molded nose skeg

[dhauch]

just made a molded skeg for my Tragi, came out great, and alot easier then i thought.
really never thought it would even come of the nose cone. :)

*i put a coat of PVA mold release on the nose cone. this puts like a plastic film on the surface.
*then 2 layers of matte and laminating resin.
*sand
*make a skeg from 1/8'' ply, then attach with balck rubber CA.
*then 2 layers of 2oz. cloth to skeg and nose cone, and one layer of 3/4oz cloth.

don't even think i'll paint it.
i'll never match the paint anyway.

dh

[Kenny Sharp]

Hi Dave,
What's a skeg, and what is it for?

[LVsoaring]

KKens, a skeg is a pointy thing like you see in the pictures, used for spot landings. It prevents the sailplane from sliding along the ground and missing the designated spot. Very critical in competition where you are awarded points for hitting the mark.

Very nice job dhauch, but personally, I'm waaaaay to lazy for all that.... a quick e-mail to Superskeg, and I'm good to go! :D

[Kenny Sharp]

:o Oh, I thought that went in back...Opps!

[Bruce1]

Dave,
A couple of us down Texas way have been molding our skegs for 5-6 years and I have a few suggestions: (1) make the blade out of phenolic. Bonds better and will never break. (2) Lay in some carbon roving at the juncture of the blade and the body running in the direction of the load the skeg blade will impart to the skeg body during a landing.All for now and thanks for taking the time to share your techniques.

[trashmanf]

what would be cool (probably illegal) is a servo operated skeg, you could slide until you hit the switch to stop :)

[Brian Wa]

Skegs are banned for all FAI events on grounds of safety.

[Kiesling]

what would be cool (probably illegal) is a servo operated skeg, you could slide until you hit the switch to stop :)

This has been done by Troy Lawicki (sp?) on his famous Duck 2M. It worked exactly as you suggest. For AMA rules it is not illegal.

Tom

[TOSSPilot]

I remember looking up one year at the Visalia Fall Fest to see a pilot grasping his hand as blood was rushing down his fingers. He made an attempt to catch his skegged plane and misjudged the grap.

Otherwise, I have not seen too many incidents were the skeg has been a safety issue. Definetely no more dangerous than a gasser with a carbon fiber prop or even a helicopter. I would not want to be hit by any.

TOSSpilot.

[Kenny Sharp]

A little blood never hurt anyone.

[stumper]

"Skegs are banned for all FAI events on grounds of safety."

they are a huge risk aren't they? many people are injured by skegs while the entire rest of the sailplane comes nowhere near them...

[Radian]

"Skegs are banned for all FAI events on grounds of safety."

they are a huge risk aren't they? many people are injured by skegs while the entire rest of the sailplane comes nowhere near them...


So instead of allowing skegs, they allow pilots to "dork" their planes in at high speed.

I guess a 60oz+ plane being flown in at high speed to "spear" into the ground is safer then a slower more level approach with a lighter touch down and a skeg to stop the skidding.......

Different points of view I guess.

Radian
www.phflyers.com

[Kiesling]

Based on my experience, the landing speed does not change much whether the model has a skeg or not. If anything I would say in practice the models without skegs land slower.

From what I have seen, the spearing of models with and without skegs is just about equal. It is more of a function of wind, how hard the ground is, and the skill level of the pilot.

Whatever the original rational was for the FAI banning skegs is, the end result is pilots are required to have better control of their models energy to land precisely. This is especially true in F3J where going over the window time has a large penalty.

In general I think that skegs are much better at preventing shin type injuries which, although rare, are the most common type with sailplanes.

FWIW
Tom

[dhauch]

made one for my Supra 130.
tried G-10 for skeg this time, and laid some carbon tow at the joint.

i'll see how this one holds up.

Bruce1, have you ever done these over a painted nose cone, like Krylon ?

thats what this nose cone was.
it had a clear coat on it, i waxed it 5 times, then put 2 coats of PVA release.
i had to cut a slit in it to get it off.

i think the wax didn't let the PVA release cover well, had a lot of fish eyes in the PVA.

dh

[davidleitch]

Skegs are banned for all FAI events on grounds of safety.

