Malibu Outrigger

[upchurchmr]

BobBill,

I had an old wooden Tornado with 4mm occume (0.160") for a deck, but it had small stringers supporting, we walked on it with no problem if you are looking for lighter weight. You should be able to search for the plans to see what was done - free.

Akas are much lighter and stiffer if they are hollow, they do have to be taller to get the stiffness. If you wanted one place to use higher tech this would be it. Either unidirectional glass or carbon on top and bottom. Anywhere you expect to put a bolt you should fill the hollow area with wood so it will not crush.

Have you seen the Gougeon's book on boat building? It is available as a free download. Corley provided the location in another thread. http://www.westsystem.com/ss/assets/...k%20061205.pdf This is the best modern reference I know. It might be applicable to the Malibu build.

Good luck, looking forward to the build pictures.

Marc

[BobBill]

Originally Posted by upchurchmr

BobBill,

I had an old wooden Tornado with 4mm occume (0.160") for a deck, but it had small stringers supporting, we walked on it with no problem if you are looking for lighter weight. You should be able to search for the plans to see what was done - free.

Akas are much lighter and stiffer if they are hollow, they do have to be taller to get the stiffness. If you wanted one place to use higher tech this would be it. Either unidirectional glass or carbon on top and bottom. Anywhere you expect to put a bolt you should fill the hollow area with wood so it will not crush.

Have you seen the Gougeon's book on boat building? It is available as a free download. Corley provided the location in another thread. http://www.westsystem.com/ss/assets/...k%20061205.pdf This is the best modern reference I know. It might be applicable to the Malibu build.

Good luck, looking forward to the build pictures.

Marc

Marc, Thanks. Was thinking about that...the aka advice is great...gave me couple of ideas too.

Planning the ama to be surfboard-like construction, foam under glass, for lightness when trailed...as Dierking noted, can always make heavier...want to keep boat weight 350 (class min) to 400.

Idea about making it higher just rang a bell regarding connection and being able to fold the iokas/akas.

I have now learned the boat does kick up some splash, so working out that problem. Do not want to widen deck as plans note...not at this point, anyway.

That and wish to have more open cockpit area need some thought, but I have some ideas, just do not want to dive in and later wish otherwise.

I have the "brother's" book and some links, which may have been disabled, and most of the material from West I have normally incorporated in past projects. A lot of it is common sense and the carbon build material and epoxy information is super.

To be candid, yourself, Tom Speer, Par, Clark, Alan W, CutOnce, Lord and some others I cannot recall now, and others describing their builds, have provided better and more practical advice, along with EpoxyMoron, Vegas and Gouvernail and some other kind and knowledgeable people on SA.

I gather and apply as needed. Invaluable.

Will keep the project posted here.

[upchurchmr]

BobBill,

You are well beyond any typical advise I would have.
I would be concerned with the idea that glass on "solid" foam (surfboard style) is automatically lighter than thin plywood. Foam sounds light but filling the entire cavity mounts up quickly. In a different arena, I have tried to do the same in secondary structure on aircraft, I always get the solid foam part ending up heavier - this may not be useful since it is significantly different types of structure . Just a concern.

I built a relatively short aka for a 5' wide catamaran row boat. It was surprising that a hollow 2" square member was enough to hold my wife and I standing on it (375#) without any glass. The upper and lower caps were 1/4" cedar and the sides (shear webs) were 1/8" Baltic birch plywood - 3 ply non marine. The plywood was cut on a 45 degree angle to the panel, the overlap of the ply to cedar was ~1/8" with an epoxy joint - no real fillets. I was completely shocked to find it didn't break and had very little deflection. After glassing with 6 OZ cloth and West I expect the strength was doubled.

This is not to suggest that design for your akas, since you will have much higher loads, just to show that the hollow design can be really good.

I had replaced some 8# per aka (hollow) members with the 2# hollow ones. The original were just built by "eye" and not tested - obviously heavily over strength.

