making Ventus wingtip tie downs- instructions

[Matt Herron Jr.]

OK, there is enough interest that I am posting instructions on how to make these. It is actually pretty simple, but you will need access to a lathe, drill press, etc.

1) download the purchased parts list here (https://www.dropbox.com/preview/Public/wingtip%20parts%20list.png?role=personal) and order the parts from McMaster. You only need two of the carabiners, or you can substitute a SS threaded link as I did: PN:8947T26

2) Machine the three parts (X2 each) from drawings provided here
https://www.dropbox.com/preview/Public/tie%20down%20jack.PDF?role=personal
https://www.dropbox.com/preview/Public/tie%20down%20spacer.PDF?role=personal
https://www.dropbox.com/preview/Public/wingtip%20tie%20down.PDF?role=personal

for the SS wing tip tie down, just print out the drawing, paste onto the sheet metal, and use it as a template for drilling and shaping

3) assembly

a) disassemble the cam handle and thread the rod into the tie down jack (thru the end with the O ring step) so that it protrudes about 1.9 inches. Re-drill the 1/16" hole in the tie down jack thru the rod and press in the spring pin so the rod can't unscrew. make sure the pin is recessed below the surface of the Delrin so it won't scratch your wingtip tube wall.

b) drop the O ring over the rod onto the tie down jack

c) slide the tie down spacer over the rod.

d) slide the wing tip tie down over the rod.

e) re-assemble the cam handle onto the rod and screw it in until the O ring is squished when the cam handle is engaged

DONE!

4) to use this gizmo, remove wingtip, and slide in the tie down. Flip the lever downward and adjust as needed for the right amount of axial retention. It should be almost impossible to pull out the tie down from the wingtip tube. Attach a rope thru the threaded link and secure the wing. I like to use a rolling hitch to cinch the wingtip down easily. See: https://en.wikipedia.org/wiki/Rolling_hitch for how to tie this fabulous knot.

Let me know how it goes!

Cheers,

Matt

[Phoenix]

Anyone here have an "extra pair" of these Ventus tie downs? It's a long shot, I know. Just thought I'd ask. Well, while I'm at it, anyone have enough left over materials who would want to make a pair at a "good price"? :)

[2G]

I caution against any glider tiedown that uses the wingtips for tiedowns. I know of no glider that was designed to have the wingtips support the entire load of the glider. Our club in Richland had a Blanik L-13 whose wings were destroyed when the mid-span tiedowns loosened and the wingtips, which were also tied down supported the entire weight of the glider during a storm. The end result was not pretty: the wings were broken at the mid-span.

I had Rex Mayes of Williams Soaring install spoiler box tiedowns in my new ASH31Mi. It is pretty easy to do:
1. Two AL blocks are cut that fit into the spoiler box (requires forming to fit).
2. Both blocks are drilled with a 3/8" tap diameter hole.
3. The blocks are epoxied into the outboard spoiler box.
4. After curing, holes are drilled thru the wing (ugh!) using the pre-drilled blocks as guides.
5. The blocks are tapped from the bottom of the wing.

Eye bolts can be screwed into the blocks which are spaced at normal small GA aircraft tiedowns. The spoiler box is located next to the spar, making it very capable of supporting high loads.

Tom

[Eric Greenwell]

On 8/6/2021 9:48 PM, 2G wrote:
> On Saturday, July 31, 2021 at 2:57:18 PM UTC-7, Phoenix wrote:
>> Anyone here have an "extra pair" of these Ventus tie downs? It's a long shot, I know. Just thought I'd ask. Well, while I'm at it, anyone have enough left over materials who would want to make a pair at a "good price"? :)

...

>
> I caution against any glider tiedown that uses the wingtips for tiedowns. I know of no glider that was designed to have the wingtips support the entire load of the glider. Our club in Richland had a Blanik L-13 whose wings were destroyed when the mid-span tiedowns loosened and the wingtips, which were also tied down supported the entire weight of the glider during a storm. The end result was not pretty: the wings were broken at the mid-span.
>
> I had Rex Mayes of Williams Soaring install spoiler box tiedowns in my new ASH31Mi. It is pretty easy to do:
> 1. Two AL blocks are cut that fit into the spoiler box (requires forming to fit).
> 2. Both blocks are drilled with a 3/8" tap diameter hole.
> 3. The blocks are epoxied into the outboard spoiler box.
> 4. After curing, holes are drilled thru the wing (ugh!) using the pre-drilled blocks as guides.
> 5. The blocks are tapped from the bottom of the wing.
>
> Eye bolts can be screwed into the blocks which are spaced at normal small GA aircraft tiedowns. The spoiler box is located next to the spar, making it very capable of supporting high loads.
>
> Tom

I've never liked wing tip tie downs for all the reasons Tom mentions, yet the Richland
Blanik is the only one I remember that's suffered damage for that reason. How could that be?

