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titanium fuselage

Question:

Thanks to the Lear Foundation originally the William Lear of the Lear Jet and Lear Fan aircraft plus many other aircraft mod programs; we are to pay the high costs of Titanium.  If memory serves me correctly Old Bill got hold of all Titanium Assets during the late sixties or early seventies. Whereupon he hoarded the metal mainly to drive the price up.
Also one important thing that was passed over is that Titanium has a memory, it will revert back to within 80 percent of its original state.
I recently retired from one of the three major Aerospace Corp’ns and had first hand TI experience.  We found that Cobalt or Carbide drills worked best, plus lasted longer.  Here again is another reason Ti Costs are so high.
Don’t know about the so called Titanium coated drill on TI drilling never had these in the corp’n shop, their purchasing department wienies were not structures oriented.
Every thing else about Ti is great and it is a good structural medium for just about anything that requires sheet metal.    -**** Posted from RemarQ, http://www.remarq.com/?b ****-  Real Discussions for Real People

Response:

It is nice stuff however, wish I could get hold of enough material, and joining technology for a couple of bike frames.  I especially like its corrosion resistance.

I seem to recall being quoted around $50/foot for 1" tubing.  That’s expensive but do-able depending on your budget.  That may have been for a bulk purchase, I’m not sure. RCteller

Response:

It is nice stuff however, wish I could get hold of enough material, and joining technology for a couple of bike frames.  I especially like its corrosion resistance. I seem to recall being quoted around $50/foot for 1" tubing.  That’s expensive but do-able depending on your budget.  That may have been for a bulk purchase, I’m not sure.

Ouch!  That would make for a VERY expensive fuse!   If anyone is interested, I have some contacts for Chinese aerospace grade 3Al/2.5V seamless tubes that will cost MUCH less (and have proven to be extemely reliable in 3 pound bicycle frames, which are stressed MUCH closer to their design limits than a plane will be – at least we HOPE so when we’re flying….). Considering the cost of carrying extra weight in an aircraft, it might not really end up costing that much more over the lifespan of the aircraft (just THINK how much you’d save on paint).  ;-) Mark Hickey

Response:

Recalling the amount of problems we had a few years ago whe Soviet titanium arrived on the market, at half the price of anyone else’s, I’d treat Chinese with at least the same level of caution. Bike frames? Sure, you can always get off and push/carry/leave it and walk.  Aircraft?  No way.  The cost of certification to a trustworthy standard will make it the same cost as the real thing. tim – Hide quoted text — Show quoted text – It is nice stuff however, wish I could get hold of enough material, and joining technology for a couple of bike frames.  I especially like its corrosion resistance. I seem to recall being quoted around $50/foot for 1" tubing.  That’s expensive but do-able depending on your budget.  That may have been for a bulk purchase, I’m not sure. Ouch!  That would make for a VERY expensive fuse!   If anyone is interested, I have some contacts for Chinese aerospace grade 3Al/2.5V seamless tubes that will cost MUCH less (and have proven to be extemely reliable in 3 pound bicycle frames, which are stressed MUCH closer to their design limits than a plane will be – at least we HOPE so when we’re flying….). Considering the cost of carrying extra weight in an aircraft, it might not really end up costing that much more over the lifespan of the aircraft (just THINK how much you’d save on paint).  ;-) Mark Hickey

Response:

Oh hog wash, Tim! All of our SR-71s were built with Soviet Titanium! And, considering WHERE that highly loaded vertical tube is located on a bicycle, well, I don’t want THAT one failing!!!! ;) Richard – Hide quoted text — Show quoted text – Recalling the amount of problems we had a few years ago whe Soviet titanium arrived on the market, at half the price of anyone else’s, I’d treat Chinese with at least the same level of caution. Bike frames? Sure, you can always get off and push/carry/leave it and walk.  Aircraft?  No way.  The cost of certification to a trustworthy standard will make it the same cost as the real thing. tim

Response:

