87 Osprey 22.2 rebuild

[305kingfisher1954]

Decided to start removing the fuel tank and deck this weekend..The fuel tank is dirty but seems to be in good shape, no corrosion on the bottom...The sending unit access needs to be woked on a little.Should I re use the existing tank or replace it since it is 25 yrs old...I am not going to have the tank access panel , only access for sending unit and hose connections.

The port stringer was dry and still attached to the hull. The port stringer is a different story..It had lifted and the foam is wet , the center stringer is wet and deterioring as well..Thinking if I should repair the existing stringers with foam and re attach or remove the stringers completely and build a box stringer system from coosa..

Appriciate your input..Thanks !

[305kingfisher1954]

More pics..

[Capt. Bob]

Should I re use the existing tank or replace it since it is 25 yrs old...I am not going to have the tank access panel , only access for sending unit and hose connections.

Appriciate your input..Thanks !

If there is really no/minimal corrosion on the outside after 25 years, then by all means you can use the tank but.....

How clean is the inside and why don't you want a hatch for future removal?

If you insist on no access to the tank, then replace the tank but I can't understand why you would rebuild the deck and not leave access.

[seabob4]

I agree with CB...in fact I think ALL boats should have a hatch that is relatively easy to remove to yank a tank.  

Make sure your access pies are directly above the fill/vent necks and the sender/pickup area.  Too many times I've pulled off a pie to re-wire a sender only to find the sender 3" or 4" offset from the pie...yeah, I can rewire it, but how the hell would I get it out??    

[305kingfisher1954]

It seems like most re builds I've seen here do not have an access panel for tank removal, only access for hose and sending units.. maybe I missed it...Maybe I'll re think it then..

[Circle Hooked]

My boat doesn't have that removable panel and i wish it did, someday i'm gonna have to get my tank out and it won't be easy.

[gran398]

You should go ahead and replace the tank. Not that much money, and terrific peace of mind.

Save the female deck portion where tank hatch fits, and the tank hatch itself. You can core what is left, and tie the new floor directly to it. Let the break be directly centered longitudinally over the stringers.

Just make sure to order the new tank to existing dimensions.

[Capt Matt]

I did not build a removable panel for my fuel tank, just access for the fill and sending unit. If you build short stringers to support the tank, do not foam it in and make sure it can breath a new tank should last 20 yrs plus. If you are going to put all the time into a rebuild just replace the tank and be done with it. After having the intention to repair the old stringers in my boat I ended up ripping them out. It was more work fixing the old than building a new stronger grid stringer system out of coosa.
In my opinion go foam free
Capt Matt

[305kingfisher1954]

I think "peace of mind " on the new tank is the way to go. I have had many quality built boats, Tiara, Pursuit, Bertram and they never had access panels to remove the fuel tanks..

I'm thinking about using  double 3/4'' Coosa Bluewater for the stringers. This will give me room for a wider tank . What do you guys think about putting a wider, shorter, flat bottom  tank in, 100 gallons ? ? The tank that came out was 80 gallons, 93'' x 8'' x 9 1/4'' at the V..(It's a V hull Tank") ...and yes I will make sure it has breathing room around the tank..


Agree, Coosa Bluewater for stringers and deck ??????

[dirtwheelsfl]

Agree, Coosa Bluewater for stringers and deck ??????[/quote]



all depends on what youre comfortable working with, and what you feel like spending. might be less to go with a single thicker core for the stringers as you might need an extra sheet to double it up like that. how many sheets to do everything under your deck matt?

[305kingfisher1954]

I was thinking about going with a thicker single 1 1/2'' for the stringer, but I was told it would be much stronger to go double up on the 3/4'' and glass in between ....that most of the strengh was in the lamination and the out layers of the coosa...many opinions..it would be much easier ansd cheaper to go with 1 1 1/2'' or 2'' stringer...the cost from between 3/4'' and 2 '' is only about $50.00 per sheet...

