Another Hull Deck Joint Project

[Triton106]

Sorry to bring up another tired old subject but I need help.

Triton 106 is a west coast boat and it has an out turned flange for hull deck joint (see drawing below - apologies for the rough drawing, but I don't know how to use a CAD software). I haulled my boat out in a local boat yard (Svendsens) yesterday and could not wait to tear off the old rubbing strake this morning. It only took a few minutes to tear it off but cleaning up the mess under it took me couple hours with a grinder.

To my surprise the joint condition is not bad. There is only one section (about 10 inches long) with loose resins (I assume that is what Aero Marine used as the joint compound). My questions are two fold:

1) Is the joint strong enough with only internal fiberglass tabbing to hold it together? I don't know how many layers of glass Aero Marine used but would guess two or three layers but they appear to be in good condition.

2) Would you replace the old rubbing strake with the same rubber one (it is still available at a local manufacturer in California - see NTA website) or would you replace it with one milled from teak?

My own instinct that the joint is not strong enough for my intended offshore ventures (yeah, sure :-) - but one has to have dreams) and some kind of mechnical (machine screw and nut) or chemical (external fiberglass tabbing) bonding externally will be needed to strengthen it. Since the joint is externally flanged mechnical means will be easier, especially in the midsection since the bottom flange has enough space to accommodate nuts. However, the screw heads (if pan head screws are used) and nuts will certained interfere with my idea of a teak rubbing strake.

I read Hal Roth extensively modified Whisper's hull to deck joint. My understanding of his writing (it's hard to tell since he did not provide any pictures or drawings) is that he completely ground off the flange and laid 4 layers of glass tapes (1", 2", 4", and 6"). That's a little more than what I have time for.

Your thoughts and experiences will be much appreciated, but I need them soon as I plan to finish the bottom job and fix the joint within this week (I know it will never happen but I like to set ambious - unrealistic - goals).



Thanks and best regards,

[Tim]

I can't speak to whether your particular tabbing is sufficient, but in general terms tabbing is certainly a sufficient way to secure a hull-deck joint. Rhode Island-built Tritons, for example, have a flush hull-deck joint that is tabbed from the inside with no other means of fastening.

Mr. Roth's misadventures with his hull-deck joint resulted from years of sailing with a leaky original joint, which was different from yours. Glassing entirely over the joint from outside is, ultimately, a fine way to address a nagging problem, but not necessarily indicated in all situations. There's no doubt such a task would result in a strong, watertight joint, but doing it correctly would take much prep, a lot of time, and a lot of finish work to hide properly. Do it if you feel the need, but don't approach the job in a hurry or only halfway.

To determine the integrity of your joint, inspect all the tabbing in all areas. Ensure that it's well secured to both hull and deck. Loose material between the flanges is quite likely irrelevant to the overall integrity of the joint, but that doesn't mean it's all hunky-dory either. Lacking any particular signs of flexing or related issues, though, it's likely that your joint is generally sound and of sufficient strength. Look for evidence of leaks, which always manifest themselves as streaked, discolored areas on the hull beneath.

If possible, I'd avoid the idea of mechanical fasteners and concentrate instead on the internal means of securing your hull-deck joint. If you feel a need to strengthen it for your own piece of mind, whether or not it's strictly called for, then you have to strengthen it. There is no easy litmus test to determine the integrity of the joint for you intended passage.

As to whether to use teak or not: well, use teak if you want to use teak. Don't use teak if you don't want the maintenance that goes along with it. Teak or other wood would look dressier than a generic rubber rail for sure, but don't dive into the change unless you're sure.

I think you have time to carefully consider what you might like to do to possibly address your hull-deck joint. If you're really going on this trip in the future, this will not be your last haulout, nor is this your only chance to attempt reinforcements. I'd suggest you keep sailing the boat and monitor more closely, as you desire, your hull-deck joint to see about leakage or flexing or signs of other potential issues before you jump ahead with any serious work. Later, if you feel the need, you can schedule the work properly to allow the requisite time for this and perhaps other more major preparatory projects.

