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Original bottom with slick seam caulk!

Framing, planking and fairing. Repair, or reconstruction. If it's hull related, you'll find it here.

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Paul R
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Original bottom with slick seam caulk!

Post by Paul R » Fri May 05, 2006 7:41 pm

Last fall I purchased my first boat/wooden boat, 18ft CC Holiday. The boat is nicely finished with 98% original wood. The previous owner and restorer dicided to use slick seam caulk on the bottom seams. I've read the pros on cons on slick seam, but wonder if any members have had experience with it and your feelings on it. It seems to me that I am locked into using this arrange ment till I decide to redo the bottom completely.

Paul R

jathomas
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slick seam

Post by jathomas » Sat May 20, 2006 9:53 am


paul, slick seam is a great product if you want to reapply it every spring. it does the job in letting the boat swell and displaces the compound over time. however there is another way but only if you keep your boat is a hoist to minimize the swelling. on my 1938 17' cc utility, i reafed out the seams with a 1/8" router blade cutting back to frest wood after cleaning out as much of the slick seam as i could get out using severl home made devices. then applyed 3M 4200 to the seams. this material will squeeze just enough to let the boards swell some and the 1/8" cut gives you room for any swelling that will occur, however, the trick is to keep the boat in a hoist and mimimize swelling, has worked for me for 5 years now. My bilge is almost always dry, except for the dripping of the shaft deal.
hope this helps, jim

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Post by Paul R » Wed May 31, 2006 7:16 pm

Thanks for the post Jim, but I am past the slick seam and onto the idea of redoing the bottom. While prepping the bottom for repaint, I found some rot in the keel to stem joint-----enough to make me dicide that it's time to take fhis old bottom appart. The question that I have now is--- do a Danenberg 5200 bottom, or a plywood, glass cloth and epoxy resin bottom. I do not have the luxury of putting a lift at my right-of-way dock and this boat will need to sit in the water for the summer. I've read Don's book and he still advocates that even a 5200 bottom should be on a lift, hence I am beginning research on the correct procedure for a glassed bottom. Any books on the subject would be appreciated

A few general questions to any and all members. Do you have a 5200 bottom that sits in the water for long durations? Do any members have glassed bottoms and how have they faired?

Paul R

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MikeM
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Bottom

Post by MikeM » Thu Jun 01, 2006 6:22 pm

Don't go with glass....or you'll be doing it again (if you're lucky). Leaving the boat in the water full time isn't the best idea but either way 5200 is the way to go. We did a bottom over 15 years ago on a boat that never made it to the water (at least not yet) and that bottom is as tight as can be. The paint hasn't even cracked. Of course we have boats in the water too with tight 5200 bottoms, no leaking, minimal,if any movement. We also have a boat with a West bottom that almost sank and is totally rotten. My mind is made up and 5200 is the only way to go.
1929 Hacker Craft Dolphin, 24'
1940 Century Utility, 17'
1947 Chris Craft Special, 16'
1947 Chris Craft Sportsman, 22'
1949 Chris Craft Racing Runabout, 19'
1952 Penn Yan Cartopper, 12'
1954 Chris~Craft Racing Runabout, 19' (For Sale)
1971 Century Arabian, 19'
1973 Dan Arena Custom, 21'

Paul R
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Post by Paul R » Thu Jun 01, 2006 7:18 pm

Mike,thanks for the post. That is a strong testament, but I do know that the Sierra Boat Company does a lot of glass bottoms, and if they all rotted out they wouldn't be in business. There has to be a right and a wrong way I'm assuming. A number of the Danenberg methods of wood to wood bedding with 5200 could still be utillized for the plywood base, and all wood could still be coated with CPES before assembly. You may be right that the process of water entrapment will get to a glassed bottom, but I still will do a lot more reasearch first.

Paul R

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Bill Basler
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Post by Bill Basler » Thu Jun 01, 2006 10:11 pm

Paul, I am not necessarily a proponent of one system vs. another. I think both have their merits although most are siding with 5200 for various reasons. If you want my long, windy dissertation on epoxy, I'll give my thoughts then we'll really open the floodgates.

