Hi
David, so that was a good explanation concerning materials. I would love to work with Dynel. But it is,was difficult in the time I was an active builder to get. As I understand it, it is a very easy material to work with and sheet hulls. In any case in respect to glass fiber, very strong and (for my important) I hate itching of glass fiber. The explanation of the different polyesters to. But here we go, we can forget it, because in the necesary dimensions difficult available. The difficult or insecure way with the silicone in the material is also an issue.? For my in the end I will stay with Kevlar. Reason, the costs coming down. For point load as measurements have shown and my own practical experience, the best. All other properties to are good (this is the reason that it is used, besides carbon now big way in aircraft constructions). That it can get fluffy when sliding depends. But a ?thick outside layer of Epoxy will prodect it. We had never these fluffy thing anyway. Laying partly with the bows in the sand. This not only with the 4000kg "Pelican", but also with the smaller and much light "Butterfly" Which I abused even more by sliding it up on sand bars, bumbing around depending on the weather before we went sailing again. By the way Jens, you life in Germany R&G Kunststoffe is selling right now Keflar 170 gram/m? roll of 2 m 0,5m breit for € 43,3. Only an idea. No unsecurity, is the material sticking or not, or will it fell of. Up to you
Cheers
Bernd ?
|
Re: Eco 5.5 Sailing Version
Hi Robert
Nice boat Hamish was building. I hope we see in the future more of the two. To the question of the luff dagger boards. The solution is very logical. The cost no place on the inside (the 5.5 is per definity no "oceanliner", every millimeter counts). Besides with the boards outside, no damage to the hulls possible in case of a collision for instance with a just floading container. For the inside dagger board one of the drawings shows for the reason of strength a piece of outside Mahogany stringer at bulkhead 3 and 4. With some overhang. So this will be always strong enough. Again, 25mm is a lot in such a small boat.
Cheers
Bernd
|
Re: Eco 5.5 Sailing Version
Hi Hamish,
When I saw in your pictures that you equipped your ECO 5.5 with two daggerboards instead of one, I also noticed that you placed them on the outsides of the hulls instead of on the inner sides.? Could you elaborate a little on your reasons for these choices? It would be highly interesting to myself and any other potential ECO builders...
Even more in detail, while the place for the daggerboard in Bernds' drawings is immediately against the hull planking, thus forcing an interruption of the chine and hull stringers between Bulkheads 3 and 4, you placed it just inside the chine and stringers, which seems a more logical choice to me.? Maybe Bernd could comment on this??
Thanks, have fun sailing while we sit out winter in the northern hemisphere!?
Robert
|
Hello David,
Thanks for your comprehensive answer. I knew that the strap material I found were made of polyamide (I read the differences).
Many years ago, I had been driving model car racing. To increase the impact resistance of the axle parts, we "simmer" these parts in water (~ 85 ¡ã C) for about 10 minutes. The axle parts were also made of polyamide (Miramid)
Yesterday I searched further and found strap material made of polyester (https://www.naehkaufhaus.de/Sicherheitsgurtband-Autogurt/Autogurt-schwarz-46-mm-p830.htm).
A "small" problem remains the possibility that the polyester yarns were treated with silicone oil ...
I work as a painter; to degrease the surface I use the industrial silicone remover - would that be a way to remove the silicone oil from the polyester fabric? At least the biggest part.
My idea: Silicone remover with a spray gun (high pressure)? through the belt material blow through and remove most of the silicone oil.
Polyester should be resistant to silicone remover, or not?!?
Certainly, my compound (polyester webbing and epoxy resin) is not comparable to the load of industrially manufactured polyester composites, but I think it is sufficient for the protection of the keels of my multihulls.
I will apply the straps to the keels in the vacuum infusion process.
I think, the material thickness of 1.5 mm will provide sufficient protection with a "possible" ground contact.
I do not want to drive onto the beach or of stones all the time.
Thank you very much und best regards,
Jens
|
Hi Jens
You probably know that polyamid (polyamide) and polyester are different materials. The long chains of molecules in polyester are linked together with esters whereas the long chains of molecules in polyamid are linked with amides. So the raw material has different chemical base and therefore different properties. For example, polyamids absorb more water than polyesters. When a plastic absorbs water, it swells. This is important when looking at the micromechanics of a composite. The swelling strains the matrix (i.e. epoxy) so that it cannot carry as much load. The matrix that is 'less strong' takes away from the strength of the finished composite. As you can imagine, it is very important to test materials after conditioning in the marine environment. Test data is available for most materials but finding data that represents performance in the marine environment is far more difficult.
Before expensive testing I try to get an idea of potential performance. One example is to compare aerospace test data for finished laminate properties and 'hot-wet'? properties. If a product has little change between these two test conditions, it is a good candidate for further testing. However, this approximation is not perfectly accurate. For example, I have found products that are eventually damaged by salt water that tested exceptionally well in fresh water.
