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new guy looking for some help

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honda-outcast

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Hey guys I am new to the forum so i thought I would introduce myself. My name is Ben, and I am an engineering student from wisconsin. I was watching a show on the discovery channel and decided I wanted to build an airboat. I have roots in honda cars and motorcycles so I decided to use a spare civic engine my friend has as a power plant. I want to keep it as simple as possible. The engine has 102hp stock and I plan to turbo it and make around 150hp. The power band is from 3000-6000rpms so I was thinking of using a 42 or 48in propeller and keep i direct drive off the fly wheel. I was wondering if you guys knew of a good place to get inexpensive but good quality wooden propellers, and what pitch I should look into. I would like to get an adjustable pitch composite blade, but simply do not have the money for a $1300 blade. Pitch wise I am looking for top speed over acceleration.
Thanks in advance for any help and info.
 
Hey Honda, welcome to the site glad you decided to join in.
I'm not the most technical or mechanical of airbaoters but I would guess if you tried to spin any prop anywhere near 6,000 rpm your gonna have big trouble in little Tokyo. My advise is two words, gear reduction.
 
thanks for the advice, I have no idea how fast you can turn props. I was using a formula I found to keep the tip speed under .9 mach and I went from there. That complicate things a bit more but that means more money more time more fun.
Does anyone know about this prop company. http://www.arrowprop.com/air.html
 
Hi Ben, welcome to the forum. Pull up a chair and make yourself at home here. You have landed in the right place.

We have users who build and run what they call minis. You can try to riffle through the archives and find them. They will be mor ethan happy to help.

I have built a lot of DD boats and your facing a few problems. 1. You cant swing any of the props at those RPM. Top RPM for most wood props (depending on length) is around 3-3300 RPM MAX! 2. Your engine wont make much power at those RPMs so you can either try to rework its power profile (a lot of work for a newbie) or 3. you can find a decent redrive for it. Depending on the thrust bearing configuration of your engine it may be unsuitable for DD application.

Having said that there have been a LOT of fairly successful VW powered airboats. Panther used to offer a line of them even. The technology is out there. I suspect you may want to consider a different engine to work with though.

I havent seen those props but they look kinda like a knockoff of the old Banks-Maxwell designs. Nothing wrong there just commenting.

Have you decided on a hull and have an idea fo the weight linits you want? Both will have a significant effect on your performance envelope.

Again, welcome to the wonderful world of airboats, we are all wonderfully addicted and will stand up anywhere and spout ..... "Helloo My name is Scotty, Im an addict, ......... how can I help you.

Scotty
 
If you are handy there are ton's of GSO480 blower motor gearboxes floating around 80% of the aircraft guy's remove the box and go to D.D. I believe these boxes run around 1.5 to 1 reduction they use a planetary set up. Any way the cheapest way to go would be use your bell housing or make an adaptor and install one of the aircraft gearboxes on your Honda. Then you can swing a bigger prop more RPM's. I have seen these boxes as low as $200 but usually around $500.
 
I was hoping there was a way to buy a gearbox or some way of not having to fabricate a reduction gear from scratch. I am handy but lack the precision and confidence to make some thing that will spin at 5000 down to 2500rpms and hold a prop. I was thinking a 1:2 ratio would work best because the motor redline is a little under 6000rpm and from what was said above 3000rpm seems like its the fastest I would want to spin a prop. As for the thrust bearing I am pretty confident it will be fine. Where would the best place be to look for reduction gear boxes. Not having it be DD it seems it would lower the center of gravity a bit too. Also would it be worth investing money in a three blade prop over a larger diameter prop. Thanks again for the help and info.
 
Just kidding about the three blade props thos are almost twice the price, but with 150ph and a reduction gear ratio of 1:2 what would be the biggest blade I would want to run, assuming its a wider wooden blade.
 
Experimental aircraft use a lot of very simple belt drive redrives in your HP range. Might spend some time surfing them, look for gyroplanes as well. Most are using some form of redrive on say EA-81 Subaru stuff. The gear drive mentioned in above posts is about the cheepest youll find though.

If its your first boat and your cash strapped a 2 blade will do fine.

If you are going to redrive it the thrust bearing wont be much of an issue.

http://www.floridaairboatpropellers.com/ ask them what prop for your application.

http://www.sensenichprop.com/sen_html/airboat.html

http://woodenpropeller.com/phpBB2/ good place to learn more about wood props.

Scotty
 
Yea the belt redrives I found were all more than $2000. I think I will go with the GSO 480 blower motor gearbox, but I am having a hard time trying to find them. Where would I have good luck coming across one of these.
 
When you use this gearbox the crank in the engine never see's thrust the thrust load is contained in the gear box also at least run a 1.5to1 a 1.2to1 will not gain you much. I run a 2.68 and don't even turn my motor 6,000RPM use the gearbox as a torque multiplier not a RPM enabler.
 
if your thinking about get a wood prop let me inform you on some things. wood props are known to blow up. i would reccommend a carbon fiber prop. yes they are a little bit more expensive but they will last you longer. and in the long run they are worth it.
 
Honda, something else to consider .....
You mentioned wanting to add a turbo to your motor. We had a post this week from another Wisconsin boater who was talking about some new sound standards that your Wildlife people might try to impose ...... 86db @ 300'.

You might want to consider not using a turbo, and with the money saved being able to get a good quality reduction drive and a quieter and more efficient carbon fiber prop.
If you kept the boat small (10 - 12' ) and light, that should work for now. Later, if you need more power you can always look at adding a turbo and just putting more pitch in the prop.

Just a thought. You have plenty of options.

BF
 
The turbo was going to be put on later, and in the import world custom tubo setups can be done quite cheap, significantly less than a carbon fiber prop. Also the turbo would quite the engine signifcantly, but I am assuming a majority of the sound comes from the prop, but I will definatly look ino those with the sound regulations. I was also looking ino using a prop shroud for noise and thrust. I think maybe my financial needs will be met if I can make this a father son bonding project. Finally I am still having no luck finding gear redrives, any advice on that would be awesome.
 
hey honda if you are seriously considering building yourself a reliable
reasnable price airboat and you are mechanicaly inclined do yourself a big favor and drop your honda motor concept. you will spend much more money , time and conciderable experimenting messing with a unused airboat powerplant concept.
find yourself a good used lycoming or continental 4 cylinder engine.
these engines are the backbone of airboating and have been used since the 1940's all the nessicery items needed are available both used and new. you can build or rebuild yourself a nice engine if you shop around for parts for around 3,000.00 and a good wood prop for 650.00 i see engines on e-bay most everyday for under 3 grand. espically up by you
they go cheap good luck to ya
 
I understand your concern with the honda engine, but I think I am going to go with it. I can't justify a $3000 dollar engine when there are airboats in the classified section for $2500 and $3500. I plan on spending $100 on the civic engine, runing a wooden prop, and buying the cheapest hull I can find. I know that this is not the correct method. I want a cheap boat that runs. This is more of a project than an actual desire for a boat, although I do love boating. The main thing I want from this boat is expirince and faith that I could build another better boat. Also, living in Wisconsin I would like to run the boat on ice and was wondering what hulls are suitable, I am asuming a metal flat bottom is prolly the best, but would like some more advice.
 
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