I need to do some re-coring of my deck, and I'm pretty sure the original core material is 1/2 inch balsa. Can anybody confirm that for me so I can go ahead and order the new core? I know it's balsa, I just can't remember the exact thickness from the last time I ripped into it. My boat is a 1983 30T. Thanks, chrisferro
Deck Core Thickness
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Chris, Since you must recore the deck and since
you are in Annapolis you would do well to go to Faucett's and get Corecell foam. It is stronger than balsa won't ever rot and costs about $ 100 per 4x8 sheet. You will need a bucket of corebond. Lacking a responce as to thickness just drill through the skin on one side and measure.
you are in Annapolis you would do well to go to Faucett's and get Corecell foam. It is stronger than balsa won't ever rot and costs about $ 100 per 4x8 sheet. You will need a bucket of corebond. Lacking a responce as to thickness just drill through the skin on one side and measure.
Balsa vs Corecell
My plan was to use either ContourKore or ProBalsa, because from everything that I have read, balsa outperforms foamcores in compression and shear strength, heat distortion, and longevity - and epoxy-impregnated balsa almost eliminates water absorption and migration. Foams are lighter, but they are susceptible to compression around fittings, they can expand and contract and even shrink in the hot sun which separates them from the fiberglass skins on top and bottom, they can simply break down and disintegrate over time, and they are more expensive. A 2x4 foot piece of ProBalsa 1/2 inch is $40, ContourKore is $32 at Defender. All I know is that my 1983 balsa deck is perfectly pristine and solid in the (few) places where no water has gotten into it. If only the original manufacturer (or previous owners) had properly installed the stanchions, chainplates, etc so that no water could get in. Oh well, then I wouldn't have the joy of re-coring... I still don't know what the thickness is, though, so if anyone knows I'd appreciate it. I could cut into it and measure, but then I'd have an open hole in my deck. I'd rather cut into it and fix it all in one day. thanks for the reply, chris
My plan was to use either ContourKore or ProBalsa, because from everything that I have read, balsa outperforms foamcores in compression and shear strength, heat distortion, and longevity - and epoxy-impregnated balsa almost eliminates water absorption and migration. Foams are lighter, but they are susceptible to compression around fittings, they can expand and contract and even shrink in the hot sun which separates them from the fiberglass skins on top and bottom, they can simply break down and disintegrate over time, and they are more expensive. A 2x4 foot piece of ProBalsa 1/2 inch is $40, ContourKore is $32 at Defender. All I know is that my 1983 balsa deck is perfectly pristine and solid in the (few) places where no water has gotten into it. If only the original manufacturer (or previous owners) had properly installed the stanchions, chainplates, etc so that no water could get in. Oh well, then I wouldn't have the joy of re-coring... I still don't know what the thickness is, though, so if anyone knows I'd appreciate it. I could cut into it and measure, but then I'd have an open hole in my deck. I'd rather cut into it and fix it all in one day. thanks for the reply, chris
Chris, I don't think that what you have read about
was dealing with SAN foam. Corecell and Airex are a breed apart from all of the other cores. In areas that need to handle compressive loads like stanchions you build solid fiber glass. The skins will never get hot enough in sunlight to damage SAN foam. 2x4 feet of balsa @ 40 dollars versus 4x8 in corecell for $100 seems like no contest.
was dealing with SAN foam. Corecell and Airex are a breed apart from all of the other cores. In areas that need to handle compressive loads like stanchions you build solid fiber glass. The skins will never get hot enough in sunlight to damage SAN foam. 2x4 feet of balsa @ 40 dollars versus 4x8 in corecell for $100 seems like no contest.
GoodPoint
That's a good point about the stanchions and chainplates - I plan on using solid glass and epoxy with high strength filler at those points. I'll do some more research about corecell specifically. So that's one vote for corecell... anybody else out there with an opinion on corecell vs balsa? thanks again, chris
That's a good point about the stanchions and chainplates - I plan on using solid glass and epoxy with high strength filler at those points. I'll do some more research about corecell specifically. So that's one vote for corecell... anybody else out there with an opinion on corecell vs balsa? thanks again, chris
Here are the data sheets for the core
materials; Print them out so you can do a side by side study. http://www.atlcomposites.com/pdf/cores_core-cell.pdf http://www.atlcomposites.com/pdf/cores_baltek_SB50.pdf http://www.atlcomposites.com/pdf/C70_data_sheet.pdf This is the web site and the data sheets for all of the material under consideration. Enjoy. The link to the home page is too long. Just search ATL composites.
materials; Print them out so you can do a side by side study. http://www.atlcomposites.com/pdf/cores_core-cell.pdf http://www.atlcomposites.com/pdf/cores_baltek_SB50.pdf http://www.atlcomposites.com/pdf/C70_data_sheet.pdf This is the web site and the data sheets for all of the material under consideration. Enjoy. The link to the home page is too long. Just search ATL composites.
