A lighter alternative?
- Thread starter JustinC
- Start date
Pete McMiller
Well-known member
Justin,
Here is my construction pics and discussion of the Devlin Pole boat I built last summer. Total weight was 70.6 lbs. and I do car top it.
http://duckboats.net.nmsrv.com/cgi-bin/forum/gforum.cgi?do=post_view_threaded;post=126154;sb=post_latest_reply;so=ASC;
Here is my construction pics and discussion of the Devlin Pole boat I built last summer. Total weight was 70.6 lbs. and I do car top it.
http://duckboats.net.nmsrv.com/cgi-bin/forum/gforum.cgi?do=post_view_threaded;post=126154;sb=post_latest_reply;so=ASC;
I've seen Pete's boat and it is a nice one.
Justin-
it's not exactly a hummer/robber style but I built a pirogue that weighed less than 40 lbs...very nice low profile....and my experience with the hybrid foam/wood boats is that they're heavy...not something I would want to try to car top...though if you make them smaller than 12 ft long perhaps won't be too bad....but I still don't think you'd get it light enough...could be wrong though....
Dani
it's not exactly a hummer/robber style but I built a pirogue that weighed less than 40 lbs...very nice low profile....and my experience with the hybrid foam/wood boats is that they're heavy...not something I would want to try to car top...though if you make them smaller than 12 ft long perhaps won't be too bad....but I still don't think you'd get it light enough...could be wrong though....
Dani
Bob B
Well-known member
Justin,
the wood and epoxy are the things that add up.
You can build it with thinner wood and sig. lower the weight but you will have to be aware that the strength is lower depending on the wood that you buy. Boat builders and esp. racers do it all the time. High end metric marine ply is expensive.
You can also use fancy stuff like carbon fiber or kevlar to get the strength but the cost goes up.
I would look for some "Door Skin" ply wood in a thinner version than 1\4" and then use thinner wood in the other parts of the boat. Coat it inside and out with epoxy to protect the more fragile wood parts.
A robber will save a bunch of weight as well.
The folks at West System have a cool magazine that covers light weight building often. Give them a call for a back issue or a little help with your ideas.
I really like the boat and the shape for some hunting and I know it can be built lighter.
the wood and epoxy are the things that add up.
You can build it with thinner wood and sig. lower the weight but you will have to be aware that the strength is lower depending on the wood that you buy. Boat builders and esp. racers do it all the time. High end metric marine ply is expensive.
You can also use fancy stuff like carbon fiber or kevlar to get the strength but the cost goes up.
I would look for some "Door Skin" ply wood in a thinner version than 1\4" and then use thinner wood in the other parts of the boat. Coat it inside and out with epoxy to protect the more fragile wood parts.
A robber will save a bunch of weight as well.
The folks at West System have a cool magazine that covers light weight building often. Give them a call for a back issue or a little help with your ideas.
I really like the boat and the shape for some hunting and I know it can be built lighter.
Pete McMiller
Well-known member
Justin,
As Bob said, the Kara is heavy because of what you make it out of. Mine came out way too heavy for a car topper and must weigh at least 120 lbs. That said, it was my first boat build and I have learned a lot since then. If I were to make another I would use much thinner but still strong framing material as I think a lot of the weight comes from the frame. Also, cut the plywood from 1/4" (6mm) down to 3/16" (4mm). Use very thin glass cloth. 3.25 oz is sufficient and has been used in two of my boats. Be very careful when putting on the epoxy as it is very easy to over do it and of course adds weight. Dropping 25-30 lbs should be doable but I'm not sure you can save much more than that without a redesign of the basic form.
Good luck and take pics if you decide to take it on. The Kara is a fun project for a first time builder and doesn't take months to complete.
As Bob said, the Kara is heavy because of what you make it out of. Mine came out way too heavy for a car topper and must weigh at least 120 lbs. That said, it was my first boat build and I have learned a lot since then. If I were to make another I would use much thinner but still strong framing material as I think a lot of the weight comes from the frame. Also, cut the plywood from 1/4" (6mm) down to 3/16" (4mm). Use very thin glass cloth. 3.25 oz is sufficient and has been used in two of my boats. Be very careful when putting on the epoxy as it is very easy to over do it and of course adds weight. Dropping 25-30 lbs should be doable but I'm not sure you can save much more than that without a redesign of the basic form.
Good luck and take pics if you decide to take it on. The Kara is a fun project for a first time builder and doesn't take months to complete.
Well, I have been doing alot of research here and I may have come up with a solution. If you have a copy of Successful Waterfowling you will know the "Gunning Johnboat" designed by Zack Taylor. Always thought the design was pretty neat and looks like it will do as I ask. I am going to draw up panel measurements and build her as a stitch and glue boat to save a little weight. Also planing on using 1/4" plywood (except the transoms which will be 1/2"). I figure the boat built with a frame is around 80lbs so stitch and glue should be a little lighter and easier to build.
Justin-
If you end up wanting to build a boat, nothing is lighter (or likely as easy) as strip construction in a light wood. Some boats can even be built hybrid with a strip hull and canvas deck. Most any plan can be converted to strip and its a fairly easy and forgiving method to build in.
Good luck.
Derek
If you end up wanting to build a boat, nothing is lighter (or likely as easy) as strip construction in a light wood. Some boats can even be built hybrid with a strip hull and canvas deck. Most any plan can be converted to strip and its a fairly easy and forgiving method to build in.
Good luck.