[Rachel]

On the subject of the rails, have you read Ray Alsup's web page wherein he describes replacing his original rails with a Trex-like product? ("Nexwood" in his case.)

Even if you ultimately decide to use some other material -- or a completely different repair -- you'd probably find his page useful, since his boat is a West-coast Triton (#256), and he describes the original joint along with his repair process. He had leaks from the joint, and - at least in his case - apparently the inside tabbing was left off in certain areas because of the liner.

On other sections of his site he works on water tanks, and various other projects.

Here's the link:

http://www.geocities.com/pegasus256/rubrails.html

A couple of photos:

[Triton106]

Tim, Rachel,

Thank you again for rescuing me from yet another potential mistake. Careful evaluation, planning, and being thorough are definitely not my strengths.

What a day I had today. Bottom sanding is one job about the boat I don't care for. It's wet, cold, and filthy paint residue mixed with water fly every where. There is got to be a better way to protect the bottom. If they can invent hybrid cars they can invent bottom paint that will last five to ten years. But I digress...

Back to the issue of hual deck joint. I decided to heed Tim's advice and focus on internal tabbing. As Tim suggested I will carefully evalute over the next season if I have leaks (which it does not seem to be case) and if the joint is strong enough. For now I plan to clean up as much as possible the exterior of the joint and refill areas where the fillings are loose. As for what material to use I ruled out rubber and Nexwood that Pegasus used. West coast Tritons have hardly any wood in the exterior. I decided a little teak strake will dress it up a little.

I did write to Ray Alsup about the Nexwood material he used. He seems to be happy with it. He thinks it will outlast any real wood. However, the traditionalist in me just cannot accept it. I know more and more wood substitutes are being used for everything from teak decks to teak and holy soles. Maybe one day I will change my view.

Thanks again. It's so great to be a Triton owner. I am wondering how much more trial and error I would have to endure if I bought a Catalina. There, I said the "C" word...

Best regards,

[Tim]

...they can invent bottom paint that will last five to ten years.

In a way, they have: ablative paints. These work as long as paint remains on the bottom, so the effectiveness and longevity is directly related to how many coats one applies.

And they don't need sanding because they wear away.

[Triton106]

While I had Blossom on the hard last few weeks (it's back in the water now) I took care a number of deferred projects, including painting the hull, replacing the through-hulls in the head with proper seacocks, partially glassing in the leaky bronze rudder tube, and painting the bottom. I also ripped out the old rub rail. the hull deck joint underneath is not as in a bad condition as I feared. I plan to clean out and fill out a few sections where the fillings are cracked and fell out. After which I plan to cover it with milled wood rub rails.

I purchased a stock of 2"x7"x12' Philippine mahogany and ripped it into 7 pieces of 2"x1"x12' rails. I now need to cut a 1/2"x5/8" dado groove in the middle to fit over the outwardly turned hull deck joint (see below for diagram). I did not choose teak because of cost and also I found that Tim and several other east coast Triton owners used Philippine mhogany for toe rails. Anyway, I read different techniques and jigs people have come up with to make dado cuts using either router or table saw. Unfortunately none of these techniques seem ideally suited for the long (12' for each section), thin, and floppy rails I have to deal with. I would appreciate if someone on the forum has this experience or knowledge that can share with me.



Thanks and best regards,

[Tim]

...I found that Tim and several other east coast Triton owners used Philippine mahogany...

No, I use only Honduras mahogany, which is markedly different from Philippine.

Mahogany works well for exterior wood as long as you keep it properly varnished or otherwise finished. It won't hold up very well if left to weather.

...ripped it into 7 pieces of 2"x1"x12' rails. I now need to cut a 1/2"x5/8" dado groove in the middle...I read different techniques and jigs people have come up with to make dado cuts using either router or table saw. Unfortunately none of these techniques seem ideally suited for the long (12' for each section), thin, and floppy rails I have to deal with.

It's a little late now, since the horse has already left the barn, but it's often easiest to rout or mill your dados in the larger, uncut board (at appropriate intervals), then cut the narrower strips after the dadoing is complete. Running thin strips over a dado cutter in a table saw can be unnecessarily dangerous and difficult; likewise with a router.

