positive floatation

Franki · May 8, 2002

Hi people, How hard is it to make a glass boat have positive floatation??? I have a very solid 17 foot half cabin with a 170kg Johnson on the back, and another 25kg of kicker motor, add fuel tanks and the usual assortment of stuff we all lug around on boat trips and this thing is heavy... I even bolted two Jarah (very very hard wood) 6x4inch beams to the stringers under the deck for extra strenght.. I have a suspecision that if the hull was compromised or it capsized, it would sink like a hot rock.. There was a bit of floatation material under deck when I got the boat, but it was waterlogged, so I took it all out. I was thinking of placing two water tight storage boxes in the boat, one right up front in the nose, and one right up against the transom. keep stuff you want to keep dry, (clothes and stuff) on a trip and have water tight doors on them.. is that a worth while idea??? would they significantly effect the floatation??? any thoughts'd be great... regards Frank

crab bait · May 8, 2002

Re: positive floatation

hi FRANKI , according to booklet i got from the US COAST GAURD , called safety standards for backyard boat builders it says,,, a cubic foot of enclosed air has 62.4 pounds of bouyancy... foam has 60.4 lbs.per cubic foot ..

Franki · May 8, 2002

Re: positive floatation

yikks, thats gonna be two big enclosures

Its kinda hard to test too isn't it? I dont' really want to sink my fully loaded boat to find out if it stays above waterline.. ok,, I have the answer, I'll buy a 20 foot inflatable.. cut the floor out, and stick my boat in the middle.. then glue it on.. that would do the job

another added benefit of that would be the increased stability at rest

regards Frank

crab bait · May 8, 2002

Re: positive floatation

i know what you mean... it blew me away when i read that ... it seems so little.. but that's what it says.. also it says if not enough floatation to install " HANDELS on the outside of hull.. as for to hold on an pull yourself up if flipped over

Franki · May 10, 2002

Re: positive floatation

Hi crab bait... I have a question.. if one cubic foot of trapped air has 60 odd pounds of bouyancy and floation material has less,, why do lifejackets work? i suppose people almost float already so just a little extra makes the difference? need a big lifejacket for my boat.. well that settles it, I'm just gonna have to not sink

regards frank

crab bait · May 11, 2002

Re: positive floatation

you answered your own question exactly .. same with boats if your TOTAL combined wieght is say 3000 lbs. it doesn't need 3000 lbs of floation... because the boat has some inherant bouancy an since it's SKUTTLED,, in the water it wiegth less .. this book explains it all..

Franki · May 11, 2002

Re: positive floatation

do they give any indication of how to work out how much floatation you need for a given boat size?? my boat is very heavy for its size.. so I am guessing that if it went down, the rear would go first and it would sink much like a rock.. it does have alittle floatation foam under floor, but its old and was half waterlogged, so I pulled as much of it as I could reach out. Is there any good cheap material that you can put under floor that won't waterlog?? (what about polystierine???? regards frank

crab bait · May 11, 2002

Re: positive floatation

yeah , that 'll work so will that expandable foam sold in hardware stores . i'm sure it's ' down unda ' ,too.. also sold in marine centers as a 2 part mix expan. foam , too .. yea , FRANK , it's in the book. all these formulas to follow not very difficult.. this mite help you ;; it's a USCG web site.. INFOLINE@MAIL.RMIT.COM can you guys call an 1-800 phone number here in the US ??

crab bait · May 11, 2002

Re: positive floatation

belay that web adress... it don't work ,sorry ....

Franki · May 11, 2002

Re: positive floatation

I'd like to get that book, unfortunatly USCG doesn't publish in Australia that I am aware of. I don't like that spray stuff, its very porous.. and that means it can water log yes?? I'd rather go to a packaging plant and buy a heap of styrofoam of them and cut it to shape with long razor and slide it up under the floor.. (and anywhere else I could make it fit.) Might have to look into that, but todays activities are: 1. Finish weilding new rollers on trailer. 2. Clean up transcom for fitment of new motor. 3. add pickups for speedo and transducer. 4. Fit said new outboard and try to adapt the steering to fit. 5. Start work on fitting new dashboart. That should keep me occupied for now, I guess I'll worry about floatation when I am much closer to actually needing it.

regards frank

crab bait · May 11, 2002

Re: positive floatation

you got your hands full ,frank .. i know what you mean about that foam being porous that's what i said/thought but the - powers- that- be said ' not so ' the foam it self does not absorb water at all..you after long discusions i foamed my boat with the stuff.. frank if you really would like to have the book .. e-mail me at crabbaitshow@webtv.net ----- i'll hook you up some how ...

