having problems w/alum.

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I'm welding some stanchions for a boat  that are .25 thick.  I'm having problems welding them (penetrating).  It looks like that I may need to pre-heat the aluminum.  any advice?  I'm using a dynasty 200 dx. in tig mode.  I also have a thermal arc fabricator 251 w/spool gun.  not having any luck. any advice would be helpful. are these machines capable to weld this job up.  do i need to bevel?  thanks
Reply:Yes, you should bevel, and preheat with a propane torch enough to put in a little base heat will work wonders.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Bevel or gap, either way works.   Your Fabricator mig should be able to weld that.   Crank it up!   Unless you pre-heat, the start of the weld will be cold, but you can help it some if your machine has a run-in speed adjustment, use it, and hang out for a bit at the start so you get the puddle going before moving forward.   Once you do get going, don't zip forward like you're in a race, feel the puddle and watch the weld melt in as you move along.  What wire are you using?  4043 sprays on smooth.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I use an arcmaster 185.  I have to turn the AC frequency way down to get enough heat for 1/4".  Use only enough cleaning to do the job.  That will add more heat too. DavidReal world weldin.  When I grow up I want to be a tig weldor.