However, it sounds like your boards are still wide enough for a stable base for cutting these grooves. You're still going to need the dado head or a router, though. You could mill them in a router table, which provides better stability and safety than freehanding the router, depending on your setup and your experience.

For safety and accuracy, use featherboards on a tablesaw to hold the pieces tightly in position against the fence and table, or use appropriate jigs for your router or router table as applicable.

The golden rule of all mechanical milling operations is this: if it looks unsafe, it probably is.

[bcooke]

If you run out of options you could probably get a local cabinet maker to do it for you. I have a local company with some pretty fancy cutting equipment that can do things no ordinary table saw or router can do. For the amount you are talking about it wouldn't break the bank.

[Triton106]

Tim wrote:

Triton106 wrote:
...I found that Tim and several other east coast Triton owners used Philippine mahogany...

No, I use only Honduras mahogany, which is markedly different from Philippine.

Tim, I am only off by one continent. How different could it be :-)? Sorry my bad... Should have read the postings more carefully.

Tim wrote:

It's a little late now, since the horse has already left the barn, but it's often easiest to rout or mill your dados in the larger, uncut board (at appropriate intervals), then cut the narrower strips after the dadoing is complete. Running thin strips over a dado cutter in a table saw can be unnecessarily dangerous and difficult; likewise with a router.

Thanks for the tip, Tim. But I would not be able to use that in this case since the raw stock is 2"x7" and I ripped it into 2"x1". The dado cuts will be made along the 2" side. Anyway, I will file the idea though for future use (I am sure I will forget it).

Britton wrote:

If you run out of options you could probably get a local cabinet maker to do it for you.

Anyway, my questions for the local lumber yard (MacBeath) probably gave away my complete ignorance with woodwork. When I left they gave me a list of local cabinet makers and said "call them if you find yourself in over your head with the project". He asked "what do you do for living?" I said "finance, what's that got to do with anything?" He said "just asking..."

[Capn_Tom]

With the use of the feather boards as Tim suggested and properly supporting the work piece on both sides of the table there shouldn't be any problem dadoing a piece that long. Assuming of course you have 25 feet of work space.

[Triton 185]

Using feather boards is a good idea for safety and to increase the accuracy of your machining. They will only work well if all of your stock is of the same thickness and width. As well, you don't have to remove all of the material in one pass - you can raise the blade over several passes while leaving the fence in the same location.

[Zach]

The golden rule of all mechanical milling operations is this: if it looks unsafe, it probably is.

Excellent rule!

[Triton106]

Tim's featherboard idea is excellent. I did not know what featherboard is until I read the following article - http://www.woodzone.com/images/tips/twofeathers.jpg

Here is a picture of what the author recommended - essentially two featherboards working together to keep the 1"x2" stock mahogany in place. I am planning to do exactly that, except I am not sure how to hold the top featherboard in place. Any ideas?

[Tim]

I am not sure how to hold the top featherboard in place. Any ideas?

Sometimes you have to build a temporary vertical fence extension (i.e. screw or otherwise fasten a tall board to the fence) to hold clamps, or some sort of jig for the same purpose. It often takes longer to set up the saw than to actually run the pieces, but it's worth the effort for important or difficult cuts in particular.

I don't often use a featherboard to hold the work down, as I find that my stock pushers (the proper term for these is eluding me right now, but I use and very much like the Saw Aid) typically work well for this, but I often use horizontal featherboards to hold the stock tightly against the fence. I have a couple magnetic ones for the table that work very well and are easy to set up and use, and are more convenient than a system requiring clamps. In the end, they all serve the same purpose, though.

[Triton106]

Tim wrote:

Sometimes you have to build a temporary vertical fence extension (i.e. screw or otherwise fasten a tall board to the fence) to hold clamps, or some sort of jig for the same purpose. It often takes longer to set up the saw than to actually run the pieces, but it's worth the effort for important or difficult cuts in particular.

That's a great idea. I envision it will look like something the below diagram (sorry for the rough drawing, I hope I convey the idea clearly).



I ordered a set of Mibro (http://www.mibro.com)dado blade from Amazon for under $40. They received pretty decent reviews from amature woodworkers on Amazon. Not sure if it is any good.

[Triton106]

Hi All,

I am pleased to report that using two featherboards (horizontal and vertical) and Mibro dado blades to make the dado groove was fairly straight forward. I did not have a long workspace. So I asked for my daughter's help to hold up the long end of the stock (she had to switch side halfway through each pass). The cuts turned out pretty well (smooth and close enough to my specification - 5/8"x1/2"). The only unanticipated complication was that I had to make two passes to cut the 5/8"x1/2" dado groove for each piece of 12'x1"x2" stock (times 6 stocks). The reason is that my Ryobi table saw arbor was not long enough to permit a 5/8" dado setup. I ended up take two passes with a 3/8" dado setup with some overlap.

The next step will involve rounding off the outside corners of the stocks (see diagram below) with a router. I am not nearly as artistic as Tim so there will not be four profiles to select from. (see Bolero project) It will be just a straight 1/4" or 1/2" round off.



Following that I will sand smooth the three outside edges with 120 paper before scarfing the 12' sections of stocks together to make two approximately 30 something feet sections. I have never scarf two sections of wood and as much as I have read about them I am not sure the proper way to do it. I suppose the scarf should be approximately 12:1 (see quote below).

Quote from Messing-about.com:

Scarf joints are often used in boat building, and they provide an easy solution to the rub rail problem. A scarf joint is a long angled joint. The long angle provides a lot of "glue surface" for the joint, making it very strong. For a 1 x 2 intended to be bent around a hull, a 1 to 12 scarf joint is ideal ... meaning that for every inch of thickness, you need 12" of length. In the illustration below, we would be looking at the 1" edge of the rub rail stock in a top view, so "X" would equal 1" (well, probably a little less, since most 1" stock is really about 3/4" thick). The "7 to 12 X" gives the recommended range of scarf joint lengths ... from 7 to 12 times the thickness of the wood. For joints where there is stress ... like bending around a hull ... its better to use 12x's the thickness of the wood.


From The Sailor's Sketchbook, by Bruce Bingham

Looking at that joint, you realize something right away. You lose 12" of length off each piece because they overlap. So for our rub rails, which have to end up at 16', you can't use two 8' 1 x 2. You could use one 8' and one 10' 1 x 2 ... butted end to end they would be 18', of course, but after the angle cut and overlapping them to make the scarf joint, you end up with 17' long rub rails. A little long is better than too short!

I am not sure if a straight scarf (as pictured above) is better than a half-lap scarf (where the scarf does not taper to a sharp point). I am also not sure how to execute the cut so that the scarfed section will be seamless. Any ideas or tips will be much appreciated.

[Tim]

I think a scarf joint with a shoulder is better since you don't end up with that extremely thin end, which is virtually impossible and quite impractical to make and work with successfully. Having a 1/4" shoulder (for example) avoids this.

Scarfing is all about careful hand work, or carefully-made jigs for routers or saws, as applicable. I don't do many "real" scarf joints and feel my way along each individual time whenever I do, so I don't have any instant tips. You make them the way you need to make them, in the end.

For what you're doing, you might consider keeping it simple and joining the rubrail pieces together in place with a simple angled joint. I don't see any great advantage in your situation to making the rubrail in a single glued-up piece. You may get better accuracy and easier installation if you plan on butting the pieces together with a 45° miter joint (similar to that seen in the photos above showing the plastic rail being installed).

[bcooke]

I concur on the shoulder.

The only tip I have I got from another boatbuilder.

According to him it is really quite simple. You make the angle and shoulder on one piece by hand and then you simply lay the two pieces alongside and trace the shape of the cut piece onto the second piece. Cut to the traced line and you will have a perfect joint. Or so I am told...

