need help with plans

Tugboat,
I'm just getting back on your posts about your sandblasting quotes. I realize you decided to walk away from steel but want to clarify something about sandblasting a boat as I don't believe those quotes were for proper blasting quality and should make things clear for other readers of the thread. As I'm lazy this morning I'll just copy and past part of my website:

"The sandblasting of a steel boat has two reasons to be. First we want to remove the mil scale to avoid it causing galvanic corrosion by reacting with the steel. We are then aiming for as white of a finish as possible. Sandblasting to white metal (SSPC-SP5 (SSI-Sa3), or NACE #1 surface preparation standard ) means what it means, the result is a white (pale grey) surface. A commercial blast (SSPC-SP6 (SSI-Sa2), or NACE #3) would leave some of the tougher scale on the metal and a brush blast ( Brush Off Blast SSPC-SP7 (SSI-Sa1), or NACE #4) would only blow the loose impurities. If you are hiring a contractor to sandblast your boat, make sure the finish you want is clear and verify that you are getting the finish you want before he gets to much done. The second purpose of sandblasting is to provide an anchor pattern to increase paint adherence. Epoxy paints work by mechanical adherence and will stick better to a gritted surface than a polished surface. The anchor pattern depends on the sands grit size. We use 35-70 (#40) sand. "

What I'm saying here is that there are different quality of blasting and if you don't precise exactly what you need done, you'll get a quote for a brush blast. If you ask for white metal blasting and are very clear about wanting all the mil scale gone, I doubt you get a clear quote. You will most likely get an hourly rate. Some contractors will actually shy away from the job.

If that quote was really for a proper white blast. Either it is for workers hourly rate only and the guy is not paying himself much, than you should expect a lot more "ching ching" for diesel and sand. Or that guy is making you an absurd favor, because he's not going to get into his money.

cheers,
Murielle

 

Hi Murielle, yea--it was looking really expensive...it seems the blasting would be about half the cost of the steel needed...for this this is an issue since steel is reputed to be one of the more inexpensive. Steel will always be my fav way to build and i ahev one other boat i built in steel..but did not blast since it was small enough to grind down to white metal (pontoons).
sadly--the costs make this big cost prohibitive. not necessarily that over three years i cant build it but because i am stubborn and want to find econimical solutions to problems...
i appreciate your posts...love your boat too!!

 

steels always been my first choice...but FC is undeniably strong and practical IF done right...

 

yes--thanks i appreciate the facts ...not accusations ...

Absolutley Mike-- steel is my first choice-im only saying that FC is a viable alternative and less money---if it is a commercial vessel--i would be goign steel..but for a crossover vessel like mine--id be comfortable with either..

 

Knut--i hope im understanding you correctly--are you talking baout a hull fitting and the puling stress?? i.e. when towing for instance the bitts are welded to a steel deck making them a part of the whole structure??..in thats sense then a bitt might pull out of fer-a-lite?? hope that i understood...

 

Pdw- please explain--i dont know what iron bark is??

off topic but --since i was asking earilier about sandblasting--do you plan on blasting her to white metal ??.or is there some happy medium in doing that? please post pics...Colvin has great designs...im guessing your either pulling a plate in with pad eyes and come alongs or some similar method? i have a bad back--do you find your in any back pain at the end of the day?--this was one reason for not doing the boat in steel for me...i can barely move when i work long periods..form back pain..hence for these reasons i had to rethink doing steel...i didnt want to post my reasons for obvious reasons...

 

Ironbark then must be a tree species not found here in Canada--there is a tree here called iron wood..i wonder if it has similar properties -in fact my tugboat will be named "Ironwood"

 

Blisters in Fer-A-Lite - yeah right NOT

Now suddenly instead of just a separated matrix on the mystery boat, it now suffers from multiple and severe blistering?

There must be a laminate involved for blistering, I have never heard of blistering that did not require a laminate issue to start the process. Or perhaps you failed to continue the statement to the possible conclusion that they had applied Gelcoat and was seeing Gelcoat blistering between the Gelcoat and skinning material on the Fer-A-Lite hull.

