Dear 7.9er's -
It looks as though I have some moisture intrusion below the mast step, and since I hope to have that puppy ("Class Struggle", #445) in the water by mid-April, I think I need to begin planning on how to do the repair.
Do any of you have suggestions as to how to proceed? I have some contacts at Harbor North in Huron (Ohio), and with the inimitable Butch Lang at Dry Land Marine in Sandusky; but I thought that if any of you folks had done such a repair you also might be able to give me some useful advice.
Fair Winds, Skip Oliver
Mast Step Repair
Moderators: Tim Bosma, Tom Elsen
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marionette
Mast Step reparir
Skip;
Did you ever complete this repair? Did you tackle it from the deck side or inside the cabin. As I was replacing wet core fwd of the mast and removed headliner, I saw dark wood on each side of the centerboard trunk inside the cabin. Didn't want to open up too much inside so I cut a section of deck under the mast plate. The glass is a good 1/4 plus thick there and then is a tapered section of plywood underneath until a flat stainless plate is exposed.
The guys I have spoken with recommend coosa board blue water 26 - has the highest compression strength (674 psi). Will bed this with West system and HD filler, then bevel the edges of the hole to add a couple layers of new glass on top. If you replace the mast plate in the original holes, you'll never see the repair.
Have not done the work yet, but putting the plans in place. ANy thoughts?
Runaway
1982 #23
Did you ever complete this repair? Did you tackle it from the deck side or inside the cabin. As I was replacing wet core fwd of the mast and removed headliner, I saw dark wood on each side of the centerboard trunk inside the cabin. Didn't want to open up too much inside so I cut a section of deck under the mast plate. The glass is a good 1/4 plus thick there and then is a tapered section of plywood underneath until a flat stainless plate is exposed.
The guys I have spoken with recommend coosa board blue water 26 - has the highest compression strength (674 psi). Will bed this with West system and HD filler, then bevel the edges of the hole to add a couple layers of new glass on top. If you replace the mast plate in the original holes, you'll never see the repair.
Have not done the work yet, but putting the plans in place. ANy thoughts?
Runaway
1982 #23
Mast Step Issue
Dear Runaway -
Wow, that post was over two years ago. Time sure goes fast when we are having fun, no?
Yes, I did work on it. After consulting several knowledgeable people, I bought a four inch diameter hole cutting bit, pulled up the mast step plate, and drilled down to the aluminum plate that you describe. What I found down there was all dry and sound, so I just glassed it all back together and went sailing.
After I glassed it back together and painted the area, a hairline crack again appeared just in front of the mast plate, so there is undoubtedly some compression going on down there, but so far it has not grown or otherwise been a problem for the past two years.
That is about all I can tell you.
Bring your boat down to Sandusky Bay for a sail some time. You are always welcome - as are the other 7.9er's. Right now we are hosting the Interlake nationals, and it is a lot of fun.
Fair Winds, AJ (Skip) Oliver
Vice Commodore
Sandusky Sailing Club
Wow, that post was over two years ago. Time sure goes fast when we are having fun, no?
Yes, I did work on it. After consulting several knowledgeable people, I bought a four inch diameter hole cutting bit, pulled up the mast step plate, and drilled down to the aluminum plate that you describe. What I found down there was all dry and sound, so I just glassed it all back together and went sailing.
After I glassed it back together and painted the area, a hairline crack again appeared just in front of the mast plate, so there is undoubtedly some compression going on down there, but so far it has not grown or otherwise been a problem for the past two years.
That is about all I can tell you.
Bring your boat down to Sandusky Bay for a sail some time. You are always welcome - as are the other 7.9er's. Right now we are hosting the Interlake nationals, and it is a lot of fun.
Fair Winds, AJ (Skip) Oliver
Vice Commodore
Sandusky Sailing Club
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marionette
MAST STEP REPAIR
MY repair is now complete and right or wrong, this is what I did:
Cut through appx 1/4 inch of fiberglass skin using a small 4 1/2 inch circular saw - essentially connecting the 4 screw holes. Use a chisel to remove layer of black/gray material under that and then removed wet plywood resting on top of metal plate. Gave this a few weeks in nice hot weather to dry out.
