Repairing Replacing Composite Stringers, Bulkheads

[svilla]

Hey Scott that is a neat product.

[OReely]

Scott,

I looked at the pictures and they brought to mind a couple of questions.

How much is this lowering cost? Labor? Material? I can see where there might be a little labor savings and maybe even a little shaved off on material costs (although I don't know what your product sells for) but I can't imagine a huge savings on either.

More important to me, you said it is better structurally. How so? Are you referring to single skin construction or sandwich (cored) construction. What exactly make this construction better.

I may be a little unconventional in my thinking but I prefer structural quality over marginal cost savings. I know some people like to save money and that is the main driver for material selection. Although I'm not one to use high tech solutions to solve low tech problems, I will, within limits, spend a little extra if it will make a better product.

[slewit]

Scott,

I looked at the pictures and they brought to mind a couple of questions.

How much is this lowering cost? Labor? Material? I can see where there might be a little labor savings and maybe even a little shaved off on material costs (although I don't know what your product sells for) but I can't imagine a huge savings on either.

More important to me, you said it is better structurally. How so? Are you referring to single skin construction or sandwich (cored) construction. What exactly make this construction better.

I may be a little unconventional in my thinking but I prefer structural quality over marginal cost savings. I know some people like to save money and that is the main driver for material selection. Although I'm not one to use high tech solutions to solve low tech problems, I will, within limits, spend a little extra if it will make a better product.

Hello OReely

Thank you for your message.

Great Questions ! OEM boat builders use our product extensively. We currently sell to over 30 major brands and via distribution in the US and Europe. With the OEMs we have produced over 250,000 boats with the product since 1994. The common experience is the product provides the following:

Reduced Weight (4-15% reduction in hull wt)

Increased Durability

Reduced Manufacturing Variance

Elimination of Hull Warrantee Issues

Reduced Labor (30-90% for stringer install)

Increased throughput

Rot-Prof Construction

The above items are very important elements in today’s very competitive OEM market. In the last few years we have expanded our product line from just stringers and bulkheads to products the replace or eliminate core.

Don’t get me wrong cored construction is great, however it is very unforgiving. If for example you do not get a complete bond on both sides of the core you loose the structural integrity of the sandwich construction. Also boat owners are more and more having issues with particular core materials that are prone to rotting when they get wet.

Moving to our new technology of Prisma framed single skin construction; we can reduce weight, manufacturing risk and greatly increase the toughness of the structure. Some pictures are attached to show you what I am talking about.

No one product is good for everyone or for every job. Our products are geared to quality builders that are looking for durability, ease of use and reduced weight.

If you send me your address and I will send you out a small sample that you can play with.

Thank you again for the great questions.

Scott Lewit

Prisma_vs_Sandwich_pic.bmp

[jb7out]

Hello OReely

Thank you for your message.

Great Questions ! OEM boat builders use our product extensively. We currently sell to over 30 major brands and via distribution in the US and Europe. With the OEMs we have produced over 250,000 boats with the product since 1994. The common experience is the product provides the following:

Reduced Weight (4-15% reduction in hull wt)

Increased Durability

Reduced Manufacturing Variance

Elimination of Hull Warrantee Issues

Reduced Labor (30-90% for stringer install)

Increased throughput

Rot-Prof Construction

The above items are very important elements in today’s very competitive OEM market. In the last few years we have expanded our product line from just stringers and bulkheads to products the replace or eliminate core.

Don’t get me wrong cored construction is great, however it is very unforgiving. If for example you do not get a complete bond on both sides of the core you loose the structural integrity of the sandwich construction. Also boat owners are more and more having issues with particular core materials that are prone to rotting when they get wet.

Moving to our new technology of Prisma framed single skin construction; we can reduce weight, manufacturing risk and greatly increase the toughness of the structure. Some pictures are attached to show you what I am talking about.

No one product is good for everyone or for every job. Our products are geared to quality builders that are looking for durability, ease of use and reduced weight.

If you send me your address and I will send you out a small sample that you can play with.

Thank you again for the great questions.

Scott Lewit

Prisma_vs_Sandwich_pic.bmp

[jb7out]

Hello Scott,

I am considering using your product for my rebuild. I was thinking that with a 4-15% decrease in hull weight that my boat may sit a little higher in the water. This in turn would raise the propeller which may lead to cavitation. Do you think this could be an issue or would the difference in draft be minimal? Thanks for your time.

[bly]

Scott, I contacted one of your sales people to look into you products for stringers on my 233 Formula project. She told me to go through Lewis Marine Supply to purchase the stringers, but they don't list very many options on their web site. I didn't see anything tall enough (to also support the sole) for a 24deg deadrise hull. Also, I am close to you in Merritt Island. Is it possible to come see your products first hand? Maybe if I bring some pictures you can give me some ideas. Thanks, Mark Galloway.

De ja vu I have two 233 projects happening and a enougher guy a few miles north of me just found out that his stringers in his 233 are gone and hes replacing them. If you make a kit up for nitzi you might have 3 more in need if the price is right? This is a little more than a hobby for us? I also usepenske board in the transom and decks that I got a good line on as well as a very good price. Apparently its been around before coosa board that came after? but everyone thinks coosa is it! It aint! Anyway if you have a 233 stringer kit in the works let us know? I also fabricated two fiberglass full flotation brackets that I made a mold to. single and twin OBs I use all fiberglass and vinylester construction with penske board for engine support.

