What went wrong?

If you're logs are up to date.  I would echo Keytone on the bike.  But your swimming and running seem a bit inconsistent as well, which will all add up, especially for your first tri.  Did you practice your nutrition on your long rides?  One of the golden rules of longer distance races that I've seen here is don't try anything new on race day.  My recommendation for next time would be:

- more consistent training (assuming your logs are correct)

- a good nutrition and pacing strategy

- a shorter distance race as a "tune-up"

- not trying anything new on race day

- following a good plan that works with your schedule 

Congratulations on finishing. 

That's not a bonk. If you bonked you would feel so weak your finish would be in question. Quick and shallow respiration and a quick pitty patter heart is a symptom of overheating. Although weakness is usually a symptom too. You took in so many gels I feel a halloween candy stomach ache reading this. Its possible you had so much sugar and junk in your stomach you were dehydrated from not geting enough plain water or just ill from all the sugar.

According to your post you took in around 2700 calories of sugar not including the redbull. Even if your race lasted 7 hours that is high.

I'd say you just made yourself sick from all the gu and powerade combo.

What about something that caused a blood sugar issue (redbull shortly before start?).  Worth some research. 

If you're interested PM me and I'll find you a link.

Good Job nonetheless

Congrats on finishing your first half!  Sometimes doing is the best way we learn.

Its good you watch your HR because that definately affects your nutrition.  In general, without knowing more about you its hard to comment, but a couple of thoughts:

I would add in not enough water.  Just good plain water...to break down all the fuel you consumed to be utilized by your muscles.  You had a big glob of nutrition in your gut but your muscles were tapped.  As crazy as it sounds with all the powerade you drank, you were probably dehydrated.

Nutrition strategy should include:  Water-Fuel-Electrolytes---if it has calories, its fuel and can't be counted as water.   So, learn your sweat rate for water and electrolytes (yes salt tabs may have been a good idea but not if you haven't tried it in training), and monitor how much food you can digest and absorb to determine fuel needs. 

Gu is made to be consumed with water, not Powerade.  As someone touched on, too many carbs at a concentration that can't be utilized. 

That part is okay.  It's the powerade on top of it.   Your stomach needs it's contents to be at a particular concentration before it can be easily digested.  When you overload it with sugar like that, your stomach can actually pull in water to drop the concentration so it can digest it.  End result is that it takes longer to digest and (if the concentration is high enough) cause your stomach to temporarily rob the rest of your body of fluids.

As was mentioned earlier, you started with a calorie deficit and tried to make up for it later.  I think that combined with a  hypertonic gut, probably led to the issue (combined with heat as well)

The short version is if you tried that exact nutrition plan in training, you probably would have found the issue.   So if you like gels, stick to gels and water in training for a while and see how you do.

Green? Really?  That doesn't seem too normal to me, a good indicator something was a little out of whack.  I'd echo the not enough H2O + a lot of undigested sugars/carbs as being part of the issue, combined with the aerobic base on the bike.  Of course, if you're still peeing green, I'd go see a doctor.... 

Lack of appropriate training. 

Sounds like you may have overdone the calories, but doubt that's what caused you to slow down. 

To finish a HIM feeling strong, you have to have very good swim, bike & run fitness.  And, sorry if this seems too blunt, you don't appear to have that from your logs.

Congrats on finishing a challenging event, though!

And I still think your focusing in the wrong area.  What you descibe is exactly what you would expect to happen in the late stages of a long race as fatigue catches up to you.  That's a fitness (and pacing) issue far more than nutrition.

P.S.  I'm really not trying to pick on you, but many of the people who struggle at long course tris feel that nutrition/hydration was their downfall.  In fact, for most of them (while their nutrition/hydration could have been better) it's simply an issue of fitness level and pacing.  Everyone likes to think they're the exception.  I've been there myself. 

If I'm using gels, I just use gels and water.  When I ran my marathon, I would take a gel just before an aid station then grab water.  1/2 cup was enough.  Now this race was supplying HEED, which is Hammer's sports drink (I use hammer gel), so on aid stations that I didn't take gel, I was taking HEED.  That was just a combo that I knew worked from training, but I always chased gel with water.

I have also done longer rides (90+ miles) on gels, Gatorade and solid foods (power bars, etc).  Again, formula determined through training, and gels and food were always chased with water, saving Gatorade for the  occasional 'in between time'.

You just have to play with it and see what works.

Although it appears your caloric intake was too high, I agree with JK that it was most likely a pacing/fitness issue.  Unless you were extremely bloated or vomiting then you were processing (albeit maybe slowly) what you were ingesting.

Great work finishing the race, now you can take the lessons you've learned and apply it to your future racing and training.

Shane

It's simply endurance. 

Look at your training load.  Rarely a week with over 2 hours of swimming, generally pretty modest biking and running--some decent weeks with some very light weeks and some modest weeks all mixed in.  There's nothing "wrong" with any of that, but it's going to take you a long time at that rate to build up enough endurance to get through a HIM "comfortably". 

Endurance just takes time and consistency.  Your consistency was mixed and your time has been fairly limited.  You can work on the former as much as the rest of your life allows and the latter just takes...time. 

Man, don't beat yourself up too much.  I did Pigman as well and that run was brutal.  There were a lot of folks crashing and burning between miles 8-11.

You finished a half-iron.  That in and of itself is an accomplishment.  The run leg of pretty much everyone's first tri tends to be a total trainwreck (I know mine certainly was).  The fact that you made it to mile 65 of the race before the wheels came off means you're doing something right.

That being said, I have to agree with what JohnnyKay has been saying.  You can get to the finish line of a half-iron in one piece on your training volume, but it will never be pretty.  You just have to put in the hours and be patient.  There are no shortcuts. 

That's cool.  It sounds like you certainly have the right idea.  Nutrition is such an individual thing that its almost impossible for strangers on the internet to give specific advice that's worth anything.

It's one thing to say to aim for 250-300 cal/hr or whatever, that's more or less the middle of the bell curve for what a person can absorb and is as good a starting point as any.  How you take in those calories is something you're going to have to figure out through trial and error.  I know for me personally, on the bike I could eat burritos and hot wings and go all day.  But on the run its straight water and one GU every 4 miles.  Anything beyond that and it feels like an alien baby is trying to kick its way out of my stomach.  But it took me a couple trips into the puke zone to figure this out.