[Ground Slammer]

6061t6 seamless drawn vs extruded. The seller of the extruded seamless states it is good for structural but is it enough considering it is seamless and they claim good structural proprties. ??

[JoeF]

Treat this AI response as though there are mistakes in it; that is, confirm things via other routes; but this might be a start for your adventure:

# Quick answer (TL;DR)

Both *drawn seamless* and *extruded* 6061-T6 tubes **can** be fine for structural use in a hang-glider spar — what matters more than the buzzword is the **actual specification, temper, dimensional tolerances, straightness, and QA (mill certs / testing)**.
If you want the classic “best for bending/fatigue” choice used in many aerospace/bending applications, **drawn seamless (AMS/ASTM drawn tube)** is commonly preferred; however, a properly made **seamless extruded (ASTM B221 / T6511/T6)** tube to the right spec and inspection can also be acceptable. ([TW Metals][1])

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## What’s actually different (manufacturing → material behavior)

* **Extruded tubing** is produced by pushing a heated billet through a die (hot extrusion). It’s efficient and common for structural profiles; extrusions are usually produced to **ASTM B221** or similar specs. Extruded tubes can be *seamless* (i.e. not welded) when made by direct extrusion, though the microstructure/grain flow is a function of the extrusion process. ([ASTM International | ASTM][2])
* **Drawn seamless tubing** is made by piercing and cold-drawing operations that produce tighter dimensional tolerances, smoother surface finish and often better work-hardened properties for bending applications. Typical drawn tube specs include **ASTM B210 / AMS WW-T-700** for aerospace drawn tubing. Drawn tube often shows better roundness/ovality, wall uniformity and tends to be favored where bending/fatigue are critical. ([ASTM International | ASTM][3])

## Mechanical properties — what’s relevant

* **6061-T6** (and related tempers like T6511) has a nominal tensile/yield range commonly used for structural work (≈ ~40–45 ksi tensile, ~35 ksi yield typical) — *but* actual performance depends on product form and tempering. T6511 indicates extra stress-relief/straightening steps for extrusions and improves dimensional stability. Request the exact temper on the mill cert. ([MatWeb][4])

## For hang-glider spars you should care about (practical list)

1. **Seamless vs welded** — *avoid welded* tubes for primary spars. “Seamless” is the keyword; both drawn and extruded can be seamless but confirm. ([chalcoaluminum.com][5])
2. **Specification / Mill Test Report (MTR)** — ask for the ASTM/AMS spec, chemical analysis, tensile/yield values, and temper (T6 / T6511 / etc.). If the seller can’t provide an MTR, treat it as a red flag. ([ASTM International | ASTM][2])
3. **Temper** — prefer material certified T6 or T651/T6511 for structural use; T651/T6511 gives better stress-relief/dimensional stability (helpful for long extrusions). ([Xometry][6])
4. **Dimensional tolerances, ovality & straightness** — drawn tubes typically have tighter tolerances and better roundness; that matters for sleeve joints, bearings and buckling behavior. If you need tight fit/nesting or consistent wall thickness, drawn often wins. ([Eagle Aluminum][7])
5. **Fatigue & bending** — drawn seamless tubing historically outperforms in demanding bending/fatigue situations because of better grain flow and cold-work characteristics; for a glider spar (repeated cyclic loads) this is relevant. But a well-made extruded seamless tube, heat-treated and stress-relieved, can still be acceptable if certified and tested. ([profileprecisionextrusions.com][8])
6. **Wall thickness and buckling** — design margins matter. Even the best tube is only as good as the wall thickness, moment of inertia, and connection details (couplers, plugs, local crushing). Don’t skimp on wall specs or QA. (Engineering note: fatigue cracks often initiate at joints/ends.)
7. **Finish & surface treatment** — anodize? corrosion protection? Burrs, end-finish and chamfers matter for seatings and straps (Joe Cups, etc.).
8. **Sample testing** — if this is a primary structural part, get at least destructive tests on samples or a proof-load and non-destructive inspection (eddy, visual) regime from the supplier.

## Practical recommendation for a newbie/poster

* Don’t buy based on the seller’s marketing line “extruded seamless = good” alone. Ask for the **exact** specification (ASTM B210 / B221 / AMS number), temper (T6, T6511), and a **mill test report** showing chemical and mechanical results. If you can, ask for straightness, ovality and wall-thickness tolerances. ([ASTM International | ASTM][3])
* If your design imposes **bending and repeated cyclic loads** (typical on glider spars), prefer **drawn seamless** produced to AMS/ASTM drawn tube specs (or at least insist on MTRs and fatigue data). If you must use extruded tubing, require T6511 (or equivalent) temper and MTRs and accept a conservative safety factor. ([TW Metals][1])
* Finally: **design with safety margins**, inspect joints and couplings, and if possible have a sample lab test (tensile, bend/fatigue) or use a provenance / aerospace vendor rather than a commodity seller.