You may not realize that fabrics for composite reinforcements generally have surface treatments to enhance wetting and adhesion to the matrix. Fabrics without the correct finish do not perform well. Here is an example: Many manufacturers of fabrics use silicone oils to lubricate their machines and even the yarns they weave with. Silicone is known to inhibit the cure of many epoxy systems. If one was to use such a fabric in a laminate, it may seem OK but perhaps would only give 1/3 of the strength of a fabric with the proper surface treatment.
David
From: "shakalboot@... [k-designs]"
To: k-designs@...
Sent: Monday, January 1, 2018 9:15 AM
Subject: Re: [k-designs] Re: beaching keel
?
Hello David,
Your message is very interesting. I'm just about to build the hulls for my ECO 68 ( ) and also thought to reinforce the keels with kevlar.
You write that polyester fibers are even more resistant to abrasion and thus more stable than Kevlar.
... I had to smile a little, because in my model airplanes I have glued landing skids under the hulls of polyamide fabric and epoxy resin for many years .... why not use it also in boat building ??
So my question: Can these reinforcements for the keels not also made of Polamid belt straps and epoxy resin?
In Germany, there are by the meter in different widths ( ) -this is car seat belt material, this is 1,2mm thick and I think that can withstand any ground contact without any problems.
best regards,
Jens
---In k-designs@..., wrote : Hi Bernd
I would have enjoyed seeing your beach landing..
Kevlar 49 (aramide fiber) is a wonderful material. It performs spectacularly for its weight when subject to impact tension loads. It is OK in? abrasion but does get fuzzy on the surface. Polyester fiber reinforced epoxy has poor impact resistance but outstanding abrasion resistance. I base this assessment on paddling custom whitewater kayaks in the early 1970s and years later working as a Materials and Process Engineer specializing in marine epoxy-composite structures.
Custom whitewater kayaks are under designed by nature and abused by repeatedly slamming into rocks and sliding across gravel bars. They must flex to absorb impacts that would destroy rigid laminates 5-times stronger and then continue down river. A fellow named Chip Queitzsch accomplished engineering tests in the laboratory (1960's I think) to develop laminates that could survive the punishment of whitewater kayaking. He focused specifically on impact properties and abrasion properties, among others. Chip developed lab tested material properties for individual reinforcements and resins as well as combinations of reinforcements. His work showed that combinations of reinforcements could produce lighter, abrasion resistant and damage tolerant kayaks than previously imagined. The reason I bring up his work is that it is the first comparison of abrasion resistance properties of kevlar fiber reinforced composites and polyester fiber reinforced composites I know of. Later laboratory work by DuPont, and Union Carbide (manufacturers of Kevlar and Dynel) confirmed Chip's comparison of abrasion properties. Based on Chips work, polyester fiber reinforced epoxy is about the best composite that can be found for abrasion resistance. It is highly tolerant to abrasion and wears smooth. Thus, it is used in high wear areas rather than general hull structure. I don't think it competes with Kevlar. As I am sure you know, Kevlar is a staple of lightweight impact resistant structural composites including custom kayak hull structures.
Later, when working as a Materials and Process Engineer, I recommended the use of polyester fiber reinforced epoxy to customers for high wear areas. It performed well for them. Also, it is relatively inexpensive and easy to laminate.
David
From: "Bernd@... [k-designs]"
To: k-designs@...
Sent: Saturday, December 30, 2017 8:50 AM
Subject: Re: [k-designs] Re: beaching keel
?Hi
Yes David the keel from my boats are overdesigned for the reason of beaching and some bumps on the way! Many sailors found us crazy what we did with our "PELICAN". Never a problem. Some scratches of course.? Keflar is otherwise the best protector. Only problem, the base has also to be strong. Even when whearing a bulletproof vest (Poliz and military) and you get hit, you get bruizes or have a broken rib. Craig your example from Hawaii is interesting. Keels on a multihull I find roundout stupit.? By the way, if the would use Keflar on the bows the would not have to rebuilt every year. Luiz was just writing that he has always to beach the boat and had never a problem. Damaging the bow or keel area was never reported from my small till the big catamarans (for my "big" is till 13,00m).? I mentioned this already elsewhere. Keflar is the most difficult material to work with, besides the costs. First you need special cissors to cut it (around US $ 100,-). You can not sand it ( try to sand a wol sweater). To apply Epoxy is very difficult, because you see no color difference is a part done or not..? A thrue story. We where sailing at the Baldenaisee near Essen/Germany with the jellow SC435.. I got hit by the main sheet and my glasses went in the water. I was so p...set that I turned the boat to land it. The landing place had a wooden front and there after gravel. I was at a good speed, just before the landing I moved back, so that the forward part of the hulls where out of the water. I was sliding with a good speed up the wood prodection and moved forwards. The boat was over the centerpoint and canted forward, I stepped of the boat without getting even wet feet. A guy was coming on in a rush. What no damage? I never could do this with my (Polyester) DART. I would have a hole in the boat. Yesss Sir, The good part of a wood/Epoxy construction with half the weight of the DART. I looked at him, "I do that always in this way"?;-) ?;-))
Bernd
|
Chris, email me. My handle at yahoo.com.? Patrick
|
Patrick,
Very impressive build.? I live in Tidewater Va. and would love to visit your build site.? Let me know if that is convenient and keep sending the great pics.
