UL-1 Repair and Modification

[CraigP]

Hello all, I had my UL-1 boat out right before I closed out for the season. This is a new boat to me, I bought it off a guy on the forum here. It had hit a log before I got it, and the original owner did a good job fixing that back up. Well, I ran it onto shore about the 3rd time out, while on a new pond. That took a toll on the rudder bracket attachment area, breaking it all out again. I got the cutting wheel out and noticed that it had been getting water behind there, and there were some minor rot and rust issues. So I decided to go for it, and remove that entire section, as can be seen on the picture below. My first plan was to construct a block of 3003 aluminum and fill in this open area. But there are all kinds of rough areas in there and I felt there should be a better way. I was also concerned about adding weight to just that side. This is a very light boat in it's native form. So I decided to cover the entire back of the transom with a T-6061-T6, 0.040" aluminum late, cut out precisely as a template of the original transom. I got some pics of that below...

[CraigP]

The biggest concern I had about the stock attachment bolt plate was how thin it is! I measured it at just under 0.040", barely enough thickness for just 2 threads. I'm wondering how many people have stripped this plate out, seems like a pretty easy thing to do. I have some pics showing this plate. It is part of a larger piece of metal that ties into the thread plate for the rudder brackets. This part of the plate still looked pretty good, so I left that section in the boat. The pic of this rudder portion has been re-flattened out by me, it was pretty puckered up by being pulled so hard with the mounting bolts...

[CraigP]

The rudder also took a hammering, it got loosened up at the hinge pretty bad. I decided to replace and upgrade it to an RCBB, dual water inlet rudder assembly. Not easy finding a replacement rudder assembly for this boat. This little baby came from Australia! I sanded off the back of the original transom and took the bead that extends out around where the two halves the of the boat are bonded together. It got to looking pretty ugly, but there was a great, flat surface to bond the aluminum plate too...

[CraigP]

It turned out very nice! I changed the rudder linkage to an aluminum ball end type, available from OSE. I also put in a Turnigy T-120 ESC and a single channel Opto Board, as well as an external UBEC. It has a Tactic radio right now, but I'm going to convert it to a Fly Sky with an external antenna. I installed a dual outlet port on the side of the hull. This is a Traxxas component. I also installed a water cooled front motor plate to provide additional cooling to the motor. The motor has the stock can cooler but I changed out the fittings for ones with larger ID holes in them. I also modified the hatch to seal without tape. This was the hardest one to do so far. The hatch on the UL-1 is really just a flimsy piece of vacuum formed plastic. So I made a frame, by cutting it out of a larger piece of T-6061-T6, 0.063" Aluminum. This had to be bent with the curve of the hull, then bonded to the hatch. There needed to be thread inserts installed in the hull, and the UL-1 is a sealed tub. So I had to cut little access points, then I made covers out of T-6061-T6 0.015" aluminum, secured by 18-8 2mm cap head screws. I tapped the fiberglass holes so I could screw the screws directly into the hull. Notice there is a top hatch, that has been siliconed down. That is the access port to get to the dual outlet cooling hoses, and get clamps in them. The boat has a stock, 2030kv motor and still has a 0.150" flex cable. I run it on 2, 2S 5200mah batteries, for 4S power. I have been running it with a 1715-17-45 ABC prop, and the boat scoots pretty good!

[srislash]

Good job Craig. I like grafting in aluminum for mounting where I can.

[CraigP]

It’s very strong, with no hull flexing at the rudder or strut. It only added 34g to the boat. I’m also thinking, since I’m adding weight to the front for balance, to change over to a 4074, 1400kv motor and raising the volts to 6s. That will give me a good increase in runtime. This boat is a blast to run! I have a T-120 in it, so I got plenty of ESC for it. At this light weight, I’m figuring on using about 50A average. This is a great learner boat for my friends to get some seat time with a hydro..

[CraigP]

Been doing some calcs on this boat... Looking to expand run time, so I found some 3s batts that will fit in the hull properly, they are 5200mah 50C. I have the T-120 ESC in there already. So I put my 3674 1400kv motor in that has a kt of 0.92 and an EFF of 92%. I had this motor in the DF29 with a data logger on it, very surprised how efficient it was! So on 6s, I’ll have right at 29-30,000rpm on it. It will fit my small ABC props, the 1715-17 for 49mph, the 1716-17 for 55mph, and the go prop, a 1717-17 for 62mph which is probably the top speed for this hull. Expecting it to pul 50-60A, so the run time should be close to 5 minutes. It snowed here yesterday and has been it the 30’s... Will it please get to spring soon?

