Fiberglass Shaft Logs

[twonahil]

What is the reason for changing out the bronze bolted up shaft alley's with fiberglass shaft tubes?

[bob lico]

world of difference when used in conjunction with PSS. seal.you have to make FG. shaft log stick out exactly 4" from edge to intersection of hull and you will pick up about 1/2 knot.i have photo`s if you want to see finished job.

[twonahil]

Bob,
Thank you. What wall thickness did you go with for the inner and outer fiberglass shaft log tubes? 1/2 a knot is a big increase!

[JohnCranston]

Bob,
I'm considering fg logs also while my boat is out of the water. Why do you get an increase in speed? Is it a big job installing the logs?
Thanks.
John.

[bob lico]

in all due respect it was capt. patrick`s idea of the FG. shaft log in combination with PSS. seal i just modified it somewhat.without getting in depth with hydrodynamics the OEM. shaft log is in a recess where it exits the bottom of the hull.when you pass a recess in the hull bottom over water it causes a drag in addition to a rotating shaft in a body of water at high speed.this water effect is almost nil under 26knt. but increases twofold as speed increases and the 31 Bertram lift up at 32 knt. and rides on inner strakes (with a perfectly balance boat) if your going to put anchors,port a potties,a/c ,holding tanks in V- berth this conversation is null and void.plowing with also kill your fuel economy. the first photo is the finished product inside with PSS. seal mounted on FG. shaft log.my shaft angle is also decreased but that is another topic.

[bob lico]

this is a view under the boat with 4" protrusion . john it is not just one modification that produces the incredible fuel economy it is the combination that enhance each other when cruise exceeds 28 knots most are rather meaningless at speeds less then 18 knots.other then the fact that they will cause the boat to take much larger waves and remain dry. john anything i could possibly help you with just post it -------------brother

[Bruce]

http://www.bertram31.com/proj/tips/shaft_logs.htm

[bob lico]

thanks bruce i did not know that captain added a total photo,explanation of the whole project.note the last line in his tip if you make the FG. shaft log extend 4" instead of flush at point nearest you MUST use PSS. seal with 1/2" water feed from gear cooler directly to seal. additional streamlining of forward edge of the top of struct,and do not cut down struct bearing in length make extra 1" stick out of struct facing bow.

[bob lico]

[JohnCranston]

Bob,
Thanks for the explanation...you're the best.
John.

[scot]

It's also one less location to bond and worry about electrolysis.

[JP Dalik]

As a matter of safety do not use the gear cooler. It's the first thing that clogs in the cooling system. Use the secondary pipe plug on the raw water pump. Install a crossover as well so both logs maintain cooling even if one engine is shut down. Do not use the gear cooler.

[Craig Mac]

J.P.---

Are you fishing your new boat?

[JP Dalik]

No Craig,
I've been fishing with a friend on his 44 Henriques. We've been doing a little green stick fishing on it. The topaz should float in about thirty days, working hard to get the cockpit de k back in and the refrigeration under control

[bob lico]

carl write this down as bertram modification # 12 ; never take a take off from raw water pump. the raw water pump flows to the fuel cooler then intercooler then marine gear cooler. A) you want the maximum cool water flowing to the intercooler for maximum performance,fuel economy.B)by taking the PSS seal off raw water pump you add 4' of hose that also out of view to critical system if hose breaks. C) if marine cooler ever clog you would have far more important situation to worry about because water flows to heat exchanger from gear cooler and water temperature alarm would go off within a minute or so with coolant temp. at 195 degrees it does not take much to set off alarm at 205 degrees .D) the PSS. seal has a solid stainless 1" wide ring riding on a solid carbon ring so it needs just a very small constant stream of water more then enough from gear cooler.want to prove it? at idle or troll gently pull back stainless steel collar and watch the circular spray coming out like garden sprinkler (always use clear reinforced hose from gear cooler to seal) ,2' of hose always visible when you open engine cover to check oil.you can just glance to observed hose,hose clamp condition.tap the raw water pump directly with 1/2" take off will coat you a higher EGT,and cooler charge from turbo will not be as efficient (reduced power ) you want the maximum efficiency of intercooler.

