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More questions (hopefully not stupid ones)

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t3rse
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More questions (hopefully not stupid ones)

Postby t3rse » Wed Dec 10, 2014 1:29 am

I've decided it's time. I'm going to try and mimic Denisesewa (viewtopic.php?f=196&t=2386805) to some extent (which is based on the seabreeze plans by Phezulu1). I found a local source of okoume (3 or 4mm, not sure which yet) that I'll be using for the core.

I've made dxf drawings to represent the dimensions Phezulu1 used:
http://www.thingiverse.com/thing:584300
Image

I've done some reading, looked at some dimensions, and read a lot of stuff that doesn't really make a whole lot of sense to me....I just want to build something to learn on honestly....

So now I've got some questions:
1. I see that a lot of things work, maybe some better than others, but that 'machine tolerances' aren't really a requirement. That said, some people seem to use flat wings, and some positive lift in the front and negative lift in the rear...why and what?

2. When someone says, "I have a 960mm mast", are they measuring from the top of the fuselage or is it the whole assembly?

3. There will be more I'm sure....

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Re: More questions (hopefully not stupid ones)

Postby Hawaiis » Wed Dec 10, 2014 2:56 am

don't worry about the angles yet, concentrate on making it rigid and strong at the joints.

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Re: More questions (hopefully not stupid ones)

Postby t3rse » Wed Dec 10, 2014 3:11 am

Hawaiis wrote:don't worry about the angles yet, concentrate on making it rigid and strong at the joints.


Thanks...some of that was directly aimed at you. ...I'm going to make the fuselage perpendicular to the board so I can tweak the lift surfaces later if need be. If I were to use one type of carbon cloth (not caring about presentation) what should I purchase? I'm not super concerned about cost....

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Re: More questions (hopefully not stupid ones)

Postby Hawaiis » Wed Dec 10, 2014 7:47 am

I am not very good at Carbon Fiber, Any Expert want to chime in?

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Re: More questions (hopefully not stupid ones)

Postby Bradn » Wed Dec 10, 2014 10:39 am

I'm sure the pretty weave cloth is only used on the outside for looks. Mine was mostly Unidirectional with +-45 Deg layers near the outside where they are more effective.

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Re: More questions (hopefully not stupid ones)

Postby t3rse » Wed Dec 10, 2014 3:25 pm

What do you mean by "near the outside where they are more effective"?

I was thinking of just using biaxial weave. What weight are you using? I suppose this line of questioning might be more geared toward the board maker forum.

edit: and I plan on gusseting or adding a flair type boss on the mast->mount point as Rev suggested elsewhere. I think I have a decent plan in place from all the great guidance I've read through here, and a few people have posted exactly how, what weights, types, of carbon/glass they've used, but I was hoping to just make a single order if possible, and I don't mind paying for it all. Also, I have a bit of West Marine epoxy laying around, and was planning on going with this....let me know if I should use something else.

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Re: More questions (hopefully not stupid ones)

Postby t3rse » Wed Dec 10, 2014 11:53 pm

A different possible direction:

I found a place locally that can make complex EPS foam shapes. Instead of using okume wood, I could have this place (assuming cost isn't too steep) cut out all the foil bits for me and I just wrap it in carbon (I know I'd need a lot of carbon but that's ok). Is this a good idea?

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Re: More questions (hopefully not stupid ones)

Postby Hawaiis » Thu Dec 11, 2014 12:27 am

From my limited experience with carbon. The best way is to make a mold, which I have not done. Another is to make a carbon skin over wood, which I have done. Works well. There are people that can make them much better with vaccum bagging etc.

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Re: More questions (hopefully not stupid ones)

Postby tkettlepoint » Thu Dec 11, 2014 1:26 am

you don't want eps inside of your foil it will off gas and may bubbles... Hawaiis knows about off gassing in foils from one he had and bubble in the plate mount. if you want to use foam you need closed cell ( corecell or dinvy) which will not off gas when they get home on the beach in the sun.

either way you need the right about and type of carbon to make it strong enough and little flex in it.

Molds are not fun to make. a lot of time and work to make them by hand. Sanding and polishing but you can do it if you take your time and have some skills. I just say watch a lot of youtube on mold making.
I just say a lot of release agent is your best friend or all your work and the plug is trash

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t3rse wrote:A different possible direction:

I found a place locally that can make complex EPS foam shapes. Instead of using okume wood, I could have this place (assuming cost isn't too steep) cut out all the foil bits for me and I just wrap it in carbon (I know I'd need a lot of carbon but that's ok). Is this a good idea?

t3rse
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Re: More questions (hopefully not stupid ones)

Postby t3rse » Thu Dec 11, 2014 1:56 am

Sounds like I need to use wood...

I could always melt out the foam but I guess in the end I'd still have to have a vent.

If i get something that works I'll consider making a mold. Sometimes I have that kind of patience and sometimes I don't...

I'm thinking of running a bit of uni up and down the mast and the on the fuselage and then using biax or weave on top. I'll sandwich the wood with glass. I guess I could get away with just uni if I run it right; I was worried about higher modulus uni and bash resistance but with a wood core it would always be repairable.

Thanks for the info.


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