ok...i've been told by someone whose experience i trust that my hulls only have a few more months out on the water. i have deck ports in front of my front pilons that have created soft spots in my deck and hulls. i'm told that the tension of the bridal wires on a high wind/chop day will soon break my hulls at this spot. i'm going to do everything i can to reinforce these spots but as an added safety precaution, what about adding a stainless spreader bar. i'm thinking 1/2" od tube with a 1/8" wall fastened to the bottom of the bolts that hold the bridal wire. i'm told this is a pretty common problem with old boats, can anyone give advice?
thx
The soft spots are caused by the foam between the fiberglass layers breaking down. If you remove the ports you can inject some epoxy to seal them back together. Mat Miller posted a tech tip off of the hobie board on how to inject thru small holes but you already have the ports. Check the inside curved surface of the hulls right in the middle. When that gets soft you are in danger of breaking the bow off.
cheers
Bill
exactly what i am afraid of. even with the epoxy injection, when i'm out on the water i'll still always be thinking 'is it going to snap when i go over this wave?'. thats why i like things to be over-engineered. i want to put a stainless rod between the tips of the hulls where the bridal wires mount to absorb any stress that would be put on the hulls by the bridal wires. after all i'm assuming its the horizontal component of the tension provided by the bridal wires that ultimately snaps the bow. this doesn't seem like a radical idea so i want to know if anyone else has tried it and with what results
thx
In addition to the above, perhaps local reinforcing with carbon fibre.
Perhaps epoxy some carbon along/underneath the lip to pick up tensile loads (toe in force).
Like an I-beam the beef is at the ends (flanges). In this case a horizontal beam,
provided the deck is strong enough to act as the web of a beam.
Carbon fibre is approximately 20x - 29x+ times stronger than glass fibre.
Websites for carbon materials:
http://www.acp-composites.com/
I don't think a solid carbon rod or tube would be able to handle the load without bucking. i'm not sure exactly how much tension i'm looking at but i calculated that a 5/8" od 316 SS tube with an 1/8" wall can handle a maximum compressive load of 281 lbs (force) without buckling. this would add an extra 4.7 lb (mass) of weight to the front of my boat. does anyone know what kind of tensile forces occur in the forestay or bridal wires. also if anyone else with an old 16 is following this and thinking about doing it to their boat before the inevitable 'permantent tow-in' i'd be happy to email you my calculations.
just let me know
justin_tesmer@fpl.com
thx-
Just buy the bridle spreader made for the H17 from Murrays. It will cost you less in the long run. I made one from a H14 boom for my H17, not too hard if you have the tools / skills. The alm boom section is plenty strong
Here is the addy from hobie for that fix http:/
I am currently trying the solution... will report.
Here's an very very ruff exercise in futility.
(the deck tapers)
Excluding the stiffness factor of Deck as the web.
(obviously should be repaired as noted by previous posts)
Moment of Inertia = bh^3/12 + A*d^2
bh^3/12 is negligible.
So using I = A*d^2 for a 12" wide deck
Checking existing fibre glass at deck flange with an area of 1 in^2
I1 = 1.0 in^2 x (6 in)^2 x (1) = 36 in^4
Adding (2)0.125 in^2 of carbon in both sides of deck flanges from bow to stern.
I2 = 0.25 in^2 x (6 in)^2 x (29) = 261 in^4
I3 = 36 + 261 = 297 in^4
Proportional change in stiffness.
I3 / I1 = 297 / 36 = 8.25
For 1" of measured deflection PER hull delta becomes
1" / 8.25 = .12 in