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New designer/builder seeking DIY feedback

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compo_pete
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New designer/builder seeking DIY feedback

Postby compo_pete » Sun Jun 22, 2014 4:46 pm

image002.png

So I started playing with hydrofoil designs today in an attempt to really dial in a DIY design before I embark on the project. I'm trying to go as simple as possible, while at the same time ending up with a kick ass setup. Here's what I've got so far. Feedback is truly appreciated.

1. Strut - 1 meter long, Symmetric Eppler 817 profile with a 15 mm camber and 120 mm cord.
Proposed construction: Molded or Vac Bagged. Carbon/Epoxy
Layup: Glass, -45, +45, 0, 90, Core (unknown), 90, 0 +45, -45, Glass (lots of 45s on outside. evidently torsion is killer). Cloth Weight: Unknown
Flange Mount to Board

2. Front Wing - 520 cm span, Assymetric Eppler 837 profile with 12 mm camber and 87 mm avg cord.
Area: ~450 cm2, 75 mm anhedral from center to tip. Aspect Ratio: ~6
Proposed construction: Molded or Vac Bagged. Carbon/Epoxy
Layup: Glass, 0, -45, +45, 90, Core (unknown), 90,+45, -45, 0, Glass (lots of 0s on outside for high bending stiffness). Cloth Weight: Unknown

3. Fuselage - 750 mm from centroid front wing to centroid rear wing. Front wing TE 100 mm forward of strut LE.
25.4 mm (1 in) dia Carbon Pulltrusion ($144 for 48 in http://www.acpsales.com/Carbon-Fiber-Rods.html)

4. Rear Wing -364 cm span, Assymetric Eppler 837 profile with 8.4 mm camber and 61 mm avg cord.
0.5 x area of front wing. Upside Down profile to create nose lifting pitch moment. 53 mm dihedral.
Proposed construction: Molded or Vac Bagged. Carbon/Epoxy
Layup: Glass, 0, -45, +45, 90, Core (unknown), 90,+45, -45, 0, Glass (lots of 0s on outside for high bending stiffness). Cloth Weight: Unknown

5. Board: Whatever I have lying around collecting dust. Preferably something with length forward of the front straps so help ease the noseplants.

Wings are a little higher aspect so they'll have a higher l/d ratio. I went with a little sweep and an AR of 6. It'll be a little harder to learn on but it'll be better after some practice. I just don't want to invest a bunch of time/money on beginner wings and then want something better after 3 sessions.

Right now I am leaning towards internet ordered 3D printed cores with vac bag carbon/glass reinforcement.

Designing the joints is going to be a lot of the effort and is what I'll be obsessing about at all waking hours until I get it figured out.

I would really appreciate any time taken to trash these ideas/specs so I can learn from the community. And I'd be happy to provide the resulting 3D models to the community along with methods/process/materials that have yielded results for me.

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windfreak74
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Re: New designer/builder seeking DIY feedback

Postby windfreak74 » Sun Jun 22, 2014 5:05 pm

Great work Compo pete!
there is a lot of valuable info on some of the threads discussed on the hydrofoil fórum.

welcome to the crowd!
and please share pics of the process!
:thumb:
Pedro

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Re: New designer/builder seeking DIY feedback

Postby windfreak74 » Sun Jun 22, 2014 5:17 pm

Comments:
front wing is on the small size . builders are leaning between 550 to 750 cm2
smaller wing means youll need more wind for wáter starts.
dry carbón weight on strut or mas should be around 500grsto 750 grs.
core is optional depending on method of construction.
i use bamboo core but the mast thickness is around 20mm to 25mm.
:thumb:

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Re: New designer/builder seeking DIY feedback

Postby tkettlepoint » Sun Jun 22, 2014 9:02 pm

looks great. one change I would do is thin out the strut alittle in all ways... 12-13mm x 100mm x 850mm will help a lot with the wings you are designing.. less drag.

but that is my 2 cents

I am doing the same just waiting for my molds... and it is killing me...

terrie
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Re: New designer/builder seeking DIY feedback

Postby danie178 » Mon Jun 23, 2014 12:43 am

wicked stuff folks great to see,

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Re: New designer/builder seeking DIY feedback

Postby Hawaiis » Mon Jun 23, 2014 5:20 am

The only thing I would change is reduce the length of the fuselage to 600mm

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Re: New designer/builder seeking DIY feedback

Postby Tone » Mon Jun 23, 2014 11:59 am

tkettlepoint wrote:looks great. one change I would do is thin out the strut alittle in all ways... 12-13mm x 100mm x 850mm will help a lot with the wings you are designing.. less drag.

but that is my 2 cents

I am doing the same just waiting for my molds... and it is killing me...

terrie
www.jellyfishboards.com


HI Terrie,

what are you getting your molds made of?

Thanks

Tony

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Re: New designer/builder seeking DIY feedback

Postby ahmthai » Tue Jun 24, 2014 9:48 am

compo_pete wrote:1. Strut - 1 meter long, Symmetric Eppler 817 profile with a 15 mm camber and 120 mm cord.
Proposed construction: Molded or Vac Bagged. Carbon/Epoxy
Layup: Glass, -45, +45, 0, 90, Core (unknown), 90, 0 +45, -45, Glass (lots of 45s on outside. evidently torsion is killer). Cloth Weight: Unknown


I just finished my first strut and I can help you out with the layup. I wanted it light, so I ended up having 3 layup iterations to get the necessary strength:

Core 8mm x 100mm hand foiled plywood (quite flexible and not very strong)
First Layup (epoxy resin):
1 x 200g UD carbon
2 x 150g Biax 45 degree carbon
Result: Longitudinal flex far too much and torsion close, but too much

Second layup (add)
2 x 200g UD carbon
1 x 150g Biax 45 degree carbon
Result: Longitudinal flex still too much and torsion OK

Third layup (add)
2 x 200g UD carbon
1 x 200g carbon twill
Result: Longitudinal and torsion flex good. The final strut thickness was 12mm.

Final Layup
5 x 200g UD carbon
3 x 150g Biax 45 degree carbon
1 x 200g carbon twill

You could reduce a couple of the layers if you started with a thicker or stiffer core. If you use glass, you will need 50-100% more cloth to get the same stiffness.

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Re: New designer/builder seeking DIY feedback

Postby tkettlepoint » Tue Jun 24, 2014 11:44 am

the only problem I see with a core in any of the parts is off gasing in the sun. A solid part will have less chance to off gas... foam will off gas. wood will too both things have air inside of them... my wood SUP that I built swells up in the water all the time ... I pull the screw when out of the water and it will hiss for 20-40sec with a lot of air pressure ...

This is one reason most ( not all ) production foils are solid carbon.

but this is just my 2 cents.

terrie
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Re: New designer/builder seeking DIY feedback

Postby Rotule » Tue Jun 24, 2014 12:06 pm

tkettlepoint wrote:the only problem I see with a core in any of the parts is off gasing in the sun.


If you use real core material (Divincell or other) they are closed cell and there is usually no problem with off gasing.

furthermore, the section of a foil is a lot smaller than a SUP (mich makes it a lot more resistant to inside pressure)


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