As for fiberglassing bottoms, I would have to agree that, generally speaking, it is not a good idea. Sierra Boat is a good example of a reputable restorer successfully using glass over wood on their restorations. You have to remember that in the Tahoe area, you are talking about a year-round climate that is incredibly dry...as in no humidity...ever. The problem with glass is that effectively eliminates moisture infiltration from the outside. But from the inside, as the wood takes on moisture in more humid climates, or from wet swim suits, beach towels, skis, the dog, rain, spray, etc, much of that moisture makes its way to the bilge, or inner planks. After months of this, year after year, the rot spores will grow and planks will become soft with rot. Once things get more advanced, the glass can lose its adhesion then you have a mess. Most boats that have been glassed will eventually rot from the inside out. Of course there are exceptions.
Bill Basler

Wilson Wright
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Post by Wilson Wright » Fri Jun 02, 2006 3:19 pm

As Bill Basler indicates there are reasons they can successfully use fiberglass at Lake Tahoe but few other areas seem to currently recognize it as an acceptable method.
Wilson Wright
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Post by Paul R » Fri Jun 02, 2006 7:55 pm

Bill and Wilson, thank you for the posts, and might I add that I am honored to have you weigh in on the subject. The two of you have a collective boat experience that far surpasses anything I could expect to achieve and Wilson, might I add that the Brass Bell is a superb piece of work----now on to the subject.

I do not know the method that Sierra Boat Company employs, but I am assuming that the planked bottom is stripped off and that a base plywood bottom is used for the fiber glass cloth and resin finish. As I mentioned yesterday, there is no reason that CPES can't be used on the plywood and frame, and 5200 used to bed the plywood to the frame. The resulting base would have greater adhession to the glass/epoxy finish and no matter what the humidity, marine plywood is quite stable. The determining factor is that I need an end result that can stay in the water without waterlog and wood movement concerns.

What types of bottoms do you have on your boats? Original, redone (5200), somthing else? How long do your boats stay in the water?

It will be at least 6 to 10 months before I begin this project, so I plan to find out as many of the pros and cons of both these systems.

Paul R

Wilson Wright
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Post by Wilson Wright » Fri Jun 02, 2006 8:51 pm

Paul:

Having said all that....I have a fiberglass bottom on my boat and it is original...But then you see the entire boat is fiberglass...My current one is a 1970 17 ft. Chris CRft Corsair ski boat...One the grand kids can hit the dock with and grandfather won't get all bent out of shape....and yet it is a classic Chris Craft...Best of both worlds for the present.
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ed laning
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5200 or FRP bottom

Post by ed laning » Sun Jun 04, 2006 7:11 am

Paul:

I vote for the 5200 bottom, just as most others. The fiberglassed bottom is Mahogany Murder. You made a comment that Danenberg recommends even with the 5200 all boats should be stored on a lift. I can't understand why he would say that other than CC boats have always been suggested to be stored on a lift or trailer so they don't incur weight-gain from water absorption, making them heavier and thus a lower top speed; period. Not because of the 5200. The 5200 acts as a rubber membrane between the inner layer and the outer layer. When the boat is left in the water for an extended time (like all summer) the outer planks still absorb water just like they did when the boat was brand new thirty, forty, fifty years ago. The membrane effectively prevents water from getting past it to the inner ply; and it follows the flexing of the boat as it charges through the waves and over boat wakes. What you end up with is a hull that is essentially identical construction to the factory bottom (that lasted a long long time) but with the advantages of a modern technology rubber membrane instead of the linseed soaked canvas that was between the bottom layers from the factory. That can't be said for a fiberglassed bottom. The fiberglass layer will work for a short while. The fiberglass layer is very brittle and is not nearly so flexible as the wood that it covers. As it bends and flexes with the wood it will fail to be strong enough and will develop very tiny hairline cracks that will allow water to enter, ever so little at first. It gradually collects more water because there is not enough surface area for ventilation to occur. Ventilation is key to preventing the growth of wood rot. Unless one were to build up the thickness of the fiberglass so thick that it is stronger than the flexible wood hull construction. Then it would not flex and develop fine cracks. But it would need to be so thick it would be a fiberglass boat bottom with a wood topsides and deck. Talk about heavy; I'd rather soak up a little water..............and know my boat is closer to traditional construction. BTW, I'm presently replacing some planks on the bottom of my Chris. I'm using the 5200 method. Also CPES.
Good luck with whatever you decide. My two cents. Ed

