Gas Tank Hatch Recore

'84Offshore

Well-Known Member
Joined
May 5, 2005
Messages
375
Reaction score
2
Points
0
Location
Long Island, NY
Yea........feel like I got a jump on the spring, last year I had to wait until spring to do the other hatch.
Now I can install it whenever the weather permits.
 

NIGHTIDES

Well-Known Member
Joined
Sep 30, 2005
Messages
230
Reaction score
0
Points
16
Looks pretty to me..! New core is a new core and that is what counts.
 

jbeyo

Active Member
Joined
Sep 24, 2008
Messages
32
Reaction score
1
Points
0
Location
wilmington nc
84Offshore,
I have a 83 Tournament 24.
Both of my hatches have been redone.
Yours look great. The only thing I did different was to not put the screws back in to hold it down.
Fill these holes with 5200 and put the hatch back in place and caulk with a marine caulk that will not mildue. Put plenty of caulk around the edges and use a wet sponge to smooth and level with the deck and you will be waterproof. No screw are better with bare feet.
Trust me they will hold and be rock solid. You do not need to put these screws back in. That is how water gets to the wood.
They will not be a problem to take back up if necessary to check your connections or clean the ground wire to the gas gauge.
Just cut the caulk out with a box cutter and pull up on the two access hatches and it will come right up.
Worst case you can try it this way and if you dont like it you can always redrill and put the screws back in.
Good luck.
 

'84Offshore

Well-Known Member
Joined
May 5, 2005
Messages
375
Reaction score
2
Points
0
Location
Long Island, NY
Thanks for the compliments.......pictures don't show the flaws.....:)

Interesting take on installation w/o screws.........
I put tape over the holes so they are already filled w/ resin.
I may take the suggestion and leave the screws out.....I'm pretty sure the caulking will hold it in place.........
 

DennisG01

GreatGrady Captain
Joined
Sep 1, 2013
Messages
6,818
Reaction score
1,209
Points
113
Location
Allentown, PA & Friendship, ME
Model
Offshore
The only thing I might suggest to the above idea is to paint the 5200 and/or resin (not sure, though, if 5200 can be painted). Both are great products, but neither are UV stable. Over time (obviously it depends on the amount of sun exposure) the resin will degrade and yellow so it should be topcoated (painted). The 5200 will start to crack, which could actually let water in. But again, I'm not sure if 5200 can be topcoated - I actually rarely use the stuff (in truth, it has very limited applications) and when I do, only in places where it won't get sun.

I do think not using screws is a viable idea and I'm in no way knocking it. However, a properly prepared screw hole will not leak, either. Overdrill, fill with epoxy, redrill and countersink. Properly countersunk is the key as it gives a greater surface area for the sealant and will keep water from seeping by. Th epoxy protects the hatch core and the countersinking protects what you're screwing into.
 

ROBERTH

GreatGrady Captain
Joined
Jun 10, 2006
Messages
1,304
Reaction score
120
Points
63
Location
Raleigh, NC
Model
Sailfish
Ok guys, it is my turn. Started noticing that the floor had more give this season, and I had vacuumed as much water from out of the wood as possible hoping it to dry out some, of course I knew better back when I was recoating my tanks last year.
So, bite the bullet and recore the hatches.
2 Hatches in this model. First one is approx. 18" X 4'. Second one is approx. 4' X 4'.
After reading the posts and links, it is all great info to go with in my approach!

I was thinking of getting the 1/2" Pro Balsa like I used on my swim platform due to how light it is and easy to work with as well as low cost. Used the 3/4 on my swim platform and have enough left over for the small panel, but too thick I think. I could use it and grind down the first 2" so that I would not have any issue with the mounting tabs.

However, it seems what Grady used here was square pieces of ply instead of balsa. Seems weird to me that they just did not use Balsa, but one mentioned maybe they just used scrap. Seems that all these pieces would not be very rigid in a floor application...

Some of you have used 1/2" ply.

So, I can get 1/2" marine ply (No voids, more layers) locally and think that this would be the most rigid material to use. However, it is likely heavier than the balsa?

So what do you think on this? I want the most rigid, but lightest possible material here. Seems cost wise, between the marine ply vs the balsa, close to same cost. But, which is more rigid? I have to believe the balsa is lighter, but wonder how much lighter?

Then, the resin. I have always used polyester resins and never epoxies due to cost, and staying with resin, I have compatibility with gel coats in most of what I have done in the past. I have found some Iso Blend Resin from Fiberglass Supply Depot that is approx. $30 per gallon. Seems to be a good resin for this application.
However, I like the wording on the Raka site about how the epoxy is lowest odor and better to use in lower temps which is where we are this time of year. Looks like I might need about 2 gallons to do this job. How much did you all use?

