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  #11  
Old 04-21-2002
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High Tech vs traditional-Comments?

Hi Jeff,
I want to know the truth but I have a real hard time believing what you''re saying about this fiberglass thing...you may not care. But if you do, can you give a number of examples? Years, brands and failures?
Thanx

Dennis
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Old 04-21-2002
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High Tech vs traditional-Comments?

Dennis:

To give you some specific examples of the boats that I referred to that I worked on that I saw banana''d or with poorly installed bulkheads:

A mid-1960''s Islander about 32 feet. The owner had raced it and managed to pull the hull deck joint apart at the transom when the knee at the backstay tang broke loose from the hull and the bolts cut through the transom. This knee was plywood and was glassed in with a single layer of cloth onto the hull. This boat also had dislodged the main bulkhead. This resulted in the cabinetry across from the head being pulled loose. There were large spider cracks on the outside of the hull at the main bulkhead which were clearly flexure cracking and pushing on the hull you could see some ''hinging'' at the bulkhead.

Worked on a early 1960''s Paceship Eastwind (roughly 25 footer). This boat had a partially molded fiberglass interior that had shifted and had damaged the deck structure above when it had rotated out of position. The surveyor was the person who taught me the term "Banana''d".

Helped a guy working on an early Columbia approximately 31 feet which had bounced off a dock and dislodged some of the glassed interior components. I helped him glass in a plywood bulkhead that had shifted. It had originally only been only spot tabbed into place on one side.

I have mentioned the Morgan IO with the hull deck joint problem.

I had a 1965 Grampian Classic 22 that had flexed and broken the joint between the aft bulkhead of the cabin where it met the cockpit seats. I reglassed that area back together.

To answer Duane''s question about why I consider external flange hull to deck joints weaker:

The bolting, caulking or adhesive surfaces on an internal flange hull to deck joint don''t show and so can be thicker in depth and have a much larger contact area. Outward turning flanges are a bit more limited in size because if constructed as solidly as an internal flange they would look very clunky.
When you think about how an internal flange hull ot deck joint works, the joint really is not in bending. It is subjected to sheer and to tension trying to pull the joint apart. But external flanges often occur below the deckline and so are exposed to a greater likelihood of damage in a boat to boat or boat to dock accident and are exposed to large hinging forces that create bending loads within the joint.

In an on-the-internet question and answer session with Hunter that I moderated a few years back, Hunter was asked about Hunter''s outward facing flange hull deck joint.

The Factory Representative answered,

"[Hunter''s] Hull/Deck joints are outward lapped flanges. The joint is prepped and then filled with 3m5200 and bolted on six inch and 8" centers (depends on the size of the boat) using 1/4" SS aircraft style nuts and bolts 360 degrees around the perimeter of the hull. It is then capped with a heavy-duty vinyl rubrail. No it might not be the best hull/deck joint but it ranks right up there with them and provides some unseen benefits. It does provide a strake for protection of the hull side and it does place hundreds of potential leak points outside the hull. This joint has been in use for 20 years and has stood the test of time. Surveys of damaged boats from Hurricanes and collisions indicate the strength is substantial, durable, and easily repaired. We do two leak tests of the boat one is done in an enclosed spray room for 4 hrs and the other is a pressure test and soap spray to pinpoint any leaks prior to shipping."

"We do use outboard lapped flanges because they are easier to construct than inboard flanges. We cycle tooling at a rather high rate and to obtain that rate sometimes we need two to four sets of identical tooling. That adds up fast because tooling is the major investment in FRP construction. I don''t argue that an inboard lapped flange is better. But I will argue that an outboard flange for the reasons mentioned earlier is more than adequate and is construction friendly. It is certainly better than a shoe box joint that provides none of the benefits of either and is more prone to leaking and harder to repair if damaged. But then so would an inboard lapped one be even harder to repair and harder to access it''s fasteners [Than an external flange]."

I suppose that the rep from Hunter is right that a damaged outward flange joint is easier to repair but I still think it is inherently weaker and more prone to damage.

Jeff



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Old 04-21-2002
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High Tech vs traditional-Comments?

Dennis, I just looked at your question again. If you are talking about the material layup issue, my sources come from a number of sources.

For example I compared the glass in a coring (depthsounder installation) from my family''s 1965 Pearson Vanguard to a plug that I had from a 1980''s era Pearson (Fuel Tank Vent). Sanding both with 220 grit paper and then putting motor oil on the same I was amazed at the clear difference in spacing of the laminations with much fatter resin lines.
After that I began to pick up samples of corings as I walked around boat yards. (They make good backing plates under a washer) When ever posible I try to identify the boat that the plug came from. It became clear that early boats generally had visibly more resin rich laminates. I had the chance to discuss this observation with a marine surveyor/ yacht designer, who was with Bristol in the 1960''s and into the early 1970''s, he basically confirmed that to be his experience as well.