Use End Grain Balsa
Chris; I am casting a vote for 1/2" end grain balsa, which is what was there when the deck was laid up.Using 2 different types of core material is asking for trouble.You will need to use either solid glass/epoxy or wood/epoxy in the areas of high compression and or sheer loads.Setting the balsa in Corebond and tamping the material will assure it fills any voids between the glass laminates and your core.Any voids will ultimately result in delamination.If you have any experience with vacuum bagging, this is an excellent way to assure a good bond. West Marine carries the WEST System of booklets on this subject if you wish to use it.The material outlay is expensive to get statred but can be used in many other areas of glass repair.I use it to lay up glass on the overhead where in many cases gravity wants to take it down.You can reach me at 904-349-6872 if you want more detailed information.Best wishes on your project! Capt.Hawk Hawkins s/v RogueWave
Chris; I am casting a vote for 1/2" end grain balsa, which is what was there when the deck was laid up.Using 2 different types of core material is asking for trouble.You will need to use either solid glass/epoxy or wood/epoxy in the areas of high compression and or sheer loads.Setting the balsa in Corebond and tamping the material will assure it fills any voids between the glass laminates and your core.Any voids will ultimately result in delamination.If you have any experience with vacuum bagging, this is an excellent way to assure a good bond. West Marine carries the WEST System of booklets on this subject if you wish to use it.The material outlay is expensive to get statred but can be used in many other areas of glass repair.I use it to lay up glass on the overhead where in many cases gravity wants to take it down.You can reach me at 904-349-6872 if you want more detailed information.Best wishes on your project! Capt.Hawk Hawkins s/v RogueWave
Corebond?
So, Capt. Hawk, are you confirming the deck thickness at 1/2 inch? And I thought Corebond was specially formulated for use with foam. I was planning on using epoxy with high strength filler - West System 404 - if I use balsa.
So, Capt. Hawk, are you confirming the deck thickness at 1/2 inch? And I thought Corebond was specially formulated for use with foam. I was planning on using epoxy with high strength filler - West System 404 - if I use balsa.
Senior Marine Suevyor
Has said, after reading all the responses, that it is more likely to be 3/8" end grain balsa. There is a CD out from a major boat Co that states the end-grain balsa core is NOT structural and not to worry about a muchy deck...;-) Seriously, as nutty as it sounds.
Has said, after reading all the responses, that it is more likely to be 3/8" end grain balsa. There is a CD out from a major boat Co that states the end-grain balsa core is NOT structural and not to worry about a muchy deck...;-) Seriously, as nutty as it sounds.
I wonder what marketing school they went to?
The last time I looked the honeycomb core on aircraft wings was what kept the skins from going off on their own. It wouldn't be very hard to demonstrate the fallacy of that major boat makers claim. Just put a piece of corrogated cardboard to soak for a little while.
The last time I looked the honeycomb core on aircraft wings was what kept the skins from going off on their own. It wouldn't be very hard to demonstrate the fallacy of that major boat makers claim. Just put a piece of corrogated cardboard to soak for a little while.
Three sheets of 1/4 inch plywood
laid across a couple of saw horses spaced about four feet will make a very springy platform and if suffiently loaded will drop the load. But the same load on a single 3/4 inch sheet of plywood will hardly bend. That is the easiest demostration that I can come up with.
laid across a couple of saw horses spaced about four feet will make a very springy platform and if suffiently loaded will drop the load. But the same load on a single 3/4 inch sheet of plywood will hardly bend. That is the easiest demostration that I can come up with.
