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gcarter
02-29-2004, 08:31 PM
My '86 Minx I'm restoring has the usual collection of gelcoat cracks in places that seem to be "hard points" i.e. on top of stringers (see photos).
If you guys would, give me a range of ideas of what to do.
Thanks in advance;

George Carter

mphatc
02-29-2004, 09:11 PM
George,

The easiest part of this repair is the the visual above deck stuff . . .

The hard part is repairing the weakness that caused it in the first place. Likely the original patches, band aid straps of roving/resin that Donxi installed between your stringers and the deck have failed, resulting in the deck / cockpit to sag down. :eek!: You'll need to restore this strength and correct the deck to hull alignment before repairing what you have shown in the jpgs.

This will likely require grinding under the deck . . and the stringers to give you good clean surfaces to which the new materials can be bonded . . Yes this job sucks! You may also need to jack the cockpit floor up to the correct height and this can be done with a small scissors jack, and proper support under and above the jack so that no other damage is done.

I have attached some images of of my Corsican stringer to cockpit floor connections which suffered the same problem.

Good luck! Not a fun job, but the end result is a boat that feels much more solid in rough water! And any squeaking you may be experiencing now, will hopefully be gone.

MPHATC

gcarter
02-29-2004, 09:20 PM
Hmmmm...
Let's see if I understand...
Pictures two & three show notches in the stringers and then the next view shows a transverse brace reinforcing the cockpit deck. Is this right?
Thanks
George

mphatc
02-29-2004, 09:40 PM
Image 1 shows a fractured connection tab.

two and three show the wear in and on the stringers from the cockpit floor transverse joint. This wear should not be there.

Image 4 shows the port stringer and the broken attachment tab in the rear, I cut the forward one, although it was fractured. The last image shows the starboard forward attachment patch that was also fractured. This supported the footwell.

MPHATC

gcarter
02-29-2004, 10:16 PM
So the tabs act as supports and shock absorbers. When you did your repair, did you replace the tabs with more of the same, or did you do something "better"?

George

mphatc
03-01-2004, 06:30 AM
I am in the process . . .

Shock absorbers . . . mmmmm . . .possibly they functioned that way, but I'm sure it wasn't intended to. My plan right now is to align the deck back to it's correct height, then support solidly, distributing the load bearing surface on the cockpit floor.

The space between the stringers and the floor is 3/4" to 1" . . easy to do with some marine plywood blocks as shims.

MPHATC

gcarter
03-01-2004, 06:55 AM
I am in the process . . .

Shock absorbers . . . mmmmm . . .possibly they functioned that way, but I'm sure it wasn't intended to. My plan right now is to align the deck back to it's correct height, then support solidly, distributing the load bearing surface on the cockpit floor.

The space between the stringers and the floor is 3/4" to 1" . . easy to do with some marine plywood blocks as shims.

MPHATC
Now I see.... Hmmmm...
What do you think about looking at industrial sources maybe, and sourcing some 80 or 100 durometer rubber or "rubber like" material to use as blocks?

George

farmer tx
03-01-2004, 09:56 AM
While we are on this subject could the pic below be one of these braces? I found this in the bildge area under the cockpit.

gcarter
03-01-2004, 10:51 AM
While we are on this subject could the pic below be one of these braces? I found this in the bildge area under the cockpit.
I think mine & Mphatc's are more like 'glass straps, about 4" wide, but who knows, could be. But then it could be excess material that was trimmed off.

George

Donzigo
03-01-2004, 11:26 AM
We also have cracks in our Classic 22 (1986). Here's our fix, we've done this on the Z-25 (1987) we had and are just before doing it again on the Cl-22:

a. We will cut with a skill saw a square around the outside of the inner floor and take the floor out.
b.We will grind out the plywood on the underside of the piece we took out.
c. Replace and fiberglass new plywood.
d. Cut the tops of the stringers with a sawsall so as to be corrected.
e. Re-install the floor and fiberglass it to the edges and the stringers.

George, if the stringer height isn't addressed, the floor will still be high and what would prevent another crack?

Lenny
03-01-2004, 11:38 AM
Donzigo, :eek: did you say "cut out the floor??? " :eek:

gcarter
03-01-2004, 11:55 AM
Donzigo, :eek: did you say "cut out the floor??? " :eek:
Lenny; I hope I don't get my hand slapped for getting off subject, but what is that in your avatar?