Using west system with high density filler, make up enough to cover plate and act as bedding for 3/8 inch thick coose bluewater 26. Aft edge had to be tapered since front of mast step is thicker than aft edge. Cut step pattern in outside edge of work area to produce overlapping layered effect when building up cloth/resin. Each layered area is about 1/4 inch larger than previous area, and each layer is 2 or 3 layers of cloth thick. Last 2 layers can completely cover bolt holes, but then drill them out again.
When there is less than 1/8 inch left to match surface gel coat layer, sand /grind last layer of cloth to get good bond, then fill with west and high density filler. Use wax paper over filler, and press mast plate firmly against filler to "seat" the plate. My plate had a dimple in it from the shoe contact, and was tapped back into shape by resting it upside down on a 4X4 and a few solid whacks with a hammer. A metal straight edge will allow you to see if it's close to flat.
Caulk the whole mess back together, plate screws too, using 3M 4200. 5200 will work too, but I didn't have any on hand.
Go sailing!
Cut through appx 1/4 inch of fiberglass skin using a small 4 1/2 inch circular saw - essentially connecting the 4 screw holes. Use a chisel to remove layer of black/gray material under that and then removed wet plywood resting on top of metal plate. Gave this a few weeks in nice hot weather to dry out.
Using west system with high density filler, make up enough to cover plate and act as bedding for 3/8 inch thick coose bluewater 26. Aft edge had to be tapered since front of mast step is thicker than aft edge. Cut step pattern in outside edge of work area to produce overlapping layered effect when building up cloth/resin. Each layered area is about 1/4 inch larger than previous area, and each layer is 2 or 3 layers of cloth thick. Last 2 layers can completely cover bolt holes, but then drill them out again.
When there is less than 1/8 inch left to match surface gel coat layer, sand /grind last layer of cloth to get good bond, then fill with west and high density filler. Use wax paper over filler, and press mast plate firmly against filler to "seat" the plate. My plate had a dimple in it from the shoe contact, and was tapped back into shape by resting it upside down on a 4X4 and a few solid whacks with a hammer. A metal straight edge will allow you to see if it's close to flat.
Caulk the whole mess back together, plate screws too, using 3M 4200. 5200 will work too, but I didn't have any on hand.
Go sailing!
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marionette
Mast step repair
Good point about the wet wood in surrounding areas. I found a soft spot just forward of the mast and tackled that from inside the cabin. THe previous owner had installed a stand up block with 4 screws through the deck. Then added a vent too. What a mess. After removing the headliner from the centerboard trunk forward to the point where the cabin drops down to the deck, I opened up an area about 13 in across and 16 in long. Another section on each side of the trunk about 5 inches as well.
The wet wood under the mast may have been caused by the bolts in the top of the plate or three holes for wiring (antenna, lights and apparent wind direction/speed instrument) behind the mast.
The initial purpose for this thread was just to figure out how to fix the area immediately under the mast without removing a huge section of deck. I guess we'll see how it pans out in a year or two.
It's amazing how wet the wood can get - with little indication of trouble from the deck side. Not soft or spongy at all - but surprisingly wet when it comes out.
PS: I contacted the folks who manufacture Coosa board yesterday. Coosa is being used as a plywood substitute and is available in many thicknesses and densities. One of the applications typical for this material is in transoms - where the gudgeon straps mount. It is many times stronger than any foam core material, and is lighter than plywood, does not absorb water either. They are sending me a sample a foot square that I intend to cut up and use under the stancion bases.
The wet wood under the mast may have been caused by the bolts in the top of the plate or three holes for wiring (antenna, lights and apparent wind direction/speed instrument) behind the mast.
The initial purpose for this thread was just to figure out how to fix the area immediately under the mast without removing a huge section of deck. I guess we'll see how it pans out in a year or two.
It's amazing how wet the wood can get - with little indication of trouble from the deck side. Not soft or spongy at all - but surprisingly wet when it comes out.
PS: I contacted the folks who manufacture Coosa board yesterday. Coosa is being used as a plywood substitute and is available in many thicknesses and densities. One of the applications typical for this material is in transoms - where the gudgeon straps mount. It is many times stronger than any foam core material, and is lighter than plywood, does not absorb water either. They are sending me a sample a foot square that I intend to cut up and use under the stancion bases.