That is not a failing of the Fer-A-Lite material or process, in fact Gelcoat blistering is the biggest issue on any boat that suffers from blistering.

Fer-A-Lite does not contain any fibers of sufficient length or orientation that would allow blistering.

If in fact there is an issue around the interface of the steel and the Fer-A-Lite material, it is because they applied the material to an armature that was not at a sufficient temperature to allow the full curing of the material.

This is clearly spelled out in several places that you must not attempt to use the material below x degrees and that the armature must be at or above that ambient temp.

A similar issue occurs on any any fiberglass hull if they do follow the temp guidelines.

Give me a break!

 

And that could answer the issue with the stern tube

Mike,

If in fact they did apply the material below the recommended temp. the following happens, you end up material that never fully sets in direct contact with the armature, the armature is nothing but a big heat sink during plastering, if the armature is too cold, the material never fully kicks.

And it is very easy to detect. Fully cured Fer-A-Lite will ring with a high pitched note, if there is unkicked material, it will respond with a hollow thud.

This would definately impact the strength of the entire matrix, and cause a reaction between the various components in the uncured mass and the steel armature.

Platt had several warnings about temp of application in his directions that shippped with the material as well as in the book he sent along.

That is not blistering as a failure of the material, that would be a failure due to improper building process, not following the clearly defined application temp. guidelines.

That would allow the matrix to separate with repeated vibrations.

I sure would like to know what part of the world, what time of year it was built.

Possibilities why the mystery boat has a problem

Did not follow proper and documented instructions in regard to:
1. Temp guidelines for application
2. Failed to skin the vessel at construction
3. Improperly applied GelCoat

So pretty much except for #2, the same issues could and do occur with production fiberglass hulls (in some instances)

 

now heres a practical question on the plans-- im going to start to cut my frames...
ive never lofted "Diagonals" before can someone-without throwing insults- explain to me if the diagonal is measured from the CL downwards on the diagonal , or is it measured outwards from the CL??..when i check it against the offsets it seems the diagonal is measured outwards to a point past a buttock. but the book says its measured downwards at an angle(or at leats thats what i got from it-ill recheck in case i misunderstood)???

 

Diagonals are generally placed so as to be perpendicular to the planks. You can put a diagonal anywhere if you so desire, it is the best measurement to the true planking at any particular piont.

Be aware of the moulded depth however (the "thickness" of the hull, as measured from the centre of the boat to the outside of the hull), some plans have inside measurements, some have outside measurements.

 

Landlubber--thank you ever so much!!!!
may i ask you to clarify for me- with regards to the offsets; in the offsets table- do the measurements given refer to the distance from the centerline to the points measuring diagonally?.or are they measured outwards longitudinally using the diagonals as a simpe reference? god its hard to explain when i don't have the plans on here to show you what i am trying to ask...sorry...

i have no trouble getting the other points...just the diagonals - want to be absolutely sure i get it right...and understand...

 

...diagonals are measured from the centreline along the diagonal, to the refference point on the lines plan, it is quite OK for you to throw in as many "diagonals" as you feel necessary to define a particular point of the hull build (as such)...they can be anywhere that pleases you, they do not have to meet the buttocks or any waterline, but of course, these points are already defined, so they often do all meet a such points. Where there are complicated shapes, 3 or 4 diagonals drawn and interpolated at those difficult areas would be quite Kosha......

 

try getting a copy of my old text book, Boatbuilding Manual by Robert Stwward, he explains well how to read the lines and offsets tables (my copy is ed3 P.81).

 

great ill look for it...yes I understand now--ill just take loft the diagonals, and measure down to the given lengths on the diagonals...there are four per view...should be enough ...i appreciate your patience landlubber...

have you seen that book anywhere??. also, im going to strat a new thread--im going to see if anyone on here would input my plans int autocad and I will pay them for renderings. I was thinking of going to full size patterns for this for ease and to speed up the build...and for accuracy...

do you know anyone that could do this?