George

Lenny
03-01-2004, 01:22 PM
...a almost finished bench seat X-18 less engine and deck bright work...decipher"able" pics will show up when it has that stuff in it and on it :D

gcarter
03-01-2004, 01:33 PM
Thanks Richard for your input, I appreciate it.
Lenny, you seem to have a different opinion about it. Tell me about it, please :confused:

George

MLerner
03-01-2004, 01:39 PM
I also have two stress cracks on my '93 18 classic at the corners of the floor beneath the dash. Let me get this straight, does this require cutting the floor out to repair? How much of the floor needs to be cut out and, pardon my ignorance in this matter, how easily is the floor re-installed after you've finished with repair? Would love some guidance here. Thanks.

Lenny
03-01-2004, 02:25 PM
It has been my experience, (from this place) and in playing with glass, that the LAST thing you would want to do is cut the inside of the tub of the C-22 or Minx or whatever. A deck off scenario would be my choice, and only choice. That IS NOT to say tho Richard, that what you propose is wrong, just not my cup of tea. :)

KRAVEN
03-01-2004, 04:12 PM
I too have had stress cracks in the foot/ski locker area on my 2001 18 Donzi.Had a hard time getting Donzi to repair. :splat: Donzi rep from Michigan set up Harrison Fiberglass to complete repairs.Found no support in area of ski locker causing excessive flexing of floor.They bored two holes in floor area and poured in 2part foam.Floor is extremely strong and has not shown any signs of movement.Excellent gel coat match,can't tell any work was ever done. :rlol:

mphatc
03-01-2004, 06:55 PM
IMHO . .

Cutting floors and holes isn't right . . . I agree with Lenny

Decks have sagged, the stringers are correct, I really believe you need to figure out why the deck has sagged!

My connecting straps were 7" square, coarse roving only. One was never properly connected, two cracked, and the third carried the whole load.
As a result my footwell contacted the stringers forward of the cockpit, the ski locker hatches no longer lined up correctly, and the joint between the foot well and cockpit creaked with every wave.

KRAVEN, foam??? did they enclose a volume beneath the deck? Pourable foam, although sold as a closed cell product has the capacity to absorb huge amounts of water when not sealed off.

MLerner, I suspect that on your 18 Classic you can access all of this from below deck like on my Corsican.

I will repair mine to be rigid, no compliance between deck and stringers.

MPHATC

Donzigo
03-01-2004, 07:41 PM
Lenny................to be sure, I would rather do a deck off repair; but, when that option is either too expensive or cannot be done easily, cutting the floor is a great option. I know it works and is not nearly as intrusinve as taking the deck off; because, I have done it. To be sure, the job is purrrrrfect.

...................to each his own. It's actually a rather simple repair, when done this way.

Ranman
03-01-2004, 10:40 PM
OK, help me get this straight. When Donzi attaches the deck to the hull, the deck includes the cockpit liner/tub as it's all one piece (this is obvious). The ski locker and footwell is a seperate piece and is installed last or removed first. Is the ski locker/footwell tabbed in too? Anyway, so they lay the whole thing in and the only real seam is around the deck joint/rubrail area. In addition to attaching the deck to the hull (tapping screws or thru-bolted?) Donzi "tabs" the hull and deck together. This is done by melding 6" X 6" squares of fiberglass cloth to the deck and hull on approx a 90 degree angle using resin as the glue. Sort of like an angle bracket, right? This is done in several places (typically where would I look for the "tabs" and how many will there be?). In order to seperate the deck and hull, these "tabs" must be carefully cut leaving half the tab on the deck and half on the hull. Am I on track here? What do you do when you put it back together? Do you cut new 6" x 6" "tabs", soak them in resin and roll them into place once the deck and hull are joined? Do you have to grind out the old tabs?

Lastly, the cockpit floor is supported by what? Is it resting on the stringers? Is is shimmed with wood to the stringers below? I find this all very facinating but since I've never seen it in person, It's hare for me to visualize.

Lenny
03-02-2004, 12:06 AM
RANDY, DONZI'S "HANG" FROM THE DECK... hence the stress crack issue. Usually the perimeter of the deck sheer shows signs of cracking from "FLEX", but also the cockpit "corners". This is due to the inflexibility of the gel-coat (very HEAVY in corners and easy to build up areas) and in your face surface areas. Then there is the two different axis's of "flexibility" in regards to gel and glass. Glass being the one that can handle it, and gel-cote, the one that cannot. Supporting the hull with "tabs" is the obvious, BUT, adding many more so TABS is going to be bulletproof. You, and I know you are larger than I, (I am 155), exert a tremendous amout of weight in the cockpit sole coming off a wave. This has a trampoline effect the way DONZI's are built, hence why you see the stress cracks..."LOCKING up this DECK/HULL" scenario and bulletproofing it will fix it,... BUT, you will see (eventually) the same result, from the middle floor taking the hit from extreme surface pressure and the "tabbing you did" showing strength... The hull needs a LOT of support in the environment of todays engines, the people, the rebelious driving attitudes and the offerings of the motors...