Cheers, Chris?
|
Hello David, Your message is very interesting. I'm just about to build the hulls for my ECO 68 ( ) and also thought to reinforce the keels with kevlar. You write that polyester fibers are even more resistant to abrasion and thus more stable than Kevlar. ... I had to smile a little, because in my model airplanes I have glued landing skids under the hulls of polyamide fabric and epoxy resin for many years .... why not use it also in boat building ?? So my question: Can these reinforcements for the keels not also made of Polamid belt straps and epoxy resin?In Germany, there are by the meter in different widths ( ) -this is car seat belt material, this is 1,2mm thick and I think that can withstand any ground contact without any problems. best regards, Jens ---In k-designs@..., <mancebodesigns@...> wrote : Hi Bernd
I would have enjoyed seeing your beach landing..
Kevlar 49 (aramide fiber) is a wonderful material. It performs spectacularly for its weight when subject to impact tension loads. It is OK in? abrasion but does get fuzzy on the surface. Polyester fiber reinforced epoxy has poor impact resistance but outstanding abrasion resistance. I base this assessment on paddling custom whitewater kayaks in the early 1970s and years later working as a Materials and Process Engineer specializing in marine epoxy-composite structures.
Custom whitewater kayaks are under designed by nature and abused by repeatedly slamming into rocks and sliding across gravel bars. They must flex to absorb impacts that would destroy rigid laminates 5-times stronger and then continue down river. A fellow named Chip Queitzsch accomplished engineering tests in the laboratory (1960's I think) to develop laminates that could survive the punishment of whitewater kayaking. He focused specifically on impact properties and abrasion properties, among others. Chip developed lab tested material properties for individual reinforcements and resins as well as combinations of reinforcements. His work showed that combinations of reinforcements could produce lighter, abrasion resistant and damage tolerant kayaks than previously imagined. The reason I bring up his work is that it is the first comparison of abrasion resistance properties of kevlar fiber reinforced composites and polyester fiber reinforced composites I know of. Later laboratory work by DuPont, and Union Carbide (manufacturers of Kevlar and Dynel) confirmed Chip's comparison of abrasion properties. Based on Chips work, polyester fiber reinforced epoxy is about the best composite that can be found for abrasion resistance. It is highly tolerant to abrasion and wears smooth. Thus, it is used in high wear areas rather than general hull structure. I don't think it competes with Kevlar. As I am sure you know, Kevlar is a staple of lightweight impact resistant structural composites including custom kayak hull structures.
Later, when working as a Materials and Process Engineer, I recommended the use of polyester fiber reinforced epoxy to customers for high wear areas. It performed well for them. Also, it is relatively inexpensive and easy to laminate.
David
From: "Bernd@... [k-designs]" <k-designs@...>
To: k-designs@...
Sent: Saturday, December 30, 2017 8:50 AM
Subject: Re: [k-designs] Re: beaching keel
?Hi
Yes David the keel from my boats are overdesigned for the reason of beaching and some bumps on the way! Many sailors found us crazy what we did with our "PELICAN". Never a problem. Some scratches of course.? Keflar is otherwise the best protector. Only problem, the base has also to be strong. Even when whearing a bulletproof vest (Poliz and military) and you get hit, you get bruizes or have a broken rib. Craig your example from Hawaii is interesting. Keels on a multihull I find roundout stupit.? By the way, if the would use Keflar on the bows the would not have to rebuilt every year. Luiz was just writing that he has always to beach the boat and had never a problem. Damaging the bow or keel area was never reported from my small till the big catamarans (for my "big" is till 13,00m).? I mentioned this already elsewhere. Keflar is the most difficult material to work with, besides the costs. First you need special cissors to cut it (around US $ 100,-). You can not sand it ( try to sand a wol sweater). To apply Epoxy is very difficult, because you see no color difference is a part done or not..? A thrue story. We where sailing at the Baldenaisee near Essen/Germany with the jellow SC435. I got hit by the main sheet and my glasses went in the water. I was so p..set that I turned the boat to land it. The landing place had a wooden front and there after gravel. I was at a good speed, just before the landing I moved back, so that the forward part of the hulls where out of the water. I was sliding with a good speed up the wood prodection and moved forwards. The boat was over the centerpoint and canted forward, I stepped of the boat without getting even wet feet. A guy was coming on in a rush. What no damage? I never could do this with my (Polyester) DART. I would have a hole in the boat. Yesss Sir, The good part of a wood/Epoxy construction with half the weight of the DART. I looked at him, "I do that always in this way"?;-) ?;-))
Bernd
|
Hi David
It was
an other time. We had in this time a SC 435, DUO 425 and the
BUTTERFLY. Everybody could land with his boat on the beaches on the
North sea. We where regular at Katwijk, Noordwijk etc. So it was
normal for us. Going to the beach with one of the small ones, set
them up and got sailing. I forgot from which year on it was for
bitten and you had to be a member of the beach clubs. The had a
connection to the beach to go or land the boats. The big players like
Hobie, Dart and some others where financing the clubs. This was the
end for us of course. We had our places still.
