ISIRC10

I'm FINISHED!!!!!

I just sealed the hulls with silicone and mounted the rudder and boy is she a beauty!
After spending a whole day of messing around with my rudder setup, I redesigned it again.
I also made a new battery pack for the LEDs - it's more profesional and it only took me 11 min to make!

Since it was rather slow when it would get on plane, I added a hydrofoil/flotation thingy to the rear end and it really works!

Will get pics as time allows... the video will be here soon (as soon as I cant get to a body of water bigger than my bathtub!)
"the show isn't over untill the fat lady sings"
Well, let the fat lady sing!
(the show ends with a short video on youtube)

ISIRC10

Some pictures!
1. the underside of the hull
2. my rudder (upsidedown)
3. my rudder
4. more of my rudder
5. rear view
6. battery pack

PLEASE CHOOSE FAVORITE:
7. - without intake
8. - with intake

PS, intake weighs next to nothing and is very realistic!

jasperrc

Very nice!

Looking forward to seeing vids. I'm curious about how she will ride in the water.

Great job

ISIRC10

I took her out to my local reserviour and she floats fine. the motor has more than enough power to get on plane - thats the good news![sm=angry.gif]
Bad news - the rudder is useless unless the boat is going at impossibly slow speeds, and when I try to get on plane the whole thing nosedives into the water[&o]

Better news - I will make a bigger rudder and test it tommorow (If all fails, I will resort to an air rudder). I will also tinker around with the motor angling and my 'plane peice' in the rear - I think I overdid it!!!

PS. I didn't make a video because I didn't want to embarass myself - It was only a test run...[sm=red_smile.gif]

500 lb. koolaid man

The motor should have the prop end slightly higher(about 5 degrees, or more if needed) then the other end of the motor. This is due to the fact that the prop will always be trying to push the bow into the water, so you have to counter-act this.

The nosediving has nothing to do with the rudder. The rudder creates barely any drag when in its center position. The reason for the nosediving is most likely either A.what I said in the top line doesn't apply to your boat or B.your center of gravity is too far forward, it "should" be about 30% from the transom(hold the boat in one hand to test where the CG is).

After looking closely at the pictures, the reason for your turning problem is(your correct) that your rudder is most likely too small. Try making it 1.5 to 2 times both the height and width. I bet you that rudder took a while to make too[:@] but then again it's all about trial and error, rite? If all else fails with the rudder, (like you said)make an air rudder, very few airboats have water rudders anyways(I understand that you like to be unique though). Also just to be safe, although I can't come up with a reason of why the rudder design you choose wouldn't work, it might be safer to make a simpler rectangular shaped rudder like the one in this picture.

Good luck.

ISIRC10

Thanks for the help!
Could you please draw a picture of how to solve the nose diving problem (I am a little bit slow this morning and I didn't quite understand what you ment by having the prop end slightly higher)
My center of gravity, as you said, is very close to 30% from the transome (actually 33.285%[sm=49_49.gif])
I was actually very pleased with how the rudder turned out so I am just going to toss it into my 'parts bin' and use it for some other boat.
PS. I like to be unique because that way, I can actually discover the problems faced by others who strayed from the beaten path and learn from my mistakes (my parents call it pigheadidness)
...so back to the beaten path, air rudders it is!
A project is never finished untill it sinks! LOL

jasperrc

I think the 30% guideline works better for a classic flatbottom. Looking at the bottom view of your hull, you really have little bottom surface area much past 50% of your hull length and the hull extensions will do little to resist the down force on the bow caused by the motor.

Would it be possible to fit a piece between the extensions that would move the rake to the leading edge of the boat?

pinky_d_brain

If angling the prop don’t work you could try moving the motor back, with how you have it set up you could ether make a longer motor bracket or add a piece of thin ply or something to move the motor back farther

ISIRC10

Well, I will try everything I can think of (and all that was mentioned), but I must ony change one variable at once. I have taken out the rear hull peice and have extended the center hull to take it's place.
I remember when I tested the boat the first time, without the plane peice installed, It seemed to get on plane without nosediving, but I was concerned that the rear would float very low. I am still experimenting...
...And have almost finished my rudders! (alluminum siding and part of a wire hanger)

500 lb. koolaid man

jasperrc is probably rite about the CG, I don't know as much about hydros as I do monos[&:] although I wish I did. If at all possible, try moving your battery pack forward and that should aid in a different CG.

I made the drawing you wanted, pretty self explanatory. Try 5-10 degrees prop end toward the sky. Do not exceed 15 degrees or you will begin to have problems. --Some people adjust this angle by adding washers "look at the red *washers* in the drawing" either place for the washers will work--

ISIRC10

Thanks for the clarification - but won't that setup push the bow further into the water (I will try it nonetheless, better to trust the experts than to sink you boat) Sometimes experts are better at sinking boats than you are!!!
Here are some pics of my updated setup:

500 lb. koolaid man

I like the rudders, nice job on them.

Ok, think of it this way, [by the way this is an overkill statement(bigtime)] If you had the angle that I have shown in my drawing, it would push the transom into the water, placing the bow higher in the water. And complete vice versa with the angle too. That's the basic concept anyways.

BTW think about this closely, if the motor of an rc airboat is completely "flat", the bow is always being pushed down. Angle needs to be applied. It's not "just" a fix for nosediving.

