Number of guy lines for a tarp shade structure

[Aloecricketmouth]

My plan is to stretch a 20'x30' tarp across my car and 9x8 bowflex kodiak tent, leaving about 6' between the two. I'm securing everything with 12" lag bolts. I'm planning to secure the short ends of the tarp (on either end of the car and tent) as close to the ground as possible and then guy lining the long sides. My question is, how many guy lines do I need? Can I run multiple lines from ?different grommets to a single lag bolt or does each guy line need its own dedicated lag?

[DoctorIknow]

A small self standing tarp needs 8 guys.
If a tarp is 20' long and has "middle" grommets, one can reuse those existing lags.
If it's really a long tarp like your 30', and you need to have 4 grommets used on one of the 30' edges, you'd need 8 guys just for that side.
The "middle" guys might need only one tie down, but maybe not. Too many better than not enough.

FOR SURE order 18" lags right now. The forces on that 20x30 need them!

[Drizzt321]

Yeah, 12" lags are too short for a big tarp like that. I say minimum for any smallish structure IMO is 3/8"-14" for shade cloth stuff, maybe a small tarp, and tents and such. A single big tarp? Need a lot bigger. For my camp 30x30 EMT conduit structure (using 10x20 tarps) I got 1/2"-18".
For a full 20x30 tarp like what you got? Definitely get 18" deep, and very strong poles.

From what I'm reading you want to put lags through the grommets on the short side (20') and use some generic poles, 8' let's say, to crest a ~20x15 space at that height, and the other 15' is the sloped area down to the ground? You're going to need some real strong poles. I'd use at least 3 poles, each with a ratchet strap to its own lag screw (get fender washers, put Lang down through the eye). 1 ever 5ft, although 4 poles wouldn't be a bad idea either. The corner poles,even though held down by the tarp to the ground, I'd add a ratchet along, and bungee ball the side grommets to the ratchet length to provide additional hold.

Problem is you'll have that 20' width unsupported underneath be a use you can't get any poles there. It'll act as a giant sail, and you'll risk tearing out the grommets at the poles from a random giant gust. Which do occur.

You'd be better off with a 20x12 (8ft height, couplers to extend the length using the 2ft cuts) 1-1.5" EMT structure to secure. A 20x12 tarp, and then 2 more 10x12 tarps from the side down to the ground. Bungee ball everything. That's basically what I'm doing, with my small trailer, although I'm using 70% aluminet for the side walls on the back and 10x20 sides.

[Aloecricketmouth]

I'm having trouble finding 18" lags anywhere, do you have any recommendations?

Also, for clarification, I don't have any poles and was just going to secure everything either directly to the Playa (on the ends of the tarp) or with guy lines from thw tarp to lags+chain links (on the sides of the tarp). I'll be using pool noodles underneath the tarp on the car (suburu forrester with cargo rack) and tent to prevent rubbing. Probably going to use the car itself for additional anchor points.

[Token]

So, if I understand correctly …

The 20’ side of the tarp is screwed to the ground on the other side of the car - uses the car as a vertical stress member to hold up the tarp - then there is 6’ of space - then the tarp presses down on the tent making it the second vertical stressed member - then it slopes down to the ground and is screwed into the Playa?

Will your tent survive that kind of load without buckling the two bars holding all that up?

[Aloecricketmouth]

I guess that's part of the question. It's my first kodiak, so this experimental for me, hence wanting to get more experienced opinions and insights before I fully commit.

[Token]

20’ tarp over a 15’ vehicle with a 6’ cab and a 4’ roof rack … or something to that effect … you will lose some paint, regardless of pool-noodles.

Uneven surfaces will be hard to get any tension on the tarp.

I’ve built tensile shade structures out there for 10 years and learned very fast that vehicles have suspensions, move and swing away in wind quite dramatically, and make very poor structural elements when it comes to directional stability.

It’s probably much better to build your design with 4 sticks of rigid pipe or poles.

Also learned quickly that long lengths of consumer grade tarp last about 20 minutes into a wind storm before getting shredded. Switched to shade cloth and real NATO cammo netting real fast.

[Aloecricketmouth]

Thank you, that's very helpful! Could you give me some recommendations for poles? I've been looking at the sectional/extendable tarp poles but I don't know how to tell what will actually hold up. Also, we'll have very little extra space in our car, so travelability is another factor.
These are a couple I've been looking at;
KOMCLUB Tarp Poles Adjustable Tent Pole
https://a.co/d/8YofmMC

Mountainsmith Steel Tarp Pole (2 Set), Silver https://a.co/d/1EDqeqX

[DoctorIknow]

I'm having trouble finding 18" lags anywhere, do you have any recommendations?

The Fastener Super Store has everything, but it's faster and cheaper to order their product from Amazon, which I've ordered from many times as lag screws became the new thing on the playa about 7 years ago.

Link below.

18" lag screws from amazon

[Token]

Thank you, that's very helpful! Could you give me some recommendations for poles? I've been looking at the sectional/extendable tarp poles but I don't know how to tell what will actually hold up. Also, we'll have very little extra space in our car, so travelability is another factor.
These are a couple I've been looking at;
KOMCLUB Tarp Poles Adjustable Tent Pole
https://a.co/d/8YofmMC

Mountainsmith Steel Tarp Pole (2 Set), Silver https://a.co/d/1EDqeqX

Oh, I’m not the right guy to recommend.

Those look nice for a picnic in an urban park or backpacking in a forest.

My recommendations start with 1 1/4 inch schedule 40 aluminum structural pipe, but you’ll need a proper big truck with a lumber rack for that

To be honest, I’d scale your design down, allot.

1. Forget about the tent being in the shade. Get yourself a nice cot and put in the shade of your Subaru. Crawl out when the tent gets too hot, sleep on the cot.

2. Use the roof rack to anchor a much smaller Heavy Duty trucker tarp. 6’ x 8’. Then use a couple three of the poles on the other side to hold it up with strong paracord. Basically a porch off the car.

3. Put the tent up so the door goes to the porch, and you’re good.

If you park your car the right way, between the tarp, tent and car, you should have a real nice shaded area throughout the day and a decent windbreak.

Here for inspiration:
https://eplaya.burningman.org/viewtopic ... &p=1188727

Here for some angles:
https://eplaya.burningman.org/viewtopic ... 6&start=30