Hooty · May 11, 2002

Re: positive floatation

Hey Frank & Crab Bait, Couple of things: Urethane (Pour-in foam) is opened cell only when inproperly mixed and mixing it is VERY tricky. If the mix ratio is 1:1, it HAS to be 1:1, not 1.1:.99. This is where folks, and even OEM's screw up. Styrofoam is o-k except gas and oil melt it. Glastron use to put it (styrofoam in polyethylene bags to keep fuel away from it. And ya'll were talking about 1 cu.ft. of air floating 60+ lbs.,remember, a cubic foot of water weights that 60+ lbs. c/6 Hooty

crab bait · May 12, 2002

Re: positive floatation

HOOTY HOOT TO THE HOOTY, thats interesting ,hooty.. i know i didn't mix it rite ... but the outside skin is soild ... still the " EXPERTS " i talked to said even when porous it holds no water.. i'll tell you i was suspishous (sp) an they didn't have a clue as how if ever it gets porous.. i took there word on blind faith.. BOY I HATE THAT !!! you gotta understand ,, how apprehensive i was doing that job ... A FALSE SENSE OF SECURIITY ... i did do one thing rite .. on my own ,, i layed down 1/8 pink owens/corning foam sheets. in left big joint gaps an duct taped all the joints.. than foamed ON TOP.. so now ,,water has a place to run thru an out...

Franki · May 12, 2002

Re: positive floatation

yeah,, I am going to do some tests.. Up the front I think I'll use styroform because it won't be anywhere that could get oil or fuel on it.. Then I'll mix some of that stuff up and try soaking it in water for a week or so.. see if it retains any water.. If it doesn't retain any water after a week, I'll do it.. (if my boats ever full of water for a week I'm probably dead

Thanks for the tips fellas.. you guys are great.. regards frank

outonbizniz · May 13, 2002

Re: positive floatation

You can get that book you were mentioning online at the cost guard site below. it is in Adobe pdf format. http://www.uscg.mil/d8/mso/louisville/download.htm

Franki · May 13, 2002

Re: positive floatation

Thanks outonbizniz I guess you should hang onto your book mr Crab bait.. the pdf is only 175k and I have a laser printer.. Thankyou for the kind offer of the booklet.. and thanks to outonbizniz for making it unnessecary that he send it.. (I hope its not too late.

regards Frank

outonbizniz · May 13, 2002

Re: positive floatation

You're welcome. It's good to see a mighty "First Mate" can make a worth contribution to help out all you craptains, uh make that captains.

Franki · May 13, 2002

Re: positive floatation

hmmm, according to that book, I am overpowered by a significant margin. I have a 100HP, (say about 90 at the prop) and if the measurements are correct in that book, I should have a 65-77HP outboard. The thing is that the book doesn't take weight into account, this boat is HEAVY.. old, the fiberglass is just about 1cm thick all the way round, (and I haven't tested the hull, thats just the gunwale.) the boat probably weighs half again more then other boats its size.. Still, we don't have alot of boat rules around here, so I guess it doesn't matter much, especially since I'm paranoid and will probably never take it over 4800rpm anyway... The main reason for the low rating is that its a narrow transom.. (just under 5 foot at its widest point.) its just under 17 foot long.) It handles well with that power, and turns predictably and runs well.. I used to run it with two 40's and it handled that well so I am thinking thats probably fine. I can't find out what the original manufacturers HP rating for the boat is. (its an old australian brand which has changed company names so often noone remembers who really made it.) Still, its a great boat, and very very solid.. the front half has a fairly decent V, but the back tapers out to be nearly flat.. and with 100hp, that adds up to serious speed for the old girl.

Only problem is that the OMC V4's chew a serious amount of fuel.. which it was more economical. still thats enough of a rant for tonight..

regards frank

crab bait · May 13, 2002

Re: positive floatation

WELL AIN'T THAT A B@TCH !!! HERE'S ONE CAPTAIN THATS PI$$ED OFF AT A FIRST MATE ! in about a week ,FRANKI , you'll be gettin' another...... went to the post office this morning.... ain't that a b@tch O'WELL no good deed goes unpunished...lol

Franki · May 13, 2002

Re: positive floatation

Hey Mr Crab bait... want me to send it back when it gets here??? ;-) regards Frank

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