Okay,
with the Butterfly it was different. We had a place in the marina
from Stellendam. This is a fishery place near Rotterdam. Interesting
water, with tide, with a big dam for water stand regulations of the
Haringvliet and the tide with of course ebb , flow. The fairway for
big ships was going in a big and wide bent. In between shoals which
where partly try at ebb. The waters around the fairway where
dangerous. With wind against tide the waves where unpredictable.
Above wind force 5 it was better to stay in the port. Also in
moderate winds we had sometimes mud from the bottom on the bridge
deck. One day, a small power boat was out. The ?driver¡° did not
know the area. One moment the where happily motoring the next moment
the where swimming and the boat was swallowed by a ?ground see¡°
how we call it. Today, the marina is gone and only the big fishing
vessels are there and other professional ships. With our extreme
light Butterfly (draft ,2m with the dagger boards and rudders up) We
had dagger boards and rudders as on some of my other designs. So we
had still rudder in the ship.
To the
material. We have had always very thick coats of Epoxy on the Kevlar.
But we where very happy with it at the Pelican. The map shows the
cove (the V on the map and the background photo page 2 KD 860) where
we where many times. Water depth, 1 m about on the deep places. In a
storm, depending on the wind direction, the water was pressed in or
sucked out and we had some heavy ground contacts. The sea berth was a
sort of basalt, sharp and pointed). Never a problem. And as you
mentioned, the Kayaks for extreme touring are made for a great part
from Kevlar. I stay for oblivious reasons with Kevlar, Dynel etc. By
the way, the two pictures from the Junk, with the potato sack sail
material had also a Kevlar bottom (was a sort of sharpie hull). The
boat was made for 9000,- Dutch Guilders, also very cheap, besides the
bottom. But he was even more nuts as we. The called him ?Ken on the
rocks¡°. He was with the boat in any hole and beach I did not dear
to go. Same, never a problem. Okay, this was in a way extreme sailing
what we did, but we had never a problem with our boats.
You are
right with the Polyester material, but depending what you do with
your boat it can be worth to think about it, but in the end Kevlar is
the material to use. As I mentioned, it is a difficult material. When
you use the set up as I show in the plans the keel areas extreme
strong. Use glass fiber as I mention in the plans, besides you would
like to make extreme voyages with your boat.
Cheers
Bernd
|
Hi David.
?????????????? I totally agree with your assessment, back when I was a young boatbuilder, also in the early 1970¡¯s I was building a fairly light cold molded keelboat where the designer had specified 4oz/yd2 glass to sheath it whereas it
was very, very common to sheath hulls of any size with Dynel so I did very basic tests where we laminated both the glass and dynel onto a piece of softwood, let the epoxy cure for a week and then beat it with a ball pein hammer, as expected the glass behaved
like, well, glass and shattered while the dynel absorbed the blows and while dented, remained intact and adhered to the substrate. For abrasion we just sanded. Not very scientific but real world. When I moved to the US in 1980 I found that the use of polyester
fabrics is a lot less common but dynel remains my go to for sheathing where impact and abrasion are the goal. We sometimes have to add sacrificial wear shoes to fiberglass boats that, through constant beaching, have identified areas that need extra protection,
often just a relatively small area of the forefoot. In these areas where we are trying to achieve a fairly thick abrasion resistant shoe we mostly use Kevlar felt which does the job well. It would just take a lot of layers of dynel to get enough thickness
as it is only available in one weight as far as I know. I agree with Bernd that having a strong structure without a keel is probably the best approach for beaching, with extra sheathing of course.
?
Steve.
?
Sent from for Windows 10
?
toggle quoted message
Show quoted text
From: David Mancebo mancebodesigns@... [k-designs]
Sent: Sunday, December 31, 2017 12:20 PM
To: k-designs@...
Subject: Re: [k-designs] Re: beaching keel
?
?
I would have enjoyed seeing your beach landing..
Kevlar 49 (aramide fiber) is a wonderful material. It performs spectacularly for its weight when subject to impact tension loads.
It is OK in? abrasion but does get fuzzy on the surface. Polyester fiber reinforced epoxy has poor impact resistance but outstanding abrasion resistance. I base this assessment on paddling custom whitewater kayaks in the early 1970s and years later working
as a Materials and Process Engineer specializing in marine epoxy-composite structures.