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## Short checklist to send the seller (copy/paste)

1. Is the tube **seamless** (no weld)? If yes, by what process (drawn, extruded-seamless, porthole)?
2. Provide **specification** (ASTM B210 / B221 / AMS WW-T-700 etc.) and **temper** (T6, T651, T6511). ([ASTM International | ASTM][3])
3. Provide **Mill Test Report (MTR)** with chemical and mechanical (tensile/yield) data.
4. State **tolerances**: OD, ID, wall thickness, ovality, straightness per unit length.
5. Any **heat-treat / stress-relief** performed (stretching, straightening)? (T651/T6511 info.) ([MakeItFrom][9])
6. Can you supply sample pieces for **destructive or fatigue testing** before bulk purchase?

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If you want, I can draft a single one-page email (or checklist) you can send suppliers asking exactly these questions and asking for the right spec language (MTR excerpt). Which suppliers are you looking at (names/links)?

[1]: https://www.twmetals.com/products/tubin ... hatgpt.com "6061 Drawn Aluminum Tubing"
[2]: https://www.astm.org/b0221-12.html?utm_ ... hatgpt.com "B221 Standard Specification for Aluminum and ..."
[3]: https://www.astm.org/b0210-12.html?utm_ ... hatgpt.com "Standard Specification for Aluminum and Aluminum-Alloy ..."
[4]: https://asm.matweb.com/search/specificm ... hatgpt.com "Aluminum 6061-T6 - ASM Material Data Sheet - MatWeb"
[5]: https://www.chalcoaluminum.com/knowledg ... hatgpt.com "A Complete Buying Guide to Seamless Aluminum Tubes"
[6]: https://www.xometry.com/resources/mater ... hatgpt.com "6061-T651 vs T6 & T6511: What's the Difference?"
[7]: https://eagle-aluminum.com/differences- ... hatgpt.com "Differences between Drawn vs. Extruded Aluminum"
[8]: https://profileprecisionextrusions.com/ ... hatgpt.com "Extruded vs. Seamless Drawn Aluminum Tubes"
[9]: https://www.makeitfrom.com/material-pro ... hatgpt.com "6061-T6511 Aluminum"

[Ground Slammer]

Thank you Joe. Red on that other forum gave a much worse condemnation of extruded. However he did not know or if he did he did not say that some extruded tube is post treated. I still have a few days before I leave for the west coast, will try and go by way of an aluminum supplier, shipping cost will kill you so picking it up along the way will help. I am now trying wicks aircraft but they are low on 1 1/2 and trying to see if they can get some more in in time for my trans continental drive. Know of any reliable suppliers? Not Aircraft Spruce... I'll postpone before I'll pay those prices.
The New Guy--I only got started in hang gliding since 1973 so forgive me.
PS Ground Slammer is comic parody on Ground Skimmer, you ever hear of Ground Skimmer Joe?

[Bob Kuczewski]

Treat this AI response as though there are mistakes in it

It just dawned on me that the current AI is a lot like the character Cliff Clavin on Cheers. They both can sound extremely good while saying the most ridiculous things. Here's an example:

Well, you see, Norm, it’s like this. A herd of buffalo can only move as fast as the slowest buffalo. And when the herd is hunted, it’s the slowest and weakest ones at the back that are killed first. This natural selection is good for the herd as a whole, because the general speed and health of the whole group keeps improving by the regular killing of the weakest members. In much the same way, the human brain can only operate as fast as the slowest brain cells. Now, as we know, excessive intake of alcohol kills brain cells. But naturally, it attacks the slowest and weakest brain cells first. In this way, regular consumption of beer eliminates the weaker brain cells, making the brain a faster and more efficient machine.

And that, Norm, is why you always feel smarter after a few beers.

As Joe said: "Treat this AI response as though there are mistakes in it" !!

Here's another example for your viewing pleasure:

https://www.youtube.com/watch?v=k6GTZrcoWEM

Cheers!!

[Ground Slammer]

You almost insult me with not knowing AI is totally untrustworthy, it's our butts on the line! I'm going to see if I can move Red's post to over here & vice versa. Amazing! Also looks like I'm buying Wicks, and I going to get a copy of the mill certificate..... not because I don't trust Wicks but the ways and means of proper homebuilts, FAA EAA .

[Bob Kuczewski]

You almost insult me with not knowing AI is totally untrustworthy,

No insult intended. The AI assault has been so quick that it's hard to know who knows what at this time. It's better to be safe than sorry.

Thanks for posting.

[Ground Slammer]

ALMOST but not actually. What is most important is linking what Joe posted with what Red posted. Let me see if I can post a link.