Can someone please give advice on the blistering in the photo? It may have been caused by a blunt impact. Just wanting to know if it is something of concern or a cosmetic repair. Many thanks.
1984 Hunter 34 issue with interior floor frame
- Thread starter Beth and Bill
- Start date
Helo and welcome Bill & Beth
Search my post
"Has anyone repaired crack in bulkhead Hunter 34"
I am original owner of 1983 h34 and have the same crack same location and much more pronounced. My crack developed approximately 15-20 years ago for no apparent reason. No impacts or hard groundings, no reason for it. Mine has been there like I said for years and I only recently chipped off a piece of gelcote and made it look a lot worse.
Note I have no issues with my compression post like other boats of this era. Which could explain the crack. I would check your compression post and I agree that an impact could certainly cause the bulkhead crack. I have had a few marine fiberglass techs look at it and due to the fact that it does not flex and has not gotten any worse in 15 years they told me not to be concerned unless it gets worse. They examined the structural integrity of the bulkhead and The rest of the bulkhead it fine. I have seen this on a few h34s and h31s in the same spot so appears to be a common defect in this boat.
I have it on my to do list to fix but I haven't done it as of yet.
A few members have given me some great suggestions. Maybe this year I will get around to it.
Here is a photo of my crack that I plan to fix.
Hope this info helps.
Search my post
"Has anyone repaired crack in bulkhead Hunter 34"
I am original owner of 1983 h34 and have the same crack same location and much more pronounced. My crack developed approximately 15-20 years ago for no apparent reason. No impacts or hard groundings, no reason for it. Mine has been there like I said for years and I only recently chipped off a piece of gelcote and made it look a lot worse.
Note I have no issues with my compression post like other boats of this era. Which could explain the crack. I would check your compression post and I agree that an impact could certainly cause the bulkhead crack. I have had a few marine fiberglass techs look at it and due to the fact that it does not flex and has not gotten any worse in 15 years they told me not to be concerned unless it gets worse. They examined the structural integrity of the bulkhead and The rest of the bulkhead it fine. I have seen this on a few h34s and h31s in the same spot so appears to be a common defect in this boat.
I have it on my to do list to fix but I haven't done it as of yet.
A few members have given me some great suggestions. Maybe this year I will get around to it.
Here is a photo of my crack that I plan to fix.
Hope this info helps.
Captain Robbie, thank you for the detailed reply. I will follow your suggestion and check my compression post. If I repair mine and it comes out nice, I will send a photo to you. Your reply has put my mind at ease. Many thanks, Bill & Beth
Bill & Beth
Glad this gives you some piece of mind.
You will find that this forum has a wealth of info and the members here are great. If you ever have anything that gives you a problem or just cant figure something out on you own ask the question.
Thousands of minds at your disposal here.
I personally have received great advice here.
Plus great place to just share your experience.
Curious to know when did your blisters appear and what caused you to notice them? Any issues from previous owners?
Glad this gives you some piece of mind.
You will find that this forum has a wealth of info and the members here are great. If you ever have anything that gives you a problem or just cant figure something out on you own ask the question.
Thousands of minds at your disposal here.
I personally have received great advice here.
Plus great place to just share your experience.
Curious to know when did your blisters appear and what caused you to notice them? Any issues from previous owners?
I have exactly the same in the same location as the Beth and Bill post; is like a really bad wrinkle and has not at all changed in the last 3 years. I also wondered if there had been an impact by the PO, but as time goes on it seems to me that it somehow happened during the manufacture.
Great description of a wrinkle in the bulkhead cross beam.
That is exactly what mine looked like untill I dropped something and chipped the gelcote. The strange thing is that it is always on the forward side of that bulkhead and never on the cabin side.
Also strange that it also is that it is almost always in the exact same spot.
Nobody that I have spoken to has ever had any impact or hard groundings. This anomaly just seems to appear for no apparent reason. I thought that perhaps it was caused by when the boat was blocked when stored on the hard for the winter, I thought maybe some hull flexing caused by the jack stands.
1. The whole in this theory is that this is one of the strongest sections of the hull. My boat has no flexing for or aft of this
bulkhead.
2. This has happened to a h34 that is kept in water all year.
3. Also happened to a h34 stored in my old original factory shipping cradle.
Doesn't seem to be any rhyme or reason to this defect and why it happens to some h34s and not to others.
Strange boat mystery.
That is exactly what mine looked like untill I dropped something and chipped the gelcote. The strange thing is that it is always on the forward side of that bulkhead and never on the cabin side.
Also strange that it also is that it is almost always in the exact same spot.
Nobody that I have spoken to has ever had any impact or hard groundings. This anomaly just seems to appear for no apparent reason. I thought that perhaps it was caused by when the boat was blocked when stored on the hard for the winter, I thought maybe some hull flexing caused by the jack stands.
1. The whole in this theory is that this is one of the strongest sections of the hull. My boat has no flexing for or aft of this
bulkhead.
2. This has happened to a h34 that is kept in water all year.
3. Also happened to a h34 stored in my old original factory shipping cradle.
Doesn't seem to be any rhyme or reason to this defect and why it happens to some h34s and not to others.