[srislash]

Been doing some calcs on this boat... Looking to expand run time, so I found some 3s batts that will fit in the hull properly, they are 5200mah 50C. I have the T-120 ESC in there already. So I put my 3674 1400kv motor in that has a kt of 0.92 and an EFF of 92%. I had this motor in the DF29 with a data logger on it, very surprised how efficient it was! So on 6s, I’ll have right at 29-30,000rpm on it. It will fit my small ABC props, the 1715-17 for 49mph, the 1716-17 for 55mph, and the go prop, a 1717-17 for 62mph which is probably the top speed for this hull. Expecting it to pul 50-60A, so the run time should be close to 5 minutes. It snowed here yesterday and has been it the 30’s... Will it please get to spring soon?

Oh man, down there!!! Still snow!!! We had some last weekend so I am of the same mind as you Craig.

NASA is calling it ‘Solar Minimum’ and should end after the 2018/19 winter. Or so I read.

So I’ll be very curious how the pitch changes in prop react for you. I did it on my Fast cat and really only noticed amp draw changes but nothing in speed. I didn’t put a lot of time into tuning tho

[CraigP]

I’ve found with these 17 degree ABC props, that the 1715 likes a tiny bit of positive on the strut. The 1716 likes neutral and the 1717 likes a bit negative, angles under a degree... These props are touchy! But they really get at it!

[srislash]

I’ve found with these 17 degree ABC props, that the 1715 likes a tiny bit of positive on the strut. The 1716 likes neutral and the 1717 likes a bit negative, angles under a degree... These props are touchy! But they really get at it!

Oh I was all negative, more negative, and I did a bit more with the 1.7’s because of the stock diameter which was only 1.3mm bigger but...
I will be revisiting it in the future. Anyway like I said, I’ll be watching.

[CraigP]

I finally got the UL-1 back out on the water today! The wind was kicking up, but it was great to get out and run this boat. I ended up putting this boat on 6S as mentioned in previous post. The boat does very well on this. I have a video that you can see it run. I wasn't really getting on the gas today, but there are a few speed spurts to get a feel for its capability. It has about a 5 minute runtime, I didn't post the whole run... It's running a tiny Prather B215 on it today. The CG has shifted back about 3/4" because of putting in the 3674 motor, which is quite a bit heavier than the stock motor. It was a beautiful day! I hope others are starting to get their rides out there on the water. Hopefully, winter is behind us!

https://youtu.be/tbOxZ2f4WQ0

[Tetefroid]

Dang that looks good. I might do that just because of how well it looks. Nice job.

[InspGadgt]

Been doing some calcs on this boat... Looking to expand run time, so I found some 3s batts that will fit in the hull properly, they are 5200mah 50C. I have the T-120 ESC in there already. So I put my 3674 1400kv motor in that has a kt of 0.92 and an EFF of 92%. I had this motor in the DF29 with a data logger on it, very surprised how efficient it was! So on 6s, I’ll have right at 29-30,000rpm on it. It will fit my small ABC props, the 1715-17 for 49mph, the 1716-17 for 55mph, and the go prop, a 1717-17 for 62mph which is probably the top speed for this hull. Expecting it to pul 50-60A, so the run time should be close to 5 minutes. It snowed here yesterday and has been it the 30’s... Will it please get to spring soon?

Which batteries are those? I couldn't find any near 5000mah that would fit.

[CraigP]

Here’s the batts sitting in the boat.. They run very well at these lower current levels.

[InspGadgt]

Here’s the batts sitting in the boat.. They run very well at these lower current levels.

Thanks! Looks like they fit nicely in there. I'll start looking around for them. Haven't seen that brand around yet.

[CraigP]

You can get them at rcsuperstore.com for $45 each. Wire in series for 6s operation. I’m running 1400kv in my UL1 with an X443 on it. It will take more prop, but you’ll pick up more prop walking too. The hull will only take so much speed...

[InspGadgt]

Prop walking?

[CraigP]

Prop walk is the same as sponson dancing, happens when there’s too much prop torque.

[InspGadgt]

Same thing as chining? I'm having a lot of problems with that now on 4s running either the UL-19 stock prop or the GrimRacer 40x57 prop. The boat is fine up to about 44mph but as soon as I hit 45 it starts bouncing all over.

[InspGadgt]

I saw in another thread someone built a pointed air dam under the boat that directed air to the sides. He then cut a hole in the webbing on the side of the boat for the air to escape. It looks like it didn't need to be glassed over where he cut out so I'm thinking on cutting the webbing off entirely. Most hydros I've seen since don't have that webbing to trap air under the boat.

[CraigP]

Same thing as chining? I'm having a lot of problems with that now on 4s running either the UL-19 stock prop or the GrimRacer 40x57 prop. The boat is fine up to about 44mph but as soon as I hit 45 it starts bouncing all over.