Jeff
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Old 04-22-2002
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High Tech vs traditional-Comments?

Hi Jeff,
Yeah, thats one of the things I was wondering about. The other things are colisions, grounding dammage (not keel) stress failures...stuff like that.
I want to be educated on all points not just the kind of boats (traditional, heavier,higher D/L) that I am used to. I will never shun these boats( T,H,HD/L). I just like to know whats going on and your brain seems ripe fer tha pickin''.
Thanks alot.

Dennis
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High Tech vs traditional-Comments?

Im not saying that early glass boats are stronger than todays boats,(thier are probally alot though). I just dont agree with you when you say some of the early boats with thick hulls are not as strong as they appear to be and the extra weight is just causing more stress. It also appears to me the eighties boats are the ones with the blister problems.Thier is an eighty something endeavor behind me full of blisters and two eighty something union 36s in front of me covered with blisters.Also I dont see an early glass boat taken from drawings of a wooden boat as a negative thing either.I would imagine alot of new boat design has evoled from the past.In my case I am doing a pretty major re-fit and I have not seen any signs of stress due to my thick hull. I am also not sure of my builders rep(chris-craft) during that time.(1965).With out getting techincal how do you explain so many old boats on the water?You would have to agree they did something right to have this kind of longevity?
thomas
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High Tech vs traditional-Comments?

What thomasstone said.

Dennis
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High Tech vs traditional-Comments?

Jeff_H,
Thank you. How wide spread where these types of problems?
I know what I think but what do you think some of the big changes where from the sixties through the seventies?

Dennis
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Old 04-22-2002
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High Tech vs traditional-Comments?

Longevity may be due to things entirely unrelated to fiberglass layup schedules and glass/resin ratios. Improved navigational tools like depthsounders, Loran, GPS and the ever more popular radar are keeping people in old fiberglass boats from finding as many rocks as they used to. Plastic (fiberglass) left to float in the water doesn''t deteriorate much - just look at all the clorox bottle lobsterpots. If they can keep from hitting anything, no wonder there are so many old boats around.
To the point about possible "under- engineering" of fiberglass contstuction, you can read just about any old boat review in Practical Sailor. Wobbly bulkheads, flexing topsides, delaminated tabbing, and crazing gelcoats due to overbending abound. Sometimes the items are fixed "after the first 50 or so hulls...". Sometimes the "factory fix" is installing a heftier backing plate. Sometimes it''s: "many owners have replaced..." Of course the marketing departments don''t call this "under-enginering" -- they call these things "improvements" in the proud history of their company and product. Have fun sailing, and don''t hit anything no matter what your boat''s made of!
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Old 04-23-2002
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High Tech vs traditional-Comments?

I guess "how strong they appear" is in the eye of the beholder. Most people equate the extra hull thickness with proportionately greater strength. All other things being equal, that would be true, but with all of the variables it is just not the case as I tried to point in my early posts on this string.

Blisters still occurs in boats built today, but by the early to mid 1980''s most quality American boat builders had dealt with the blister problem and had changed resins, and layup practices to combat the problem pretty successfully.

I never said that glass boats were literally built from woodenboat drawings. What I said is that they were engineered using wooden boat engineering interprelated to glass construction and the properties of glass were sufficiently different to wood which resulted in designs that did not use fiberglass very well. This approach to the fiberglass engineering did not necesarily place material where it was needed and had too much material where it was not.

Chrris Crafts were considered to be extremely well built boats for their day. They were designed by Sparkman and Stephens who were the leading yacht designers (probably world wide) during that era. S&S probably had the absolutely best engineering information that was available and their boats from that era have held up exceptionally well.

Lastly, to address your question about the number of older boats on the water somehow showing that they were well constructed. If you sailed in the 1960''s, the popular sail areas were no less crouded with boats than they are today. Huge numbers of fiberglass boats were constructed in the 1960''s and 1970''s. (In 1968 something like 10,000 new sailboats over 30 feet were constructed in the US while just over 3,000 were constructed in the year 2000 up from a low of 2200 boats in the early 1990''s.) But when you are out on the water early fiberglass boast represent a small percentage of the boats out there. Over the years I have seen or heard of a fairly large number of these older boats going to the landfill. While many of these boats died of economic rather than structural problems, there has been a significant reduction in the number of older boats out there.

Jeff
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Old 04-26-2002
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High Tech vs traditional-Comments?

Jeff, Are you saying that if you took a new Hunter (thin and light) and an old Alberg (thick and heavy)of similar lengths and did a sort of nautical ''demolition derby''with them, the Hunter would be left standing, or floating???
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