Pourable compound, composite and wood for stringers and transom.

[peacekeeper6]

So as I dig out my stringers I really wanted to go with a composite material and was sold on the Coosa but the price is astronomical for my size boat. I bought 3/4 inch marine plywood for about 110 dollars a sheet, I figure if I did the whole boat in marine grade I'll spend roughly 16-20 sheets for 110 a sheet coming out to roughly 1760 on the low end and 2200 for the high side. Coosa for the same amount of material is triple that number. So Coosa is out of the question and honestly I think I can find a composite for what the Marine Grade is going to cost, if not a bit more.

I found Nida-Core honeycomb which I assume can be used as a good core as long as I laminate with fiberglass. (http://www.merrittsupply.com/product...lain-h8pp.aspx) Am I correct in assuming that this is the correct item I need to replace the stringers and transom in my boat as long as its laminated with 1708? This seems like the most cost effective solution but you still have to measure, cut, tab, scarf the pieces together and on a 35 foot boat that could be quite a project in itself.

I then found multiple pouring compounds (Arjay, Seacast, Carbon Core, Nida-Bond) that seem like great alternatives and I can pour everything at one time (transom and stringers together) they range from around 130.00 - 205.00 per pail. If I do the math correct and do a 1 for 1 thickness replacement (1.5inch for the transom 1 inch for the stringers) then I should need roughly 30 pails (for that quantity price goes to roughly 100 per 5 gallon pail) which is 3000.00 bucks. It seems like for ease of use this seems like a middle of the road route for ease and a composite material.

All in all am I missing something here? Can I do a 1 for 1 replacement with the ceramic pourable compound? I am assuming because I cut my stringers out expecting to redo in wood that I will have to re-laminate the pourable anyway or at least tab it to the hull. I am not asking for differences on the products them self (unless you JUST CANNOT use a certain product for stringers as well as the transom).

i included a picture of the grid system before they were completely cut out, but all stringers and bulk heads have about 1 -3 inches of material left that is still tabbed to the hull. Of course if I decide to use wood or a coring material than I would definitely grind these little tabs out. My inner stringer is 24inches high at the highest point, the outter stringers are roughly 17inches high at the highest point. Both stringers run about 288 inches from transom to bow.

 

[funk6294]

That's one serious project!!!! Here's my 2 cents on this (and it's probably worth less than that). My understanding of the pourable items is they need to have the fiberglass already in place to form a wall or cavity to put it into. Since you already cut out the old stringers, wood, glass and all you will need to do a lot of work to recreate a cavity to pour this into. If you use the plywood you just need to bed and glass into place the new wood. It would be much easier than trying to build a hollow stringer to pour the composite into. If you glass the new wood in really well it should last a long time. BTW, look forward to following along!

 

[peacekeeper6]

I have done research in making the "mold" and it is not nearly as involved as fitting all the new wood in place and scarfing it in. Plus the material is much easier to work with. I can rebuild the mold with ease I just wonder if the 1 inch pour would be structurally sound enough to do the job. I contacted a few buddys who have used the pourables and they had about a 1inch by 7 foot piece left over we wailed on it pretty hard and it was tough as a brick.

 

[mickyryan]

pour able stuff I thought always relied on fiberglass to increase its strength maybe I am mistaken but id do plywood and fiberglass if you already removed the base glass .
also keep in mind weight to strength ratio , that product is allot more dense" heaver" then wood

 

[peacekeeper6]

pour able stuff I thought always relied on fiberglass to increase its strength maybe I am mistaken but id do plywood and fiberglass if you already removed the base glass .
also keep in mind weight to strength ratio , that product is allot more dense" heaver" then wood

From what I understand a 1" stringer per run should be around 22 pounds while the pourable compound looks to be 7.2 pounds per gallon. A 5 gallon pale weighing around 36 pounds? The real question is how much can I pour with 5 gallons.

 

[mickyryan]

hmm I know a sheet of 1" plywood weights like 80 lbs if I recall and I remember somone saying here 5 gallons don't go far at all like maybe one stringer? Plywood Thickness and Weights:
Sanded Nominal Thickness
1/4 3/8 1/2 5/8 3/4 1-1/8
Actual Thickness
1/4 11/32 15/32 19/32 23/32 1-1/8
Approximate weight per 4x8 sheet
22.0 28.5 40.6 48 60.8 84.5

 

[peacekeeper6]

Well thats even better than I predicting, I mean if I can pour one 35 foot stringer at for 5 gallons that reduces my need even more.

 

[jbcurt00]

Probably not 1 35ft stringer.

IIRC 5gals doesnt do a typical runabout transom. sphelps

You dont use a moveable/re-useable mold for the pour in. Unless you pour the stringers out of the boat. In which case you'd still have to shape and cut them to fit same as the wood, but harder to work with. And you still have to glass them in.