1) the Blanik is particularly vulnerable, with a very light wing loading. It was parked
facing directly into a 70 mph (peak) wind during a strong storm, with the spoilers closed,
and the tail on the ground instead of raised.

2) the gliders I see tied down by the tips more recently (the Blanik incident was about 30
years ago) have much higher wing loadings, which would increase the wind speed required to
lift them off the ground. Some have the spoilers extended, many have wing covers, the
uncovered flapped gliders usually have negative flap selected, and all those actions make
it harder for the wind to affect the glider.

3) This might be the big one: most pilots put their glider in the trailer when very strong
winds are forecast! The effort to put that Blanik on it's awkward trailer was great
enough, it discouraged that approach, but it could've been parked in the big Quonset
hangar, which would've protected it.

Sooo, I no longer worry about most gliders tied down by the wing tips. I'd still be
concerned about any low wing loading glider, like Blaniks or 1-26 and similar gliders.

I wish some aeronautical university professor would have a student do a thesis on the
effect of wing and tail covers on glider tie-down forces. The professor I asked about that
said the quickest way to get that thesis was to offer a grant for the project, but I was
too cheap to followup :^)

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

Here at Ely we get strong winds from thunderstorms. One thing I have noticed is that, during strong winds, the wing covers billow up, effectively creating a spoiler spanning the entire wing. Still, we sometimes don't put the covers on ahead of storms because dust gets under them which is rubbed against the wing by the flapping covers.

My preference is to tie the glider down using its strongest point: the main gear. I put a wing wheel on one wing, which is tied down. The other wing is not tied down at all. I have had other pilots question me why I don't tie it down. I explain that the glider is tied down at the main (the wing wheel just keeps the wing from slapping the ground), and, amazingly enough, the free wing will stay on the glider at speeds up to 160 mph.

Tom

[Eric Greenwell]

I've occasionally used this method when the ramp tiedown points are so poorly spaced, my
normal tiedowns near the spoilers won't work. It often seems more secure, and easier, than
methods using multiple wing stands and straps, particularly on cables that are not very
tight. And yet, it's rarely used.

[2G]

Right - I forgot to mention the problem of loose cables. Most at Ely are pretty tight, but one area (by the old terminal building) lacks enough anchors to make them as tight as the others are.

As a stop-gap for badly spaced anchors I carry my own steel cable that I can stretch between two anchors, but it is only 50 ft. and I have to use a come-along to tighten it (something I don't travel with).

One step left out on installing spoiler box tiedowns: the spoilers may have to be trimmed slightly to clear the AL blocks.

Tom

[AS]

>> ... I have to use a come-along to tighten it (something I don't travel with). <<
Try this: https://www.harborfreight.com/1-4-quarter-ton-lever-chain-hoist-67144.html?_br_psugg_q=chain+hoist
Not too heavy and bulky and can come in handy for all sorts of things.

Uli
'AS'

[2G]

Still too much to carry on a out-of-town trip. Here is what I use at home:
https://www.harborfreight.com/2-ton-cable-winch-puller-61964.html?_br_psugg_q=come+along

It is really nice to have tiedowns that fit standard GA tiedown spacing, but it may overlap adjacent aircraft. I can make it work if I am on the end of the line and the plane next to me is high-wing. Since I went to Heber City several years ago the FBO now makes all gliders tiedown in the dirt far away from any other GA aircraft (haven't been back).

Tom

[Dan Marotta]

Does the FBO at Heber City own the tie down ramp, or have control of it
through the airport authority?

Dan
5J

[2G]

They definitely don't own, but manage it for the city. They are not particularly glider or GA friendly - one fill up of a biz jet gets more sales than a year's worth by a GA plane.

Tom

[Phoenix]

Any specs on the O ring? Size? Thickness?

On Monday, April 30, 2018 at 12:18:38 AM UTC-4, Matt Herron Jr. wrote: