Monday, April 23, 2018

LNVT Felt Window Channel Replacement

Replacing the felt window channel has been a long standing problem because there's nothing commercially available which easily accommodates an LNVT's 10mm thick glass.

10mm Safety Glass

The solution described here uses off-the-shelf, 3/8", PVC channel but modifies it to suit our 10mm glass.  The repair process is straight forward: remove each windows' outer and inner retainers and their glass panes; install the new, PVC window channel and; reassemble each window.  Naturally, the devil is in the details so, here are the details.

To better understand the repair it's helpful to know how the windows are made.

This diagram is a cross section of a starboard side window, looking towards the bow.  The windows are made of three pieces of stainless steel: (1) the window frame; (2) the inner, or sliding pane retainer and; (3) the outer, or fixed pane retainer.

The felt window channel, which we'll be replacing, fits inside the inner pane retainer.

Above, the inner and outer glass panes are shown in their respective retainers.

Eight screws hold each retainer in place: 2 along the bottom; two along each side and; two along the top.

Now that we know how the windows are made, let's get busy repairing the channel.

Step 1: Modifying The New Channel

From Trim-Lok Catalog 700, Page 4.

The above illustration shows how the channel is made.
From Trim-Lok Catalog 700, page 7.

Trim-Lok's 1375-3/8 is the replacement channel we'll be using.  It comes in rolls of 250'. You'll need one 8' piece for each window.  For hull numbers 1 through 29 there are 11 windows: 7 in the saloon/galley and 4 in the wheelhouse.  For hulls 30 through 76 there are 9 windows: 7 in the saloon/galley and 2 in the wheelhouse.

Before and After Removing the Gripping Tongue.

Modifying the new channel is a two step process. First, using a razor knife, shave off what Trim-Lok calls the gripping tongue. Don't cut too deeply as the metal underneath the PVC will be exposed. While cutting too deeply adversely affects appearance it doesn't affect performance.

Tools of the Trade: 1375-3/8 Channel, Restrike Die, Punches, Rubber Mallet, Razor Blades and Epoxy.

Next up, we need to enlarge the width of the channel. To do this a restrike die and some punches need to be made.

Using the Punch and Restrike Die.

Restrike Die, 1375-3/8 Channel and a Punch.

It's called a restrike die because while Trim-Lok already formed the PVC into a u-channel shape, we're going to restrike it to make it a little wider.  The restrike die is made of three, roughly 2' long, 3/4" thick pieces of hardwood.

U-Channel Restrike Die Dimensions.

The two 2-1/2" wide boards need to be securely attached to the 5-1/2" wide base board because they'll take a big side load when the channel is expanded.   I recommend using both glue and screws/nails to hold them to the base board.

U-Channel Punch Width.

I made several punches, each just a hair thicker than its predecessor.  When restriking the channel it's easier to approach the desired width in several iterations rather than in one fell swoop.

Please note that the dimensions shown above worked for me.  Your dimensions might be different.  The overarching goal when modifying the channel is that the final product fit snuggly into the stainless retainer.  Doing this guarantees that the glass will slide easily in the new channel.

Step 2: Remove the Glass and the Retainers

Tom Blackwood, Thistle Dew 37VT46, Cleaning the Window Frame.

The picture above shows the window frame after both the inner and outer retainers, and their glass panes, have been removed.

Outer Retainer and its Glass Pane. Note the Two Screw Holes.

Inner Retainer and its Glass Pane. Note the Two Screw Holes and the Two Square Drain holes.

After the retainers' screws are removed the retainers can be pushed out using small pry bars or tapped out with a wood block and hammer.  Be careful not to bend or kink the retainers.  Finally, give the retainers and window frame a good cleaning.

Step 3: Install the New Channel

Dave Howell, Nellie D 37VT63, Works the New Channel Into Its Retainer.

The first order of business is to dry fit the channel into the retainer.

Heat Helps Relax the Channel.

Really pay attention to getting the entire channel firmly pressed against the retainer as the success of this project depends on it.   A little heat helps, especially in the corners, to get the channel seated solidly.  In the upper left in the picture above you can see that the break in the channel aligns with the break in the retainer. 

Next, the inner retainer and the channel (without the window pane) are temporarily placed into the window frame.

A Punch with a Radiused End Helps Assure the Channel is Tight Against the Retainer.

Next, the channel will be cut to length. Before doing so however, make certain the channel is bedded solidly against the retainer.

Time to Trim the Channel to Length.

An 8' length of channel will be about 4" too long.  Cut the channel leaving a 1/4" overlap. Then, press the channel's two butt ends together and push them into the retainer.

Cutting Channel Drains which are Aligned Over the Retainer's Drains.

The new channel needs two drains cut into it otherwise rainwater will collect within the channel.

Cutting Drains Reveals the Channel's Aluminum Skeleton.

Cut the channel's drains so that they're the same size and directly over the retainer's two drains.

Removing Staples.

Using a pair of needlenose pliers remove the exposed staples.  I recommend removing only three staples as removing more overly weakens the channel.

The next few steps will take place on the workbench so remove the channel and the retainer from the window frame.

Liberal Use of Tape Holds the Channel Tightly Against the Retainer.

Glue the entire length of the channel to the retainer with a thin bead of polyurethane caulk.  I used Loctite PL but 3M's 4200/5200 or anything similar will work just fine.  The glue prevents the channel from moving or sagging when the window is opened or closed.  As the picture above shows, tape is used to hold the channel securely against the retainer while the glue sets.

After the glue has set, and using the eight retainer-to-window frame mounting holes as guides, drill holes through the channel.

Step 4: Reassembly

Put the glass pane into the channel/retainer and the channel/retainer into the window frame.  Install the eight screws which hold the retainer to the window frame--don't forget to put a sealant on the screws' threads.

Silicone--a Lesson Learned--if Expired it's Runny and May Not Harden.

The last step is to reinstall the outer retainer and its pane of glass.  This is the fixed pane, i.e. the one that doesn't slide.  As such, it doesn't need any Trim-Lok channel but, instead is held inplace with silicone caulk.  Install the eight retainer-to-window frame screws.  Again, don't forget the sealant on the screws.

While standing outside the boat push the fixed pane towards the inside of the boat.  As the picture above shows, the silicone caulk goes between the outside of the window pane and the outer retainer.  Putting painter's tape on the glass, before applying the silicone will make for a much neater job.

In closing, the modified Trim-Lok channel has been used aboard Nellie for the past nine years.  The technique described above has proven trouble free for the past five years.

Literature Search:
  1. Lady's, 37VT08, window channel solution
  2. Patrick Mitchell's, Elnora 37VT37, window channel solution..
  3. Philbrooks LTD's window channel solution for Tess II 37VT22.
  4. Randy Miller's, Hiaqua 37VT03, window solution.

Tuesday, April 17, 2018

An Old Salt Trick

Experienced skippers don't need a knot log to know how fast the boat is going--they merely observe the location of the bow wave.  

The pictures below we're taken while sitting atop Knock Off 37VT66's wheelhouse.  At 4.5 knots the bow wave is about even with the front of the wheelhouse.  At 7.3 knots it's even with the midship hawse cleat.

By the way, it's a displacement hull's inability to get over the bow wave that results in maximum hull speed