Death of an Impulse

[nickB722]

Well I've got some sad news to report. Today I was out running the family dinghy as a retrieval/rescue/driver platform boat for my friend's Impulse 31. On the first run of the day (30 seconds after his normal mid-run heat check) and 3rd on the boat, it took a little hop, bounced once, and stuffed (popping both hatches off despite tape and the latch) at about 15 mph accelerating out of a turn.

In the 10 seconds (yes it was only 10 seconds as the motor of the rescue boat was running and it happened less than 30 feet away) it took to get to the crash scene, the hull filled up with water and sank FAST by the stern, never even bobbing up. All he's got left is the outer hatch, transmitter and his spare prop/batteries. I lost my pair of Dynamite 4500 NIMH packs in the crash.

20 minutes of a visual search turned up negative, as did an hour and a half of using fishing gear, treble hooks, and a 200 pound retriever magnet. The next step will be trying to find a diver, but it's a decent sized area where we were running, and the water is murky, so recovery probability is low at best. Needless to say he's ticked (and so am I having lost batteries too).

The guy he spoke to at Horizon was sympathetic, but it seems that they won't do anything for him. Call me crazy, but with a decent amount of foam in the bow (plus two extra blocks that filled up the areas next to the battery tray that I made for him) the boat should float even with a decent amount of water in it. I'm starting to wonder if the boat has enough flotation to stay up at all if the hatches are breached following seeing this one go down.

Maybe there was a bad pour of foam in the front of that particular boat, or it isn't designed with enough reserve buoyancy for the extra weight of the NiMH packs. It did not seem as though the hull was damaged in any way from the wreck as there was NO trace of it on the surface afterwords (having seen plenty of full scale unlimited hydro and offshore wrecks, there's ALWAYS some parts on the surface when a hull is destroyed). As a naval architect in training this is something I'll be looking into, but it's too late for this particular boat. $300 worth of boat and $80 worth of batteries gone in a flash...

Not sure if Darin or anyone else could stop in and shed some light on that situation (as far as the foam being enough to hold the bow up for more than a second or two before this beautiful boat doing its best Titanic impression). I wish the guys in product support could back and support this product with the same passion that he puts into designing/racing and helping us with setups. After seeing how fast she sank and that HH can't do anything about it, I doubt I'll ever be spending money with them again.

I guess I just needed to vent, but if you guys have any thoughts on what could have happened I'd like to hear it. Obviously with the experience most of you guys have, you've probably wrecked more boats than the two of us have owned combined, so maybe I was naive to expect a whole hull of foam (not branded Boston Whaler) to float after a pretty benign accident.

[dana]

that sux man. sorry to hear. use pool noodles from now on

[nickB722]

I don't even bother with pool noodles, I've got some sample pieces of a really light closed cell foam designed for boat cushions and pool mats, it's lighter than pool noodles and came in a big block so i could carve any shape I wanted. Even this couldn't keep this one afloat... Mine's drydocked until we figure out what happened to his because something just seemed very wrong about how it went down so fast.

[dana]

Are boat cushions designed to float with weight on them? Have you tried weighing your impulse, then using a weight to see how much of your foam it will take to float it?

[nickB722]

This foam is, it's similar to the stuff used in pool mats (only it doesn't need the coating), so yes, it holds weight and floats very well (well enough to be certified by the Coast Guard as a throwable life preserver).

I haven't weighed the boat then calculated the foam, but I'm planning on modeling the hull and running some analysis to see how the boat could've sank so fast with our damaged stability program.

[dana]

Be awesome if you guys could get the hull back. That would tell so much

[nickB722]

For sure! If one of my diver buddies can recover it I'm thinking I could borrow the tow/test tank at school for a bit and run some tests to see what it takes weight wise to sink her.

[stadiumyamaha]

the stock foam is enough to keep it bobbing in the water for a very long time even with the heavy batts.
I had a esc failure in my impulse which blew the taped lid off and the boat sunk but the nose still floated. Also, I was running two 4s 5300mah batts that are probably as heavy as the nimh that you ran.
Any chance that the throttle hung open and it stuffed in to the bottom of the lake? I've recently seen a video of this happening. Just a thought. Hope you get it back.