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Post by Wood Commander » Sun Jun 04, 2006 1:50 pm

Paul, here are a few more theories on fiberglass on wood boats. They will be worth every penny that you pay for them, at least!
Anyway, I have never seen fiberglass stay adhered to wood over a long period of time. It will usually slough off in large portions. I beleive that this is due to the two different expansion and deflection characteristics of the two different materials. And I also think that there can be a problem with the resin wicking into the wood to some degree and possibly "starving" the covering of all of it's needed material. Now mind you here I am talking about fibeglass cloth and resin over wood, on either planking or plywood panels. After a portion breaks away from the wood, water has a path in and usually can't escape causing a lot of problems.

Another situation that can be found is when people encapsulate a piece of wood, like say a frame member, in fiberglass resin. The failure here is a little different than the "sloughing" off of the previous example. Once again, a stress crack developes as the wood flexes or you have a screw hole opening or gouge that lets water in where it can't get out. And once again rot can grow wild from the inside out.

I am aware of one man who has successfully fibeglassed wood and other boats and has written a book about it. His name is Allen Vaitses and the book is called something like- "How to Fiberglass Wooden Boats' or something close to that. Unfortunately it is out of print, because it is a great book. In his book Mr. Vaitses describes his covering of large boat hulls and topsides with fiberglass and the critical use of mechanical fasteners through the semi- cured layers of fiberglass to stabilize the layers. And he explains the critical difference between using fiberglass cloth and fiberglass mat in the laminate. While cloth is stronger, ends of the cloth strands that get exposed by sanding or other means can wick moisture down through the entire coating causing failures in the laminate and trapped water problems.

Mr. Vaitses documents and tracks about ten of the boats that he has done over a period of time exceeding about five to seven years at the time of the book's printing that shows his methods holding up extremely well. He mainly used this method on larger boats of all types of construction including steel. Many of them were boats that were nearly ready to be scrapped. One example talked about a steel hulled sailboat that he could push his fist through an area of the bottom. His method stressed making the structure sound first and then fiberglassing. He also talked about how the extra weight of the fiberglass added to the boat was negated by the extra bouyancy area on the hull and the lack of water absorption into the wood, and in some cases the boat rode higher in the water. Mr. Vaitses in many ways was building a second fiberglass hull over the original boat. This method may not be quite as well suited to smaller boats that do a lot of riding on and are launched off of a trailer often. But if the laminate is thick enough, it should be OK. How thick that would have to be and how much it would affect the original look of the boat and it's bottom is unknown. He does discuss only fiberglassing the bottom and routing out a "releif" groove just above the water line to "tuck" the fiberglass into and keep water from above from running down and into the fiberglass- to- wood transition joint.


Bret
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1953 35' Commander "Adonis III"

1970 23' lancer project

Paul R
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Post by Paul R » Sun Jun 04, 2006 8:08 pm

Thank you Ed and Bret, I appreciate your time and thoughts. Bret, I will try to find a copy of Mr. vaitses's book -----possibly ebay. I should mention that I am no stranger to the properties of wood ----I make my living building custom cabinetry and furniture and I did graduate engineering school as a plastics major, though I never worked in the industry. I apprciate the idea of trying to maintain the soft ride that the original bottom produced and of course it is also important that the original look of the boat be maintained.

All of the posts have given me ideas on experiments in methodology to alleviate some of the problems that have been suggested. Bret, I had already decided on a routed tuck rabbit at the waterline for the glassing, but the sloughing problem has given me ideas on ways to achieve better adhesion and intergration of glass, resin, and plywood base. A few test systems are in order.

When it comes time to do this project, I will certainly let everyone know which method I've choosen and any discoveries I've made along the way.

Paul R

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Bill Basler
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Post by Bill Basler » Sun Jun 04, 2006 11:32 pm

Paul, this is an excellent thread on a pretty important issue relative to all who are on the fence as to how to restore their old boats. I will add a bit more to what Bret and Ed have said. First of all there is nothing that Bret or Ed have said that I disagree with. Both of them make good points and I agree with all that they say.