Custom whitewater kayaks are under designed by nature and abused by repeatedly slamming into rocks and sliding across gravel bars.
They must flex to absorb impacts that would destroy rigid laminates 5-times stronger and then continue down river. A fellow named Chip Queitzsch accomplished engineering tests in the laboratory (1960's I think) to develop laminates that could survive the punishment
of whitewater kayaking. He focused specifically on impact properties and abrasion properties, among others. Chip developed lab tested material properties for individual reinforcements and resins as well as combinations of reinforcements. His work showed that
combinations of reinforcements could produce lighter, abrasion resistant and damage tolerant kayaks than previously imagined. The reason I bring up his work is that it is the first comparison of abrasion resistance properties of kevlar fiber reinforced composites
and polyester fiber reinforced composites I know of. Later laboratory work by DuPont, and Union Carbide (manufacturers of Kevlar and Dynel) confirmed Chip's comparison of abrasion properties. Based on Chips work, polyester fiber reinforced epoxy is about the
best composite that can be found for abrasion resistance. It is highly tolerant to abrasion and wears smooth. Thus, it is used in high wear areas rather than general hull structure. I don't think it competes with Kevlar. As I am sure you know, Kevlar is a
staple of lightweight impact resistant structural composites including custom kayak hull structures.
Later, when working as a Materials and Process Engineer, I recommended the use of polyester fiber reinforced epoxy to customers for
high wear areas. It performed well for them. Also, it is relatively inexpensive and easy to laminate.
From: "Bernd@... [k-designs]" <k-designs@...>
To: k-designs@...
Sent: Saturday, December 30, 2017 8:50 AM
Subject: Re: [k-designs] Re: beaching keel
?
?
Yes David the keel from my boats are overdesigned for the reason of beaching and some bumps on the way! Many sailors found us crazy what
we did with our "PELICAN". Never a problem. Some scratches of course.?
Keflar is otherwise the best protector. Only problem, the base has also to be strong. Even when whearing a bulletproof vest (Poliz and
military) and you get hit, you get bruizes or have a broken rib. Craig your example from Hawaii is interesting. Keels on a multihull I find roundout stupit.?
By the way, if the would use Keflar on the bows the would not have to rebuilt every year. Luiz was just writing that he has always to
beach the boat and had never a problem. Damaging the bow or keel area was never reported from my small till the big catamarans (for my "big" is till 13,00m).?
I mentioned this already elsewhere. Keflar is the most difficult material to work with, besides the costs. First you need special cissors
to cut it (around US $ 100,-). You can not sand it ( try to sand a wol sweater). To apply Epoxy is very difficult, because you see no color difference is a part done or not..?
A thrue story. We where sailing at the Baldenaisee near Essen/Germany with the jellow SC435. I got hit by the main sheet and my glasses
went in the water. I was so p..set that I turned the boat to land it. The landing place had a wooden front and there after gravel. I was at a good speed, just before the landing I moved back, so that the forward part of the hulls where out of the water. I
was sliding with a good speed up the wood prodection and moved forwards. The boat was over the centerpoint and canted forward, I stepped of the boat without getting even wet feet. A guy was coming on in a rush. What no damage? I never could do this with my
(Polyester) DART. I would have a hole in the boat. Yesss Sir, The good part of a wood/Epoxy construction with half the weight of the DART. I looked at him, "I do that always in this way"?;-) ?;-))
?
|
Hi Bernd
I would have enjoyed seeing your beach landing..
Kevlar 49 (aramide fiber) is a wonderful material. It performs spectacularly for its weight when subject to impact tension loads. It is OK in? abrasion but does get fuzzy on the surface. Polyester fiber reinforced epoxy has poor impact resistance but outstanding abrasion resistance. I base this assessment on paddling custom whitewater kayaks in the early 1970s and years later working as a Materials and Process Engineer specializing in marine epoxy-composite structures.
Custom whitewater kayaks are under designed by nature and abused by repeatedly slamming into rocks and sliding across gravel bars. They must flex to absorb impacts that would destroy rigid laminates 5-times stronger and then continue down river. A fellow named Chip Queitzsch accomplished engineering tests in the laboratory (1960's I think) to develop laminates that could survive the punishment of whitewater kayaking. He focused specifically on impact properties and abrasion properties, among others. Chip developed lab tested material properties for individual reinforcements and resins as well as combinations of reinforcements. His work showed that combinations of reinforcements could produce lighter, abrasion resistant and damage tolerant kayaks than previously imagined. The reason I bring up his work is that it is the first comparison of abrasion resistance properties of kevlar fiber reinforced composites and polyester fiber reinforced composites I know of. Later laboratory work by DuPont, and Union Carbide (manufacturers of Kevlar and Dynel) confirmed Chip's comparison of abrasion properties. Based on Chips work, polyester fiber reinforced epoxy is about the best composite that can be found for abrasion resistance. It is highly tolerant to abrasion and wears smooth. Thus, it is used in high wear areas rather than general hull structure. I don't think it competes with Kevlar. As I am sure you know, Kevlar is a staple of lightweight impact resistant structural composites including custom kayak hull structures.
