of the members have added AC. If you are in the South they usually go with a unit around 16,000 it's. Up north you can probably shrink that size a bit.

On the 31the generator is usually outboard of the port or starboard engine and batteries are usually moved to go under the deck in the companion way between the engines.

Remember keep the weight as far aft as you can. One member has the AC compressor in the cabinet in the stand up head on a fly bridge cruiser. That. Helps keep the weight towards the aft end.

Thank you.

These things can accommodate a sea keeper too? Seems like it would start to get cramped quick.

after a enormous amount of research i found out Cruise Air makes a unit specificially for A/C bridges in large sportfishing boats (60' + ) they have high speed turbo fan on small units like 10-12,000 btu. the head in a FBC has a wall to wall vanity with a shelf .install unit 2" from main bulkhead on 1" thick rubber pad with short hose from drain pan thru wall to engine bilge .cut 18" off shelf ,resupport it and a 6" duct comes out top of unit, install along back of sink drain to back of refrigerator. mount diversion box with 6" in right side and 4" left side and 4" bottom . duct 4" bottom under floor and come up in back of port hanging locker with 90 degree grill facing salon the other 4" duct goes along hull side to straight grill on far starboard side next to hull side of V-berth .this causes a circular flow of heat or a/c around v-berth into saloon and toward the return air(a/c unit ) in vanity. quiet ,no exposed ductwork ,extremely efficient . a word of caution if you take "easy way out" and put a/c unit in middle of v-berth you have destroyed the balance of boat (law of levers ) 50 pounds in v-berth 10" forward of main bulkard would take 500 pounds of ballast to balance boat!

Edited.

Hi,
I've put a 3.5 kw Whisper Piccolo gen in just in front of the fuel tank. It's weighs just 70 kg.



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I put a new tank in, which it higher than the original. All in all I calculate that I have only list about 50 litres of fuel, but have kept the weight further aft. This makes up somewhat for the lighter, 4 cyl Yanmars that I have put in. I have two 260 ah batteries under the deck between the engines.
A/c going under the sofa bed on port side main cabin.

David

excellent fit on that genset . keeping weight as low as possible,centered on keel , and aft of main bulkhead . smart!

Thanks guys. That looks sharp on the generator install.

Bob I've seen numerous posts from you and you've spoken about weight distribution. In a flybridge I can understand that this is critically important with all that weight forward of both the cabin pilot house and flybridge. Is there anything I can read or we can read about Weight distribution on Bertram 31s? I saw your post about how 50 pounds in the forward area of a boat equals 500 pounds aft, how is this calculated? In addition , on my Bahia Mar I have added approximately 1000 to 1500 pounds of weight with a marlin tower and air-conditioning without any appreciable decrease in performance. Perhaps different 31 both designs are affected differently by weight distribution or I am not sophisticated enough to determine the lack of performance. In reality I think most of the weight I added was aft and has been beneficial. I would love a synopsis of your thoughts on this and wonder if it has been discussed anywhere else. Thank you

Nice clean install David. Did you relocate the fuel tank?
My original tank sat up to the bulkhead.