[OReely]

Hello Scott,

I am considering using your product for my rebuild. I was thinking that with a 4-15% decrease in hull weight that my boat may sit a little higher in the water. This in turn would raise the propeller which may lead to cavitation. Do you think this could be an issue or would the difference in draft be minimal? Thanks for your time.

What you refer to as cavitation is more correctly called ventilation. Ventilation is the phenomenon of air getting pulled into the water path of the prop. Cavitation is a different phenomenon. You shouldn't have any issue with ventilation of the prop due to the boat sitting higher in the water.

The boat could be a little more tender, but I doubt it's anything you would notice.

[bly]

What you refer to as cavitation is more correctly called ventilation. Ventilation is the phenomenon of air getting pulled into the water path of the prop. Cavitation is a different phenomenon. You shouldn't have any issue with ventilation of the prop due to the boat sitting higher in the water.

The boat could be a little more tender, but I doubt it's anything you would notice.

I beg to differ. My favorite projects are taking formerly heavy IOs out and putting much lighter OBs on thge same boat. Then taking as much of the plywood,wet plywood from the 60s or 70s and replacing with light weight cored construction. I have done a few boats and had a chine that has been under water by 3 inches now floating above the water by an inch. In dual and more engine applications the outboard lower units could become ventilated when the boat is on plane and even higher out of the water. A single engine will not. Yes I have called this cavitation by mistake instead of ventilation. Sorry

[slewit]

Hello Scott,

I am considering using your product for my rebuild. I was thinking that with a 4-15% decrease in hull weight that my boat may sit a little higher in the water. This in turn would raise the propeller which may lead to cavitation. Do you think this could be an issue or would the difference in draft be minimal? Thanks for your time.

Hi DownIntheKeys

Great question !

In the case of a rebuild we should look at the weight of the materials you are pulling out vs. what you are putting in. In most cases we are replacing wood stringers with lighter weight composite stringers. In a 20-24ft boat you would see perhaps 200lbs of reduced weight.

Where we get the big weight reductions is when a boat is designed from the beginning for Prisma stringers. We do this all the time supporting the major OEM's builders. With wood stringers we are attaching a very thin and very rigid frame on the hull. This results in an abrupt and sudden change in stiffness in the hull bottom near the stringer. Boats with wood stringers will typically have thicker hull laminates to deal with the stress concentration and the larger span between supports (stringers). Often when a wood stringer hulls are subjected to extreme loading it is common to find crack lines in the hull gel coat and/or laminate that run parallel to the stringers.

Prisma stringers provide a wider footprint. These wider foot print stringers allow the boat designers to remove thickness out of the hull laminate. We can do this because the composite preform distributes the loads better giving a softer landing and its wider footprint results in shorter unsupported spans. This combination allows the builder to reduce the hull thickness and save weight. These weight reduction can be significant enough to that a smaller engine can be used or a trailer with one less axle. (see attachment for flyer we give the OEMS for the boat owner).

So as you see the OEM’s are really in the best position to save weight. As part of the design process the boat designer would be evaluating the placement and type of propulsion the boat should have. In today’s economic environment most of the OEM’s have figured out that reduction in weight offers many advantages. We have one OEM that made it a business focus to reduce weight and cost and created a lightweight series of boats from their standard boat line. The same 20 foot hull that had a 150 HP outboard now had a 115HP outboard. The result was a boat that was over $10,000 less expensive has better fuel efficiency and gives effectively the same performance. I think with gas prices and the cost of everything going up the builders the builders that focus on delivering innovation and value to the customer will be the winners.

In your case, I suggest we consider the overall project. If you are simply going to replace the wood stringers and bulkheads with Prisma, the resulting weight savings may provide an opportunity to get somewhat better performance out of your boat by a change in prop pitch. I do not expect it would create enough of a change that would require you to rework your propulsion.

When doing a more extensive job. For example, rebuilding the deck, adding large fish boxes, adding extensive storage, a pilot house, towers and the like then it would be advised to evaluate the change in weight along with closer evaluation of the structure and the impact the changes you are making are going to have on stability and performance.

I hope this answers your question.

Thank you

Scott

[slewit]

De ja vu I have two 233 projects happening and a enougher guy a few miles north of me just found out that his stringers in his 233 are gone and hes replacing them. If you make a kit up for nitzi you might have 3 more in need if the price is right? This is a little more than a hobby for us? I also usepenske board in the transom and decks that I got a good line on as well as a very good price. Apparently its been around before coosa board that came after? but everyone thinks coosa is it! It aint! Anyway if you have a 233 stringer kit in the works let us know? I also fabricated two fiberglass full flotation brackets that I made a mold to. single and twin OBs I use all fiberglass and vinylester construction with penske board for engine support.

Mark Galloway

If you are close by or if any of you are would like to Tour the Prisma factory please contact me.

slewit@aol.com

321-252-4566.

Scott