The Coosa Board seems to be great suff, if exspensive, but never having to worry about rot again is worth it. I couldn't get the specs to download from the company website. What's the compression strength of the Bluewatern 26?
You did it right by fixing what you could from below. The 7.9's mast base reinforcement is a double edged sword. The fact that it sits on the DB trunk makes it vey strong and even though the deck caves in, the mast stays up. The flip side is that you can't repair that spot from underneath.
You did it right by fixing what you could from below. The 7.9's mast base reinforcement is a double edged sword. The fact that it sits on the DB trunk makes it vey strong and even though the deck caves in, the mast stays up. The flip side is that you can't repair that spot from underneath.
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marionette
Coosa Board
My previous post on this thread reads "674 psi" for the compression load of Bluewater 26. It is the highest density material they make - and is in varying thicknesses of 3/8 up to 2 inches. I called them on Friday, and they are very helpful. The only problem is that if you order the stuff from a distributor (Jamestown Dist, and Burlap induesties) it comes in a 4 X 8 or 4 X 9 sheet and it's around $200 - of course prices will increase with thickness. I was hoping to locate a local boat repair yard to purchase a scrap from, but the rep offered me a "sample" one foot square = just what I needed for the stancion base repairs next on my list.
You may find load specs on the Jamestown site.
By the way, when I explained to the Coosa rep that I was using a piece of bluewater 26 under the mast, she said that was a perfect replacement product for the point loading under the mast. Do you know how big the plate is? and what does it rest on?
Runaway
1982 # 32
You may find load specs on the Jamestown site.
By the way, when I explained to the Coosa rep that I was using a piece of bluewater 26 under the mast, she said that was a perfect replacement product for the point loading under the mast. Do you know how big the plate is? and what does it rest on?
Runaway
1982 # 32
Like I said, I tried downloading the specs from their site and couldn't get it to work, that's why I asked. I don't have the plate in front of me but it's about 6" x 12" x 3/8" thick. Ours was so corroded that it's kind of hard to tell how thick it was to begin with. Water seeping into and staying in a spot where stainless steel machine screws and aluminum plate comes together = a battery!
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marionette
Coosa Composites
Dave; I looked on their website as well. I guess you'll need to call them directly. Also, Jamestown is not a coosa distributor, but Eastern Burlap (Norfolk) is. I bought a few items from them before starting this project and found good pricing - much better on the core cell foam and west epoxy than Jamestown or Defender ( about 50% savings on the foam).
My guess on the 600+ psi is incorrect, and I don't remember where that figure came from! But I want to use Coosa for remaining repairs under the lifeline stancions. We'll be ready to launch soon thereafter.
Runaway
1982 Hull 23
My guess on the 600+ psi is incorrect, and I don't remember where that figure came from! But I want to use Coosa for remaining repairs under the lifeline stancions. We'll be ready to launch soon thereafter.
Runaway
1982 Hull 23
Thanks. 600 lb psi sounds pretty high for any type of foam board [even if it does have glass in it] that only weighs in the high 20's per cubic foot, but hey, I've been wrong before. This is a fix that I never want to do again, no matter how long I might have the boat! The load at the bottom of a 7.9 mast with five big guys hiking in heavy air and full backstay/rig tension is way higher than that. The design of the mast base and the way that is sits on the mast step causes severe point loading, so even sitting on the SS base and a good thickness of fiberglass, I might be a little leery. I need to get my hands on a small section and make a test laminate and TEST it on my hydraulic press. Even though I don't hail from Missouri, I'm one of those "show me" kind of people!
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marionette
Mast plate and bad plywood
Dave, I agree that the point loading is quite severe. While disassembling the mast step I noticed two interesting developments. The thickness of the fiberglass under the plate transfers some of the load along the deck exterior glass layer. With the sponginess of the wet plywood under the plate, there are spider cracks in the glass on either side of the step area toward the forward part of the step but at the base of the curved area where the shape changes from vertical to horizontal.
Also, the point loading of the step plate resulted in a dimple of sorts, distorting the plate area downward into the glass step base at the point where the half moon shaped shoe makes contact.
Do you think it would be of any benefit to add another 1/4 inch of stainless plate there to spread the load better?
