t-foil sections

[BenR]

Has anyone ever used the RG-8 section for a t-foil, is seems to give a much higher lift for AOA, max lift at 8 degrees compared with 14 degrees for the popular NACA63-412 section. This should also give a much higher lift/drag ratio not to mention the fact that you can get away with a smaller (cheaper) foil. It is thin at 10.8% but that just gives less drag again as long as you can make it strong enough.
I assume there are all sorts of problems with cavitation associated with this foil but I can't seem to find any good analysis as it was developed for gliders in the 80's and dumped fairly quickly after if was adopted.

[roland_trim]

From http://www.worldofkrauss.com/foils/1165

[roland_trim]

It is not massively different from Kevin's section for the E6 rudder.

So whilse we have no experience of this section I can say that the main problem we have had with the similar section is making it with the concavity at the back.  Even when you idealise the back edge as a "flat bit" fairing the foil up is fairly tricky.  We never completed the home build rudder we tried to make a year ago for that reason.

I'd reccomend having close look at the Daemon foil on Ronin/SK4/Riot for how it has been handled by the pro's.

[BenR]

I was looking at exactly that page, It stalls later, lifts more, drags less on paper it looks quite good. Just wondered if anyone has any experience with it.
When you compare it to the NACA 63412 it seems to win, but there has to be a reason no-one uses it. As I think Will said on another topic, the h105 seems popular too as it is specifically designed as a low speed hydrofoil. I cant seem to find a dat file for that so it isn't much use to me.

[BenR]

yeah the concave shape makes it pretty hard to fare, female moulds and prepreg seem like the only way to do it well. Did you ever get anywhere with your double L and cross piece mould?

[phil_kirk]

My current construction has a concavity at the back.  I think it is reasonably fair.
I am fairing in a bulb arond the rudder lift foil intersection with bog but made it too fat initially and now have a lot of difficult sanding ahead of me.

[Stuberry]

Have you read any of Tom Speer's stuff?

http://www.tspeer.com/

He suggests the H105 section.

[roland_trim]

yeah the concave shape makes it pretty hard to fare, female moulds and prepreg seem like the only way to do it well. Did you ever get anywhere with your double L and cross piece mould?

Little progress due to "other project". Will be digging the L moulds to restart in the very near future as I need a foil for EJ and Evo. If it works, you will be welcome to borrow it.

IMHO I'm not convinced by either the "use pre-preg" or "female moulds reduce fairing" arguement. The latter really depends on how good the moulds are and the ammount of buggeration needed to join top to bottom. I think both are due some serious head scratching for us home builders.

I am fairing in a bulb arond the rudder lift foil intersection with bog but made it too fat initially and now have a lot of difficult sanding ahead of me.

Owch. Enjoy it Phil. Looking forward to getting back to TSC....

[Phil Alderson]

I have H105 as a dxf, and also as a blender 3d model. I got some plugs machined up a few years ago and have some molds in the garage at the moment. They seem to work OK for making foils, I have made a couple so far, and have got better with each one.

[dave_ching]

I have the plugs for Phil's mold so if anyone wants to make another set of molds it shouldnt be a problem

[BenR]

hmmm, tempting, What are the dimensions of the plugs?

[Clive Everest]

If you want accurate low cost plugs try:
http://www.foamwings.co.uk/Pages/Site/Default.asp
They have a computer controlled hot wire cutter that will cut Styrofoam wings for model aircraft.
You are restricted to linear tapers but the quality is very good (I am sure that competition model glider flyers are pretty demanding) and the cost works out at ~£10 per section.

I have made hydrofoils out of 2 or 3 sections, having taken glass moulds off the foam blanks.
I have also put wooden stringers in the Styrofoam and laminated straight onto them.

By being careful with the temperature control I have even managed to cure prepreg on the Styrofoam.

I suspect that they could cut a one use foam mould. Great for rapid development.

Barry is very helpful.

Clive

[ade white]

Hi all; does anyone have a T-foil section or a complete T-blade surplus (that they want to sell)? I am planning/thinking of either making, or finding 1 to test lifting sweet dreamzzz arse out the water to gain a bit more speed!

[Graham Bridle]

Ade,

I have an Aardvark spare T + Stock, you're welcome to borrow it to see how it goes, I would only use it if I broke my demon foil.

In fact you wuld have done me a favour if you'd said last week, as I had a hell of a time getting 2 T foils and Eddie in the car .... one of them nearly stayed in Pwhelli !

G

[Torchy]

Sam and I are hoping to run a DT school project for his GCSE around foils then (hopefully) make the foils at the sticky weekend. The school probably have the tools to make the foam core around which to plonk (that's a technical term) the carbon.

I'm very hazy about the internal structure of foils so was planning to start a thread soon with Sam and sort out design etc

We have a plain rudder to convert to T-foil and want to make a long dagger board for Loco.

Fancy joining in Ade? Might persuade the school to do the difficult bit for 2 T-foils and a dagger or two. Roland said 'Do they have a CNC...?' something-or-other when I mentioned it and if they do this is apparently 'good'...yes I am that hazy about the detail