Originally Posted by Boatguy30
I know it is on here somewhere, but what did you end up with the glass schedule for the underwing to hull
what Richard is showing seems way overkill and I added the Searunner
wing stringer which he doesn't account for.
Jeff, I was in regular consultation with John Marples at the time, about glass schedules, rigs, etc... As far as I know, our 34 was one of the last ones built. We were glassing under there in about '92 and '93, and a lot of Searunner's frequent failure points were made evident to John by that time, which he passed on to me. (Builder/cruiser's feedback is invaluable. It means far more than one's personal experience)!
He considered the center longitudinal wing seam to be one of the places MOST in need of beefing up. The chines, cabin
& wing radii, etc. got heavier glass too, for a different reason. It adds very little weight to the boat to heavily glass the stress points and "elbows"...
OLD GLASS SCHEDULE:
Most of the old construction manual is obsolete, and now only considered a starting point. With newer building practices, high tech fabrics, and epoxy resins, along with LP paints, a practical service
life of well over 50 years became possible. The "Manual" made sense for the materials available back then, and quicker build/shorter lifespan intentions of the day.
THAT CENTER SEAM:
The problem with that center wing seam is that the ply is held rigid at it's edges, AND by a longitudinal ply bulkhead right under this seam. Even with the athwartships stringers in there, the left half of the wing, and right half, can flex up a bit on hard wave impact. The edges and center can not flex with them, as they are held absolutely rigid. The result on many searunners, is "zippers" from the glass over this seam opening up as these panels
Once there are glass "zippers", then water gets in, ply swells, and the tapes start to fail.
As suggested by John, this is what I did:
I made a lot of 2", 4" and 6" glass tapes of very heavy = dense biaxial glass fabric
. The stuff was a beast to wet out, and I had to go slowly, but it could be done. I would stagger the widths and fair the edges first with a layer of "Microlite", then sand the considerable hump fair, with a minimum of glass removal
. This made the mid wing joint absolutely bulletproof!
I used the same 3 layer schedule on all of the chines as well, because I unfortunately got into this project
after another builder
started it, leaving out some critical steps, (like half of the thickness required on the heavy glass buildup on the inside of the chines' troughs). This is, btw, one of the main reasons our project
took so long. I found myself correcting other's "shortcuts" that weren't really... The price
has to be paid up front, or years down the line.
For Searunners that DO have the correct 1/4" thick heavy glass buildup on the "inside", I would put just one 4" wide run of heavy biaxial fabric
on the exterior of the chines. IF you put on a nice radius... the ply is sanded to paper thin on these edges, (or completely away), so the extra glass is a good idea here.
On the wing fillets... I had glassed over my small Silica fillets, then applied large Microlite fillets over these. Being purely cosmetic, these larger fillets only got 5 coats of epoxy. 8 years later, these outer fillets had developed shallow cracks in their front 4', due to vibration from pounding over the years. During this year long re-fit, I applied 2 layers of much softer (= more flexible), and lower density bi-axial fabric, over the front 4' of these newly repaired fillets. The cracks had only been cosmetic, but I didn't want them to return. 10 years and 20 countries later, and they have never returned!
PLY SEAMS, as well as TRANSOM, WING, & CABIN
For all of these I made hundreds of feet of Bias cut glass tapes... again in staggering widths. (If you knew what you needed, and did it mass production style, you can cut enough tapes for an entire boat in 1 day)!
We had a 5X9 work table, with an optional fold away pressboard cover on it when cutting glass. We would roll out our standard 10 oz fabric, and using a straight edge with dress maker's "pizza cutter" for fabrics, we would make what we needed in short order. All you do is hold the metal straight edge at 45 degrees to the edge of the fabric. This bias-cut fabric is FAR more flexible than standard selvedged edge glass tape, so rolls over tight radii like a charm. (I could glass a golf ball with it)! Also, since all of the fibers go across the seams joint, it is TWICE as strong for a given weight, than standard glass.
I used 2 staggered layers of bias-cut tapes (like a 4 and a 6"), over ALL of the hull
, wing, and cabin ply butt seams. On transom radii, cabin radii, wing edges, bow & stern extensions, and ama to topside radii... I went with 3 layers. (2, 3, & 4")
the NEXT day, with my Porter Cable RO sander, I would feather these out to perfection, removing perhaps 40% of the glass, (& weight), but leaving full thickness in the 1" over the joint. It goes really fast, if you time it right.
Searunner radii are vulnerable to zippers! I have never had a radius glassed this way get a zipper. My only failures were to the hatches, which were originally under glassed for the fact that they flexed. Now, with carbon fiber in the corner seams, they too have been fixed.
THE 3 STEMS:
These got multiple staggered glass tape layers, more on the bottom half, near the WL.. They were just a couple of layers thick 8" aft of center, but 3/16" thick in the middle 2"! This is the main IMPACT zone! You will hit flotsam...
BROAD AREA GLASS SCHEDULE:
I stuck with the original 1 layer of 4oz on 80+% of the boats surface, except switched to 7 oz on the front 6' of the wings to stiffen the ply a bit. This may or may not have been useful?
Below the WL got many times this thickness, I don't really remember exactly... The "bottom" of the hulls, however, and 6" up the sides, got between 1/8" and 3/16" of glass everywhere. It is a very small % of the boat's surface!
The really heavy glass went on the mini keel
(@1/4" thick) and I have a 3/8" thick solid glass wormshoe.
The CB and rudder/skeg are glassed at a MINIMUM of 1/8" thick, with the for and aft edges (at ALL possible impact zones), being a full 3/8" thick! This is hard to do, as it changes the shape. The trick is to make the wood level of the blades too small/thin, in these areas, to make room for the glass later.
WHY GO TO THE TROUBLE:
Because, as has happened to us... when you go through a dozen hurricanes, beach the boat, have the wind
blow the water right out of your marina regularly, run up on an oyster
rake at full speed, snag a crab pot with the CB, WHACK the hull with your SCUBA
tank, slip with the blade when scraping barnacles
, etc... you DON'T want to immediately have to haul out
, because you exposed the wood part of your boat.
It IS a lot of trouble to do all this up front, but imo, it's time and money well spent, IF you plan on serious cruising, and want it to be a "good trip".
Most older Searunners were under glassed in these vulnerable areas, (ESPECIALLY minikeels, the CB trunk & blades) and since they are only 10 or 15% of the surface of the structure, extra glass here "alone", is well advised, in spite of the extra weight. In new construction, you can mostly make up for it with cored composite interior panels
, as Roy & I have.
How this specifically Searunner stuff applies to your Vardo cat, I have no idea, it's your call. I would look at the engineering, determine the loads or impact likelihood of ALL joints & seams, then estimate their cumulative sq/ft of surface area. Then, IF it is only 5 or even 10% of the glassed surface of the boat, going with bi-axial or bias-cut tapes, or multiple "extra" layers of glass on hull bottoms & blades, may only add a couple of hundred pounds to the boat?