Pro’s for using Ti If you live in the land of OZ where people have gobs of money, don’t scratch metal and do EB welding then a Ti component will be lighter and more corrosion resistant than a steel or aluminum component. Con’s for using Ti. Composites are a much stronger, lighter, more corrosion resistant and cost effective solution than Ti. Cost, machinability, weld ability and predictability of Ti all suck. Likely hood of having to shot pean or replace an expensive Ti part because you scratched it is high. Likely hood that you will be killed because you built a homebuilt aircraft with Ti and didn’t have an expensive FAA mandated inspection program is much higher than with steel aluminum or composites. Other things to consider For the ultimate in fixed wing aircraft construction, composites offer the best strength to weight ratio with far more reasonable serviceability for the typical homebuilder. Today Ti frames in fixed wing aircraft are not appropriate even for the most exotic military applications, composites rule now. Ti is still a good material for small highly stressed fittings and helicopter rotor system components, but not recommended at all for homebuilt aircraft. Likewise some people would say the same for composites verse metal construction. According to the RV folk "Friends don’t let friends fly plastic aircraft". While the composite technique requires a bit more skill and is a little less forgiving it is still within the capability of the average hombuilder. Ti is not for homebuilders. How about a discussion on the pros and cons of titanium? Obviously special welding, weight and cost are considerations.

– /            John Roncallo              /

Response:

To John Roncallo:
All I can say is AMEN and good job.
My earlier entry didn’t have much force as to explain TI is Extremely Expensive.
Un less you Are Billy Gates or one with his Financial Status.
Forget TI, stick with the materials that are easier, and more readily available.
   -**** Posted from RemarQ, http://www.remarq.com/?b ****-  Real Discussions for Real People

Response:

Other things to consider [for using Ti]: For the ultimate in fixed wing aircraft construction, composites offer the best strength to weight ratio with far more reasonable serviceability for the typical homebuilder. Today Ti frames in fixed wing aircraft are not appropriate even for the most exotic military applications, composites rule now. Ti is still a good material for small highly stressed fittings and helicopter rotor system components, but not recommended at all for homebuilt aircraft. …….While the composite technique requires a bit more skill and is a little less forgiving it is still within the capability of the average hombuilder. Ti is not for homebuilders.

As to titanium being used by the military but not for homebuilders, I came across a graphite composite structure that was also a government project using a rather exotic construction method, yet one that might be adaptable to homebuilts. This past Friday I was at the Virginia State Fair, and not just for the rides and cotton candy. They had a Technologies Exhibit Hall and a group from NASA’s Langley Research Center down in Hampton came up to Richmond with displays of a number of new and interesting technologies they’re developing. One in particular caught my eye, that of a 8 foot lower wing section made of graphite composite with the ribs and spar molded into place. This was a military grade piece of work. What enabled this to be done was stitching the graphite layers together with Kevlar thread. The main skin was more of a monocoque construction, at least 10 layers thick, with the ribs and spar fabric stitched into place like "L" brackets placed back to back so the lower portions laid on top of the skin structure and was then stitched down into place. They had a small sample that was not epoxied, about a 12" x 4" with rib sections in place. Very stiff with the Kevlar stiching up and down its length. I can see how this would limit the friction and shear forces acting on the binding substrate (epoxy, vinylester resin, etc.) thus allowing higher loads on the structure than an identical layup without the stitching. The stitching was perhaps 8 to 10 stiches per inch and about 1/4" between rows, much like the stitching you see on parachute harnesses where the D-rings and snap fittings are sewn in. And this is what got me to thinking about it’s applicability to homebuilding. During my college days when I was skydiving, I had a rigger friend who I used to watch make custom rigs. His sewing machine was the same as I later saw used by Army riggers. Very heavy duty and capable of stitching through 5 layers of 5000 lb. test webbing material. A rigger’s sewing machine could probably handle making composite ribs and spars in this fashion with fewer layers, though not entire wing skins. The only problem would be how to build a pressurized system to force the epoxy completely through the layers and leave no voids. Vaccuum would probably not be sufficient to pull it through all the sewn layers. The use of chilled pre-preg cloth with the adhesive in place could solve that problem. Anyway, it’s a bit of NASA research technology that I thought you might like to know about, and it may be possible to use it to increase the strength of smaller composite parts for homebuilt aircraft without any measureable increase in weight. Regards, David Pincus

Response:

Perhaps a good use for Ti would be the firewall, a fairly small piece that could use the characteristics to advantage. Kenny P.

– Hide quoted text — Show quoted text -On a different group a friend was asking about titanium fuselages. I remember seeing a ad in Sport Aviation a while back, but darned if I can find it now. Anyone here familiar with that info? How about a discussion on the pros and cons of titanium? Obviously special welding, weight and cost are considerations. Ken Bauman Before you buy.

