dmont's flatback build

[dmont]

Thanks for the replies. I think I will take the old bow eye out and poke around the holes to see if the wood is bad. Will probably end up cutting out and beefing it up.

[dmont]

I have completed a little more work on the boat. The new bulkheads have been glassed over. Two layers of 1708 tape (3" & 6" wide) were used for tabbing, then one layer of 1708 was used to cover the bulkhead plus overlap tabbing. One more layer of 1708 was laid in the bottom of the boat between each bulkhead that extends up the bulkheads and stringers a few inches. Should be sufficient. 4lb density foam was used for the bulkheads.
I notched out the bulkheads for two rigging tubes; one 3" for engine controls going to the console, and a 1.5" for fuel line going forward to the tank.
The bulkheads were coated with waxed gelcoat after the resin cured to seal it

The pour foam I used in the bow was also covered with tabbing around the outside then one layer of 1708 across all the foam, then waxed gelcoat. I laid several layers of 1708 in the bottom of the hull between the stringers just aft of the foam work in the bow. I figured this would be a high impact area and would benefit from being a little thicker.

The next step is to do a lot of grinding in preparation for closing in the holes where the windows in the hull were, and grind around the hull/deck seam in preparation for the deck going on. There also needs to be some grinding and patch work done on some old repairs, some of their glass didn't quite lay flat in a few tough corners and curves.

[RickK]

Nice progress.

[dmont]

I forgot to mention I also picked up an outboard for this boat. It is not my first choice but it will get the job done for a while. It is a 2000 model Johnson ocean pro 150. Carbureted. It won't get the fuel economy I want but it will get the job done. Weight is 370 lbs. I know the history of the motor also so that helps.

[Ulysses485]

Coming along! Nice choice of power. Didn’t realize till seeing one the other day how much smaller they are than the big V6 225 on my 81’. Weight is just right for a flatback. Keep the pics coming! 

[dmont]

A little more progress.
The old windows have been filled in from the inside of the hull. I will glass from the outside once the hull is flipped. I used 1/2" coosa as the core material. I set the coosa flush with inside of the hull. This left about a 1/4" inset on the outside of the hull. I will grind out a nice wide bevel on the outside before glassing and this should make for a very strong repair. Here are a few pictures.
Dry fit of coosa core (I cut out some plugs from coosa to fill in those round holes also):

coosa glued in with poly resin thickened with cabosil plus 1/4" glass fibers:

glassed in with 6 layers of 1708, working from smaller to larger:

sealed it up with some waxed gelcoat:


next on the agenda is to glass the rigging tubes in place, make some small repairs to the stringers (fix some damage done while cutting the old deck out), and fab and glass in a flat panel for the fuel tank to sit on in the area where the windows were.

[RickK]

Nice. Any progress is good progress.

[Tampa Bay Mike]

Coming along nicely. The window repair looks nice

[dmont]

Progress....
I had some pour foam work to do where the old livewell was cut out in the window area. There was some uneven foam that I did not want to fill with putty, it would have been a lot of putty. So I opted to foam it. I came up with the idea to just tape some heavy plastic over it and leave a little opening in the top to pour into. It was ugly to begin with, but with a little cutting and sanding it turned out great. A good tool to do quick foam shaping is a flexible dovetail saw. Here are a few pictures of that...


Slight blowout... I figured it would be easier to over fill then have to go back and pour more foam or make putty.






The next step was to glue and glass in a piece of honeycomb to the bottom of the boat to give the fuel tank a flat spot to sit. I drilled a couple 2" holes in the honeycomb and poured foam in the void below it. Very solid. I also notched out the bulkhead for the fuel fill and lines to run through. I would have preferred to make the notch smaller, but I wanted a way for water to get out if it was to get into the fuel tank compartment. There was still plenty of strength there plus I added a few layers of glass over that area.




Next picture shows the blocks glassed in for screwing fuel tank brackets to. I used some 1x PVC trim board for the blocks. They hold a screw really well. Also mocking up console, bench seat, and rigging tube locations.


fuel tank in. I used 1" aluminum angle for hold downs. I put some layflat hose I had sitting around below the tank to cushion it. It is solid.


I have about a 1/2" of space between the bottom of the deck and top of the tank fill. I will definitely be putting some stiffeners under the deck to make it not flex over the fuel tank.