But,... a 10 pounds per gallon, you don't want ANYMORE resin or tabs than neccesary... :)

mphatc
03-02-2004, 06:47 AM
Lenny,

as part of the ongoing rebuild . . the desire is to strengthen the deck supporting method and avoid future cracking of the cockpit floor and deck.

let's expand this thread . . extra tabbing and supporting the deck to avoid future stress cracking

Going back to KRAVEN's repair, imagine an enclosed volume under the deck, filled with foam and completely sealed from water . . . this should function to distribute the load caused by "trampolining" of the deck, and save the cockpit floor from cracks. If one was to place a sheet of plastic tightly under the deck above the foam prior to pouring in the foam mixture, future hull deck separation should easily be possible, if it ever became necessary.

OR

Avoiding pourable foams, they scare me for their ability to absorb water, freeze and destroy boats stored outdoors in the cold! BTDT a few times too many!

My thought was to build a flat top on the stringer that matches the floor of the cockpit, full length of floor, 8" wide on top of the stringer, then tab that to the floor all the way around. The foot well being a separate piece is only held in place with tabs that will get reinforced with better tabs.

thoughts anyone . . . please!

Mario

gcarter
03-02-2004, 07:07 AM
I'm sure glad I asked this question. Getting lots of ideas.
But the real reason "glass tabs were used by Donzi is because that is the media they work in & it's cheap.... Duhhhhh! Not because it's the best. Probably these boats were never intended to last 30 & 40 years.
Well, what I was thinking about was a transverse angle bolted to the rear of the vertical leg of the rear seat front, extending below the bottom of the cockpit floor & it would land on two more longitudinal angles bolted to the stringers ( think engine mounts). something similar could be done in the footwell area. Inbetween these transverse angles a series of blocks of 'glassed plywood, hard rubber or 100% PE could be attached to the floor like Mario was suggesting.
The main thing this idea accomplishes is to mechanically spread the load transversely accross the floor at the front & rear, and shim it in between.
What do you think?

George

Ranman
03-02-2004, 08:18 AM
DONZI'S "HANG" FROM THE DECK...

So the tub is suspended from the deck and the cockpit floor is not actually resting on anything?

Was I on target with my other questions? Where might I find the tabs on my boat?

gcarter
03-02-2004, 08:23 AM
So the tub is suspended from the deck and the cockpit floor is not actually resting on anything?

Was I on target with my other questions? Where might I find the tabs on my boat?
Hi Randy;
On my Minx, if you pull up the central floor hatch, and remove the liner/ fuel tank cover, stick your head down in the bilge and look to either side at the level of the top of the stringers, you'll see"patches" of 'glass. These are some of the tabs. Also if you crawl through the ski storage area and look aft on either side, you'll see some more. Actually my Minx has about 14 tabs (I think) the're some more under the rear seat and battery box.

George

mattyboy
03-02-2004, 08:30 AM
my 16 was tabbed all the way around the floor locker and up by the ski locker but on the 16 the ski locker is off to one side( well atleast on the 3+1 seating) The ski locker was bolted onto the deck not sure on the bigger models my deck did seem to sit squarely on the stringers I seem to get more stress cracks in the corners of the rear seat that is just hanging in the wind


Matty

Hot foot
03-02-2004, 10:10 AM
I like the angle bracket solution suggested by George. This is similar to what I was planning for my '65 16. I have the deck off and all core material replaced. Replacing the original tabbing in the confined space with gravity working against you isn't a pleasant proposition. The brackets if bolted together would make future removal easy and could possibly be installed without removing the deck if the wood coring is still good. I would try that before cutting out the floor.

Lenny
03-02-2004, 10:42 AM
My sixteen was tabbed in about 6 places only. It rested about 3/4" above the stringers...