Chining is different. That’s the boat dragging on the non-trip surfaces. You see that more in V hulls and Cats, but a hydro can dig a chine on the corner, normally results in a the boat flipping sideways. Prop walk induces a side to side oscillation, dancing from one sponson to the next.

[InspGadgt]

Chining is different. That’s the boat dragging on the non-trip surfaces. You see that more in V hulls and Cats, but a hydro can dig a chine on the corner, normally results in a the boat flipping sideways. Prop walk induces a side to side oscillation, dancing from one sponson to the next.

Interesting...that's what I've been told chining is...bouncing from one sponson to the other. GrimRacer calls it "Chine Walk" in this thread: https://forums.offshoreelectrics.com...how-to-stop-it
At any rate that's what i'm having...the side to side oscillation really bad. I've just tried sharpening and balancing one of my props and I was hoping to test it out this weekend to see what a difference it made. But I ended up having to work.

[CraigP]

It’s just a word, no big deal... I come from full size boat racing and that term was usually applied to flat bottom hulls.

A dull prop can certainly cause this. If the prop is sharp, the diameter may be too big for the hull. I get my batts out across the sponsons to put weight out as far as I can. It’s called (in my world anyway) centrifugal damping. Think of ice skaters, when they come in for their final spin, they start with their arms (or weight) out. The spin is slow... Then they slowly bring their arms in and the rotational speed increases to a max speed when their arms are tucked and hands on their chest. That’s how they designed the ISS to rotate the center section at the right speed to simulate gravity.

If you put all your weight on the boat’s centerline, then you have virtually no damping at all. My batteries length is 90 degrees to the centerline.

[InspGadgt]

Your right it's no big deal and I mean no offense. I'm just trying to keep things straight. As a new person to boats I hear a lot of different terms for the same thing so it can get confusing so I'm just trying to make sure I'm clear.

Yeah I was postulating in another thread that maybe these hydros should be designed to run the batteries in the sponsons for that exact reason. That and the lower CG should help to reduce blow overs. Basically the wider out you put the mass the more it will resist rotating. Just like the figure skating example you mentioned...not only do they bring their arms in to increase their spin speed, they also extend them to slow down and stop their spin as well. While it will take more force to get the mass moving further out...the downside is once that mass is moving it has more momentum and is harder to stop rotating. So once the walking hits a certain point there will be no stopping it from going over. (One of my never finished majors in college was physics)

[InspGadgt]

Anyway back to the idea of cutting off all the webbing. Here is the post I mentioned where someone made a V type airdam and cut holes in the webbing to allow the air to escape. https://forums.offshoreelectrics.com...008#post720008

It looks to me like the hull isn't compromised by cutting the hole in the webbing...which leads me to think I could cut off all the webbing and still not compromise the hull. I'd like your input on if you think this would compromise the hull. I'm thinking it will go a long way to calming down the boat. For my own piece of mind I'd like someone else's input before I start cutting on fiberglass that could potentially compromise my boat.

[InspGadgt]

So I did it...I cut off the webbing to try and help calm the boat down. Hopefully I didn't just make it worse. Anyway I have to wait for parts to come in to try it out because I split the collet nut trying to tighten it the other day.

Webbing removed.jpg

Webbing removed 2.jpg

[InspGadgt]

Didn't get to test this weekend due to the hurricane that almost hit us. Hopefully I can this coming weekend.

[InspGadgt]

Didn't help

[CraigP]

It needs the proper weight balancing and an aero wing up front. I velcro’d in a 90g weight on the left side, just in front of the battery. That helped it a bunch to about 50mph. I then built and added an aero wing to the front (some call it a canard wing, but it’s not). This is a reverse-lift wing, designed and placed on the boat to come into Max downforce at about 4-5 degrees of bow lift. I took it off of the UL-1 and put it on my dual motor DF34, which needed it more.

Wings are complicated, need to be calculated out and built to a template. Or just “wing it” and carve one out of a good piece of hickory and throw it on there! Many say good things about aero dams in the air tunnel. They can solve one specific problem at a given boat attitude, but tend to make problems outside of those operating areas. But I’m not going to get into it on the website. Just look at the problem thru your own eyes and apply what you think will fix it. Best way to learn, instead of listening to a bunch of asshats like me!

[InspGadgt]

I used a carbon fiber helicopter blade cut down as a front wing. I made sure the curvature was facing downward so that it would add downforce instead of lift. It looked cool but didn't really help. I plan to try it again but add some spoiler to the back for more downforce.

90g! I tried 200g but mostly centerline. I only put 2 ounces on the left side. Sounds like I might need more.

Even asshats can have a good idea or 2 :)