Strange boat mystery.
I don't own a hunter and have no experience with the particular kind of damage you are showing here. However, it looks like the spot is located on one face of a threshold step. If the factory layup was consistently thin at that spot, do you think just walking and steping on it might compress that face over time and cause the buckling and breaking of fibers until it separates and cracks? It looks like there is the slightest of depressions across the top of the threshold right above the cracks.
- Will (Dragonfly)
- Will (Dragonfly)
I guess anything is possible however the entire bulkhead integrity is sound no voids or flexibility anywhere. I think it's just poor quality control on the bulkhead manufacturing. I ask people in the fiberglass industry does fiberglass expand or contract with temperatures and 90% say no but I wonder. Like to ask and engineer from DuPont.
http://onlinelibrary.wiley.com/doi/10.1002/app.1989.070370713/abstract
From the abstract of:
Thermal stability and degradation studies of polyester resins
Authors
- First published:March 1989
Meaning, there is some thermal instability in polyester resins.
Taken from: http://www.lewcospecialtyproducts.com/reinforcement-fabrics/Properties-of-Fiberglass-Fabrics
Lewco Specialty products, Inc.
REINFORCEMENT/COATING/LAMINATING FABRICS
Reinforcement/Coating/Laminating Fabrics > Properties of Fiberglass Fabrics
"Properties of Fiberglass Fabrics
CHEMICAL RESISTANCE- Fiberglass textile fabrics will not rot, mildew or deteriorate. They resist most acids with the exceptions of hydrofluoric acid and phosphoric acid.
DIMENSIONAL STABILITY- Fiberglass fabrics will not stretch or shrink. Nominal elongation break is 3-4 percent. The average linear thermal expansion coefficient of "E" glass is 5.4 by 10.6 cm/cm/°C.
GOOD THERMAL PROPERTIES- Fiberglass fabrics have a low coefficient of thermal expansion and relatively high thermal conductivity. Glass fabrics will dissipate heat more rapidly than asbestos or organic fibers".
-Will (Dragonfly)
I was going to reply to Capt. Robbie's post, but Will already did. One clarification and another comment:
☼ The coefficient of thermal expansion is a number times 10^-6 (not 10.6), meaning 10 to the power of -6, and can be given as per °C or °F (or even K). The length units don't matter because they cancel each other out. You multiply this coefficient by the length of the object you're concerned about, and it will tell you how much it will grow for a temperature increase of 1° (of whichever scale).
☼ I think the number given (5.4*10^-6) is actually for glass mat, not polyester resin. When I look up glass fibre reinforced polyester resin (FRP), I see numbers around 25*10^-6, but for glass around 4 - 6. For reference, stainless steel runs around 14 - 16, and carbon steel about 8 - 10. Aluminum is 21 - 24. So FRP will expand slightly more than aluminum alloys, and more than twice as much as steel. For perspective on the size of the numbers here: if a boat was 5m wide (just for example) and the temperature went up 10°C, it would get about 5,000*10*25*10^-6 = 1.25mm wider, or about 0.050" (just under 1/16").
I did not find a number for polyester resin all by itself, but since the number for FRP is so much higher than glass alone, I have to presume that the resin all by itself is much higher number. This means that the resin-to-glass ratio of the layup is going to affect the thermal expansion properties significantly.
And all of this doesn't matter unless you have different materials bonded together, for example steel encapsulated in FRP. Then the difference in thermal expansion can cause the bond between the materials to let go, or the weaker material itself to break. If you only have one material, it peacefully grows and shrinks without any issues.
☼ The coefficient of thermal expansion is a number times 10^-6 (not 10.6), meaning 10 to the power of -6, and can be given as per °C or °F (or even K). The length units don't matter because they cancel each other out. You multiply this coefficient by the length of the object you're concerned about, and it will tell you how much it will grow for a temperature increase of 1° (of whichever scale).
☼ I think the number given (5.4*10^-6) is actually for glass mat, not polyester resin. When I look up glass fibre reinforced polyester resin (FRP), I see numbers around 25*10^-6, but for glass around 4 - 6. For reference, stainless steel runs around 14 - 16, and carbon steel about 8 - 10. Aluminum is 21 - 24. So FRP will expand slightly more than aluminum alloys, and more than twice as much as steel. For perspective on the size of the numbers here: if a boat was 5m wide (just for example) and the temperature went up 10°C, it would get about 5,000*10*25*10^-6 = 1.25mm wider, or about 0.050" (just under 1/16").
I did not find a number for polyester resin all by itself, but since the number for FRP is so much higher than glass alone, I have to presume that the resin all by itself is much higher number. This means that the resin-to-glass ratio of the layup is going to affect the thermal expansion properties significantly.
And all of this doesn't matter unless you have different materials bonded together, for example steel encapsulated in FRP. Then the difference in thermal expansion can cause the bond between the materials to let go, or the weaker material itself to break. If you only have one material, it peacefully grows and shrinks without any issues.
We wish to thank you for all of your great answers. They were very helpful! 5 weeks until we get our boat in the water.