[nickB722]

I did consider the stuck throttle scenario, that's why we stuck around for about 20 minutes after the wreck just looking around hoping it would bob up like that Revolt. Plus, it didn't sound like the throttle was engaged as the boat took that last hop (not sure if he was off the throttle that quick or if there was some kind of electrical issue).

I still don't know how it could sink, especially since the stock foam seems to be enough for most people's use... Guess he (and by extension me) got unlucky. I just hope HH can do something if my scuba guys can't get it back.

[dana]

The only chance hh can do something is if you get it back.

[d.a.v.e]

I added about 3oz of expanding foam and it seems to float really well with that in addition to what was already in there now. It would float before but not not much more then the point of the boat would be visible.

[ray schrauwen]

I'm guessing here but, if there was a possible crack in the front deck, the hull would not trap an air bubble like most to keep the nose above water.

was your added foam cut pool noodles?

Were the 4500's a pair of 2S or 4S??

If it is real murky there are many other possiblities, It could be snagged on or part under somthing too?

What tape are you using that comes off so easy??

The best hatch tape I've ever used is RENFREW brand clear hockey tape. Get it up here at Canadian tire but, they are getting replaced by garbage 3M brand that looks thge same but comes off with water. I've never tried PB or AQ tape or any other brands.

[d.a.v.e]

No my 3oz was the liquid stuff you mix up and pour in.

[nickB722]

There weren't any cracks in the hull when it was placed in the water for that run Ray, it did have one small stress crack in the bottom of the hull from shipping, but it was patched with CA and epoxy.

The added foam was a light closed cell foam block.

The 4500s were 6 cell NiMH packs. The extra weight compared to LiPOs is a concern I have about how quickly the boat went down.

The area is murky due to a mucky bottom and full scale boat traffic nearby (Operating at idle/no wake speeds with propwash churning the bottom), but it's not a weedy area and there was no debris present at the scene of the accident.

The tape was ProBoat's hatch tape as the hockey tape I'd normally have in the race/rescue kit I had aboard was in my hockey bag from a game this past week.

[dana]

Have you gone back to see if anything has washed ashore or anything? It's like you got trapped in the Bermuda triangle or something

[nickB722]

I went back three times after the incident (first with fishing gear, then the magnet/trebel hooks, then with a flybridge boat for a higher perspective), no such luck. I did file a report with the park and I'm planning on going back at some point this week when I get the chance (hopefully with a diver or fish-finder of some sort).

[dana]

I'm dying to know wtf happened to this boat... How deep is the water where its lost?

[nickB722]

You're not the only one Dana haha. The depthsounder had the area pegged at around 6.5-7 feet below the bottom of the boat, which draws about 3 feet of water, so it's about 9-10 feet deep. Problem isn't so much the depth as it is the visability. Even at surface level the vis is about a foot at best, and that would certainly get worse the deeper a diver would get. It just isn't a safe recovery for anyone without experience in murky water recovery.

[Neubs]

I am sorry to hear about your Impulse. Sounds very strange for it to go down so fast. Like others have said, I am very interested to find out what happened. I hope you can recover it.

[roadrashracing]

Any chance that maybe the hull split when it hit the water and broke in two?

[Jersey Crewmax]

That really suck, very surprised it sank like that considering the amount of foam in it. Hope you guys get it back and that some of the electronics are salvageable.

[nickB722]

Well after 3 hours of dragging the bottom with a net yesterday turned up no results. In that time there was only one possible hit, but it turned out to just be a thicker layer of muck on the bottom. It seems she's gone for good.

As for a potential split, it was something I considered, but it didn't appear to be the case, and if it was, it stands to reason that there'd have been some debris to recover.

[dana]

Dang

[IRON-PAWW]

Stuffing & submarining seem to be a problem this boat has. It has happened to me several times. The last time it happened I got a really good view of the boat shooting under the water because it was so clear. Underwater the hatch tore off and of course the boat instantly filled with water. But mine bobbed back to the surface with the bow pointed skyward. But because my reaction time sux, I powered on beneath the surface a few seconds no prob. So......maybe your boat did end up further away than you think. Also possible that it got stuck mid water column due to buoyancy not being quite enough for it to surface. Damn odd all the same.

Oh wait... You actually saw it go down didn't you (just reread). Water currents must have moved it?