Flatback Fireboat Rebuild

[gran398]

Hi, just spoke with Chris.

He said that if you think the cracks are caused due to stress (transom, chines, etc.) then you'll definitely want to beef up those areas from the inside, otherwise they'll come back. Mentioned to him your work so far (transom, stringers, tabbing, deck) he thinks you're good to go, but feel it is worth mentioning.

If the cracks are not caused from stress and due to age/shrinkage, spend less time/eliminate the first step on the prep below.

Said to take a dremel tool and gouge out down to glass, at least 3X  the width of the crack. Then come back in and fill with a commercially available marine grade vinylester fiberglass-impregnated putty. Said this stuff hardens like a rock. You can fill the little finish stuff with the cabosil mix or bondo.  

Then longboard...then spray with Duratek clear high-build primer. Then longboard/finish. Then spray the gel.

[CLM65]

Thanks Scotty!  I don't know if they are stress or shrinkage related, but regardless I have beefed up the inside in those areas quite a bit already.  Tell Chris I appreciate his advice!

[CLM65]

Craig, remember what the bottom of my boat looked like lol thats one more reason why im bottom painting it again.

Yea, I guess I can use that as my last resort, but since it will be lift-kept, I really don't want bottom paint.

[RickK]

Craig, did we miss the install of the sole?

[gran398]

Thanks Scotty!  I don't know if they are stress or shrinkage related, but regardless I have beefed up the inside in those areas quite a bit already.  Tell Chris I appreciate his advice!

Sure will, he's a good guy.

He also said if you had any questions/ need advice, just call. So I'll PM you his #

Rick, think I may have jumped the gun on the sole...sorry 'bout that.....

[CLM65]

Craig, did we miss the install of the sole?

Nope, made it, but didn't install it yet.  Robb Young, who flipped the boat, recommended leaving it out to keep it lighter for the flipping.  He said that is how they typically do it.  Just needs to have the stringers and bulkheads in.  Which means I have a sole in the backyard that I need to figure out how & where to store for a month or two or more

[RickK]

Wow, I would think you need the sole in to tie everything together.  Guess I learned something new today.

[CLM65]

Finally got to spend a little quality time with the boat, and made a decent dent in bottom paint removal




Kinda scary and disappointing to find all these cracks in the gelcoat that were covered by the bottom paint.  Some of them are random, and some look more like the result of an impact of some sort.  I did take a dremel tool to a few of them, and so far they seem to terminate at the fiberglass, so I'm leaning towards shrinkage/age related, possibly affected in some way by the bottom paint.  Which is a whole lot better than structural cracks.




I plan to take the dremel tool to most of them, as suggested above by Scotty/Chris, which is going to take a while given the quantity of cracks I have.  On the ones that look like spider webs, I will probably grind down that whole area and build back up with mat and vinyester.  Does this sound reasonable, or does anybody have other suggestions?

[Aswaff400]

looks exactly like my hull bottom! which is why im putting bottom paint back on... may do that next week....

[RickK]

What kind of power tool did you use on the bottom Craig?

[CLM65]

looks exactly like my hull bottom! which is why im putting bottom paint back on... may do that next week....

Aaron, don't take this the wrong way, but I'm glad to hear that your hull looked like this!  It gives me a little comfort knowing that mine isn't the only hull with these little cracks all over it!

[gran398]

Craig, I hate to see this, especially since I had it before you.

Guess all those years sitting in the lake didn't help our cause.

I'm thinking we call Eugene, show him these pics, and get his thinking. One consideration (time, labor and money savings) may be to tape her up above the waterline and blast the gel clean off the bottom, start with a fresh substrate.

[CLM65]

What kind of power tool did you use on the bottom Craig?

My primary tool is a Bosch 1250DEVS



I bought this when I first started the rebuild.  I don't have a large air compressor, so the commonly used DA sander was not an option.  This thing has a "normal" and "aggressive" mode, and has been worth every penny I spent on it.  I am using 40 grit sandpaper to remove the bottom paint.

I am also using my angle grinder with a poly abrasive disk on it.  This disk eats the bottom paint pretty quick, but does not eat the gelcoat quite as quick.  Still, it can leave a little dimple in the gelcoat, so I mainly use this to remove the outer layers of bottom paint (until the gel just starts to show), and then finish it off with the Bosch.  This helps the sandpaper last longer.



As both tools are fairly aggressive, it is very important to keep the tools moving and avoid letting them sand too much in one spot.  So far, I am pretty pleased with how it is turning out, but a little fairing putty will be needed here and there where I may have gotten a little distracted.

[CLM65]

Craig, I hate to see this, especially since I had it before you.

Guess all those years sitting in the lake didn't help our cause.

I'm thinking we call Eugene, show him these pics, and get his thinking. One consideration (time, labor and money savings) may be to tape her up above the waterline and blast the gel clean off the bottom, start with a fresh substrate.

Yeah, so much for a pampered lake-kept boat!  I have though about calling Eugene, and I was also going to call Chris but it got too late today, so I may do that Monday.  My little experiment with the dremel tool today leads me to believe that it really won't be too bad to chase the cracks out - maybe a day or two of my time - and then whatever it takes to patch the hull back up.  As long as the final product is satisfactory, I'm good with it.  No one said this was going to be easy, right?

[RickK]

Thanks bud.  I assume (without checking the model # first) is that it is a Random Orbital?
The "poly abrasive disk" is just a brutal scotch pad?