Response:

The main reason for use of Ti alloys in aircraft is its high strength to weight ratio AT ELEVATED TEMPERATURES.  Unless you expect to track your speed with a Mach meter instead of an ASI don’t even consider Ti alloys.

So you;re saying that maybe I should be using Ti for my homebuilt SR-71 instead of Stits?  ;-) Russell

Response:

Likewise some people would say the same for composites verse metal construction. According to the RV folk "Friends don’t let friends fly plastic aircraft". While the composite technique requires a bit more skill and is a little less forgiving it is still within the capability of the average hombuilder. Ti is not for homebuilders.

I seriously disagree.  Please tell me, as an inspector of homebuilt aircraft, how I can determine in a completed composite aircraft, whether or not someone has improperly mixed a batch of epoxy, thereby GREATLY degrading the strength of the composite?  How can I determine if someone has failed to remove the peel ply between two internal layers of the lamination after the aircraft is completed?  How can I determine, on the finished aircraft, if the proper materials were used for interior laminations and if they are properly oriented and bonded to the rest of the structure?   As you say.  A well constructed glass airplane can be perfectly safe. However, a poorly constructed one can LOOK fine, and be anything BUT perfectly safe.  I do not know how to reliably tell the difference. Do you? — HighFlyer Highflight Aviation Services

Response:

The main reason for use of Ti alloys in aircraft is its high strength to weight ratio AT ELEVATED TEMPERATURES.  Unless you expect to track your speed with a Mach meter instead of an ASI don’t even consider Ti alloys. Best regards, Rob Housman

– Hide quoted text — Show quoted text – To John Roncallo: All I can say is AMEN and good job. My earlier entry didn’t have much force as to explain TI is Extremely Expensive. Un less you Are Billy Gates or one with his Financial Status. Forget TI, stick with the materials that are easier, and more readily available.    -**** Posted from RemarQ, http://www.remarq.com/?b ****-  Real Discussions for Real People

Response:

Pro: light weight, heat resistant, STRONG Con: COST, COST, COST My company looked into using titanium for some parts several years back.  Expect to rivet it.  It takes specialized welding equipment to weld it (the kind my company — a metal fabrication company did not have).  If you rivet it, expect to go thru a LOT of drill bits.  It is like stainless steel in that respect.  If I remember correctly, it is lighter than steel or stainless steel, but is NOT lighter than aluminum.

I was unaware of the need for special welding equipment needed to weld titanium! What is needed is an atmospheric chamber, welding in a box of argon. I have welded dozens of defect free titanium parts using standard TIG equipment inside a box similar to a sandblasting box made out of cardboard, duct tape and a welding helmet. Positive argon pressure was maintained with a continuous low volume low pressure purge(after the initial high volume purge to eliminate all "air" from the chamber) plus the normal gas flow through the torch was maintained while welding. — Bruce A. Frank, Editor               "Ford 3.8/4.2L Engine and V-6 STOL BAFRANK(at)worldnet.att.net              Homebuilt Aircraft Newsletter"                                  | Publishing interesting material|                                  | on all aspects of alternative  |                                  | engines and homebuilt aircraft.|                (-o-)/        AIRCRAFT PROJECTS CO.                 ___/           Manufacturing parts & pieces                 /             for homebuilt aircraft,                0     0          TIG welding While trying to find the time to finish mine.

Response:

That said, I’d recommend anyone contemplating welding ti structures to hold their butt in the air seek help from an experienced aerospace welder. Mark Hickey

Rule-of-thumb was if there was no discoloration and it didn’t break when hit with a ball-peen hammer it would take the workload. Used to weld Ti angle clips used with bolts when rock climbing with this "card board box" method(and used dozens of them myself). All were strain tested to 5000 lb proof load AFTER a leader fall simulation of 200 lbs from 10 ft using steel cable (no elastic give). None ever broke. Ti is easy to weld but can be easily contaminated by several gasses in the atmosphere. Any contamination shows up as some other color(blue, green red, pink, yellow, purple) than the base metal. All such contamination caused low strength failures which were sometimes dramatically brittle (like glass). I have never seen a failure where there was no discoloration, but I still hit the part with the hammer. — Bruce A. Frank, Editor               "Ford 3.8/4.2L Engine and V-6 STOL BAFRANK(at)worldnet.att.net              Homebuilt Aircraft Newsletter"                                  | Publishing interesting material|                                  | on all aspects of alternative  |                                  | engines and homebuilt aircraft.|                (-o-)/        AIRCRAFT PROJECTS CO.                 ___/           Manufacturing parts & pieces                 /             for homebuilt aircraft,                0     0          TIG welding While trying to find the time to finish mine.

