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Second home brew mono

Old 07-04-2007, 07:27 AM
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crashbuilder
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Default Second home brew mono

Hi there,

Well my second home build is progressing nicely; hope to get her in the water this weekend. You have to excuse the photobucket links but my Mac can't upload to the forum.

http://s183.photobucket.com/albums/x...urrent=1-1.jpg
http://s183.photobucket.com/albums/x...urrent=2-1.jpg
http://s183.photobucket.com/albums/x...urrent=3-1.jpg
http://s183.photobucket.com/albums/x...&current=4.jpg
http://s183.photobucket.com/albums/x...&current=5.jpg

Some details:

Length: (hull) 15”
Beam: 5”
Deadrise: 20 degrees
Construction: Balsa, ply a little glass
Motor: Feigao 380-14S 2820kv or Ammo 28-45-2700kv Motor I have both
Batts: 8 1100mah cells
Props: Octura X 430 or X432
Hardware: homemade aluminum and brass sheet

Let me know what you think …..

Here’s a dumb question for you guys, both my motors are pretty much the same size and kv, how come the Ammo has a max current of 50A while the Feigao is only 29A?

One more question: Do I have to glue my push rod wire to the bellows? The friction fit seems pretty good
Old 07-04-2007, 08:06 AM
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Default RE: Second home brew mono

There's always a certain satisfaction with making your own boat!

About the motor amps: I don't know first hand, but I've read that the Ammo motors are terribly inefficient and that could be the cause of the increased amperage.
Old 07-04-2007, 08:07 AM
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Default RE: Second home brew mono

Got any pics of the inside?
Old 07-04-2007, 08:18 AM
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crashbuilder
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Default RE: Second home brew mono

If that's the case it's a real pity ..... it almost cost twice as much as the Feigao
Old 07-04-2007, 08:31 AM
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Default RE: Second home brew mono

Here's one of the inside ... it's not pretty. All the gear was taken out for painting and decal application. Still need to put in some velcro and a some kind of antena set up.

http://s183.photobucket.com/albums/x...&current=6.jpg
Old 07-04-2007, 11:02 AM
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Default RE: Second home brew mono

So does it look good ... will it do 30mph?
Old 07-04-2007, 11:23 AM
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Default RE: Second home brew mono

On tower's site it says the Ammo's are 89% efficient, so maybe they're not that bad. I don't know...never used them.

As far as 30mph, I wouldn't think so. Your motors are right size, but are probably a little low on the kv to get up enough rpm's. And just from the pics of your boat's inside it looks like it might be somewhat heavy. Also, your rudder looks rather large so it might create a bit of unecessary drag and on a small boat you notice EVERYTHING more. I don't know anything about your hull, but it looks like it'd be pretty quick and fun.

BTW, I normally put a TINY drop of CA on the end of the pushrod seal just to keep water out. But you could just pack it with marine grease if you'd rather do that.

Go run the thing! Take a vid and post it.
Old 07-04-2007, 11:31 AM
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Default RE: Second home brew mono

Thanks for the input.

I'll trim down the rudder.
What's a good weight for a boat like this? She weights less than 17oz with everthing installed.
Old 07-04-2007, 08:13 PM
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Default RE: Second home brew mono

I must correct my weight ..... it looks more like 22oz ..... these kitchen scales can be a bit tricky unless you've got a close standard weight to calibrate by .. then adjust. Sorry ... a bit heavy?
Old 07-04-2007, 09:30 PM
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Default RE: Second home brew mono

To tell you the truth I'm not sure what a good weight would be for it. It looked like it'd be heavy because in your pics it looks like you used quite a bit of epoxy. I did quite a bit of searching and for the micros and most of them run 12 ounces and below. 16oz = 1lb. I found a couple of rtr cats that are longer (18in vs 15in) and wider (6.3in vs 5in) and weigh under 11oz.

Your boat looks great, I wish I could scratch build like that but I'm just do damned impatient! Just start with a small prop and work your way up.
Old 07-04-2007, 09:31 PM
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Default RE: Second home brew mono

Just go run that son of a gun and see how it does!
Old 07-04-2007, 10:05 PM
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crashbuilder
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Default RE: Second home brew mono

Will do ....

Just did a float test ... she sits deep just like the last one ... I was hoping for more "free board" if I've got the term right ... hell just put it in the water and hit the throtle .. I agree!
Old 07-05-2007, 04:00 PM
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Default RE: Second home brew mono

i would start with maybe a 26mm and work up to 32mm cf would be fine for a wile but when you decide you want more speed then go metal
Old 07-05-2007, 04:08 PM
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alloutcustom
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Default RE: Second home brew mono

hey i would really like it if you even have plans for it to make a copy for me, that is a sweet looking boat, especially since you made it yourself!!!
Old 07-05-2007, 04:36 PM
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Default RE: Second home brew mono

So how'd she run?
Old 07-06-2007, 08:02 AM
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Default RE: Second home brew mono

Haven't had a chance to run her yet, I'm hoping to get to the pond tomorrow. Unfortunately my first run will have to be on a 30mm prop, but I'll take it easy. There no hobby shops here so getting stuff's a bit of a pain.