priceless you understand the law of levers well the application in ANY 31 bertram configuration is the main bulkhead in fbc.,sedan,sportman,and in your case a couple 6" forward of engine box would be the balance point. i had access to travel lift using one strap on centerline so i was able to experiment with horizontal balance point any time i wanted.i say horizontal because vertcal in a different situation much more affected by weight at uppermost point on top of boat a example would be putting a analog type 4kw open array radar (about 75 pounds with stand) on hard top above bridge this would be 11' above water line and would definitly contribute to roll ,if you have lightweight 4 cyl. diesels with reverse chines out of water when boat is at idle speed you going to feel it with port or starboard wave action ok thats easy to understand as well as a bahia mar less likely to roll due to centroid of gravity being closer to water line. lets go to horizontal plane and the wight effect on all 31 bertrams . the balance,out of balance theory becomes much more dramatic with boats horizontal plane angle with boat going forward and on plane. now we draw a imaginary line down the keel line with main bulkhead being the centerline of balance (Raymond hunt`s original design with 413 "Chryler engines and cast iron b/w gears ) about 950 lbs complete) sets the reverse chines submerged completely as a counter balance to 24 degree deep Vee from bow to stern. the taper from midships to stern ,tumblehome and lifting strakes design only works with a 31 that rides bow proud and weight forward of centerline will diminish that ride in rough water accordingly. the object here is to ride on top of the waves to about 5' which is the most you should encounter unless a freak storm comes up. all 31`s should have the water breaking under the pillars on fbc. and same balance point 1' in front of engine boxes on bahi mar.so now we come to the law of levers using the center point as reference.the hatch in the center of Vee birth is 10' in front of the engine box so putting a 50 pound a/c unit in that spot would take 10 ' X 50 pounds = 500 pounds to correct.now that is on a gasser or 1000 pound power plant aka. Volvo,cummins ,etc bertram . the seat of the pants effect would be felt immediately in waves in excess of 4' be it head seas or quartering seas . the boat will "stuff" every third or fourth wave depending on how out of balance she is. the 31' bertram is the best design hull ever built HOWEVER if you defeat the original design you pay the price. i could tell you many stories over a 17 year period like you have the option of experimenting with props once you have the balance correct. personally the best rough water boat would be a bahia mar with 3126 cats , "bring it on mother nature"
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thanks, awesome explanation. will pay much more attention to weight now

looking back on my post i wanted to reiterate ,there are two acting forces to contend with; the vertical balance is not critical in a little weight change especially on a bahia mar,sedan . the difference in weight between a old fashion 4 kw open array and a state of the art digital unit is perhaps 45 pounds multiply by the height off the water line. a fbc. with tower and cactus mount on top would feel a touch more roll if the boat was taking waves directly broadside like drifting for shark while on a behia mar hardly noticeable .my main contention is horizontal balance that can beat you up on a ride to or from offshore canyons or create a dangerous situation coming into a washboard inlet .this is why i come up with two distinct tell tale observations ;when at cruise is the water breaking under the main bulkhead line with the entire wet area from that point forward completely out of the water and number two does the bow chock EVER go under water with water going over the deck in 5' seas.

Carl,
I lost tank area where the gen is now. So I moved the rear of the tank back around 6 inches, reducing the size of the aft bilge, and raised the height of the tank by about 6 inches. As I said before, I lost around 50 litres in all with the new, plastic tank. It wont affect my cruising/fishing plans.
This effectively moves the fuel moment further aft, and adds the weight of the gen back there. Together with removing the anchor windlass and chain up front, I'm hoping this helps keep the weight distribution as it should be, now I have lighter 4 cyl Yanmars.

David

Bob Lico et al - anyone ever ballast way back to drop stern? Our soft-top express with 230hp Yanmars and only 170gal fuel sits barely in the water in the aft at rest - rides very good, but definitely not getting all the work out of the hull design with cabin creature comforts and extra glass mid ship on the express. Was thinking of glassing some metal plates and putting aft outboard of stringers to spread out some additional weight back there. Thoughts?

do you fish with it? if so salt water ballast in stern like bait well is the best solution because family days bait well is empty and used for storage . a ride across Buzzard bay when wind kicks up just take on 30 gallons of water and put those chines under water and bow lift and little bit makes a huge difference . remember the lever formula you are add 240 pound at transom.a sedan also has a nice weight advantage with the driver and passenger sitting over engine box that is in essence having 350 pounds or so added to engine weight in your case (2)) 4 cyl. yanmars 900 pounds plus human weight = 1250 pounds which is 750 lbs from design weight.240 lbs on transom line is about 9' from balance point you will improve ride dramatically unless you have a A/C in Vee birth , captan/windless on bow ,50 pound anchor,chain in rope locker,tons of heavy weights in port and starboard storage area in Vee birth.just like cargo ships use your head . Vee birth for pfd`s,docking lines,rain gear,boots, nothing heavy!.use hanging locker for perishables and what ever for day trippers.cockpit for heavy weights.whenever you see white caps and you want to cruise at 24 plus knots you HAVE to have the first 8 to 10 ' of hull out of water to let wave crest to break under balance point if not you will take a beating.