naca section

[jejojoy]

hi
i am a naval architect student from india doin my project on hydrofoil crafts.i am plannin 2 select naca section 64-206 for the foil.wer will i find lift and drag particulars of the section.i ve downloaded xfoil but itz too complex .any one got lift vs angle of attack curve for the same section.i tried procuring the book "theory of wing sections" but itz too costly for me.

[Toot]

I have that book. If you just want the charts or plots for an airfoil or two, I'd be glad to scan them for you....

If you tell me what attributes you're looking for, I can go through the book and make a couple of selections that meet your criteria.

There's not much info in there, however, on low Re numbers.

[jejojoy]

thank you sir
i wud like to know abt the lift vs angle of attack curve ,lift vs aspect ratio and lift vs drag curve .my craft has got a length of 22 metres and a speed of 36 knots.naca section in my mind is 64206.is tat ok?my mail id is navarch_jejo@yahoo.com.

[Tim B]

If X-foil is too complex for you, read the user manual. X-Foil is the simplest 2D panel method I've ever used. It is worth remembering though that the NACA sections were designed for use in air, and water has different properties, not least, cavitation.

Tim B.

[Toot]

Sorry it's so large, but I didn't want to reduce it for fear it would become illegible.

I'm posting it here, should anybody more knowledgable than I care to comment on it.


I'm guessing you'll be looking in the Re = 3e6 range. Be sure to save the file for yourself as I doubt I'll be hosting it for very long.

[jejojoy]

sir,
thankyou very much 4 ur help.is the curves given for infinite aspect ratio?i am plannin for an aspect ratio of 3 .so shud i transform the coefficients to aspect ratio of 3?

[Toot]

Originally Posted by jejojoy

sir,
thankyou very much 4 ur help.is the curves given for infinite aspect ratio?i am plannin for an aspect ratio of 3 .so shud i transform the coefficients to aspect ratio of 3?

yes that's for an infinite aspect ratio. To my knowledge, no charts exist for different AR's. You have to figure it out yourself based upon spanwise efficiency and so forth- it's a whole chapter or two in the book and it's sufficiently complicated that my little brain will not permit me to casually discuss it as there's a lot more to it than a simple calculation.

Do some research on "spanwise lift" and "span lift distribution". That should get you going in the right direction.

[jejojoy]

sir,
i wil b searchin it sir.what section do i select for a strurt?

[Toot]

Originally Posted by jejojoy

sir,
i wil b searchin it sir.what section do i select for a strurt?

Something thick if it will be supporting a lot of weight and taking a pounding. And uhhh... something with a symmetrical cross section. lol

I can't help any more than that. Most 15 year olds know more about boat design than I do... I just hang around here for the free coffee and donuts.

[jejojoy]

sir
i am a little bit confused abt d take off speed.how can v fix it.i ve read tat it is almost half the maximum speed.du one actually need a drag cuve to determine the take off speed or any formulas available

[Toot]

You've gotta help yourself a little, man. I don't know squat about designing boats, let alone hydrofoils.

L = Cl * p/2 * v^2 * A

Beyond that? I can't really be of assistance.

[paulhanley]

If you're designing a boat, likely someone has done it before.
Identify what makes your boat unique, weight, length, beam ,speed, method of construction, and of course, it has hydrofoils.
Review designs of similar boats first.
You are starting from scratch and making a lot of work for yourself.
If designing the hydrofoils is the purpose of the exercise, take an existing design for the powertrain and hull and modify the foils for an improvement in drag/stability/cavitation as you consider necessary for your goal.
It's not cheating to use a good idea that's been proved to work. Obviously, there are copyright issues, if you intend to make money out of it, but this doesn't sound like the case. Engineers have used known components for years and then improved on them. Don't beat yourself up working from scratch.
Know this doesn't help with the calc. But given hull and output power there should be a similar hydrofoil section and strut configuration as a starting point.