Oppinions of Prather Lap Cat 1 Hulls

[Too-Fast]

I just re-built a Prather LapCat 1 3.5 hull. What are your opinions of this hull and what kind of performance can I expect from it? I run a stock 3.5 K&B with 25% Sig... for fuel. Can I jump to 35%? Any estimates on how much this beast should weigh ready to run? I have a Gold Carb, should I jump to this carb right away, or am I asking for troubles?

 

[DaddySundown]

My son races one of these hulls. They have an advantage in the turns. Wide open in, through and out of the turns. ;D They run flat down the straightaways. You must keep the hull light as possible. We do not run a radio box because of the weight. We just fill the to cowl with foam so that when it is upside down it floats high to keep the servo's from being submerged. We put the receiver in a balloon and tie wrap it to prvent it from getting wet. Bottom must be straight, no hooks or rockers. 35% nitro would be better and it would really like 60% nitro. The gold carb is a good choice.

Alan

 

[topfuel443]

This was my second tunnel ive ever had, I had a os on it I think, It was a great boat to get the feel with. It wasnt exactly an allout race machine, but a great boat none the less, and almost indistructable. very strong boat. not sure how much mine weighed but it was definately heavier than My current race boats. Definately go to the gold carb. stick a tuned pipe on it and bump up to 50 or 60 %. youll like it ;D ;D

~ James

 

[Jeff Torgalski]

Yeah, even though the guys at the hobby shop raise an eyebrow when you tell them 50% nitro, that's the norm for .21 K&B's. If you don't run in that neighborhood, the engine won't run very strong. The best I've found at my hobby shop is 40% nitro, but you have to be concerned with oil content too! Don't run car fuel, we are talking about plane or boat fuel. Somewhere between 16-20% oil. The more oil the better, to be on the safe side.

I picked up car fuel w/ 12% oil, and they wouldn't let me return it.

Many people here add a few ounces of castor oil from SIG to new fuel.

 

[[email protected]]

DSD, nice paint job!

I could never get my boat to turn until I added about 4 1/2 oz of buck shot up into the right sponson. They are very fast boats and will take a beating!

 

[Too-Fast]

Great Info guys! Just the stuff I am looking for. I tried to run today with my standard set-up before applying your advice. Lets just say it was a rough day. First a chop started from a gust of wind which caused me to torpedo the boat. Then, for the rest of the day I could barely get 3 Laps out of the boat without stalling out. Outdoor temp was barely 60 and the H2O temp is still below 50. The 35% Nitro made an improvement, but still the boat stalled out. I adjusted the needle from 3.25 to 3.8 turns. Still no luck. My only luck was with a very small prop that runs at the redline. I tried a X437-3, X440-3 and they ran great for 2.5 laps and it died. I run a OS A3 plug. Any ideas? I will include a picture in the next couple days.. Do I have to mix my own fuel to get to 50% plus Nitro? Will an OS powerhead fit my K&B Leg? Would this be a smart move?

 

[Too-Fast]

Great Info guys! I tried to run again today. It was 60f outside and the water is still below 50f. My boat ran great for 2.5 laps and continued to die out. I adjusted mixtures, changed the plug (OS A3 w/ 35%N), still no luck. I put on a very small prop that runs at Redline and this seemed to work. My X437 and X440 would not run though. Any Ideas? Can I fit an OS Powerhead on a K&B Leg?

 

[Jeff Torgalski]

I asked Jerry Dunlap the same question. I would reccommend getting to know the guys at your LHS, and asking them if they can order something. If you get in with a boat club (like me) you can all pitch in and get something good, too. Here's what Jerry Dunlap wrote to me.....

Jeff

I use 65% Wild Cat fuel. It has 18% lubrication and I usually add a couple of oz. of castor oil from Sig.

I'm not advocating 65% fuel, but I do know the .21 size motors like the nitro. Wild Cat also makes 45% fuel. Mike Z. likes Byron's fuel and it comes in various levels of nitro. There's lots of good model fuels, Red Max, Power Master, O'Donnell's.

Jerry D.

Oh by the way, your K&B will give you plenty of trouble free use, no need to switch to a different powerhead. I would run on the rich side, then lean gradually. I would rather have my boat bog a bit on the top end of the revs, than stall out completely and waste most of my day. It's better if you let it bog on the rich side for the sake of the piston and cylinder, too. They lean out during the course of your run.

 

[[email protected]]

Try a McCoy 9 or Rossi 7 plug. It might help. If not use two cooper washers on your plug and try it that way. Sometimes if your head clearance is to tight this trick will help keep the motor running longer.

 

[Mike Hughes]

When running a stock water cooled K&B then you will want to run the needle at about 4.25 to 4.5 turns. If you can't get it to run there then there is possibly something wrong with the motor. Back it out another turn and run it. Lean on it out until you find lean again and back it up. If this does not work it is possibly that the PTO has bad bearings. Another thing to check is if there's some crud on the needle. If there is it won't matter where you set it at. It ain't gonna work. Take the needle out by removing the seat clamp off the carb. This is the what the needle threads into. Give it a nice wipe down and reinstall. I would also suggest bumping the nitro up to 50%. I race on 60%. Little motors like high nitro. It should run with the 440 no problem.

Mike

 

[duc]

I know you guy's all love nitro but maybe on this short hull you don't need that?

I run 20% and the only thing which is stopping me getting behind 50 mph is the length of the hull, not the power of the engine.

 

[Kris Flynn]

Hey Oscar, check your PM's please...gotta ask you something

Thanks

Kris

 

[not2bright]

i have one of these and a lap cat 3. good boats not the fastest but still good i run mine on 45% bryon and it goes like stink! the lap cats are great first boats the lap cat 3 was mine