Also, it's always goog to be a little suspicious of these new products, but as I disassembled the mast step and got to the plywood, I found a nickle sized hole (void) where a knot fell out of the ply. Surely this is not a mark of good construction or quality control on the part of the builder.
Runaway
1982 #23
Also, the point loading of the step plate resulted in a dimple of sorts, distorting the plate area downward into the glass step base at the point where the half moon shaped shoe makes contact.
Do you think it would be of any benefit to add another 1/4 inch of stainless plate there to spread the load better?
Also, it's always goog to be a little suspicious of these new products, but as I disassembled the mast step and got to the plywood, I found a nickle sized hole (void) where a knot fell out of the ply. Surely this is not a mark of good construction or quality control on the part of the builder.
Runaway
1982 #23
I was building boats 30 years ago and if we had to rummage through the plywood to find perfect sections for everything we never would have gotten anything done. Boat building is a high overhead, high hours, low profit margin business and 98% of them aren't concerned with making sure that EVERTHING that goes into the laminate [that we can't see] is on the up and up. I am serious about finding a small section of the Bluwater 26 and making a test panel, just to see how it holds up to severe point loading and compression.
At the risk of repeating myself for the umteenth time, water intrusion is the key. If one was to rebuild the step [or any other area] and then overdrill and fill the holes for the mast step machine screws, two major things would be accomplished. If it ever did develope a leak, no water could get past the epoxy filled plug and into the deck and if you mix some graphite powder and high density filler into the epoxy that was used in the fill, these plugs will now have some resistance to compression and will help spread the load. The compression is what leads to leaks to begin with by breaking the seal between the caulking and the fittings. Then the materials inside get damp and more compressable and it snowballs. Even if non water absorbing maretials are used under the step, if that area still compresses even a little over time there will be internal stress cracks somewhere. Water will find it's way into these and then into the balsa in the surrounding deck. The extra SS plate under the step would help but it would raise the mast unless you built it into the deck repair. Is that what you mean?
I ordered some 11 oz carbon fiber to use in rebuilding the mast step area, when I finally get thet far. Carbon is way stiffer than SS and MUCH lighter, and in an area this small, not too much more in $$.
As in all boats, there are areas that could have been engineered and built much better. The mast step is a weak point in the 7.9 as far as holding up to the riggers of use goes. Some creative thinking combined with logic and modern materials should solve the problem.
At the risk of repeating myself for the umteenth time, water intrusion is the key. If one was to rebuild the step [or any other area] and then overdrill and fill the holes for the mast step machine screws, two major things would be accomplished. If it ever did develope a leak, no water could get past the epoxy filled plug and into the deck and if you mix some graphite powder and high density filler into the epoxy that was used in the fill, these plugs will now have some resistance to compression and will help spread the load. The compression is what leads to leaks to begin with by breaking the seal between the caulking and the fittings. Then the materials inside get damp and more compressable and it snowballs. Even if non water absorbing maretials are used under the step, if that area still compresses even a little over time there will be internal stress cracks somewhere. Water will find it's way into these and then into the balsa in the surrounding deck. The extra SS plate under the step would help but it would raise the mast unless you built it into the deck repair. Is that what you mean?
I ordered some 11 oz carbon fiber to use in rebuilding the mast step area, when I finally get thet far. Carbon is way stiffer than SS and MUCH lighter, and in an area this small, not too much more in $$.
As in all boats, there are areas that could have been engineered and built much better. The mast step is a weak point in the 7.9 as far as holding up to the riggers of use goes. Some creative thinking combined with logic and modern materials should solve the problem.
Coosa Bluewater 26
Dave; I received two 1 ft squares of bluewater 26 today from Coosa Composites. One piece is 3/8 and the second 1/2 inch. I have carved out a space about 5 in X 8 3/4 on the underside of the deck and under the aft 2 lifeline stancions. Will be custom fitting one half inch section on each side and then glassing it in before adding the steel plates.
All I have to do yet is replace the fwd hatch, knotmeter and depth and we're good to launch. If you sent me an email response to my last message, that email address was shut down and I forgot to update it in my profile.
All I have to do yet is replace the fwd hatch, knotmeter and depth and we're good to launch. If you sent me an email response to my last message, that email address was shut down and I forgot to update it in my profile.
Runaway
1982 #23
1982 #23