This is where she stands. Hopefully next week I can get the rigging tubes glassed in, then run fuel hoses and a couple wires while there is no deck. Will probably mount a bilge pump while there is plenty of room to work. I need to remember to cut the glass off the drains I put in the bottom of the bulkheads too.
My plan is to make a template of the deck then build it in two pieces on my shop floor (using honeycomb). I will dry fit the individual pieces. I'm hoping I can get the deck in the boat in two pieces with the cap on, not going to take the cap off.
Any advice on anything?

[Capt. Bob]

Lookin" good.

[Ulysses485]

Great Progress! Coming along nicely. A few questions regarding your plans for structure. I see a break in the stringers just aft of the fuel tank. Are you running rigging through there and tying that back together. I would think between the weight added forward of this break and breaking the waves about this point, your going to want to add that longitudinal structure back. Additionally, did you already glass and re-tab the existing stringers back to the hull bottom? As the years went on, it seems they laid the stringers thicker. Just about every flatback that I have seen rebuilt has stringers that look quite beat up (cracked, snapped, falling apart) where the semi-v (72ish-89ish) typically has stringers that are in tack and just full of wet foam. I would naturally attribute this to a hull (12 degree deadrise) that cuts the waves better and doesn't bang as much as a flatback. However, I would bet that the stringers in the flatback aren't built quite as thick as the models built afterwards. Also, are you draining all the compartments to the bilge? Just my .02 for what its worth.

[dmont]

Great Progress! Coming along nicely. A few questions regarding your plans for structure. I see a break in the stringers just aft of the fuel tank. Are you running rigging through there and tying that back together. I would think between the weight added forward of this break and breaking the waves about this point, your going to want to add that longitudinal structure back. Additionally, did you already glass and re-tab the existing stringers back to the hull bottom? As the years went on, it seems they laid the stringers thicker. Just about every flatback that I have seen rebuilt has stringers that look quite beat up (cracked, snapped, falling apart) where the semi-v (72ish-89ish) typically has stringers that are in tack and just full of wet foam. I would naturally attribute this to a hull (12 degree deadrise) that cuts the waves better and doesn't bang as much as a flatback. However, I would bet that the stringers in the flatback aren't built quite as thick as the models built afterwards. Also, are you draining all the compartments to the bilge? Just my .02 for what its worth.

I will use the break in the stringers as a place to run fuel fill and vent hoses up to the side of the boat, there is also a notch in the chine stringer in the same place that I will use for the fill/vent. These notches were done from the factory stringer mold. I am wondering if aquasport was planning on putting in internal fuel tanks and that was the reason for these stringer notches? I will not be putting any material in there to tie them together, other than the deck. Even with the notches there is still plenty of material there for stringer strength, plus I added 5 layers of 1708 in the bottom of the boat tying the stringers together there. The strength of the deck will keep the boat from wanting to "fold" up lengthwise there too.

Yes, stringers have been heavily tabbed back to the bottom of the boat, probably 5 or more layers of 1708 counting tabbing and full width pieces going from stringer to stringer.

All compartments will drain to the bilge. I glassed in pieces of 2" PVC pipe that were ripped in half in the bottom of each bulkhead prior to building the bulkheads. These drains did get glassed over while building the bulkheads just to make things easier. I still need to cut them open. I want any water that makes it below deck to be able to drain out.
Thanks for the comments.

[Tampa Bay Mike]

Sounds like you've thought it all out. I'm doing the same thing with the floor mold on mine. One thing I can suggest is to cut your glass a little longer and trim it afterwards. I cut all my layers perfectly, folded them all up in order and marked them, but when I laid them down for glassing some were a touch short. It's like the weave tightened up while folded. I had a roll of 4" 1700 tabbing glass that I ran down the edges. Not a big deal but something to keep in mind.

[dmont]

I'm trying to get this boat done! working on it at night mainly. Here are more progress pictures:
Fuel lines ran and rigging tubes installed. My pull string for the fuel sender wire got tangled up with the fuel line inside the rigging tube (using compressed air to blow it) so I just zip tied it on the outside...
There is a slight low spot on the fill hose, hopefully that wont be an issue. What do ya'll think?


drain holes in bulkheads opened up:


blocks screwed, glued, and later glassed in at transom for deck support:



Getting there! Starting on a deck template soon, and will be putting the deck together. I think the deck will go pretty fast. Atleast it will be glass work on a flat surface, that is always a plus.

[Tampa Bay Mike]

Is the white rigging tube for your engine controls and cables? If so you may want to test run them before you put the deck down to make sure they can bend around those 90s. Easier to adjust them now if needed.