Derek
I see that you are pursuing another option, but I'd suggest thinking about building a Kara out of a composite like Coosa. Take a look at Coosa or the like, they are glass reinforced foam panels for marine fabrication (used in transoms, floors, etc...) that come in a great diversity of densities and thicknesses and are structural and can be used just like wood (cuts nice, holds screws, etc...). Were I to want a light marsh boat, no question I would look at doing it this way. It will be a little spendy, but you could get it very light and it would build lightning fast, especially since the material is waterproof without coating. Coosa makes some very light/low density that would work great for the framing and a diversity of heavier panel types for the sheathing.
Ray
Well-known member
I love the look of the KARA, but the weight has always been an issue. If you are experienced in frame on molded, or stitch and glue construction you can make a KARA much lighter. But you will need some knowledge before hand, which can only be gained from building boats or building something else that requires conceptual processes rather than following plans step by step.
One way that may result in a lighter KARA is to build the frame a couple of inches narrow than plan, cover with battens to creat a form, and then cold mold it with thin, wide cedar veneers on the bias. Cover the outside with kevlar and the inside with 3oz high strength glass from RAKA. The frame is not used in the final boat but you will need some ribs and they can be thin cedar laminations covered in tape. This might get you an 80 pound or less boat.
an example of cold molding a canoe http://www.westsystem.com/ss/assets/Uploads/laminated.pdf
As mentioned up above there is also the Hybrid. Rich has posted here before but gets poo-pooed often due to the size of his boats and the materials used (ACX and luan door skins) (and they are "ugly). However, the concept behind the Hybrid is still valid: a one person marsh boat that fits into the bed of a truck and can be made in two weekends. The link above takes you to the main site for buying plans. The original plans can be found on here under the boat specs in the marsh boat listing.
Over on the duck hunter refuge boats and blinds forum there is a sticky documenting the construction of hundreds of Hybrids - 156 pages now. It shows the multible variations of the boats being built as well. I think I might have built one of the lightest Hybrids at 63 pounds. It is the largest boat you can build out of two sheets of plywood. Extremely stable (more stable than my foamer), hides in low grass, car tops easy. However it does not paddle well due to its short length and huge wet surface area. It motors very well with a 3hp and a 400 pound load.
http://www.refugeforums.com/refuge/showthread.php?t=602498&page=156
If you have no issue with spending money, then as Tod mentioned there are other composite materials to be used. Core Cell foam has a density of 5.5 pounds per cubic foot. ACX fir plywood is over 30 pounds per cubic foot. Core cell is thermal moldable so you just need to heat it to get it to take a bend to form the hull. However, you will need to use a lot of cloth layers and a kevlar layers to protect it. Once it has glass on both faces it has a similar strength to fir plywood based on testing by the US Navy. WEST systems did a panel testing between the various build materials and have a great article showing cost along with other data.
http://www.westsystem.com/ss/assets/Uploads/06-Flatpanels.pdf
The main issues with composite panels are their cost and shipping. Most materials are shipped in 4x8 sheets and you will have to pay for trucking cost. Core cell can be found from one retailer in Florida in 24x48 pieces that can be mailed. I priced out a boat design I am thinking and it will be just under $900 for the core cell. Plywood would be less than $200. Now Tod has me thinking about Coosa.
One way that may result in a lighter KARA is to build the frame a couple of inches narrow than plan, cover with battens to creat a form, and then cold mold it with thin, wide cedar veneers on the bias. Cover the outside with kevlar and the inside with 3oz high strength glass from RAKA. The frame is not used in the final boat but you will need some ribs and they can be thin cedar laminations covered in tape. This might get you an 80 pound or less boat.
an example of cold molding a canoe http://www.westsystem.com/ss/assets/Uploads/laminated.pdf
As mentioned up above there is also the Hybrid. Rich has posted here before but gets poo-pooed often due to the size of his boats and the materials used (ACX and luan door skins) (and they are "ugly). However, the concept behind the Hybrid is still valid: a one person marsh boat that fits into the bed of a truck and can be made in two weekends. The link above takes you to the main site for buying plans. The original plans can be found on here under the boat specs in the marsh boat listing.
Over on the duck hunter refuge boats and blinds forum there is a sticky documenting the construction of hundreds of Hybrids - 156 pages now. It shows the multible variations of the boats being built as well. I think I might have built one of the lightest Hybrids at 63 pounds. It is the largest boat you can build out of two sheets of plywood. Extremely stable (more stable than my foamer), hides in low grass, car tops easy. However it does not paddle well due to its short length and huge wet surface area. It motors very well with a 3hp and a 400 pound load.
http://www.refugeforums.com/refuge/showthread.php?t=602498&page=156
If you have no issue with spending money, then as Tod mentioned there are other composite materials to be used. Core Cell foam has a density of 5.5 pounds per cubic foot. ACX fir plywood is over 30 pounds per cubic foot. Core cell is thermal moldable so you just need to heat it to get it to take a bend to form the hull. However, you will need to use a lot of cloth layers and a kevlar layers to protect it. Once it has glass on both faces it has a similar strength to fir plywood based on testing by the US Navy. WEST systems did a panel testing between the various build materials and have a great article showing cost along with other data.
http://www.westsystem.com/ss/assets/Uploads/06-Flatpanels.pdf
The main issues with composite panels are their cost and shipping. Most materials are shipped in 4x8 sheets and you will have to pay for trucking cost. Core cell can be found from one retailer in Florida in 24x48 pieces that can be mailed. I priced out a boat design I am thinking and it will be just under $900 for the core cell. Plywood would be less than $200. Now Tod has me thinking about Coosa.
Very thorough Ray. Since you have fancy numbers in there, I'll step up and say that Coosa comes in densities that start at 15 and go up to 26 (which is a proxy for marine plywood in strength, but lighter). A frame out of nautical 15 and skins out of one of the heavier would be sweet. I've never held the 15 in hand though, so I may be wrong.