More on Cores
Chris; My 34 deck is 1/2 of end grain balsa;30's are either 3/8's or 1/2".You should be able to tell easily if you are removing any hardware beforehand.Corebond can be used to bed any core.Epoxy can as well. Balsa core/Nida core/or U-name-it cores are all structual, WHEN laid up between FRP.A core is the center[vertical] leg of an I beam.The glass laid up on either side forms the top & bottom of the I.The core when properly bonded completes the entire structure.To calculate the bending radius of an cored panel one uses the I Beam calculations from standard Engineering math. Epoxy resin with 404 structual filler will work extremely well.If you are not going to vacuum bag these repairs I would at lease add some sort of weight to the top to compress the balsa( or whatever you choose to use??) into the putty. By the way, I am a graduate of a professional Yacht Design & Engineering school, a member of the Society of Naval Archetects & Marine Engineers[SNAME], a member of The American Boat & Yacht Council[ABYC], and have spent the last 30 years as a professional boat builder. Cheers-Capt.Hawk s/v RogueWave
Chris; My 34 deck is 1/2 of end grain balsa;30's are either 3/8's or 1/2".You should be able to tell easily if you are removing any hardware beforehand.Corebond can be used to bed any core.Epoxy can as well. Balsa core/Nida core/or U-name-it cores are all structual, WHEN laid up between FRP.A core is the center[vertical] leg of an I beam.The glass laid up on either side forms the top & bottom of the I.The core when properly bonded completes the entire structure.To calculate the bending radius of an cored panel one uses the I Beam calculations from standard Engineering math. Epoxy resin with 404 structual filler will work extremely well.If you are not going to vacuum bag these repairs I would at lease add some sort of weight to the top to compress the balsa( or whatever you choose to use??) into the putty. By the way, I am a graduate of a professional Yacht Design & Engineering school, a member of the Society of Naval Archetects & Marine Engineers[SNAME], a member of The American Boat & Yacht Council[ABYC], and have spent the last 30 years as a professional boat builder. Cheers-Capt.Hawk s/v RogueWave
Capt. Hawk, I have a question concerning the
accomadation of compressive loads on cored structures. Would it be reasonable to substitute end grain pressure treated wood for light weight core in the areas of high compressive loads?. My theory being that the combination of compressive and off center loading seems to be the primary cause of water infiltration and subsequent rot.
accomadation of compressive loads on cored structures. Would it be reasonable to substitute end grain pressure treated wood for light weight core in the areas of high compressive loads?. My theory being that the combination of compressive and off center loading seems to be the primary cause of water infiltration and subsequent rot.
Cores/Decks/Loads
Ross; The failure of balsa core decks in some areas on Seidelmann yachts is a function of poor bedding/ construction techniques in areas of fastners/hatches/ports/travelers/and ANY hole drilled into the deck.I have laid up over 80 decks in my career and in the old days( '80-'81-'82-'83) not much thought was given to the migration of water into the balsa[wood] areas.In the case of my 34('82), there was not one place where the balsa core was cut back 1/2" and a putty of epoxy put into the edge.In later years of boat building we realized that a plywood insert at the area of a port/hatch /etc. AND the proper sealing of that wood PLUS the correct bedding compound could help to eliminate the kinds of problems I found in RogueWave.Every port was cut out with no more than a sealant placed between the port and the (wood) balsa core.Over time, you will find that water intrusion begins to "rot" the edges of the end grain balsa.On RogueWave I found every thru the deck placement was done to old standards.Today, each drill hole into the deck area should be enlarged and epoxy pumped into that area to form a solid plug.Then if you drill thru ,you expose no core material, and with a good beddding compound you seal the epxoy fillet and there is no chance of water getting into the core. In the days that the Seidelmann yachts were laid up many yacht buiders had not addressed these problems.Some of the more advanced manufactors began to put indexed placement of wood/ or aluminium / or solid glass plates to help seal these areas. To answer your question: any dense material...wood/aluminum/FRP plate , properly prepped and sealed will carry the compression loads. In the case of high loads...ie- travelers, we used an aluminum plate coated with polyester resin , and then bedded into core-bond to handle the types of loads seen in winches/tracks/travelers.Standard plywood(exterior grade or better) sealed with epoxy ,depending on the thickness, is a very good core in some areas.If a thin wood is used, then a backing plate is best, but in some applications a fender washer is ok....this is a function of the material + the thickness+ the load.For example: if you have a 1/2" ply in a high load area of the lifting nature, that may have too little thiness without a good aluminum backing plate. When we talk about compression loads, mainly we are dealing with the compression of screws holding down some type of fitting...ie-stanchions.Stanchions are in the static position under compression from the very hardware which attaches them to the deck.However, they also, will come under sheer loads(side) and in some cases upward loads(lifting) if lines are lead under the life lines in a fouled line situation.Crew members boarding by grabbing the life lines is one of the loads which work the base of the stanchion until a break in the bedding coumpound causes failure of the seal.If you have a solid base..ie, glass, epoxy,wood sealed in WEST, them the problems are not as great. Seidelmann owners are finding that many short cuts where taken in the building proscess......as did many other builders from that day.Today we can repair almost any type of problem with the excellent choice of state of the art materials we have available .When using a core material, be sure to place a solid plate in the area of extreme loading.Hope this is a help??.As always I can be reached at 904-349-6872 for any consultations...no charge to any Seidelmann owners. Fair Winds & Following Seas: Capt.Hawk RogueWave-S34 custom offshore
