Help with a boat I built from Plans

[rcflyer55]

First I will say BE KIND I built this boat several years ago from plans. It was my first attempt at building a boat. I built the rudder myself with no idea how(okay you can bust my nuggets on the rudder).

The boat is called a "Mosquito" it is a wood Cat.(I fiberglassed mine)
the specs are:

Length 21"
Beam 7"
weight 2.25lbs
Motor 05 Can brushed.

My boat has a speed 600 in it and without batts it is 1lb 12.4 oz

With 6 cells it weights between 2lbs 8.6 oz and 2lbs 9.1 oz
With 7 cells it weights between 2lbs 10.2 oz and 2lbs 11oz

The prop has a 5.5 on it,I got it from Hobby Lobby(the only place I knew that sold boat stuff at the time), and it screws on


The boat really never gets to speed it seems and with the 7 cells it cavitates like crazy. It cavitates with the 6 cells too but not as bad. It seems to catch better in turns then in a straight line. Can that be?

My thoughts are that I have been putting the batts in the canopy so I think the CG is to high. Also I do not know where the CG should be. I've read on here that Cats should be 30% from the transom. (I think?)

The drive shaft(solid, again from hobby lobby) and the center is about 1/8 BELOW the sponson of the boat. I think this may be wrong as well.

The rudder is 2 5/8" from the transom.

ANY suggestions other then burning it? I'd like to use it as a rescue boat. Which BTW I never thought of before I read these forums. I just assumed I'd need to buy a rubber raft of something.

If there is any info I left out that would help let me know. I tried to get some video the other day but it rained out. So I attached some pics. If I need to take other pics to help let me know.

[Fluid]

Two obvious problems are the prop and the shaft angle. The prop may be a lifting design, which would cavitate badly. Combined with the shaft angle it will drive the bows down at speed. If the motor is a bit weak in Kv - and it may be - you won't get enough speed to make the cat design really work. The high dihedral angle of the sponsons also contributes to poor performance. Try a y534 prop first, then try a flex cable to get the drive angle parallel to the bottom - don't burn it.




.

[blastoff]

The fact that you made 100% of your boat makes it one of the nicest on the forum !!! I would like to see more 100% scratch built boats !!!
Rock On !!!

[shockerman80]

there are alot of boats on this forum that have been 100% scratch built. Almost all of my hulls are done that way. (only one that i bought used to bash with)

[rcflyer55]

Thanks for the help and the kind remarks. I found the plans in an old issue of RC Modeler and though it would be a good project. WHen I bought the wood I realized it would not make sense to buy wood for only 1 so I now have 6+ hulls built and glassed. I made a plug for the whole canopy and was planning on vacume forming them out of PETG. Just never got around to it. I built the first one out of wood and I don't enjoy sanding all that much.

[rcflyer55]

been looking but can't find a Y534 How do I figure out a substitute for a Graupner prop?

[Dr. Jet]

Try an S33 Graupner. 33mm x 1.6 pitch. A K-Series Graupner prop is about 1.4 pitch. A K-34.5 may work as well. The Y534 is 34mm x 1.5 pitch

[Stealth Assassin]

I would also say IMHO... Also, not enough tunnel depth vs. sponson width. Along with the motor not being In the fair kv range for what Is needed to get her flying.

But, what do I know.

[rcflyer55]

did not get the new prop yet but here is some video of it running with a 7 cell 1900mA NiMH pack

http://www.youtube.com/watch?v=IxexfG9nhrM

[Simon.O.]

The video is a little grainy / pixelated, but hey, I like it !
Your vids are 100% better than mine................I have yet to work out how to film and drive at the same time.
It is great to see a hand made boat that runs well, be proud of what you have and strive to sqeeze more performance out of it with minimal cost.
Adjustments and small structural changes can make a big difference.

The main reason I like OSE is that there are many very talented people who are more than willing to help with making a boat perform better without spending wads of your cash, although if you tell them that you want to spend cubic dollars they will help you do that too.

I design and make my own boats too and at the moment I am using brushed motors and Ni.. cells. Don't ever feel behind becaues you don't have BL and lipo systems.
I used to and then realised that I can have a lot of fun with what I have.

Have fun and feel free to ask for help, that is what this is all about.

Cheers

[twinscrew]

I think you tube compresses the videos, I may be wrong, but it seems like a lot of videos there are grainy.

Nice boat, I can hear the cavatating, but it seems to happen on and off.

[rcflyer55]

I tried to upload an .AVI version but after 2 hours of waiting it did not show up there. So I had to compress it. Sorry

[rcflyer55]

SO, I've done a little work on the hull. I added 7/8" to the aft 4" or so of each sponson and tapered it down to the original sponson.
I did this to get the prop 1/4" above the sponsons. It was a lot of work and I did not take pics because it was 90* out and I did it outside because of the sanding.

It might have been easier to pull the stuffing box out and adjust it but then I would have to re-adjust the motor too. So I went this way. I didn't re-glass the wood(balsa) so I put 2 coats of poly on it and then painted it.

I also bought new nimh batts for it. I was using 5+ year old car batts. The new ones are 6 cell 3000mah.

I hope to run it and the mean machine today and see how each project is running now.

[rcflyer55]

New video added

Here is the first of 2 videos after I did the work on the boat. We had 20+ mph winds the evening I ran the boat so it did not run well.

http://www.youtube.com/watch?v=B5wHKlYCcC8

[rcflyer55]

Here is the boat on a better day with no wind. For some reason the esc keeps cutting out, but the cavitation is much less.

http://www.youtube.com/watch?v=EzA3cFPbqlI

(watch in "high Quality" mode)