ISIRC10

OK[sm=idea.gif]

You just made my life SOOOOOO much easier! Thanks a bunch! I should have everything sorted out and painted by tommorow - Then I can bring her to soccer practice tommorow and distract the coach and players so we don't have to run as much! (he makes us run 4 miles as a warm-up!!! ...talk about overkill...[X(]LOL

PS, those rudders took some time (I 'borrowed' one of my sister's wirehangers to make the rudder brace - hence the color!)
BTW, those rudders are superlight and will probably be trimmed - still need testing though... wish me luck!

ISIRC10

I have finished the rudders and have painted the rear section of the center hull. I did some small adjustments to the motor angle - which did not help.[&o]
At least the rudders work!
would it help if I added a Balsa hydrofoil to the front if the boat? Or should I just stick to angle adjustments?

ISIRC10

I have SOLVED the problem!!!
I added the hydrofoil (peice of balsa) and the nosediving stopped and I could finally reach plane!
I have high hopes that I will be able to take her out tommorow for a photoshoot and sea trials![8D]
I am the happiest boy in the world!

I STILL CANT"T DECIDE WHAT MY NEXT PROJECT WILL BE -
- AN AIRBOAT/OUTRIGGER POWERED BY A WEEDWACKER ENGINE
OR
- AN ELECTRIC HOVERCRAFT

I NEED HELP DECIDING!!!![&:][]

asmithnc

How about a Nitro Powered Flat bottom with 50 mph top speed. I'm close but not yet there. How about giving me a run for my money.

ISIRC10

I can't make it Nitro Powered because I don't have and engines or experience!

ISIRC10

I GIVE UP!
I went and ran the boat on the Delawer River and it was a big dissapointment.
It wouldn't go strait and would spin out at the slightest touch of the steering.
It couldn't get on plane and when it turned/spun out, water would cover the decks.
Even worse, I was waked by this stupid moron on a jetski and the boat was smashed against the rocky shoreline.
Now the hulls have cracks in them and begin to draw water.
I HAVE SPENT TOO MUCH TIME TRYING TO BE INGENUETIVE WITH THIS BOAT![>:]
I will salvage all I can and trash it! (with school quickly approaching, I don't have any time to fix the stupid thing and work out its problems!)


[sm=angry.gif][sm=disappointed.gif]
I guess that the hull was too heavy in the end
Thanks for your support and help - without it, I would have never gotten this far.
sigh... another failure...
guess I should stick to the beaten path -
I will build my next project from plans!
...sorry for this big dissapointment, I feel like I let you guys down (then again, I feel that way about myself too

jasperrc

I'm sorry you feel that way about it, but we all have boats that didn't work out the way we hoped. I still think you could do something to help it out if you are willing to try.

Rather than use a foil up front, fill in the whole front section between the points with foam or something similar with a nice rake. This will give it more bouyancy and may help with the digging in.

ISIRC10

Well, you see, it no longer digs in! Instead, the rear sinks down as if trying to get on plane and never does!
must be the weight of the boat+not enough thrust...

I did learn a TON of things from this build though!

500 lb. koolaid man

Damn jet skier[:@] That REALLY sucks.

"...sorry for this big dissapointment, I feel like I let you guys down (then again, I feel that way about myself too" Give it one more shot! You've put too much work into this boat to quit here! I think you have very little left to fix it and have it running good again. Here's what I'd say to try. ---To get it to go straight, add spin fins, maybe trim tabs too, very easy to make. And fix the cracks of course.

"Well, you see, it no longer digs in! Instead, the rear sinks down as if trying to get on plane and never does!
must be the weight of the boat+not enough thrust..." Hmmm... you might have overdone the angle of the prop like I explained earlier. Note the fact that it was doing the opposite before, nose diving.

I understand if you wanna quit this project, (or if the hull is now located at your local dump) but I'd give it one last shot. Sup' to you.

I'd say for your future project go with a 3 point gasser.[8D]

ISIRC10

Yeah, I really don't know why some of them are sooo abnoxious! (I don't really know what is so fun about them - all you do is ride back and forth[sm=confused_smile.gif])

I would have another try at this boat but I have school tommorow and I amd going to be buried with homework and sports untill june!

Remember when I said that the wood had many imperfections and how I filled them in... well, I used a waterbased filler so now most of it is gone[X(]
- that make the paint peel off exposing more (crappy) wood so I just threw it into the trash (though I did salvage some very usefull parts)

It was really stupid of me but I guess that I have learned!

500 lb. koolaid man

Ok... fine... only one last request... Pictures just for kicks(If you don't mind).

Mr_Byte

Well, that was a great effort. Too bad about the jetskier (obnoxious punks, many of them) but I had a thought about the tendency to spin that you're boat had.

I built a mostly flat-bottomed hull a few years back, it was 4ft long and 2 wide, had about (as I recall, and may call it the wrong thing) 1" of Vee, or to say, from the sides of the hull to the center of the transom, the bottom would drop 1 inch. So, not alot of vee, may have been .5", I don't remember exactly now.

I never had the spin problem, and I know you couldn't vee your hull. I thought I might have problems like yours when I built mine, so I'd added 3 1/4" square strips on the bottom, one down the center, and one each centered between centerline and sides (sorry....not enough coffee yet) to help keep her straight.