[slippery73]

I was thinking about going with a thicker single 1 1/2'' for the stringer, but I was told it would be much stronger to go double up on the 3/4'' and glass in between ....that most of the strengh was in the lamination and the out layers of the coosa...many opinions..it would be much easier ansd cheaper to go with 1 1 1/2'' or 2'' stringer...the cost from between 3/4'' and 2 '' is only about $50.00 per sheet...

Go with the single 1 1/2" or 2" for the stringer.  Your more likely to have strength issues with the two 3/4" layers because your still relying on a proper bond between those two layers. Strength is relative to how its used, the double lamination may be stronger on its horizontal axis, but on its vertical axis like it will be used in your boat.... doubt there's much difference in strength.  Think about how a 2x4 will bend  easily on the flat, but turn it on edge.... good luck.  

You'd be better off building a trapezoidal stringer like the factory design to be honest.

[Capt Matt]

I built my stringers out of 20# density 3/4 inch coosa and doubled it up with 1708 in between. With the stringers being roughly 18ft long I reversed the cuts so they came out as one solid stringer. After shaping and fitting the stringers I then biaxled the whole stringer, set and fit it in cabesoled then triple tabbed it with more 1708. It was way over kill but that is what I wanted as my boat will see 10's of thousands of hours of use.  For the bulk heads I used 3/4 coosa. Once wrapped and then triple tabbed in the grid stringer system seems like the strongest way to go and is the closest to what they build on high end production boats. ie Schaffer. Everything locks together. I chose not to put any foam back in the boat, after removing all that wet foam I could just not bring myself to do it.
By the time the stringers where all glassed in they are about 2 inches wide. I used 5200 to stick the floor down to the stringers and did not use a single screw, I made the deck with about a 1 inch crown in the middle so the water runs off to the sides.
The 11/2inch 26# bluewater coosa I used for the transom is crazy strong with 2 layers of roven fiberglass though it. The sheet for the transom was expensive compared to the sheets of 20# 3/4. It seems with the coosa 26 a piece of 11/2inch is more than twice as much as a sheet of 3/4 26.
If I remember right for the stringers, bulkheads deck and casting platform I used 8 sheets of the 3/4 and this left me enough scrap to build the short fuel tank stringers,hatches, under the bow cap and gussets too.  I think for the total build I bought 10 sheets of 3/4, 1 sheet of 11/2 and 1 sheet of 1/2 inch to do the transom cap and transom cabinet. I also built my console out of 3/4 coosa which was kind of a waste but I had the material so I used it.
For fiberglass supplies I used a full roll of 1708, pretty much a full roll of 11/2oz mat,  60gals of resin and 1/2 a bag of cabasol. I re-glassed the whole inside of the hull with 1708 after having it sandblasted before I started to build and made fiberglass panels for the gunnels which used quite a bit of material.
I had never worked with coosa and found it to easier to cut and shape than wood and you can use all the same tools you would use with wood. For what you save in weight using the coosa you can way over build and still end up with a lighter and stronger end product than using wood and best of all you never have to worry about rot if something is not quite perfectly sealed.
Capt Matt

[slippery73]

I built my stringers out of 20# density 3/4 inch coosa and doubled it up with 1708 in between. With the stringers being roughly 18ft long I reversed the cuts so they came out as one solid stringer. After shaping and fitting the stringers I then biaxled the whole stringer, set and fit it in cabesoled then triple tabbed it with more 1708. It was way over kill but that is what I wanted as my boat will see 10's of thousands of hours of use.  For the bulk heads I used 3/4 coosa. Once wrapped and then triple tabbed in the grid stringer system seems like the strongest way to go and is the closest to what they build on high end production boats. ie Schaffer. Everything locks together. I chose not to put any foam back in the boat, after removing all that wet foam I could just not bring myself to do it.
By the time the stringers where all glassed in they are about 2 inches wide. I used 5200 to stick the floor down to the stringers and did not use a single screw, I made the deck with about a 1 inch crown in the middle so the water runs off to the sides.
The 11/2inch 26# bluewater coosa I used for the transom is crazy strong with 2 layers of roven fiberglass though it. The sheet for the transom was expensive compared to the sheets of 20# 3/4. It seems with the coosa 26 a piece of 11/2inch is more than twice as much as a sheet of 3/4 26.
If I remember right for the stringers, bulkheads deck and casting platform I used 8 sheets of the 3/4 and this left me enough scrap to build the short fuel tank stringers,hatches, under the bow cap and gussets too.  I think for the total build I bought 10 sheets of 3/4, 1 sheet of 11/2 and 1 sheet of 1/2 inch to do the transom cap and transom cabinet. I also built my console out of 3/4 coosa which was kind of a waste but I had the material so I used it.
For fiberglass supplies I used a full roll of 1708, pretty much a full roll of 11/2oz mat,  60gals of resin and 1/2 a bag of cabasol. I re-glassed the whole inside of the hull with 1708 after having it sandblasted before I started to build and made fiberglass panels for the gunnels which used quite a bit of material.
I had never worked with coosa and found it to easier to cut and shape than wood and you can use all the same tools you would use with wood. For what you save in weight using the coosa you can way over build and still end up with a lighter and stronger end product than using wood and best of all you never have to worry about rot if something is not quite perfectly sealed.
Capt Matt