Later, when working as a Materials and Process Engineer, I recommended the use of polyester fiber reinforced epoxy to customers for high wear areas. It performed well for them. Also, it is relatively inexpensive and easy to laminate.
David
From: "Bernd@... [k-designs]"
To: k-designs@...
Sent: Saturday, December 30, 2017 8:50 AM
Subject: Re: [k-designs] Re: beaching keel
?
Hi
Yes David the keel from my boats are overdesigned for the reason of beaching and some bumps on the way! Many sailors found us crazy what we did with our "PELICAN". Never a problem. Some scratches of course.? Keflar is otherwise the best protector. Only problem, the base has also to be strong. Even when whearing a bulletproof vest (Poliz and military) and you get hit, you get bruizes or have a broken rib. Craig your example from Hawaii is interesting. Keels on a multihull I find roundout stupit.? By the way, if the would use Keflar on the bows the would not have to rebuilt every year. Luiz was just writing that he has always to beach the boat and had never a problem. Damaging the bow or keel area was never reported from my small till the big catamarans (for my "big" is till 13,00m).? I mentioned this already elsewhere. Keflar is the most difficult material to work with, besides the costs. First you need special cissors to cut it (around US $ 100,-). You can not sand it ( try to sand a wol sweater). To apply Epoxy is very difficult, because you see no color difference is a part done or not..? A thrue story. We where sailing at the Baldenaisee near Essen/Germany with the jellow SC435. I got hit by the main sheet and my glasses went in the water. I was so p..set that I turned the boat to land it. The landing place had a wooden front and there after gravel. I was at a good speed, just before the landing I moved back, so that the forward part of the hulls where out of the water. I was sliding with a good speed up the wood prodection and moved forwards. The boat was over the centerpoint and canted forward, I stepped of the boat without getting even wet feet. A guy was coming on in a rush. What no damage? I never could do this with my (Polyester) DART. I would have a hole in the boat. Yesss Sir, The good part of a wood/Epoxy construction with half the weight of the DART. I looked at him, "I do that always in this way"?;-) ?;-))
Bernd
|
Hi
Yes David the keel from my boats are overdesigned for the reason of beaching and some bumps on the way! Many sailors found us crazy what we did with our "PELICAN". Never a problem. Some scratches of course.? Keflar is otherwise the best protector. Only problem, the base has also to be strong. Even when whearing a bulletproof vest (Poliz and military) and you get hit, you get bruizes or have a broken rib. Craig your example from Hawaii is interesting. Keels on a multihull I find roundout stupit.? By the way, if the would use Keflar on the bows the would not have to rebuilt every year. Luiz was just writing that he has always to beach the boat and had never a problem. Damaging the bow or keel area was never reported from my small till the big catamarans (for my "big" is till 13,00m).? I mentioned this already elsewhere. Keflar is the most difficult material to work with, besides the costs. First you need special cissors to cut it (around US $ 100,-). You can not sand it ( try to sand a wol sweater). To apply Epoxy is very difficult, because you see no color difference is a part done or not.? A thrue story. We where sailing at the Baldenaisee near Essen/Germany with the jellow SC435. I got hit by the main sheet and my glasses went in the water. I was so p..set that I turned the boat to land it. The landing place had a wooden front and there after gravel. I was at a good speed, just before the landing I moved back, so that the forward part of the hulls where out of the water. I was sliding with a good speed up the wood prodection and moved forwards. The boat was over the centerpoint and canted forward, I stepped of the boat without getting even wet feet. A guy was coming on in a rush. What no damage? I never could do this with my (Polyester) DART. I would have a hole in the boat. Yesss Sir, The good part of a wood/Epoxy construction with half the weight of the DART. I looked at him, "I do that always in this way"?;-) ?;-))
Bernd
|
I beach my kd650 rotinely, actually every time we sail...until now zero problem... --
?Att,
?Luiz Boms ?Tel_21_982763737
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Hi All, The bottom of the KD860 has 2 x ply, plus glass plus epoxy paint plus anti foul plus internal structure, it all adds up?making it strong enough for beaching?no problem. I have sailed on a few cats in Hawaii and although they had keels these did not touch the bottom instead the bows would bounce up and down on the beach. I spoke to one shipper he said when they pull the boat out for maintenance they grind the bottom/bow back and re glass. It was a solid glass boat though.? I guess it depends a lot on where you sail. Where I live there is very little difference between high and low tide . Beaching a keeled cat will see you stuck in the sand if not carefull. The little waves driving your keels inch by inch deeper into the sand.?A flat bottom is much easier to beach and retrieve. Craig
On Saturday, 30 December 2017, 8:12, "mancebodesigns@... [k-designs]" wrote:
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I don't think beaching keels are suitable in general. They can work on cobble or rocky beaches but are not effective on sand or mud beaches. They also add wetted surface, so performance suffers. Also, they are not very good protection from big rocks.