[Hirilondë]

If there will be much bending in getting the rubrail on in its entire length then an 8:1 or better straight scarf is the probably the best choice as it is the strongest. Shouldered scarfs like Tim describes look nicer, but aren't nearly as strong and may break when put under strain. What happens is that the shouldered portion of the joint cracks first, then the whole thing lets go or breaks. I find them harder to make myself, but everyone is different. Fitting the pieces to each other in place on a curve will not come out nearly as fair as creating the entire length, then bending it into place.

If it were my project, I would mill all of the pieces separately first. I would then scarf them into 2 lengths slightly greater than needed with an 8:1 straight scarf. Then apply them as one continuous length to the boat in a dry fit. Next I would pre-varnish them with a couple of coats, including the back and channel. Then lastly bed and fasten them on for the final time and varnish until satisfied.

[heartofgold]

I really must concur with Hirilondë. When I used to be a boat whore, I used this exact technique on a several boats. Pre-scarfing the joints does make an unweildly (is that a word?) piece, especially on longer boats, but really makes it easier to get that "perfect" joint around the bend of the hull.

On the other hand, I like Tim's process when doing a repair to a damaged rail, which, of course does not apply here, but is good to know.

[bcooke]

When I used to be a boat w***e

What are you now?...

[Tim]

I agree about pre-scarfing and gluing the pieces in a typical toerail installation (though I hadn't thought of the issue with the shoulder during bending--good to know), but my point in this case was that sometimes, depending on the situation, this may not be necessary.

With Ray's external rubrail, I thought there might be a good chance that it could successfully be scarfed in place with a simple miter cut without sacrificing fairness or appearance, saving a bit of work and avoiding those long, unwieldy pieces. It depends on where the breaks in the pieces fall, what the curvature is at that area and adjacent, and other considerations that depend on the circumstances at hand.

If the overall strength or appearance is compromised by in situ installation, then I'd certainly suggest pre-gluing the scarfs to make one continuous length.

[heartofgold]

What are you now?...

Well I am still a slave to my own boat, but I no longer prostitute myself out to work on OPBs (other people's boats). My secret identity by day is a computer programmer--but shhhhhhh--don't tell anyone.

[Triton106]

Thanks everyone for your help. On the decision to scarf in-situ with an angle joint or pre-scarf with a straight 12:1 scarf I need further help. Please see below a modified Triton layout (the only layout drawing I can find but ignore the modification I have been toying). The sections I am scarfing together are 3 sections of 12' of 1"x2" Philippine mahogany. The total length will be approximately 34' to 36' long depending on the type of joint I choose vs. Triton's LOD of 28.5'. Given these parameters is it better to do 45 degree angle joint or 12:1 straight scarf?

[Tim]

Better (i.e. most fair): always the pre-scarfed, full-length piece.

Most practical for your situation: full-length if you can build and handle the piece effectively. Otherwise, go the other route.

[Triton106]

Thanks Tim. I plan to attemp to pre-scarf the sections for the learning experience if nothing else. If plan A should fail, I will go with the back-up plan of scarfing in-situ.

[Triton106]

Hi All,

A quick progress (actually very slow) update and then I have another question.

Update: the scarves are done. 7:1 straight scarf is the best I could do given my limited tool and work space. Nontheless they are done and appears to be strong enough for the application. I have sanded down the two completed sections and applied one coat of Cetol (I wish I had the time to apply 8 coats of real varnish) for now. I plan to put on two more coats.

Questions, given the outwardly flanged hull-deck joint of west coast Tritons I can only envision that the rubrail would have to be glued on instead of mechanically fastened (if screwed on, the screw heads will most likely split the upper and lower lips). So my question is what is the best material for bonding the mahogny rubrail to the flange. Epoxy would seem to be able to creat a strong bond between wood and fiberglasss but I am concerned that it is not flexible enough. Adhesive sealants such as 3M 5200 or Sikaflex 292 are flexible but I am not sure they are as good adhesive as epoxy. My choices are (so far):

1. System 3 Gelmagic epoxy
2. 3M 5200
3. Sikaflex 292

Any informed opinion and experience would be much appreciated. If you have used othe products I should consider please do share.