Ross; The failure of balsa core decks in some areas on Seidelmann yachts is a function of poor bedding/ construction techniques in areas of fastners/hatches/ports/travelers/and ANY hole drilled into the deck.I have laid up over 80 decks in my career and in the old days( '80-'81-'82-'83) not much thought was given to the migration of water into the balsa[wood] areas.In the case of my 34('82), there was not one place where the balsa core was cut back 1/2" and a putty of epoxy put into the edge.In later years of boat building we realized that a plywood insert at the area of a port/hatch /etc. AND the proper sealing of that wood PLUS the correct bedding compound could help to eliminate the kinds of problems I found in RogueWave.Every port was cut out with no more than a sealant placed between the port and the (wood) balsa core.Over time, you will find that water intrusion begins to "rot" the edges of the end grain balsa.On RogueWave I found every thru the deck placement was done to old standards.Today, each drill hole into the deck area should be enlarged and epoxy pumped into that area to form a solid plug.Then if you drill thru ,you expose no core material, and with a good beddding compound you seal the epxoy fillet and there is no chance of water getting into the core. In the days that the Seidelmann yachts were laid up many yacht buiders had not addressed these problems.Some of the more advanced manufactors began to put indexed placement of wood/ or aluminium / or solid glass plates to help seal these areas. To answer your question: any dense material...wood/aluminum/FRP plate , properly prepped and sealed will carry the compression loads. In the case of high loads...ie- travelers, we used an aluminum plate coated with polyester resin , and then bedded into core-bond to handle the types of loads seen in winches/tracks/travelers.Standard plywood(exterior grade or better) sealed with epoxy ,depending on the thickness, is a very good core in some areas.If a thin wood is used, then a backing plate is best, but in some applications a fender washer is ok....this is a function of the material + the thickness+ the load.For example: if you have a 1/2" ply in a high load area of the lifting nature, that may have too little thiness without a good aluminum backing plate. When we talk about compression loads, mainly we are dealing with the compression of screws holding down some type of fitting...ie-stanchions.Stanchions are in the static position under compression from the very hardware which attaches them to the deck.However, they also, will come under sheer loads(side) and in some cases upward loads(lifting) if lines are lead under the life lines in a fouled line situation.Crew members boarding by grabbing the life lines is one of the loads which work the base of the stanchion until a break in the bedding coumpound causes failure of the seal.If you have a solid base..ie, glass, epoxy,wood sealed in WEST, them the problems are not as great. Seidelmann owners are finding that many short cuts where taken in the building proscess......as did many other builders from that day.Today we can repair almost any type of problem with the excellent choice of state of the art materials we have available .When using a core material, be sure to place a solid plate in the area of extreme loading.Hope this is a help??.As always I can be reached at 904-349-6872 for any consultations...no charge to any Seidelmann owners. Fair Winds & Following Seas: Capt.Hawk RogueWave-S34 custom offshore
Project is done (almost)
Thanks for all of your responses. I did go with 1/2 inch Probalsa from Jamestown Distributors, and it worked like a charm. I cut out a roughly 18x24 inch rectangle, chopped all of the old wet core out with hammer and chisel (most came out easily), dried the inside with a hair dryer for about an hour, then filled the space with the new core and thickened epoxy. Now I have to sand it all down, grind the perimeter, put new fiberglass/epoxy on the perimeter, sand it all down again, and paint it with non-skid. Then I just have to do the same thing with the port side of the deck. Piece of cake (somebody please kill me...)
Thanks for all of your responses. I did go with 1/2 inch Probalsa from Jamestown Distributors, and it worked like a charm. I cut out a roughly 18x24 inch rectangle, chopped all of the old wet core out with hammer and chisel (most came out easily), dried the inside with a hair dryer for about an hour, then filled the space with the new core and thickened epoxy. Now I have to sand it all down, grind the perimeter, put new fiberglass/epoxy on the perimeter, sand it all down again, and paint it with non-skid. Then I just have to do the same thing with the port side of the deck. Piece of cake (somebody please kill me...)
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