Then to the cloth. After grinding smooth, should I put down a layer of 1708 or just resin (thickened/trowled) and then a couple layers over the wood? Will of course 45 degree edges and fair, add extra layers of glass to edges.
Which is more rigid? Chopped strand mat or 1708?

I want to ensure these are very rigid as these spans are fairly wide and want to ensure I have the strongest platform approach here.
 

onoahimahi

GreatGrady Captain
Joined
Dec 9, 2012
Messages
483
Reaction score
1
Points
18
Location
Boston MA
ROBERTH said:
However, it seems what Grady used here was square pieces of ply instead of balsa. Seems weird to me that they just did not use Balsa, but one mentioned maybe they just used scrap. Seems that all these pieces would not be very rigid in a floor application...

Some of you have used 1/2" ply.

So, I can get 1/2" marine ply (No voids, more layers) locally and think that this would be the most rigid material to use. However, it is likely heavier than the balsa?

So what do you think on this? I want the most rigid, but lightest possible material here. Seems cost wise, between the marine ply vs the balsa, close to same cost. But, which is more rigid? I have to believe the balsa is lighter, but wonder how much lighter?

Then, the resin. I have always used polyester resins and never epoxies due to cost, and staying with resin, I have compatibility with gel coats in most of what I have done in the past. I have found some Iso Blend Resin from Fiberglass Supply Depot that is approx. $30 per gallon. Seems to be a good resin for this application.
However, I like the wording on the Raka site about how the epoxy is lowest odor and better to use in lower temps which is where we are this time of year. Looks like I might need about 2 gallons to do this job. How much did you all use?

Then to the cloth. After grinding smooth, should I put down a layer of 1708 or just resin (thickened/trowled) and then a couple layers over the wood? Will of course 45 degree edges and fair, add extra layers of glass to edges.
Which is more rigid? Chopped strand mat or 1708?

I want to ensure these are very rigid as these spans are fairly wide and want to ensure I have the strongest platform approach here.

I did this last spring on my Wellcraft before I sold it and got some good pointers on Hull Truth at this link:
http://www.thehulltruth.com/boating-for ... panel.html

I followed the approach recommended by FX10. He convinced me to save my money and use polyester resin instead of epoxy and that CDX plywood is okay too. I got the plywood and the fiberglass at Home Depot. As he said, it was a pretty easy job.

My Wellcraft floor panel was about 1/2 the size of my two Sailfish floor panels combined so I would say you will need 2 gallons for your Sailfish.

The Wellcraft also used little squares of plywood like the photo that started this thread - this seems strange since it wouldn't offer any stiffness or strength. I was guessing that the little squares were used as a way to slow down rot by isolating the individual pieces but that is just a guess.
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
The plywood in my hatch really looked like scrap. Maybe not but there sure were a lot of different size pieces. Anyway I used the balsa for weight savings and it was interesting to work with. The balsa probably does not save a lot of weight but it is lighter and I wanted to work with balsa just to see how it went. I used two gallons of WEST system on my Sailfish hatch I have some left over but needed to buy two. The WEST does not smell much and you can work it in colder temps. That said The Poly would have been quite a bit less expensive. If I did not need to do it this time of year I would probably opt for the poly resin just to save a buck. I believe I sourced my supplies from Mertons fiberglass they were helpful and shipped quickly. The gentleman I spoke with was very knowledgeable, not just someone taking an order. He recommended a stitch mat for the final layer of mat. I'm sure there are a lot of different ways to skin this cat but that is what I did. As I mentioned above I think the most important thing is not to let the screws penetrate the core.
 

ROBERTH

GreatGrady Captain
Joined
Jun 10, 2006
Messages
1,304
Reaction score
120
Points
63
Location
Raleigh, NC
Model
Sailfish
It sounds like it is a good idea to not allow the wood core to extend to the screw area and just beef up the void between the edge of the wood to the edge of the panel with some extra layers of glass. That way, there will never be any wood exposed.
Is anyone familiar with the ISO based resin?
This is what it says about it:
Our polyester resin is a Iso blend resin, this is a perfect no-run, no-sag resin for marine repairs and boat construction. Iso resin is more flexible and waterproof then your traditional 100% polyester resin. Ideal for repairing hulls, decks, cabins, and tanks. Good for repairing all boat surfaces. It is mixed with MEKP catalyst to harden. This resin is a low profile resin that does not need wax for it to dry tack free. This is the resin that most of the boat builders use when building new boats.

What I like about this is it says more waterproof. Not so sure I like the flex, but from a resin perspective, I guess that is actually what you want so it does not crack/craze under pressure like walking on a panel and relying upon the glass and wood to stiffen.

It also sounds like I can add layers without sanding as it does not need wax, yet final layer will be tack free.
 