This is probably more discussion you don't need, take it for what it's worth. (Free ????)

I saw a newer Hobie 18 which has a very small feature for deflecting spray in the fwd hull surface. No idea how well it works.

Good luck.

Marc

[BobBill]

Marc. Much appreciated. Feel free to toss all you want at me, I am wide open for suggestions and advice.

The ama I had in mind would be close to 11' MO original, save the idea of wave piercing bow and the surfboard like composition, might be a bit longer...foam shaped then glassed with epoxy and painted etc.

Would be a bit more trouble than wood, but the ease of set up and travel with light ama seems worth it...at least at this point.

[Corley]

Marc's providing a very salient point here on a small boat, ply can often be the better solution. Foam Sandwich is great when you have large areas on a large boat where you would otherwise need many stringers inside the skin to support the loads. It's also great on decks where you can have large unsupported areas with minimal reinforcement.

[BobBill]

To be honest, the idea came from Dierking's book on building his Ulua and Wa apa outriggers...the foam glass idea.

Dierking uses or used foam with a ply center line or vertical lengthwise stringer, which seemed, to me, quite a good idea, even if these designs are significantly lighter.

I can go either way, but lighter is better for what I have in mind...and, as noted by Marc, such an ama would have to have more depth (height), it seems.

But, I know squat, so have at it.

[upchurchmr]

BobBill,

I might have mispoke. I was trying to suggest a hollow Aka (crossarm) would have to be taller in section than a solid one, to get equal strength. The hollow one would be significantly stiffer for equal bending strength.

My understanding of the ama is that you should set the displacement you want first (100% or greater if you want to fly the vaka). The stretch out the length to make it thin so it will have less wave drag. Personally I always thought and 11' ama on a 18' vaka was too short. While I know many designers make tall thin amas, I always thought you would have less drag from a more semicircular type hull, but a more jerky ride.

Marc

[BobBill]

Originally Posted by upchurchmr

BobBill,

I might have mispoke. I was trying to suggest a hollow Aka (crossarm) would have to be taller in section than a solid one, to get equal strength. The hollow one would be significantly stiffer for equal bending strength.

My understanding of the ama is that you should set the displacement you want first (100% or greater if you want to fly the vaka). The stretch out the length to make it thin so it will have less wave drag. Personally I always thought and 11' ama on a 18' vaka was too short. While I know many designers make tall thin amas, I always thought you would have less drag from a more semicircular type hull, but a more jerky ride.

Marc

Marc, I see your point. Jerky being hobby horsing...I am limited to 17 by rule with 19 foot hull, and planned to do the aka be removable and attach via hinge-pins (like dual pin door hinge) metal locks about three feet to four feet from ama.

The akas would be about 2 feet above water. Had not thought about the wave drag...they have to be flat as well. So, I could form ama with high deck/attachments or add tall brackets per plans. I figured the former, somehow, using Dierking's ideas about the shaped foam/glass piers or plain high deck ama, which seems the better choice.

[BobBill]

Originally Posted by upchurchmr

BobBill,

I might have mispoke. I was trying to suggest a hollow Aka (crossarm) would have to be taller in section than a solid one, to get equal strength. The hollow one would be significantly stiffer for equal bending strength.

My understanding of the ama is that you should set the displacement you want first (100% or greater if you want to fly the vaka). The stretch out the length to make it thin so it will have less wave drag. Personally I always thought and 11' ama on a 18' vaka was too short. While I know many designers make tall thin amas, I always thought you would have less drag from a more semicircular type hull, but a more jerky ride.

Marc

Marc, I have been mulling all of the above over and other stuff, and now leaning your way with ply idea over foam...for lighter and more practical ama, plus hollow akas, but now moved to slightly wider hull bottom and higher freeboard on main hull, and now wondering how to determine the CLP when two hulls present.


Great advice...thanks.

Slowly coming around. I am very deliberate...