Response:

I was unaware of the need for special welding equipment needed to weld titanium! What is needed is an atmospheric chamber, welding in a box of argon. I have welded dozens of defect free titanium parts using standard TIG equipment inside a box similar to a sandblasting box made out of cardboard, duct tape and a welding helmet.

Heh heh heh… I can imagine the exciting possibilities of welding inside a cardboard box….  but this does appeal to my Rube Goldberg nature! Positive argon pressure was maintained with a continuous low volume low pressure purge(after the initial high volume purge to eliminate all "air" from the chamber) plus the normal gas flow through the torch was maintained while welding.

Another method (one used in the bike biz) is to drill venting holes at the junction of tubes (i.e they end up inside the weld), and to simply plumb the gas into every open end of the tubes.  Then, flood the weld with gas with your "normal" TIG welding setup to cover the outside of the weld. It might be possible to do the inside gas using a lot of aquarium tubing and corks (see, I TOLD you I like Rube Goldberg solutions). That said, I’d recommend anyone contemplating welding ti structures to hold their butt in the air seek help from an experienced aerospace welder. Mark Hickey

Response:

Pro: light weight, heat resistant, STRONG Con: COST, COST, COST My company looked into using titanium for some parts several years back.  Expect to rivet it.  It takes specialized welding equipment to weld it (the kind my company — a metal fabrication company did not have).  If you rivet it, expect to go thru a LOT of drill bits.  It is like stainless steel in that respect.  If I remember correctly, it is lighter than steel or stainless steel, but is NOT lighter than aluminum.

True, it’s "heavier" than aluminum, but you can use a lot less of it and end up with a structure of the same strength (or use the same weight and end up with a stronger structure). It also has the advantage of being impervious to the elements (i.e. no more worries about rust) and has fatigue characteristics that give it just about unlimited life as long as you don’t flex it enough to bend it permanently (unlike aluminum which will theoretically break eventually (though that’s not a problem if "eventually" is 10x the realistic service life of the plane. Other advantages include the fact it doesn’t "grow" much during welding (keeping the structure much straighter than steel) nor does it require any heat treatment to get back its strenght post-welding. Welding it *is* difficult, and is best left to the experts.  Even a tiny bit of oxygen or nitrogen can embrittle the weld.  The good news is, bad welds tend to show up as discoloration, Mark Hickey

Response:

On a different group a friend was asking about titanium fuselages. I remember seeing a ad in Sport Aviation a while back, but darned if I can find it now. Anyone here familiar with that info? How about a discussion on the pros and cons of titanium? Obviously special welding, weight and cost are considerations. Ken Bauman Before you buy.

Response:

Pro: light weight, heat resistant, STRONG Con: COST, COST, COST On a different group a friend was asking about titanium fuselages. I remember seeing a ad in Sport Aviation a while back, but darned if I can find it now. Anyone here familiar with that info? How about a discussion on the pros and cons of titanium? Obviously special welding, weight and cost are considerations. Ken Bauman

For a homebuilt-class of airplane (2000# max gross) titanium may get you a few pounds, which is scratch, compared to fixed weights, such as engine, prop, wheels/brakes/tires, avionics, instruments, canopy, etc. It has excellent corrosion resistance, however.

Response:

With some experience of fabricating sheet metal parts for aerospace applications, the quick answer is, "Don’t" .  About the only place where Ti will score over Al is in terms of strength retention at elevated temperatures, and I don’t think any homebuilt is likely to have that sort of speed. The top limit for Al alloys is around mach 2.2, Concorde speed. Matter of fact, that’s what limits C’s speed. tim – Hide quoted text — Show quoted text – On a different group a friend was asking about titanium fuselages. I remember seeing a ad in Sport Aviation a while back, but darned if I can find it now. Anyone here familiar with that info? How about a discussion on the pros and cons of titanium? Obviously special welding, weight and cost are considerations. Ken Bauman Before you buy.

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