Brian

Not sure of the precise definition of skeg, but they are allowed in F5B

[glderguy]

Skegs arent dangerous, but landing w/o one can be. Ive seen more people hit themselves with skegless planes than get injured by skegs/skeged
planes. I was the one who sliced open the hand at Visalia on a retriever malfunction induced pop off. Wasnt trying to catch the plane, rather put my hand out to keep it from hitting me. The dangerous thing about that incident was not the skeg but the infamous "landing mode" on the old 8103 that I forgot to turn on while making a quick landing - came in hot, pulled flaps which of course didnt work due to landing mode being off. I dont use that radio anymore and now flaps are always on. BTW that little incident landed me in the hospital as cut was to the bone, 2/3rds of the way around thumb, two weeks missed work and several months of therapy to insure thumb would have proper range of motion again.
Walter

[Brian Wa]

For F3B and F3J competitions the FAI sporting code states the following.
Part 5 - Technical regulations
Rule 5,3,1,3.b)
No fixed or retractable arresting device (i.e. bolt, sawtooth-like protuberance, etc.) is allowed to slow down the model aircraft on the ground during landing.
The underside of the model aircraft must not have any protuberance other than the tow-hook and surface control linkages. The tow-hook must not be larger than 5 mm in frontal width and 15 mm in frontal height.

The skeg was banned on grounds of safety, if a model hit you the skeg would rip you open like a knife.
The nose radius of the model is also defined to stop stiletto noses, which could kill if they hit you in certain places.

The FAI takes safety seriously, the rules are not there just to spoil your fun.

[glderguy]

The FAI is wrong. Its as simple as that. Skegs prevent far more injuries than they produce.
Walter

[Wildewinds]

The FAI is wrong. Its as simple as that. Skegs prevent far more injuries than they produce.
Walter

^^^
Yep. Most injuries occur from planes sliding after they hit the ground.

The only way a skeg can hurt someone is if they're trying to catch it. That doesn't happen very often in competitions.

[mlee8249]

Well, you're really looking at two different arenas of thought when looking at the typical AMA TD event and the FAI events. The main difference is that the AMA TD events have become landing contests where the outcome of many contests are determined by the landing points alone. Planes have become so very efficient that getting the common task times of 5, 7, 9 and 10 minutes on a flight is not hard. (unless the sky is falling!). So, then it becomes a matter of landing on time and on a very small target zone. Let's look at places like Visalia and SWC in Phoenix. They don't use the typical landing strip or landing circle. They use something taken from the sick imagination of the Pilsbury Doughboy and have you land on a pizza. I'm not kidding! So, here is the shape of a pizza with a couple of slices taken out in the part that is centered and facing away from you, towards the approach side. You would think that hitting that missing slice would be the high points, but it's actually zero. Then you have the "hop-scotch" landing zone, where you have 5 boxes drawn on the ground, in a straight line. Hit the 1st and 5th box, and you score 15 point. Hit box 2 or 4, and you get only 10. Hit the dead center box and you get 25. Where is the logic in this? I dunno.

Now, look at the FAI. They use a 10-meter circle, with the max points at the center and that center spot is one meter wide...39 inches. AMA TD can be as small as 1 point per inch. Brutal! In FAI, there is more emphasis on the time in the air, making the landing a bit less important. It's still important, but not to the critical degree as found in AMA TD. So, being that the points in TD are so important, pilots use the skeg to give themselves a decided advantage. Even F3J pilots will stick the nose into the ground to prevent the slide, provided the ground is soft. (Not good to do in Phoenix).

So, that's the practical side of why we use the skegs so widely in the States. If you wish to address safety, please consider one more thing. In most AMA TD events, the Contest Directors normally tell the pilots that they need to approach the landing zone from a given direction , and sometimes even make them fly down a set "lane" of approach. In FAI, the pilots may approach the landing zone from any direction, save for one that takes them directly over the heads of the other pilots. So, it is not unusual to see models approaching from every direction on landing. Add to this the fact that in F3J, this is a mass-launch, man-on-man flight event where there could be 8 to 12 pilots launching and landing at one time. They launch from winch lanes that are 20 meters wide, side by side, all at once. Mid-airs are common on both launch and landing. You want to talk safety? Go watch an F3J event someday and that will make you think twice about whether the FAI addresses safety any better than the AMA.

Mike Lee