Plywood core in hatches

[Scott]

Need some help/guidance....

The 53" x 31" sheet of plywood to recore the fuel hatch......I put holes in it to allow the Fairing/bonding compound to ooze through and coated with resin.....

The 1/2" plywood has a slight cup or bow in it now (I even placed cinder blocks on it to stop it from cupping too much)....

Do I dare use this in the deck??? I'm concerned that it will cause the skin to either cup or have a crown in it ( depending on how I put the plywood in the skin...cup up or cup down ) I dont want to risk losing the skin...

[FELLOW-SHIP]

HA SCOTT
IT SOUNDS LIKE A JUDGMENT CALL ON YOUR PART ON THIS ONE. I JUNKED MY OLD SKIN’S THEY LOOKED TO BAD AND WASN’T WORTH SAVING. I HAVE HAD SOME CUPPING AS WELL BOTH ON THAT PIECE MINE IS ABOUT 8 ‘ LONG AND SAME AS YOURS WIDE AS WELL AS ONE BIG PIECE THAT COVERS ALL THE DECK FROM THE END OF THAT PIECE YOU ARE WORKING ON TO THE SPLASH WELL AREA. BOTH HAD SOME CUPPING. I USED TWO 2” X 2” 8 ‘ LONG FUR LAMINATED PIECES ON BOTH SIDES OF THE DECK ABOVE THE GAS TANK AND THEN 2 PIECES 31” IN THE FRONT AND BACK THAT PROVIDES A MUCH FIRMER LIP FOR ME TO DRILL AND SCREW 2” SCREWS TO SUPPORT AND HOLD DOWN MY NEW DECK. I TOOK THOSE 2” X 2” AND EPOXY, SCREWED AND THEN GLASSED THEM TO THE STRINGERS (BOTH SIDES) ABOVE THE GAS TANK I BUILT THEM UP TO BE EVEN WITH THE LITTLE LIP THAT WAS ON MY ORIGINAL DECK. I ALSO MAID TWO BULK HEADS IN FRONT AND BEHIND THE GAS TANK AND EPOXY, SCREWED AND GLASSED THE 31” 2” X 2” TO IT. WHAT I DID IS MAKE A BOX ABOVE THE GAS TANK FOR ADDED STRENGTH TO SUPPORT THAT DECK. I HOPE YOU ARE FOLLOWING ME I KNOW A PICTURE WOULD BE BETTER BUT I DON’T HAVE ONE TO SEND YOU RIGHT NOW. I HAVE BEEN BUILDING THIS BOAT BETTER THAN ORIGINAL AND IN THIS WAY THAT DECK IT REALLY VERY FIRM.
FELLOW-SHIP [img]images/icons/wink.gif[/img]

[capesams]

SCOTT:

CUP up...all things sag in time. IT's the way the clowns store it at the yard these days. there to lazy to put a third sticker in the middle, so the whole pile sags in the middle they just don't care because there not the ones useing it. [img]images/icons/mad.gif[/img] P>S don't use ply with 3 layers it's crap. most good ply today is made with exterior glue anyway. the more layers, the stronger the ply.REG. underlayment used in homes today is the same as the marine ply, how do i know this .. a good friend spent his life makeing plywood. And i've spent a life time useing it. Hope this helps.................steve

[hermco]

Use the cut square method of adding a plywood core and you eliminate the problem of trying to use a solid sheet of warped or cupped ply.Or better yet use a foam core and you will be able to give the boat to your grand kids and they will give it to theirs. [img]images/icons/smile.gif[/img]
d.h.

[ April 25, 2002, 09:10 PM: Message edited by: HermCo ]

[Scott]

DH
Thanks for that....I've been thinking that way also (foam) but....Now I'm considering running two stringers 48"x1"x1/2" the length of that hatch to straighten it out...I have the room to put the stringers in (2.5" to 3") and I assume as long as the wood is flat before the resin and glass go on the back I'll be OK ??? Yes or no??

[hermco]

It's the glass that you put over the wood/foam that will give the strength/stiffening effect use at least two biaxial fabrics and it should work. [img]images/icons/tongue.gif[/img]

[ April 26, 2002, 07:17 AM: Message edited by: HermCo ]

[FELLOW-SHIP]

HA SCOTT
THE THING THAT COMES TO MIND FOR ME IS THE GAS TANK AND GAS FILL LINES IN THAT AREA. I HAD A NEW TANK MADE 12” HIGH AND I USED ¾ PLYWOOD FOR THE DECK THAT THE GAS TANK SITS ON. THE GAS FILL COMES FLUSH AGAINST MY HATCH. IN FACT IT CONCERNED ME THAT IT COULD RUB OR PUSH AGAINST THE 90 DEGREE GAS FILL BRACKET. I ELECTED TO CUT A AIR VENT/ ACCESS AREA OUT OF THE DECK AT THAT LOCATION FOR THREE REASONS FIRST TO PREVENT ANY RUB, ALSO FOR ACCESS TO THE FITTINGS AND MY GAS SENDING UNIT THAT IS ALSO IN THE SAME AREA AND FOR A VENT TO THE TANK. I REMOVED THE 4 VENTS THAT WERE ON THE OUTSIDE OF THE HULL THAT HELPED VENT THAT AREA WHEN I DID ALL MY HULL WORK. MY CONCERN FOR YOU WOULD BE THAT YOU GIVE ENOUGH OPEN SPACE IN THAT AREA “JUST ENCASE”. IF YOU ADDED ONE OR TWO LAYERS OF GLASS ON THE BOTTOM OF THE HATCH THAT WOULD STIFFEN IT UP AS WELL WITH OUT LOSING SOME OF THAT SMALL SPACE BETWEEN THE TANK AND THE DECK. THE SMALL CUP MIGHT GO AWAY WITH THE 1 OR TWO LAYERS OF GLASS IF YOU PUT THEM ON THE CONVEX SIDE. JUST A THOUGHT.
FELLOW-SHIP [img]images/icons/wink.gif[/img]

[Scott]

DH
Thanks again for the info. Its great resource having your input on this site!!

This is how I intend to lay-up the hatch.
(For what its worth this is how I was instructed to get a good stiff hatch)

1. Vinylester inside the skin (I’ll attach a pic of the skin that this is all going in)
2. 1.5 oz mat on top of that
3. Bonding putty next …a thin layer
4. ½” plywood core…..(If I use the piece that’s been coated with resin I will most likely put two stringers the length of the core to pull the “cup” out)
5. A layer of Vinylester and 1808 Biaxial (with 3/4oz mat stitched to it) cloth with the 3/4oz mat surface bonding to the plywood.
6. Then I was informed to place another layer of mat (1.5oz) on top of the 1808 to finish the back surface of the hatch ….

Seems to me that this thing is going to be pretty stiff( need a nuclear bomb to get this thing apart [img]images/icons/grin.gif[/img] ) and as long as the plywood is flat during curing it should work….. What do you think?….

Fellow-Ship….Good point about the fuel fill pipe….originally (at least with the tank I now have) the pipe and vent was at the front of the tank and was actually under the deck that is in the console and not under this fuel hatch/deck.

Where is your Fuel fill/vent….I think I saw Billybob’s in the center of his tank