Rootsy
03-02-2004, 11:08 AM
dear god i don't even know how to see under my tub on the 16... either side of the ski locker (running down the C/L of the hull) is a big foam block... the ski locker is screwed to the tub. from the engine compartment there is pretty much a solid wall at the back seat with just a drainage hole... no way to see up under the tub there either... i may be able to peek around the side of the tub... from the tub / ski locker joint but doubtful... and well the only access through the floor is the round inspection cover for the tank sending unit... i only have one or two small corner stress cracks in very inconspicuous places... i sure hope nothing else moves... i may only go 155 or so but i know that nothing gives when i step in.. the 16 feels very solid... anywho... i'd let ya all know what my boat has done but i can't see JACK CRAP!!!!

Root - blind

Ranman
03-02-2004, 12:28 PM
Root, I'm in the same boat as you (is that a pun) with the 18. No way to see under the tub. I've got the same foam blocks and "wall" in the engine compartment. I'm 250lbs and it feels solid under me too. The only thing I've noticed is stress cracks at and around the raised square seat bases, especially on the driver's side (go figure). They are all hairline cracks and are obviously from the stress placed on the seat mounting bolts when my fat ass is bouncing off waves.

gcarter
03-02-2004, 12:33 PM
Root, I'm in the same boat as you (is that a pun) with the 18. No way to see under the tub. I've got the same foam blocks and "wall" in the engine compartment. I'm 250lbs and it feels solid under me too. The only thing I've noticed is stress cracks at and around the raised square seat bases, especially on the driver's side (go figure). They are all hairline cracks and are obviously from the stress placed on the seat mounting bolts when my fat ass is bouncing off waves.
Randy, is there a liner in the center floor storage area that you can remove?

George

Ranman
03-02-2004, 01:04 PM
No, Unlike older models my center floor storage area is molded into the tub. In other words, the tub is all one piece, including the center storage area. I think the deck mold has been tweaked over the years. My tub now has the center storage molded in and has the raised seat mounting bases.. I don't think older models have these. I've included a pic of a late model classic deck that illustrates the molded in storage and now it seems the raised bases are gone too. Changes, changes.

gcarter
03-02-2004, 03:29 PM
Well Randy, you really made it clear to me the center storage area is molded into you cockpit floor!!! :bonk: :bonk:
So for yours and Jamies benifits; I'm posting some photos...
1) Looking upward and aft at the Stbd stringer... you can see how wimpy
this tab is and maybe damaged, this is where my worst cracking is.
2) Looking at stbd stringer with tab wrapped to the bottom of the floor (at
top of pic) this is immediately aft of the gas tank.
3) From ski storage tray looking aft at tub. The tab you see is right over the
gas tank.
4) Looking fwd port side at back of back seat, this is where I would bolt in
an angle. The thing at the right is the molded in battery box. It has two
tabs tying it to the hull bottom, not the stringers. I was able to get this
view because the transverse frame has been cut ou because it was
broken. Mentally consider the weight of three fat asses continually
coming down on this tab, and it's easy to understand whats happening
to the gelcoat.
Thanks for your indulgence;

George

Murphy
03-02-2004, 03:59 PM
Our solution to this on my 86 Classic 22 was to cut out the damaged areas of fiberglass, removing only as much material as necessary to make room for new fiberglass tapered in for an even surface. Under the rear cockpit area we installed a full length piece of stainless steel angle to provide support all along the base of the seat. The center cockpit stringer supports originally installed are pretty thin, so we cut these out and replaced with thicker glass. Once this was complete, we made a cardboard cockpit template and then cut a piece of 3/8 marine plywood to exactly fit the cockpit floor. We routered the edges to exactly match the curve in the floor to wall transition. This was treated with a penetrating sealer, expoxy bonded to the original deck, and then pop riveted through the original deck with stainless rivets every 12 inches. There is absolutely no give or movement in the deck now. In the process, we cut off the old fiberglass seat pedestals and installed new thru-bolted swivel seat supports We also cut a new bilge access hole and custom fit a drop-in cooler into the opening. The new carpet will have a cutout for the cooler to make for easy access. Total time, about 3-days. Just be careful when drilling for rivets not to drill into the gas tank or gas line. We didn't but it would be easy to do.

Murph

Ranman
03-02-2004, 04:26 PM
Well Randy, you really made it clear to me the center storage area is molded into you cockpit floor!!!

Sorry, re-reading my post, it looks like I said the same thing like 3 times and then threw a pic in for good measure. :bonk: :bonk:

Anyway, I really appreciate these pics and the following discussion. I am no expert, but like I said, I find this interesting. It really helps me understand how our boats are put together. It will also help calm me if I'm ever faced with a deck removal.

soaking up the info...