ROBERTH

GreatGrady Captain
Joined
Jun 10, 2006
Messages
1,304
Reaction score
120
Points
63
Location
Raleigh, NC
Model
Sailfish
If you all think this ISO resin is a good idea, I can purchase both my glass and resin from same company. This is the glass I am eyeballing:

Fiberglass Biaxial Cloth is a #1708 E-glass Biaxial (+/-45 degree) Cloth with 3/4 oz mat backing.
held together by light stitching
Flat non-crimped fibers yield reduced print-thru and higher stiffness than woven fabrics
Ideal for repairs, tabbing, and reinforcing.
For every yard of 50" 1708 biaxle it takes about a half gallon of resin.


Sounds like this is much better to use over woven cloth as they say it has a higher stiffness which is what I am looking for.
Second, they say how much resin it uses.

The resin use says I would need a gallon based upon 1 layer,but likely I will get 2 gallons and add an extra layer and build up around the edges as well.

So, from onoahimahi's link, this is what I think I need to go for:
Grind down to smooth, roll bed of resin with layer of 1708, roll out smooth and remove bubbles, wet wood and hot lay onto 1708 and weight down. Then fair the edges, 2 layers of glass over wood. Everything precut and ready. Should be able to do all in one day. What I did last year on the swim platform was cover the finished product with wax paper and then added the weights so that I could just do it all in one sandwich.

I can heat the garage as needed, just hate the smell for a day, but dealt with it all last winter on other projects, so this smaller project I guess we can just deal with it.
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
Not familiar with the ISO resin but it sounds good. The cloth I used was stitchmat but not biaxial -I don't think. It appears to be plenty strong. I put a layer of glass cloth on the bottom of the hatch (not the stitchmat) then a layer of WEST then the core material. Then another layer of WEST then stitchmat was last over the core with a good coat of WEST. For the edges I wanted to keep the core close to the edge for strength so I dilled out core with small hole saw in the area where the screws were located an filled the area with thickened resin and then drilled it out after. I also drilled into the stringers with a larger bit and filled the holes with thickened resin so the screws went through the cover and into the resin in the stringer so no contact with wood in the cover or stringer. It should work I think, it is very strong.

The smell should not be a big deal as you will finish the same day. I used to work on surfboards in the winter and it was not a big deal. The WEST system was nice but for the cover I probably would not bother with it again. I also did a wood panel for rear of the cockpit and the WEST was really nice for that. I would use WEST again in a heartbeat for that type of work. The back of the cover not so much.
 
  • Like
Reactions: JackStraw

DennisG01

GreatGrady Captain
Joined
Sep 1, 2013
Messages
6,818
Reaction score
1,209
Points
113
Location
Allentown, PA & Friendship, ME
Model
Offshore
Although there's many ways to skin a cat... in regards to the screw holes, I also like the 'overdrill, fill with epoxy and redrill method'. The only thing I would add, and maybe Jeff already did this, is before you fill the hole with thickened resin, wet it out with unthickened resin first. This will give even a better bond between the thickened resin and the wood since the unthickened will saturate the wood better.

Again, keeping a skinned cat in mind, I don't think it's necessary to put a layer of glass between the hatch and the new core. Instead, I would wet out both the hatch and the wood, then goop down some thickened resin (mayonaisse to peanut butter consistency) and spread it with a 1/4" notched trowel. Sort of like how you lay down a tile floor. This way it fills any irregularities between the hatch and the new core. Weight it down (but don't go overboard with the weights) and whatever squishes out can be used to fillet the sides of the core.
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
Good points Dennis. I went back and forth on the extra layer of mat between the hatch and the core. Finally I went with it for a couple of reasons. The hatch on the Sailfish is quite large and the back side was still a bit uneven and very flimsy after removing all the junk pieces of ply. I figured the extra layer would add some rigidity right under the deck and give me a nice even surface for the core to adhere to. The deck appeared a bit thin in spots so the extra layer solved that, in my mind anyway. In addition and this is mostly because of my skills or lack of them I was worried that if I glassed in the core all at once and the panel was warped some I would have fit issues later. By laying down the layer of mat I was able to make the panel more rigid and try fit it. The deck came out fine and true and in addition was much more rigid than before but flexible enough it still could be shimmed if needed before core install. I should add that because of where I live shipping on solid balsa board was prohibitive (there was no local source either) so I went with the balsa that is 1" wide strips held together a scrim/ net sort of thing. If I was using ply or solid board like you guys I might not have bothered. The nice part of this product is they just roll it up to ship. With all that done I then installed the core material let it set up checked my work then laid on the stitchmat. In short the extra layer was more for my peace of mind than a structural fix.
 

DennisG01

GreatGrady Captain
Joined
Sep 1, 2013
Messages
6,818
Reaction score
1,209
Points
113
Location
Allentown, PA & Friendship, ME
Model
Offshore
I'm pickin' up what yer puttin' down!

