Need input on core material selection

[FlowMaxx]

This winter I have a project and would like to make the correct decision on core and transom material. I have done quite a bit of reading and have come to the conclusion that properly sealed balsa is the most superior for strength. While strength is very important to me, longevity and "no-rot" is what I am most interested in. The boat is used heavily and mostly for waterskiing so it gets wet constantly. Also plenty of pleasure boating as well.

What other products have you guys used with good success? Looking for ideas and input before I make a final decision and place an order.

I do plan on sharing the restoration on here for anyone that is interested.

Thanks in advance for any replies.

[Smoking Joe]

There is nothing wrong with ply. It is both cost effective and strong. THE SECRET IS TO MAKE SURE IT IS WELL SEALED. Timber transoms only fail if they get wet or physically abused. Personally I only use epoxy resins when using wood. Have a read through this rebuild thread and you will see how we do a timber transom and the lengths we go to to make sure it stays dry. Most rot starts with water leaking into the transom core from appendages bolted through the transom.
I would also recommend two knees to brace the transom.

http://www.screamandfly.com/showthre...ve-to-Outboard

[FlowMaxx]

Is there a problem with adhesion when using epoxy up against an original polyester layup?

[Smoking Joe]

Not at all, epoxy adheres well to polyester however the reverse does not work. Obviously the surfaces to be glued need to be clean and the surface scuffed. Epoxy adheres well to wood where as Polyester really needs to encapsulate the wood to stay stuck.

[97 TWISTER]

I really like Thermalite board made by Space Age Synthetics. Its lite weight and water proof and very easy to work with. They have many densities for use in different applications. It seem pricey when you look at the per sheet price but if you factor in the time and materials it take to make wood water tight I think its cheap. You can use bedding compond (cabosil/resin) to set it or panel bond adhesive. The only downfall is you can't screw into it but I use panel bond adhesive to set my seat bases, battery tray, foot throttle ect... I have used it on a few projects and will never use anything else again. I use it for floors, stringers, bulkheads, transoms. or where you would use wood. I haven't done one yet but it would work great for splashwell deletes. If you decide to use it make sure you let me know I would like some more and we can split the shipping. Last time I ordered they had a bunch of 1/2 that the made for somebody and they backed out on the order and it was very resonable, they also have blems. I deal with Brian and if you are intrested I will send you his number.

[XstreamVking]

For the re do on my V-King I used vinyl resin, 1708 glass, coosa board, and divinnycell core. This combo has worked well for many yrs with a lot of motor on the boat. Also not afraid to use it in salt water and big waves. Not one crack or any other glass problem. Not the cheapest or the most expensive. But is proving to be more than adequate.

[FlowMaxx]

Great input guys, I really appreciate it. So I assume then that, like epoxy, the vinylester resin bonds just fine to the original poly? What did you do for prep?

[XstreamVking]

6'' Grinder and 36 grit disc's. Then glass right after.

[OFFSHORE GINGER]

Quick mention , and that is most Boat Co's to this day still use ply for the transom , Skater , Fountain , Cig , Tiara , S-2 Yachts , etc , etc , and not to mention that 90 % of the transom's i re-do ..................are done using Ply with a few done using Thermo Lite Board http://www.spaceagesynthetics.com/th...teproduct.aspx which is Coosa's biggest competitor & cost's less , with seconds sometimes being available ( scratch & dent ) and to view and compare i will throw this link out there http://www.coosacomposites.com/ Personally in my opinion if i was you i would go with Ply depending on the size of your wallet , and just curious what Epoxy do you have in mind , and not to mention that going with Epoxy is a very good / wise choice !!!!!

[XstreamVking]

Ginger, Isn't the reason for plywood transoms to lessen the vibration of the drives into the boat?

[tunnels]

This winter I have a project and would like to make the correct decision on core and transom material. I have done quite a bit of reading and have come to the conclusion that properly sealed balsa is the most superior for strength. While strength is very important to me, longevity and "no-rot" is what I am most interested in. The boat is used heavily and mostly for waterskiing so it gets wet constantly. Also plenty of pleasure boating as well.