Plans? Sure .... but there pretty basic, what format do you want them in. I can't post a PDF file (it's a Mac thing) do I just email it?
Old 07-06-2007, 08:09 AM
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Default RE: Second home brew mono

are those the plans in the pic? you could e mail it. if you could do adobe that would be the easiest for me.

sorry you posted at the same time i did!!!! opps
Old 07-06-2007, 08:11 AM
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Default RE: Second home brew mono

Nope .... tomorrow if all goes well
Old 07-06-2007, 09:06 AM
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Default RE: Second home brew mono

What are you using for a hinge on your rudder? Did you make all that by hand? If so that's fantastic work man. I hope it runs great for you.
Old 07-06-2007, 09:53 AM
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Default RE: Second home brew mono

Thanks ... for all the comments.

Nope that was just a quick sketch. the plans show all the formers etc. actually there only around 12 parts in the hull proper.

Adobe Illustrator? What version CS2?

The rudder hinge is a small brass hinge that I cut down to fit the rudder and standoff bracket. When you trim the hinge the movement gets a bit sloppy, but all you need to do is pull out the hinge pin, drill out the holes and install a larger pin.
Old 07-07-2007, 11:13 AM
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Default RE: Second home brew mono

so howd she run? good speed? vid?????
Old 07-07-2007, 10:10 PM
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Default RE: Second home brew mono

Well I went to the pond!

Didn’t start well, put on the X430 put her in; did a little circuit at 1/4 throttle then she stopped dead. I had to wait 5 min for her to blow ashore, seems the coupler came off the motor. Tightened everything up then discovered that the drive dog was just spinning on the shaft. I had soldered it but I’m not the best with an iron.

Nothing I could fix at the pond … so home again, luckily the pond’s only 20 min form the house. Fixed the drive dog and put some CA on the coupler.

Back at the pond, did a few circuits at 1/4 throttle everything seemed OK but I had major cavitation. I tried increasing the speed but the prop wouldn’t hook up. As these things go I got a bit frustrated and nailed it …… she finally hooked up sped forward ten feet hit a piece of chop and rolled.

10 min later she bobbed ashore upside down. I spent that time trying to figure out how I could justify the purchase of another Rx and ESC! Well to my surprise she was completely dry. ( I didn’t realize that rx reception was compromised when your antenna is submerged) My hatch has no fasteners or velcro, it’s just a flat plate that nestles on a lip in the hull …. But electrical tape seems to be a good hatch tape .. not a drop!

Did another run … easy on the throttle but even at 1/2 she still wouldn’t grab … just burbled along … and I wasn’t about to go all out again …. so I played it safe and brought her in.

Motor wasn’t warm, and even while cavitating there was a pretty good water flow from the cooling system. So …. Bigger prop ..X432 …. Wow! Big difference she engaged at about 1/3 started planning and porposing.

Is this starting to bore you?

Anyway ….. so I adjust the trim tabs … really flattened out the ride .. Probably a bit too much … wet … forcing the nose down but still running level. The problem now was that once you got to about 3/4 the boat started to roll to the right (looking from the back) It was so bad that if you tried to increase speed the boat would actually roll over … which it did a few times!

Spent ages playing with the tabs to overcome this but by the time it was starting to run ok I’d used up both my packs …. time to go home. Never got to full throttle! But she’s pretty quick …. Don’t know if I’d really want t go much faster … I lie, but at 3/4’s it really starts to eat up pond.

Now for the questions:

Am I correct to assume that if you can touch it and hold it, indefinitely, (batts, ESC and motor) …. not uncomfortably hot, that you are good to go?

Is this rolling a torque issue? Do you drop the opposite tab to correct? That seemed to help. Or do you reposition batts etc. to compensate? NB: this rolling only occurs as the speed increases..1/2 throttle up.

My boat doesn’t balance at 33% .. a bit further aft. I can’t move the batts forward cause the cooling jacket is in the way. Yes the trim tabs compensate, but it’s not running “loose” it’s being forced back into the water … a very controlled and smooth ride, nice and flat. I’m sure I’m losing speed (I still haven’t given it 100%).

Should I weight the bow?

She wasn’t even hot … so is a bigger prop in my future? … Once I get this roll thing sorted.

I guess that’s it …. I’d really like some input

The wife and the little one might join me tomorrow … video might be a possibility.
Old 07-07-2007, 10:33 PM
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Default RE: Second home brew mono

most guys reposition the batteries to compensate for torque roll.
if you can hold it for 5 sec. and u dont have to take your hand off then your motor heat is good. if it is not even warm i would prop up. not much tho, just a little at a time.
by aft what do u mean towards the back? 27-30% is good for just about any mono.
lift up the tabs and if it runs too loose then put them down in small increments.
thats about it except, GET A VID!!!! srry cant wait to see it.
Old 07-07-2007, 10:36 PM
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Default RE: Second home brew mono

maybe more pitch and less diameter could help with your torque roll. idk for sure tho.
Old 07-08-2007, 08:51 PM
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Default RE: Second home brew mono

A little video ......

http://www.youtube.com/watch?v=4058nDW0dI0

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