If you want abrasion protection for sand, mud and fine gravel, I think polyester reinforced epoxy is better. I am thinking of Xynole polyester or Dynel polyester fabric. Either is far superior to glass cloth reinforcement. These products are relatively heavy when saturated with epoxy. However they would generally only be needed for the forward 40% of the hulls, from chine to chine.
I think only people who know they will be beaching their boats often should worry about it anyway. My wife's small trimaran is simply anchored in ankle-deep water when coming ashore. We have 12-foot tidal range here, so she looks for sandy spots. After 7-years, the hulls still look great.
David
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Okay you have read in the meentime the other comments, which underline my feeling to. At last, Nobody was telling that the do not work, but insufficient when slow. No pointing qualitay and a lot of leeway. I am wondering, did ?you have understand what I was descriping some letters ago? That the boat needs some underwater area that the panels can work. Which the KD860 has not ?(one feet if you like, if this is more easy for you to understand).That AV boards are unworkable, again , you do not read letters correctly. On our Pelican with a length to beam ration of 1 : 14 (which automatic means more draft, the work). Again a complaint against boards. Self the center board which in no case can damage a hull. Do you understand the importance of that? NO holes in a hull, no blub, blub and swim after the boat has sunk.? I had a good laugh about the other issue. Sacrificing ?beach keel¡°. When I look at the extreme heavy boats at the Junk Rig Association, beaching would logical mean a disaster. I use a layer of Keflar on my smaller desings till (till about 8 m). We had Keflar also on the Pelican keel flat, happely so, because we had the boat sometimes ?on the rocks¡° (I do not mean in my Vodka). Sometimes when we where out with our "Butterfly" in Stellendam. Low water, so the boat on the sand. Lying in the sun. Shit the water is coming. Ursi my wife complaining. Can we not stay a bit longer? Why not, so I with my back under the forem bean and slide the boat a little higher up on the sandbar, good for another 15 minutes. ?Sand with pepples etc. I have still photos from this outings. Sorry, can not show them, these photos are, in our narrow-minded world ?seen today ?as porno. We never where wearing clothes when we where sailing. At last, boats from Bolger and Michalak and Layden (Paradox) sail beztter with the keel stringers on the outside. The sail better to windward as boats with the stringers on the inside. The work as AV contraptions. With wonderment I see photos from very crute endplates on some monos. The owners are enthusiast (by the way, the function as AV plates), now my boat is listening to my rudder much better.? There is of course much room for ?improvements of the AV panels, but not in the context of the group. So, at last, please keep us free from ?free discussion¡° nobody was asking for. We are a boat builders group. When you have someting to show us (I mean a boat) you welcome to show us. Otherwise let us build our boats withot bothering us.
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I don't think beaching keels are suitable in general. They can work on cobble or rocky beaches but are not effective on sand or mud beaches. They also add wetted surface, so performance suffers. Also, they are not very good protection from big rocks.
If you want abrasion protection for sand, mud and fine gravel, I think polyester reinforced epoxy is better. I am thinking of Xynole polyester or Dynel polyester fabric. Either is far superior to glass cloth reinforcement. These products are relatively heavy when saturated with epoxy. However they would generally only be needed for the forward 40% of the hulls, from chine to chine.
I think only people who know they will be beaching their boats often should worry about it anyway. My wife's small trimaran is simply anchored in ankle-deep water when coming ashore. We have 12-foot tidal range here, so she looks for sandy spots. After 7-years, the hulls still look great.
David
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Agreed. Sticking to farming implements, might be best for all.
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Dear All .
Please may this Man continue doing what he is good at..designing things that are ploughing fields.?
On Dec 29, 2017 16:32, "StoneTool owly@... [k-designs]" < k-designs@...> wrote:
??? One aspect of the KD 860 that bothers me somewhat is the lack
of any sort of sacrificial "beaching keel".? With either the AV
panels, assuming that they would work with a very sharp chine,
something nobody hear has related accomplishing (making them work
at all), or Bernd's single pivoting centerboard, or luff boards,
there really is nothing but the hull bottom to take the abuse if
one beaches the boat.? Pete's low aspect ratio keel on Oryx should
provide at least something for the boat to stand on.? The only
photo I've seen of these keels is the one below, and they seem to
be aft of the CG.?? Interestingly the forward end of the boat
appears to be solid decked....... something I had not observed
before, and something I do not like at all.? One aspect I liked
about the KD 860 from day one was the fact that the bridge deck
began well aft.