[JP Dalik]

SMHLMAO

[Carl]

...so many ways to skin a cat.

[bob lico]

carl i know you like the engineering view so lets look at this situation in a different light. cummins 6BT is rated at 220 hp if we stick a intercooler on it with block jacket water you get 270 hp. rating and if you sea water cool the intercooler you get a 330 rating. obviously the intercooler makes a dramatic difference in a marine diesel engine.60 hp gain from just reducing temperature of water to intercooler.that being said the raw water pump has a 1 1/2" output to fuel cooler and on to intercooler.if i syphon off 1/2" hose from output (1 1/2 ) would you say i reduced the raw water flow to intercooler by at least 20% . the water just flows out the PSS seal quite useless like i said in the above post.not going to get into metallurgy discussion but the stainless to carbon joint can work with a stream of water from a water pistol!!!! i have the extreme with 4" pultrusion of F/G sticking out bottom of hull and has been in use for 10 years with zero maintenance,actually the weakest point of the PSS. seal is the rubber membrane boot that slides over shaft log.a little off subject i take at least 10 Bertram brothers every rendezvous for a test ride on the Phoenix to confirm the agility and the performance numbers are exactly as i stated with 10 people on board the performance is three plus knots more then any 315hp cummins/yanmar in a FBC..one of the factors for maximum economy,performance is to get the coolest and most volume water to intercooler.

[Carl]

Bob- I can't argue that taking water from intercooler will have some effect...but its a 3/8" barb and even thats a bit of an overkill. Most people I know tee into an exhaust water hose and steel water that way...Down side is that exhaust seems to carry some junk with it that can clog hose...I know this as we had one running warm and after I pulled that hose the amount of water coming out...lets just say I can piss harder. Cleared a few flakes and back in business.

All in all, a small % lost to most goes unnoticed.

[Rawleigh]

I pulled mine out of an outlet on the bottom of my Sendure tank. No change in cooling performance that I can see.

[Tony Meola]

..lets just say I can piss harder.

Carl

Are you trying to point out how young you are compared to the rest of us?

[Carl]

[quote="Tony Meola"

Are you trying to point out how young you are compared to the rest of us?[/quote]



LOL...

Nah, just saying even with a small stream the the gland only ran warm.

[scot]

Bob,

220 hp if we stick a intercooler on it with block jacket water you get 270 hp. rating and if you sea water cool the intercooler you get a 330 rating. obviously the intercooler makes a dramatic difference in a marine diesel engine.60 hp gain

The temp of the charge air is not the only difference. All these engines, 220, 270, 330 use different injectors and different lift pump (P7100) set ups (i.e. MORE fuel). The lower temp of the charge air only makes it possible to add more fuel, which equates to more hp. All diesel engines make more power with larger injectors and more fuel in the mix.. but if the engine is going to live with more fuel, you have to add more cooling to the charge air.

So, the 60hp gain you described is not a function of the charge air cooler alone, but rather a combination of more fuel + more charge air cooling. Without additional cooling the larger injectors in the higher hp engines would fry the pistons. Plenty of Dodge trucks out there running the marine 6BTA 370hp injectors with the same charge air set up as the 210hp motors.. but they can only live at lower sustained rpms and light loads because of the charge air temps. Put them under a marine load and they would make 370hp for a few minutes lol. Make the air colder and they can survive.

In conclusion, the colder the charge air, the more power you make but more importantly, the engines needs colder air to live at higher fuel burn rates.

[bob lico]

scot trying to keep post simple! we could go on and on ,yes the sea water cooler allows more cooler fuel,and yes i have a special turbulent coolest air possible but that on Carl`s list already.all the recons use the 7100 series pump with different cam adjustment and i never mention 370hp .the post was to illustrate the increse power output by keeping most volume,coolest water to intercooler other peripherals don`t enter the picture they are assumed .