Best attach point for a GRS on a Windlass

[V]

Hi,

I have a GRS on my Windlass. Originally the cable for the chute was attached to the airframe at the bottom where the axles join. Needed to do some repair on the trike as a result of the Conties storm and since I was working in the area, started thinking about this attachment: since most of the weight (engine, wing, pilot, etc.) is above this point, what are the chances for the trike flipping upside-down after deploying the chute. The wing surely has some counter-balancing effect, since it might generate some lift (or drag, rather) during the descent. However, in case of a wing-separation, I feel, the trike is more than likely turn upside down, which is certainly not desirable.

The manual recommends attaching the cable to the bottom where it was and then recommends running it all the way up to the wing. For one, my cable is ways too short to do this and for other, a steel cable of this length is an awful amount of extra weight.

Any other recommendations, suggestions (other than chucking away the GRS - I'd like to keep it as a last resort ? Thanks!

Cheers,

V.

[Trikenut]

Hey V,
I have heard of people mounting them on the pylon. I know of a few people who have done this. The only one who's name I know is Tjeerd Beens. (Mark Becker's flying partner in Flying the Fish/Falls/Blue)
I would reccomend, however, that you contacted Solo Wings. http://www.solowings.com
Hope this helps...
Ross

[Morph]

There is the mounting point, i.e. where you put the canister goes and then there is the cable attachment point. It is, as you suspected, insanity to attach the cable to the axles. Trike will invert on deployment and you are going to have to pray that your seatbelts keep you in place. The wing will no longer be flying so will not tend to remain at the top. To me the logic says, it must be attached such that the aircraft drifts downwards with all 3 wheels and suspension below you to help absorb the impact. Also it has to be attached in such a way that if you do have wing seperation, that the chute cable attachement point doesn't go with the wing. i.e. don't attach it to the hangpoint.

The canister must be mounted in such a way that the rocket going off doesn't hit anything like the wing, engine, prop or occupants. The other thing I have thought of is if the rocket goes off to the rear the cable under tension once the chute inflates will tilt the wing forward, i.e. nose down, and as a result the pilot will have the trapese bar pressed firmly into his chest or stomach at the full weight of the trike and it's occupants. I reckon this could be quite uncomfortable.

Speak to Abe on this forum he is the agent.

The pic is CLU-less's trike. HIs canister is mounted on above the motor. Skidmark can make up the mounting point out of Nylon if you ask him nicely enough.

[Wargames]

Yesterday,

Who is that two sexy, slim guys standing there??

[coastwise]

Hi V

I have seen an installation done on a windlass where the cable is attached at the base of the pylon and root tube and then taken up the pylon with cable ties and lastly a metal bracket which clamps the cable against the pylon about three quarters of the way up, which would then effectively move the hang point of the brs to the point of the pylon where the bracket is to prevent the trike flipping upside down. The cable used was fairly thick, but felt light compared to other cable types I have handled, so not sure where the owner obtained it. The cable was also long enough to feed back down the pylon to the attachment point on the brs.

Hope this info helps.

[Trikenut]

That pic Morph posted is exactly what I am suggesting...

[V]

Thanks for the suggestions. I'm happy with the canister attachment, it is done about the same way as on the pic of CLU. (Hi CLUless, was nice to chat at Diemerskraal the other weekend.) What I'm worried about is the cable attachment. For now I've moved it up to the hang-block and fed it through the safety cable, thinking that in case of a wing separation it'll keep the chute attached to the airframe. Apparently there have been incidents where the safety cable didn't hold up ...

Thanks coastwise for the idea of attaching the cable to the root and taking up the cable on the pylon. My cable should be long enough to go above the pilot's head. I saw some nice stainless steel U-bolts at a sailing shop the other day, I wonder whether they would be strong enough for the application. They had no official ratings if I remember correctly.

Cheers,

V.

[V]

I have seen an installation done on a windlass where the cable is attached at the base of the pylon and root tube and then taken up the pylon with cable ties and lastly a metal bracket which clamps the cable against the pylon about three quarters of the way up, which would then effectively move the hang point of the brs to the point of the pylon where the bracket is to prevent the trike flipping upside down.
Hope this info helps.

Would something like this (in the stainless steel version) be strong enough to keep the cable clamped against the pylon, say at the pilot's head level and create a pivot point:



In the shop where I've seen them can not give any indication for the strength ...

[Abe]

Hi Flyers!
This has been an enlightening conversation with everyone posting valid and well thought to the point observations.
(Unlike some goings-on on other forums!)
Yes, I agree to put the hang point up high, but of course anchoring the cable lower to the strong point where the seat frame joins the mast. Consider that the engine might depart on losing a prop blade.
Aiden, may his soul fly in peace, thought that the suspension cable will easily cut into the back of the wing to offer a fairly level descending attitude under parachute. Some Windlass/Aquilla GRS fitters have expressed doubt if the light cable staying from the back of the wing keel will give way, but under 5.5g's I bet it will. On the 912 Aquilla Aiden agreed the best mounting position for the cannister to be above the engine, and I advocate it even on the 2-strokes. Doing so will keep the suspension cable above the prop arc during deployment.
Fitting an emergency parachute seems to ensure that the airplane will never need it!
FlySafe,
Abe. (www.galaxysky.cz importer)
Dave of Dreamwings is your agent in KZN.

[V]

Thanks for all the inputs. I lifted a pic from the GRS manual to illustrate what has been recommend/what I'm planning to do:

1. There seems to be agreement that the canister is best attached to the pylon above the engine. I've got this in place already.
2. Also, there is agreement that the cable should be attached to the airframe, best at the base of the pylon. This is what I'd like to do.
3. The cable needs to be attached to the upper part of the pylon or around the hang-block to allow for a descent in an upright position. Since my cable is too short to reach all the way along the pylon to the hang-block, I'd like to opt for clamping the cable to the pylon above the canister as marked on the image.

GRS installation

grs-install.jpg (23.27 KiB) Viewed 2244 times

Now, the last question is: what ready-made, available material (clamp, u-bolt, etc.) would be suitable for clamping the cable to the pylon?

The GRS manual indicates a 40-45 kN maximum force at various points of the cable. While I think that the clamp needs to withstand less, 45 kN seems to be a good reference value. What kind of clamp will keep a cable attached to the pylon in case of a 45kN side-ways force?

Thanks!

Cheers,

V.

[Abe]

Hi V,
I keep a stock of completed 8mm2 PVC covered steel cables in popular lenghts for GRS mounting. 4m is just right for a Windlass or Aquilla low mount, high hang. R200 +VAT collect.
FlySafe!
Abe.

[V]

Thanks Abe, you've got PM. With the 4m cable I can do the installation properly.

Cheers,

V.