In you post a couple notches back you mentioned
I am assuming that the planked bottom is stripped off and that a base plywood bottom is used for the fiber glass cloth and resin finish.
If I am understanding your point correctly, I think we should all clarify "fiberglass" a bit. As a person with an engineering degree, you are likely familiar with modern Glass Reinforced Fiberglass (GRP) construction methods.

All manufacturers of modern day fiberglass boats have developed their own preferred way to build up the hulls of their boats with a process that most refer to as a lamination "schedule". This schedule is nothing more than a recipe...or a series of steps and materials that give their boats the desired strength, weight, etc. A lamination schedule defines what type of gel coat, (how thick, what type), followed by what type of fiberglass material to eliminate print-through, followed by what other types and weaves of glass fabric to provide strength in various directions under various loads, etc. The finished hull is often made up of dozens of layers of cloth, including some exotics like kevlar or carbon fiber. Most modern hulls are even cored with things like end-grain balsa, core-mat and so forth. This "schedule" provides the very structure of the fiberglass boat, the only exception being stringers and longitudinal members for additional structure. This is a much different meaning of the word "fiberglass" than the fiberglass Sierra is applying.

While the actual materials are the same, the fiberglass applied by Sierra is a single layer (I think) of lighter weight cloth, applied to the outside of a wooden boat that is built by traditional wood construction methods. In other words, the glass acts as an outer water proofing skin...it is not meant to be structural. One layer of glass cloth is too thin to be considered structural, so the boat still needs to rely on its original construction to maintain its shape. As far as I know, (I could be wrong) the outer planking of these fiberglass bottomed boats is still there. In fact with the outer planking removed, you are really talking about a very different boat structurally. If you wanted to remove the outer planks of a vintage boat, you would most certainly need to engineer and apply a muti-layer fiberglass laminated botom in order to achieve something with structural integrity. On the "Sierra" method, a thin fiberglass overlay is saturated with vinylester or epoxy resin, and is feathered at the waterline to the original planking. Again, this creates a water proof outer skin, but it is negligably structural.
Bill Basler

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Post by Paul R » Mon Jun 05, 2006 8:09 pm

Bill,You make a very good point about the structural difference between a true GRP boat, a traditional wooden runabout, and the waterproof membrane that Sierra Boat company applies to their customers wooden hulls. I have emailed the service dept. of Sierra and inquired about their method of glassing-----I have yet to hear back. As you mentioned before, solid lumber,(mahogany), will move throughout the seasons and work against the bond of a resin/glass overlay, so I really doubt that Sierra Boat is glassing over the original solid mahogany bottoms.

A boat refinisher/restorer on my Lake in Massachusetts, remade a Century Resorter into a rear cockpit racer. He used two layers of 1/4 inch ply covered with two layers of glass cloth and epoxy resin. He also coated the interior with the epoxy resin. The Bottom is 5 yrs. old and in perfect condition, but he only uses the boat occasionally and it does not stay in the water for weeks on end.

My concept at the moment is to use a combination of 1/8 and 3/8 ply with the 1/8 being bedded with 5200 to the frame and the 3/8 being cut and applied with 5200 and screws in a similar fashion to mahogany planks with up to a 1/2 inch space between these planks for glass stringers to be laid into. The outer surface of the 3/8 ply would also be kerfed in a cross hatched pattern up to 1/8 inch deep to facilitate a more aggressive mechanical bond with the final two layers of glass and resin. Before applying the plywood. it would be treated with CPES as would the frame members of the boat. I plan on doing some mockup testing with different resin and glass combinations to come up with the best end product for the application.

I really appreciate everyone's input on this subject, it has given me a lot to think about. Don Danenberg's book was also an eye opener, and if I had the luxury of being able to use a lift in my docking situation, I wouldn't think twice about the subject, I would just do a 5200 bottom, but since I can't use a lift,I want to explore all the possibilities for this bottom replacement.

Paul R

ed laning
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Post by ed laning » Mon Jun 05, 2006 9:06 pm

Hi Paul,

Good that you are eager to research all aspects. I don't follow as to why you think the boat must be kept on a lift. I always viewed that as a nice little option if an owner was so inclined. I just don't see it as being important. I see lots of wood runabouts tied to the dock, floating, for the whole summer; and I can't imagine the weight of absorbed water in an 18 footer exceeds maybe a hundred pounds. Probably more like 50. Someone please correct me if I'm wrong.