Rootsy
03-02-2004, 06:11 PM
trust me randy.. we have the equipment for serious, pain free, deck removal... should this ever become necessary in my neighborhood :D

gcarter
03-02-2004, 06:13 PM
trust me randy.. we have the equipment for serious, pain free, deck removal... should this ever become necessary in my neighborhood :D
Jamie, does it have INTERNATIONAL HARVESTER written on it? :rlol:

George

Scott Pearson
03-02-2004, 07:10 PM
You guys are reading into this floor thing way to much. My floor in my 1968 18 was a mess. I dont think that all the cracks where due to stress. I think most of them where just from old age and poor care.

I have about a week into fixing all the cracks in my floor. I "V" them all out with a sharp dramel tool and fill them with Rage Body plastic. Yes....this is the same "Bondo" used on cars. I primed the whole floor, Block sanded it and painted it. Its been 3 years and not a crack showing . And I never even tabed the liner or ski locked back in !

As for me..I dont use any gelcoat or anything that is made to repair a boat. I treat all restorations on my boats like they where Corvettes. Hay....its fiberglass!



(NJ)Scott

mphatc
03-02-2004, 08:25 PM
Scott,

Interesting comments in your post.

We haven't met yet, though I look forward to your first Donzi Club party at the new clubhouse! :sombrero: :rlol: :pumpkin: :)

With all respectto you and your absolutely beautiful boat!, how often does your 68 see rough water . . . possibly it needs to see more air time? :smile: :eek:
I will be rebuilding my Corsican for HARD use, as my end of Winni sees 5-6 foot waves every weekend, and don't want to go into again 5 years from now. Admittedly the boat has minor problems now and it is 35 years old, but it has also spent it's life on a flat water Arkansas river . . . . as a ski boat.

My floor trampolining required that I re-tighten all rub rail screws after every day of use. This joint shouldn't flex that much, and I can't see any way to support it without strengthening the floor support structure.

Please share your thoughts in greater detail.

Thank you,
Mario

Scott Pearson
03-02-2004, 09:11 PM
Mario,
I dont use my boat as often as most but when I do use it I dont baby it at all. There are plenty of people who have riden with me and have seen me drive my boat to know . See Pictures.

As far as the screws in my rubrail I have never touched since I have restored my boat. Its all in the prep work. The reason why the screws will losen is because of the wood being soft that is along the hull sides. Also I use 5200 on all my screws. They are as tight as the day I put them in.

One more thing. A Sharp keel boat rides considerably harder then a rounded keel boat. So in theory....my boat should develop more cracks sooner.

(NJ)Scott

gcarter
03-07-2004, 08:35 PM
Boy, but I've learned a lot about the construction of my Donzi since last week.
The last thread with this title had a post by Scott Pearson (anybody ever notice haw many Scotts there are on this site, is it something like NASCAR where you have to be named Jeff or Dale to succeed?) that stated he just routed them out & filled them. I can understand that. Gelcoat is much more brittle than the 'glass/resin substrate composite under it, so it cracks.
But my problem is more than cosmetic. As described in the older thread, the cockpit or tub sits on glassed wrapped spacers between "tabs" which hold the cockpit & stringers together.
The problem is at the rear of the cockpit floor, there is about 6" to 8" space in front of the rear seat (vertical) leg that is cantilevered over nothing. When the boat is in use with two or three people on the seat, there is the potential of 500 to 600
Lb landing on the stringers @ four to six G's (who knows how much). See thumbnail 1 (sketch). Then there are pics of a spacer, aft end of the cockpit with cockpit floor sitting on the stringer with no support and deformed, also a pic shot across the floor showing the distortion.

I came up with a simple, inexpensive solution that can be accomplished without splitting the deck (at least on boats built during the period mine was built).

gcarter
03-07-2004, 08:54 PM
The solution is to bolt a 2" X 2" X 1/4" angle to the back of the rear seat base, and land that angle on two more angles bolted to the stringers.
I originally purchased a 5' angle and quickly figured I couldn't get in front of the battery box with the deck on. So I split the angle and bolted it in in two pieces. In the view of the stbd stringer looking fwd, you can easily see there is a space over the stringer to nthe floor bottom. It was probably raised about 1/2". In the next view, youcan see the row of bolt heads across the front of the seat base. If I can find some 3/8" SST acorn nuts, I'll turn the bolts around so all you'd see is the acorn nuts. While the floor hasn't flattened out yet, it probably will some over time. I still haven't installed the bolts holding the angles together. The total cost was about $50.00.
Any questions?

Regards;
George