Turn Fin Troubles

[Capt. Crash]

I read every post about this boat here and saw several problems noted with the turn fins breaking off but can't remember what thread I saw them in...therefore this thread. After reading about the problems...I decided to take a look at mine tonight as I was preparing it for testing tomorrow. Guess what....mine is broke too! It also has water in the hull. My boat has around a dozen runs on it.

I'm dropping thin CA into the crack and running anyway....I can't help it...ain't got time to fix it proper tonight and I have a very limited window weather wise to run this weekend. So...I will deal with a proper fix later.

So...it appears we have a weakness in the boat! :glare:

[skibo2]

The thread you are looking for is this one "UL-1 first run + videos". It is under the UL-1 topic heading.

As a footnote, I have contacted Aquacrafts Warranty dept. regarding the weakness and they are looking into the problem as well.

[Capt. Crash]

My hull is broke all the way through or I wouldn't have water inside. I will need to find a way to strengthen the bulkhead too. Here is my quick fix to make the fin breakaway. I got rid of 2 bolts and since I didn't have nylon bolts so I used a nylon zip tie instead. I also reshaped (rounded) he fin so it would be able to swing up.

I'm off to the pond....results later. :smile:

Crash

[Steven Vaccaro]

I have 3mm nylon screws. I tested them and under pressure the mount area still flexes before breaking the screw. The upgrade will have to be 2 fold. First strengthen the mount area. One of the members suggested squeezing a bunch of epoxy into one of the mounting bolt screw holes. But now that its wet I think I would suggest against that. Maybe use a aluminum plate jb welded like Properchopper did. Secondly use some 3mm nylon screws.

[Capt. Crash]

I like the epoxy idea...I may try that anyway. The temp glue job held up. I put about 6 miles on her yesterday and she was still together. My average top speeds were around 43.5 mph while I did get a high reading of 45.3 mph on the first 5 lap run. Stock adjustments/setup other than a somewhat sharpened Grim Racer 40x52 3 blade prop. She had a 3oz GPS velcro'd aft and it seemed to make her light on the sponsons. Next runs I will move the batteries all the way forward to see if this helps. I've not messed with prop depth yet. (The conditions were not perfect for a top speed run. I ran with 60 degree batteries (Max Amp 5250 30Cs) and they were not topped off before the runs and had been off the charger for several hours.) Hopefully more testing tomorrow.

Crash

[Rex R]

if you want your batteries to last, you need to physically warm them to at least 80F before running...I've got a 2.5 ton solar powered battery warmer ;).

[Capt. Crash]

I put the 2nd set in my front pockets but they still only warmed to 65....it was in the low 40s out. This summer they will be plenty warm....:doh: I need a small warmer of some kind.

Well I went ahead and injected about 8cc of 30 min. epoxy into the two screw holes (after reading about someone else doing this on this board). I oiled up the screws and replaced them while the glue set. I may still add a aluminum plate to the outside of the bulkhead too.

One more problem...maybe...I'm not sure. Since I had water inside I decided to heat up the hull a little with my heat gun to try to dry it out a little. Guess what happened...I got a soft spot that sank in when a ran my finger over it to test how hot it was.....rrrrrrrrrrrrrrrr! There must not of been any fiberglass mat or....the resin/epoxy is thin there or something. See pics.

This is way back on the sponson but maybe not on the contact patch enough to affect it...I don't know...any thoughts. I could run it without bondo and see how she does?

[SweetZ28]

Man that stinks... I was going to get a UL1 when it first came out but i am kind of glad i passed and did not get one maybe in the next few months or so they will fix the fin problem.....the way i see it they need a whole new type of fin that will fold up if it hits something because even if the hull was super strong if you hit a floating object at over 40 with the turn fin they have on it now any hull will break in my opinion...

[Capt. Crash]

Ok...I bondo'd the indention and tested again yesterday. Before the testing I did notice that the turn fin had hit something hard. I somehow missed the slight flattening of the knife edge when I worked on it before. I sharpened it back up before the testing. This might explain what happened to my turn fin. That is good news because I didn't want to think it was so weak it just cracked under the stresses of normal use. I'll bet that turtle was wondering what hit him!

I ran her through about 6 miles of choppy water today (winds 10-20mph) and everything held up nicely. On the smooth end of the pond, I was hitting the tight hairpin at full throttle putting as much lateral force on the fin as possible.

Stock (7/8" measured from the bottom of the strut to the bottom of the hull) prop depth, at least this how mine came. Grim Racer 40X52 3 blade. I used MaxAmp 5250 30C's. After a few runs...I to had to move the batteries as far forward as I could get them and put the GPS in between them due to the windy 20 mph conditions I had to run against on the returns. First rip was exactly the same as Saturdays 45.3 mph, with all the rest of the runs in the 43-44 mph range. I re-sharpened/balanced the prop...and it made no difference where the batteries or GPS were located either. Looks like this is what you get with this prop...and I am plenty happy to run at those speeds as least for now. I was running 7 laps or about 1 mile heats...average lap speeds were around 29mph...total time about 2 1/2 minutes to run the heat.

Crash