Ed

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Post by Paul R » Wed Jun 07, 2006 8:23 am

Ed, the original owners manual supplied with a new Chris Craft suggests that the boat be kept raised out of the water for maximum performance and to prevent the wood from becoming water-logged. It also states that after the boat has been in the water for a few weeks, considerble water will be absorbed into the hull, that will increase the weight of the boat as much as 10 per cent of its total weight. The greater problem as described by Don Danenberg is compression set of the planks. This is where the wood fibers get crushed as a result of the excess expansion of plank against plank, resulting in loss of resiliancey!

The manual does state that the raising of the boat is not essential, but will be benificial. Another thing to consider though is that back then Chris Craft and other boat companies expexted these boats to last maybe a dozen years and the bottoms to last maybe six years.

Paul R

ed laning
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18' CC weight, etc.

Post by ed laning » Wed Jun 07, 2006 10:35 pm

Paul, So how much does a 18' CC weigh? 2000 lb? I expect the 10% figure is a little overstated but even if it is accurate that's still only 200 lbs. A little closer to the weight of my beer-bellied chum from high school than to my anorexic 13 year old niece. Still not that much effect on performance. And the 200 lbs assumes they expect the engine and marine gear will also absorb 10% weight. I bet the real number is more like 5%. I wonder how much the GRP bottom would weigh. Sure I've heard of wood compression. From what I have seen, on a properly built bottom it takes sooooooooo many years to occur that this is a non-issue. Especially compared to the grief that comes from covering a wood bottom with GRP. That the manual states raising the boat is beneficial but not essential fits with my interpretation. As for their boats only living (12) years and the bottoms only (6) years we all know that is out of whack as evidenced by the large number of boats that have been run 30 or 40 years. Mine is on year number 43 and going strong. Some of these boats are overdue for bottom replacement but many are nicely serving their owners on a regular basis. It depends how well they have been cared for. I'm of the opinion that Chris Craft was in the business of selling new boats, and they had a marketing dept. The point I'm trying to make is that a traditional construction wood bottom has been documented to last decades. With the new technology of CPES and 5200 it just gets better. There are far too many horror stories about wood boats slathered with GRP that seem to be doing great after about five years only to suddenly reveal a huge surprise that has been lurking beneath the surface. It's good that you have education in plastics and GRP. I too have some knowledge of the subject having spent 22 years in the industry, most recently as General Manager of a small firm solely devoted to molding GRP. Maybe that's why I like wood.
After going back and proof reading this it sounds a little strong. Sometimes email comes across that way. I don't intend for this to sound so terse, just trying to make a point. Anyway, wood boats are fascinating, whether it be the complexity of the wood construction assembled by master craftsmen or the sheer beauty of the designs. As I said before, good luck with your research. Please keep us in the loop on what you learn and whatever you decide I hope it works out well.
1978 22' CC Dory outboard

Paul R
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Post by Paul R » Thu Jun 08, 2006 7:08 am

Ed, I appreciate your points and I didn't take the tone as terse. I agree that there are probably a lot of GRP horror stories and I certainly want to avoid being one of them. I am just at the beginning of the process and will want to do some mockups and testing of both a 5200 bottom section, and my ideas of a GRP laminated bottom sectionl. The results will be know to all ----good, bad or indifferent.

Again, thanks to everyone for so much input.

Paul R

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E-J Ohler
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Post by E-J Ohler » Wed Jun 21, 2006 9:52 am

Paul, I just read the thread of this topic and like to ask you how your tests went.
As in the beginning you stated you would not start for another 6 to 9 months that was last year.
Where are you now as you were convinced to go the fiberglass route even with the majority of responses advising against it.
I agree have a good battery and automatic bilge pump and leave her in.
My wooden boats never leaked water in that the bilge pumps could not take care of once a week, although they are/were lap-strake and plywood type CCs
All CCs were built to keep water out but because we don't usually know the specific history of storage the wood might have seen very different moisture contents which is the killer, to dry is not good.
As Ed said the little absorption would not influence the performance.
You could go the original way (linseed cloth) and boat another 40 years, especially if you store it 60-75% humid environment.
let us know about the tests and good luck.

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