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Bedford

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wow.. nice looking boats on here.. I'm still stuck with my 65cm design bare hull.. to small displacement vor my electronics :(

 

But why do you all make the hull out of a structural shell that has to be stiff? would it not maybe be lighter to just glass over a foam core and make holes in the foam for the electronics?

 

please give me some input here or I'll have to start over building once more in the end^^

 

If the boat were very small - maybe. The problem with the foam is that it would work well if you carved it then glassed it - but you will have a very difficult time constructing a consistent hull shape this way. By strip planking with balsa, you can easily get a repeatable shape with relatively little fairing to do. You could pour foam into a shell of a hull...but why? Also, solid foam, if not the right type or used properly, could also absorb or trap water giving you a bigger weight problem.

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If the boat were very small - maybe. The problem with the foam is that it would work well if you carved it then glassed it - but you will have a very difficult time constructing a consistent hull shape this way. By strip planking with balsa, you can easily get a repeatable shape with relatively little fairing to do. You could pour foam into a shell of a hull...but why? Also, solid foam, if not the right type or used properly, could also absorb or trap water giving you a bigger weight problem.

 

well, I used bulkheads cut out of thin balsa or plastic. I then put them between the single foam blocks every 7cm (2"+3/4th of an inch?) and sanded down the foam in between by hand untill I reached the bulkheads.. than epoxy and fairing, epoxy with glass, fairing, epoxy, fairing, spraypaint, done...

my first hull built that way (without the spraypaint) was stiff enough for sailing I'm sure.. only when I dissolved the foam inside to save weight, the really thin layer of epoxy left would sagg in between the bulkheads as If bending inwards and eventually crack if I lifted the hull somewhere else than at the bulkheads..

 

what do you mean: not a "consistend" hull shape?

and I would hope for that kind of hull to be just as dry/waterthight as "normal" hulls.. no water touching the foam..

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wow.. nice looking boats on here.. I'm still stuck with my 65cm design bare hull.. to small displacement vor my electronics :(

 

But why do you all make the hull out of a structural shell that has to be stiff? would it not maybe be lighter to just glass over a foam core and make holes in the foam for the electronics?

 

please give me some input here or I'll have to start over building once more in the end^^

 

 

Done that. Built my first 4 or 5 hulls out of foam. It's very heavy. You wouldn't believe the difference between a styrofoam hull and a balsa strip hollow hull. And it's difficult to attach things like chainplates to the foam blank.

It is also much much much easier to attach structure (keel support, mast support, rudder stock, servo mounts) to a bare shell.

 

There are 2 neat things about a foam hull though. Unsinkable, great for heavey weather. And it's very easy to shape something new. I've only built one boat from plans (out of 11 or 12) - I like to experiment. It's easy in foam. Saw a blank, rough shape with a belt sander, hand sand to shape. When you're happy, saw it into sections, trace them onto patterns for shadow stations and plank a balsa hull. :P If you don't have good hands, and good eye, and imagination, you might end up with funny looking boats, but it's super easy to try it.

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well, I used bulkheads cut out of thin balsa or plastic. I then put them between the single foam blocks every 7cm (2"+3/4th of an inch?) and sanded down the foam in between by hand untill I reached the bulkheads.. than epoxy and fairing, epoxy with glass, fairing, epoxy, fairing, spraypaint, done...

my first hull built that way (without the spraypaint) was stiff enough for sailing I'm sure.. only when I dissolved the foam inside to save weight, the really thin layer of epoxy left would sagg in between the bulkheads as If bending inwards and eventually crack if I lifted the hull somewhere else than at the bulkheads..

 

what do you mean: not a "consistend" hull shape?

and I would hope for that kind of hull to be just as dry/waterthight as "normal" hulls.. no water touching the foam..

 

 

I thought he meant "not fair" at first (which is patently untrue) but re-reading I think he means it would be hard to build a bunch of boats with little deviation. Hard to free form shape something the same way twice. He's right.

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well, I used bulkheads cut out of thin balsa or plastic. I then put them between the single foam blocks every 7cm (2"+3/4th of an inch?) and sanded down the foam in between by hand untill I reached the bulkheads.. than epoxy and fairing, epoxy with glass, fairing, epoxy, fairing, spraypaint, done...

my first hull built that way (without the spraypaint) was stiff enough for sailing I'm sure.. only when I dissolved the foam inside to save weight, the really thin layer of epoxy left would sagg in between the bulkheads as If bending inwards and eventually crack if I lifted the hull somewhere else than at the bulkheads..

 

what do you mean: not a "consistend" hull shape?

and I would hope for that kind of hull to be just as dry/waterthight as "normal" hulls.. no water touching the foam..

 

I meant "consistent" (did I have that misspelled at one point? I don't remember fixing it...anyway...). I didn't think about gluing blocks of foam between wood shadows...you could certainly do better that way. I didn't mean to be a hater.

 

Separated my molds this evening - once I got an opening started, I hit it with water and it came open like butter.

 

412020186_4d3ecee180.jpg

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I meant "consistent" (did I have that misspelled at one point? I don't remember fixing it...anyway...).

 

nah, its ok, I know the word.. I'm just not sure what you mean by it.. my dictionary gave me 14 translations for it :blink:..

consistent as is thight, equal, continuesly, analog, durab le, permanent etc..

 

what were you trying to tell me about "consistent hull"? ;)

 

 

I didn't think about gluing blocks of foam between wood shadows...you could certainly do better that way.

so if I use wood shadows I do get a "consistent" hull, do I?

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So I'm building a small model boat for a tech class in school, and all I need for the grade is the hull and one (moving) mechanical piece. I want to have that piece be a canting keel and I'll put a rig on it on my time.

 

Has anyone done any canting keels, and if you have, do you have pics? Advice?

 

The boat is 2ft long, built probably out of either glass or wood. No class, just for fun.

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So since I'm apparently no longer allowed to edit my posts (?) and I want to bump it anyway:

 

I saw earlier in the thread that multi's less than 48'' tend to be hard to handle, what if you put a t-foil on the rudder (a la Stealth F16). Should that help the pitch poling? Make something around 36'' long by 24'' wide with t-foils.

 

Sail-able or no? Should I stick with the mono? I want to go as fast as possible, but I also want to have it be reasonably easy and cheap to build.

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I saw earlier in the thread that multi's less than 48'' tend to be hard to handle, what if you put a t-foil on the rudder (a la Stealth F16). Should that help the pitch poling? Make something around 36'' long by 24'' wide with t-foils.

Sail-able or no? Should I stick with the mono? I want to go as fast as possible, but I also want to have it be reasonably easy and cheap to build.

 

A T-foil on the rudder is fine------until it comes out of the water. Then it's instant "Pitchpole City"

 

The main reason for multis pitchpoling is the lee bows digging in and the water pressure on the foredeck pushing the bow down.

 

The real answer is to increase the bouyancy in the bows AND have rounded foredecks which can pierce the waves, like IDEC.

 

Also, if you want to go as fast as possible and have it easier to build, choose a Trimaran. Agreed it is three hulls to build--against two, but thats childs play compared to the problems of sorting the control arrangements on a Cat. The tri is really just a bouancy stabilised monohull, and all the sail and rudder control "Gubbins" are in one hull, just like a monohull model.

 

Come to think of it a scale model of IDEC would be nice. :lol:

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