??? It was discouraging to me to see the AV panels more or less
abandoned as unworkable for the 860 in this discussion, but at
least the two solutions do not sacrifice the shallow draft that is
so attractive.? It's an unfortunate fact of life that designers
like Bernd do not net enough from their work to be able to do a
lot of R&D.? I can't imagine plans sales even paying the
bills.? It's not like the America's Cup where people with hugely
deep pockets and throw millions in to R&D.?? That makes it
largely a collective effort between designer and builder, and in
many ways that's a good thing, and I'm deeply grateful for men
like Bernd who labor designing boats out of love for boats, and
give so generously of their time, to make these boats a success.?
I've often asked uncomfortable questions in my posts, but my
intent has been to promote free discussion and view and understand
this design that has captured my imagination as honestly as
possible with all it's brilliant innovation as well as it's
shortcomings, and their solutions.??? As a man who has engineered
and designed quite a few complex systems, and built them, I know
how it works, and things I've built that I thought were bullet
proof have often needed revision.?? The things I've designed and
built are NOT floating on the oceans of the world, but harvesting
crops in the field.
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? H.W.
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Show quoted text
?
??? One aspect of the KD 860 that bothers me somewhat is the lack
of any sort of sacrificial "beaching keel".? With either the AV
panels, assuming that they would work with a very sharp chine,
something nobody hear has related accomplishing (making them work
at all), or Bernd's single pivoting centerboard, or luff boards,
there really is nothing but the hull bottom to take the abuse if
one beaches the boat.? Pete's low aspect ratio keel on Oryx should
provide at least something for the boat to stand on.? The only
photo I've seen of these keels is the one below, and they seem to
be aft of the CG.?? Interestingly the forward end of the boat
appears to be solid decked....... something I had not observed
before, and something I do not like at all.? One aspect I liked
about the KD 860 from day one was the fact that the bridge deck
began well aft.
??? It was discouraging to me to see the AV panels more or less
abandoned as unworkable for the 860 in this discussion, but at
least the two solutions do not sacrifice the shallow draft that is
so attractive.? It's an unfortunate fact of life that designers
like Bernd do not net enough from their work to be able to do a
lot of R&D.? I can't imagine plans sales even paying the
bills.? It's not like the America's Cup where people with hugely
deep pockets and throw millions in to R&D.?? That makes it
largely a collective effort between designer and builder, and in
many ways that's a good thing, and I'm deeply grateful for men
like Bernd who labor designing boats out of love for boats, and
give so generously of their time, to make these boats a success.?
I've often asked uncomfortable questions in my posts, but my
intent has been to promote free discussion and view and understand
this design that has captured my imagination as honestly as
possible with all it's brilliant innovation as well as it's
shortcomings, and their solutions.??? As a man who has engineered
and designed quite a few complex systems, and built them, I know
how it works, and things I've built that I thought were bullet
proof have often needed revision..?? The things I've designed and
built are NOT floating on the oceans of the world, but harvesting
crops in the field.
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? H.W.
|
??? One aspect of the KD 860 that bothers me somewhat is the lack
of any sort of sacrificial "beaching keel".? With either the AV
panels, assuming that they would work with a very sharp chine,
something nobody hear has related accomplishing (making them work
at all), or Bernd's single pivoting centerboard, or luff boards,
there really is nothing but the hull bottom to take the abuse if
one beaches the boat.? Pete's low aspect ratio keel on Oryx should
provide at least something for the boat to stand on.? The only
photo I've seen of these keels is the one below, and they seem to
be aft of the CG.?? Interestingly the forward end of the boat
appears to be solid decked....... something I had not observed
before, and something I do not like at all.? One aspect I liked
about the KD 860 from day one was the fact that the bridge deck
began well aft.
??? It was discouraging to me to see the AV panels more or less
abandoned as unworkable for the 860 in this discussion, but at
least the two solutions do not sacrifice the shallow draft that is
so attractive.? It's an unfortunate fact of life that designers
like Bernd do not net enough from their work to be able to do a
lot of R&D.? I can't imagine plans sales even paying the
bills.? It's not like the America's Cup where people with hugely
deep pockets and throw millions in to R&D.?? That makes it
largely a collective effort between designer and builder, and in
many ways that's a good thing, and I'm deeply grateful for men
like Bernd who labor designing boats out of love for boats, and
give so generously of their time, to make these boats a success.?
I've often asked uncomfortable questions in my posts, but my
intent has been to promote free discussion and view and understand
this design that has captured my imagination as honestly as
possible with all it's brilliant innovation as well as it's
shortcomings, and their solutions.??? As a man who has engineered
and designed quite a few complex systems, and built them, I know
how it works, and things I've built that I thought were bullet
proof have often needed revision.?? The things I've designed and
built are NOT floating on the oceans of the world, but harvesting
crops in the field.
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? H.W.
|
Bernd Kohler
Robert Twiss