I'm not sure where coosa gets its claims of weight savings, but its not hardly any different weight than okoume marine ply. The 26lb density board is the same weight equivalent of BS1088 okoume, the 20lb board is slightly less. But not enough to make any difference in a boat this size.  BS1088 okoume would be equivalent to a 26lb rating. Lower density foams will weigh less

Most people fail to understand what these products intended purposes were for.  Most all of these composites are designed for in mold construction, half of which were developed for aerospace industry and should be vacuum bagged or infused. When they aren't used for the system they were designed for they start to lose their benefits.

The only benefit I see to Coosa vs. plywood is rot resistance. Weight is the same as a comparable marine ply. Not sure how the strength compares to plywood as their testing data is by request only. I'd say its not impervious to rot either, I've drilled into numerous foam composite transoms that have had wet foam and water seepage after drilling.  So I know it will absorb water under certain conditions.

Most of the time a lighter weight foam panel will suffice, thats where you'll see weight savings. The higher density foams 20lb+ are made for areas where compression strength is a concern, like a transom where a bolt would crush the core if tightened.  For stringers, bulkheads, knees, etc.  A 10-15lb foam would still probably be overkill.  When used like this the foam is acting more as a form for the glass than as a structural member.  Thats where wood and foam differs, wood used to be the main structural member of the part. It was probably glassed over for water resistance only. Foam is the opposite, its not the main structural member, the glass is. Its simply there so the glass has something to lay against. However, builders sometimes don't understand the engineering behind these products and how they should be used.

[305kingfisher1954]

Thanks for all that information....More decisions now...prior to reading your posts I was pretty much decided to go with a double 1 inch stringer that would give me close to 2 1/2'' inches when glassed in. The only reason I decided to go with the double stringer is because I can stagger the joints as opposed to having 1 butt joint in a single stringer. The total length on the stringer is about 17 ft, so I was thinking of getting the 1'' x 4' x 9' long coosa and only having 1 butt joint on each side, of course I will stagger the joints. I spoke with Efrin the tech rep for Composit One and he said for the transom use 24lb to 26lb density with 1 1/2 oz mat and on the stringers and deck use a 15lb density with 2415 stiched mat and use Plexus 590 to glue the deck own.

I am working with an experienced boat builder on this project that does very nice work, but I'm having a hard time getting him away from marine plywood, he swears by this, but he's willing to try the coosa, so I'm want to present this to him in a positive note and have all the correct information!!!  Marine plywood is great too, but all it takes is one guy forgetting to seal a bolt when he installs the motor, or any other unsealed penetration and your on your way with water and  rot issues...

If I do use a single stringer 2 inches wide should I re enforce the butt joint or will the glass work take care of it..just seems like a weak  link the chain..I dont mind a little over kill on the stringers which I'm thinking a double 1 inch stringer will be..

There is also a difference on the density for the Coosa for the stringers..I was told use 15lb and you guys are using 20lb...Is there a big difference ??   Double 1 inch stringers with staggered joints or 1-- 2 inch stringer with one butt joint..??? Thanks ...