What other products have you guys used with good success? Looking for ideas and input before I make a final decision and place an order.

I do plan on sharing the restoration on here for anyone that is interested.

Thanks in advance for any replies.

In production in the boat company I been working at we use 100% sold glass transoms
No wood no problems nothing to ever rot and as strong as !!. the solid glass panel is big enough to cover the area were the motor mounts and a reasonable amount of full width glass one side to the other under the panel then stick the panel in place and then another lot of glass over the whole width again . sound like a lot but when its weighted against a wood and glass transom ours were actually lighter and never have to ever worry ever again in your life time or the life of the boats !! Food for thought !! and sound transfer never happened because its solid !!

[OFFSHORE GINGER]

Ginger, Isn't the reason for plywood transoms to lessen the vibration of the drives into the boat?

Good question , and to tell you the truth , i have never given it much thought because it has alway's been the manfactures choice considering i have worked at a few Co's with one building boats for Fountain , Cig , Platinum , and the Navy Seals , with Ply being a requirment , and not to mention that Coosa was a condersation after a trial period ( one boat ) that went to the way side .............because it did not fit the bill .

[XstreamVking]

Guys at Nor-tech use ply for transoms. I asked why, and they gave that as the primary reason.

[tunnels]

Solid glass transoms !! We were making a collection of two other companies boats , 9 different models in all of various sizes and shapes ,and converted all of them to solid glass construction ,including replacing the crappy wooden stringer system they had been using for the past who knows how many years , plus replaced the ply used in the floors with a glass nida core glass floor inside , The owners of the company's could not understand why they had never thought of all this long time ago !! is quicker , easier to manufacture and install during and making of the boats . everything is solid glass and the only core is under the floor and its never going to soak any water ! its honey combed plastic !! . so when you drill the motor mount holes and hull drain its all solid glass every where even grab handles and what ever get screwed or bolted to the transom its all on solid glass ! the centre is where the meat is and the outer sides are naturally thinner but coreless and with your motor splash well stuck and glassed to the transom it forms a bracket each side and its absolutely rock solid like a brick wall !! Noise and vibration is a myth ! from the outside there no way of telling its solid glass and inside its flow coated and again no real way of telling !! adding the weight of all the materials used between solid and wood the solid came out lighter over all by a few kilograms . Having been the instigator and doing the changes I cant understand why powerboat companies persist in the antiquated thinking and make the change or switch to all glass !! it make perfect sense and is easier , quicker and overall lighter ! and with a chopper gun is a continuous operation just one piece get fitted straight after the other !!so saves time as well . But I suppose the old die hards in the boating industry (and its full of them ) cant accept change and better newer ways !!

[tunnels]

Ok ! I used to own a old boat made in 1975 a golden oldie !! had a good hull and it had a glass grid inside with a ply and solid wood transom ! it started it life as one of the old 16 inch transoms and some one converted it to a 20 inch but the wood they added made it way to high and the old omc 75 used to cavitate so I needed more room and a step back so chopped the whole transom off and rebuilt my own to take a 25 in motor 115 hp and no wood or core any where in the transom . I used shape alone as the strengthening factor curves in just 2 different directions and a very small spashwell and a narrow transom deck I made the whole assembly on my work bench and when finished I introduced it to the back of my boats and glassed it all round the perimeter inside and out and extended the glass floor back to join up to the lower part of the new transom because of the new shape Hung the motor set the height and on the first run I was amazed at the difference it had made . I honestly can not understand why people make transoms with plywood , or want to use a core of anything !! solid ended up at 50 mm thick when was all finished its absolutely as tough as can be ! there is no fear of ever over tightening mounting bolts or squashing the core , and all the boats in the place I was working all have solid glass and there's no way you could damage it even if some on ran into the back of the boat !! everything is tied together and never ever have to replace it for the life of the boat !! cosa board and what ever else !! why ?? why do you want a core at all ?? beats the hell out of me !! same with stringers and girders and floors why use wood ??? this is 2014 and will be 2015 on this side of the planet so why are you living in the dark past ?? procrastination and backward thinking !!