I suggest you link the Donzi build here and the composite topic there?

Try to keep the composite topic and discussion here, otherwise it may get confusing to follow whats been discussed and where.

 

[peacekeeper6]

I jest at the 35 foot, the boat over all is 35 feet. I would say that each main stringer run is 26 feet with the outters being around 20 feet. The are not all 24 inches high that is just at the highest spot on the inners and 17 at the outters. So I would definitely have to do some measuring to figure out just how much I will need when I pour them level. I am researching more now and have found people that have done it so it definitely is possible.

 

[peacekeeper6]

http://forums.iboats.com/forum/boat...d-hull-repair/10210200-1987-donzi-f33-restore the restore

 

[Woodonglass]

You can use 3/4" Ext. Grade Plywood @ $35 a sheet Once it's coated with resin and glass It'll last as long as you own the boat and long after that as long as you maintain the boat properly. Honeycomb is not a suitable material for stringers unless you use twice the amount of glass as normal and then you could use Cardboard since the glass would be of sufficient thickness to carry the load. I seriously doubt that using the pourable composites could ever be cheaper than the normal wood and glass method. And I doubt it would save that much time either since you have to build forms for the stringer pour and that would take longer than making a wooden stringer. Composites are Great if you don't want to worry about poor maintenance cuz they'll never rot no matter how much water penetrates down below the deck. I can't see the cost benefit ratio being equitable.

 

[peacekeeper6]

Im pretty meticulous when it comes to maintenance but it seems that no matter how much maintenance i do its always something unforseen that ruins it all. Ill keep weighing the options. I am reading about a four winns that has reformed stringers made of nidabond its interesting. If the cost is dead set in the middle of coosa and wood ill probably go the pourable route.

 

[ondarvr]

There is no perfect right or wrong answer, it comes down to the one you feel more comfortable with.

It's not simple to make the mold for using the pourable products, but it can be done, if the stringers structure was still in place it would be much easier. Nidacore doesn't work well as a stringer core, it's not that it can't be used, only that even though it doesn't rot, it doesn't add strength in that direction, so it's just something to wrap glass around. Coosa adds strength and no rot, but pricy. Plywood can be cheap and easy, but may rot at sometime in the future if it gets wet. If you add a little extra glass to plywood so that if it rots there's still plenty of strength, it works OK.

If I was to do it I would probably go with hollow stringers, use a 2x12, maybe stacked and/or side by side to build it up as needed and use it as a mold to make the hollow glass stringer, then cut them to fit the hull shape.

 

[DeepBlue2010]

Are you sure of your math in calculating the # of sheets required to redo the boat. 16-20 sheets of ply is about 512-640 Sq-foot of ply!!

Not saying you are wrong but just want to make sure.

 

[mickyryan]

I fully understand you wanting to get away from wood but think about this , my boat was 38 yrs old when the stringers had to be redone , and that was only because some one left it outside to rot if you feel 30 yrs is not long enough for a material to last .... lol and if follow the way stringers are done here I'm betting it will last 60 yrs easily well maintained

 

[peacekeeper6]

The plywood math is a rough estimate but correct. The stringer grids are very deep + transom and decking and bulkheads. I also get the wood answer and know that with proper prep it'll last forever, its that one pounding of the waves that ever so slightly cracks the fiberglass and allows water intrusion I am worried about. Or the ever so slight flex of the transom bolts from the verados that allows that minuscule water intrusion that starts this process again. Im 30 its time to hang up the boat flipping and just keep one and I figure this is the one to keep might as well throw some real money at it so that I can keep it for ever and pass it to the kiddos. And they wont have to post on Iboats 2.0.com

 

[gm280]

The plywood math is a rough estimate but correct. The stringer grids are very deep + transom and decking and bulkheads. I also get the wood answer and know that with proper prep it'll last forever, its that one pounding of the waves that ever so slightly cracks the fiberglass and allows water intrusion I am worried about. Or the ever so slight flex of the transom bolts from the verados that allows that minuscule water intrusion that starts this process again. Im 30 its time to hang up the boat flipping and just keep one and I figure this is the one to keep might as well throw some real money at it so that I can keep it for ever and pass it to the kiddos. And they wont have to post on Iboats 2.0.com

Ha peacekeeper6, If you have the time, money and willingness to do it, go for whatever type material YOU like. Like stated before, there are no wrong or right ways, just different and costlier ways. Pick one and have at it. But do post your efforts and progress along the way. We love pictures on here and like to see boat project progress. :thumb:

 

[Dangerwil]

I used cypress for my stringers in 2 projects. Polyester resin. I expect it to last long after I am gone. Sounds to me like you should pour main stringers. Use coosa for bulkheads under deck. Anything above deck just glass quality wood. Poly resin, epoxy will get expensive fast. ymmv