Was the balsa in 1" "cubes" or strips? I only ask because I've never, personally, seen it in strips. Balsa is good stuff - in cubes, it's oriented such that it's called "end grain balsa core" - sometimes just referred to as balsa mat. That's a very good thing since even if one of the cubes gets wet, there will be very little, if any, transfer to another cube. Because the grain runs vertically, each cube is pretty much an entity in and of itself. I wouldn't be worried one bit about the integrity of a hatch (or even an entire deck) constructed with balsa. That's a very sound way to build.
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
End grain balsa 1" X 2" blocks in the form of strips 1" wide and 48" long held together with a net sort of fabric on one side. This stuff http://www.mertons.com/Floatation/scored_end.html Normally this product is used in an application where one wants to have a curved panel. The company I got it from sells a lot of it for a rounded contour panel and because it is inexpensive to ship as opposed to a flat panel that will probably arrive broken anyway. They just roll it up and put it is a box. It worked very well. If I had a reasonable source for 1" cube solid board I would have preferred that but it was silly money to get it here. The solid board I feel would be more rigid due to the resin on both sides of the board but this stuff worked great. The Merton's people were very helpful.
 

ROBERTH

GreatGrady Captain
Joined
Jun 10, 2006
Messages
1,304
Reaction score
120
Points
63
Location
Raleigh, NC
Model
Sailfish
Sounds like there might be a difference in the Baltek vs the Pro Balsa. First being the price for Baltek is $25 for 1/2" and Pro Balsa is rounded to $38.

From what I can tell, they are the same except that the Pro Balsa is already pre coated with thin resin film to aid in bonding.

For $13 more per sheet, I wonder if it is worth it? Thinking it might soak up less polyester resin if pre coated and less weight as a result. For you all that used the Baltek, did it seem to soak up a lot of resin? I recall that when I used the Pro Balsa before, it did not. I have been getting the Pro Balsa from Jamestown Distributors.
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
The pro balsa does look to me similar except for the coating of resin. By the description the individual blocks must be coated and not the entire surface so you can contour it. I would like to have found some of the sheets with both sides coated entirely but that did not work out, I don't remember if the balsa I used soaked up a lot of resin, not gallons of it anyway. It makes sense that the pro balsa would soak up less resin and be easier to work also. When I did my project it was very humid and when the balsa came I cut it to fit, mixed my resin and stuck it down. I put the short ends I cut off aside and a day or two later I saw that in the humidity they had warped a bit. I am not sure if the large portion would have done that if I had not used it right away but just so you are aware. The pro balsa might do better in that situation too.
 

ROBERTH

GreatGrady Captain
Joined
Jun 10, 2006
Messages
1,304
Reaction score
120
Points
63
Location
Raleigh, NC
Model
Sailfish
I 3/4" Pro Balsa I have laying around looks just like the day I purchased it, so maybe you have a good point in that it would be more stable and not absorb the humidity as much.
I have a couple of small scrap pieces on my desk at work and today, I was torquing it to simulate pressure to see how flexible it was. If you bend it away from the scrim, I could not break it. If you bend it away from the non scrimmed side, it will snap due to the vertical grain.
That made me think about the pressure under foot when walking on it. Of course, it will be soaked in resin and sandwiched between layers of glass, so unlikely it will break or stress as much as this test, but in comparison with plywood, no way could I have broken a piece. So, thinking that the plywood would be more rigid in the same application.
I can get the 1/2" Doug Fir Marine Ply locally for $89. I called to check today, so thinking I will settle on the plywood over the balsa for this one. I do wonder why Grady did not use Balsa in the floor panels but they did on the full transom width swim platform. Maybe there is something about the larger span that warrants the plywood over the balsa. Just sayin'........
 

JeffN

Well-Known Member
Joined
Jan 16, 2007
Messages
584
Reaction score
7
Points
18
Location
Nantucket, Ma.
If Grady had used one piece of plywood I might agree but the pieces under my deck were very small and many different sizes. I just don't see any good reason for that except to save on dump fees by selling the scrap and shipping it out the door. Don't get me wrong I love my boat but I truly can't see a good reason to build a core that way. I am not an engineer though and it did last almost 30 years. There are cross braces over my fuel tank that help support the deck on mine. Once the balsa is fastened down with resin I feel the humidity thing is not an issue, it sat for a few days without the top layer and did not move a bit. I thought about a plywood core but with the cost of gas any weight off the boat is weight off the boat. That may be silly but what the heck. I see no downside or advantage with balsa or ply other than weight. My balsa cored deck appears to be very robust. From what I read everybody here has used ply for their core. Frankly I was curious about working with the balsa core - just because I guess. At the same time I did my deck I rebuilt the panel at the rear of my cockpit. I thought about Starboard for ease of care but did the math and the ply with a glass coating was quite a bit lighter than Starboard so I went with that and again shipping to the island was an issue. The ply was available locally. Go with the ply and don't look back.