cork screw in tub

[dwilfong]

Just pulled a new tub out of the building jig and it has a small cork screw in it. It is out by about a 1/16" over the total length should I scrap it or can I shim the sponson tubes to make the boat square.

 

[TERMINATOR]

Just pulled a new tub out of the building jig and it has a small cork screw in it. It is out by about a 1/16" over the total length should I scrap it or can I shim the sponson tubes to make the boat square.

i dont know a ton about riggers but i bet it will mss with the setup .. but ask chris wood i bet he will tell you to scrap it.. idk david, just my 2 pennies..

terry

 

[Chris Wood]

yep.

others might disagree. but that is WAY to much to get it right.

sorry man.. been there before.

try making sponsons and get the last pc to sand and distroy it on the sander 4hrs later lol..

good luck

 

[Marty Davis]

Just pulled a new tub out of the building jig and it has a small cork screw in it. It is out by about a 1/16" over the total length should I scrap it or can I shim the sponson tubes to make the boat square.

David:

I don't agree with Chris about this. I have had many boats that had a slight twist in them and they ran great. As long as the center section is stable.

Secret is to set them up correctly with the right amount of attack angle on the front sponsons and then set up the rear of the boat. I would suggest that you look at http://rcboat.com/setup.htm and this will lead you through the correct way to set up a rigger.

Marty Davis

 

[TCHedOff]

Dont scrap it Dwilfong if you are willing to put some elbow grease into it. My JAP .12 was a partially assembled FF boat that had a twist in the tub.

I was able to get it perfectly flat. It just took alot of time, some epoxy & ALOT of hand sanding. I had to roughen the bottom, apply epoxy, let dry.... then sand (and repeat a few times). I taped 2 full sheets of sand paper to a 30"x5"x3/4" piece of MDF (any flat surface'll work) so the whole bottom was sanded at the same time. You have to press down lightly (or the twist will flatten out and you will get nowhere - ask me how I know that :lol: ) so start w/rough grit (I used 100 to start for a number of passes) and then 220 till you've removed almost all the epoxy on the high points (a diagonal line down the hull - hold bottom up towards a bright light and you'll be able to see your progress). Periodically check against a straight edge lengthwise and also with a square crosswise and by laying tub on your flat surface w/a light on the other side and see if you can see any light shining thru under the tub. Repeat process til you've got it. When I got real close I used one of those 4" long razors blades you get on scrapers instead of sand paper. On the other hand - DONT ask me how long this took! :lol: I'm sure I picke up some extra weight from epoxy but not as much as you might think (most was removed)... boat is 2 1/4 lbs rigged & w/painted.

 

[Ron Zaker Jr]

Just pulled a new tub out of the building jig and it has a small cork screw in it. It is out by about a 1/16" over the total length should I scrap it or can I shim the sponson tubes to make the boat square.

I agree with Marty. Just get the angles right, and shim it properly and it will be fine. Most tubs end up twisted after years of running anyway.

Ron Jr

 

[Tom Foley]

Definitely save it ...compensate for it as you finish the boat and it might end up straight . besides ...after you crash it 50 times it will never be as good as it is right now !! :lol: :lol:

 

[dwilfong]

That is why I love this form you guy have seen it all and done it all.

The tub is for a FE build of the Kep's rigger when i loaded all the bat pacs in to the tub it ended up flat. So I guess when I set up the boat I should have it in running set up and then set up the boat.

As far as sponson angle of attack the boat will have all kinds of power, some were around 6hp. would it be beneficial to use a aggressive angle to hold boat on water at high speed.

the calculations on paper at max cell count are 6HP 60000RPM with a AB CNC 5077 are some pretty fast numbers.

 

[shoboat]

David,

Some of your calculations are not going to pan out once you put the boat

in the water. There are very few electric boats pulling 60K on the propeller.

If they did, they would be very close to 200 MPH. I just got back from a time

trial and we didn't see anything like that. We did see an electric boat in the high

90's though. If that propeller is in S.S. you will be all right, if it is aluminum it will

bend the blades.

Good Luck Testing,

Mark Sholund

 

[dwilfong]

David,

Some of your calculations are not going to pan out once you put the boat

in the water. There are very few electric boats pulling 60K on the propeller.

If they did, they would be very close to 200 MPH. I just got back from a time

trial and we didn't see anything like that. We did see an electric boat in the high

90's though. If that propeller is in S.S. you will be all right, if it is aluminum it will

bend the blades.

Good Luck Testing,

Mark Sholund

Thats why I said on paper thy are very high numbers. Not that high.

2770KV

7 cell 10000 mah 20c 25c burst

80 percent motor ef

15 percent prop slip

57394RPM loaded

140MPH

50x77 prop

the 6 cell looks more realistic

49195RPM

120MPH

If I can push this hoping for at least 100MPH. The weight of the boat will be about 4.6lbs.

 

[T.S.Davis]

David, I'm guessing your thinking 8XL motor. Do NOT pump 10s into that motor. You'll be torching parts. Even 6s will likely be too much for an 8XL.

There are very few FE guys that have crested the 100mph mark. At least in the states. Maybe a dozen total. To get there requires more than raw power and rpm.

I noticed your in Florida. If your serious about going crazy fast look up Chris Harris. He's one of the fastest FE guys in the US.

 

[dwilfong]

David, I'm guessing your thinking 8XL motor. Do NOT pump 10s into that motor. You'll be torching parts. Even 6s will likely be too much for an 8XL.
There are very few FE guys that have crested the 100mph mark. At least in the states. Maybe a dozen total. To get there requires more than raw power and rpm.

I noticed your in Florida. If your serious about going crazy fast look up Chris Harris. He's one of the fastest FE guys in the US.

The motor is a 6XL rated at 6s 110amp 2000wat constant load and 50000RPM. the ESC is rated at 200amp 7s.The pacs are 2&3s 10000mah 20c 25c burst.

Have set the boat up to use 4,5,6and7 cell arrangement. The balance can be maintained with small lead weights in the radio box at the back of the boat.

Of course all the components are from china will see if thy live up to there claims.

Could sure use some help at setting up the boat. Believe me I completely under stand it takes more than power. How can I get in contact with Chris Harris.

This is just a starting point can start off with 4s and work my way up. If the motor dose not live o'well try some thing better. the motor compartment will be big enough to put a 1527 in it.

 

[Speed Jr.]

I just have one question...... If one or both of the sponsons break off, whats gunna happen? :unsure:

May want to do a test in the bath tub just in case....

Larry Jr.

 

[dwilfong]

I just have one question...... If one or both of the sponsons break off, whats gunna happen? :unsure:
May want to do a test in the bath tub just in case....

Larry Jr.

I was thinking the same thing not if thy broke off just trying to get it on plane from a standing start. I have a pool too test it in. It will be water tight threw the whole tub. It will have each bulkhead sealed to its self. If you notice there are 4 bulkheads for that reason. But it still may not float. I will let you know after I throw it in the pool.

 

[PHM Racing]

This boat has 1/8" twist in the tub from front to back

, this tub sat for 2 years before it was finished and twisted over time , we called it the TPOS :lol: :lol: ran good thou for a tpos , i still have the tub , so i would havt to agree with Marty on this one , since we did it to see if it would work.
Mike