Thanks and best regads,

[Hirilondë]

Either #2 or #3 will work, 4200 or Sikaflex 291 might be enough as well. Two concerns/questions I see with a bedding adhesive only are:

1. What are the fore and aft end details?
2. How will you secure them while the adhesive cures?

OK, three questions:

3. How were the originals secured?

It can be done without mechanical fasteners, but I envision a tedious process of clamping and/or bracing.

[Triton106]

Hi Dave,

Thank you for your input. The fore and aft details are quite simple (I assuming you are asking about the attachment points near the bow and transom). While I don't have a picture to show you I am attaching a picture of another west coast Triton Pegasus. The forward end ends with the stemhead fitting as it shows in the picture. The transom ends at near 90 degree angle with the rubrail on hull deck joint on transom.



I imagine the clamping and bracing will be tedious as you suggested. As you can see even though Ray Alsup, the owner of Pegasus, used broad head screws to hold the rail on he still ended up using numerous clamps along the rail while it cured.

The original rubrail is rubber and it was just glued on. It only took a easy pull to rip it off the boat. The only part that refused to come off is the part I reglued with 5200 a couple of years ago because that section was falling off.

Is there any reason you picked 5200 and Sikaflex 292 and not GelMagic? What do think of West System G/Flex?

[Hirilondë]

I hadn't imagined you could actually clamp to the toe rail as shown in the picture. If you can do this as shown it will make all the difference. The hardest part of securing a toe rail are the 2 ends. I couldn't see doing it on your rub rail without mechanical fasteners as well as adhesive, but it appears you may be able to.

If you can cut/shape the forward end to meet your stem head fitting and leave it long aft for a dry fit and clamping you will get a feel for the process you will be encountering. This will also make the aft end fitting and shaping more accurate. With a toe rail the loads at the ends are quite high as the result of bending. I have found no good way to simply clamp (there is nothing to clamp to). But this may work for your rub rail. Only a dry run will show for sure if this is so.

Once you have actually gone through a successful dry fit, and worked out the detail of the joint to the transom piece, you will be ready to bond it. I have never used G/Flex. It surely seems strong enough having read through the specs. The added flexibility makes it seem like a good choice for this application. The trouble with epoxies for complicated time consuming process like yours is that it drools and has a relatively short working time. I can see you wearing a lot of it by the time you get the piece properly aligned and clamped. I can see a lot of it on your topsides as well. And if it has started to cure before you can clean up you will have a real mess. I have never used Gel Magic either, its working time is even less, though it supposedly won't run/drool. I have yet to use 292 for such a project as this. But I do like its consistency better than 5200. It has more body, and stays put without drooling better. 5200 fast cure isn't quite as strong as regular 5200, but has a better consistency. But again, time is of concern here.

Try a dry fit. If you can get the whole rub rail in place, and both ends cut/shaped to fit doing so then you are well on your way. Doing so will also help you determine how much time the application will take. This will affect your choice of adhesive. Keep in mind you will have a good bit of cleaning of the ooze out to do after clamping. The rub rail may need some scraping or sanding to finish cleaning it after cure, but your hull had better be really cleaned well before cure.

I can see a wooden rub rail looking really good. This project will be tedious, but the pay off should prove worthy.

[Tim]

For installing something like a rubrail, sometimes open working time with the adhesive is key. Epoxy products are great for a lot of things, but epoxy has a short pot life that greatly complicates installations like yours, unless you have 10 people ready to work with you; this is one benefit to using adhesive sealants (5200, Sikaflex 291-292) instead of epoxy: the open time is long, making them more user-friendly for something like a long rubrail installation. You have to work fast with epoxy, so you need more people (or else have to be really fast and good on your own), and have less room for errors or repositioning. And haste makes waste.

If you can successfully and easily clamp your rail for the period of time required for the polyurethane adhesive sealants to cure properly, then these would be the right choice for your installation. 5200 is tried and true, and effective, but its full cure takes days, so you will need to leave the clamps on accordingly. As Dave mentioned, it tends to drool more than some other adhesive sealants, which may or may not be an issue. The appropriate Sika product would work well also. Use what you know, and what you're comfortable with.