So my co-worker has this idea to build his own heaver than air blimp. A blimp that will supply almost all (80%-90%) of total lift and then build it as an airfoil so he can create the remaining lift via forward lift, or possibly a rotatable prop (so he can do vertical take-off and rotate them for forward thrust). I've been telling him he needs to use aircraft engines, or even these paragliding back-packs to his thrust, but he's stuck on car engines due to cost.

I keep reminding him that car engines a meant for low duty, high power and are meant for high shock use (like popping the clutch a 6,000 RPM) so they are inherently stronger and heavier built. He asked me today about using the Chevy LS1 engine. With the small amount I know about it, it's a heavy V8 making a few hundred HP. Great output, but I'm not sure if it will be the best bet for what he wants.

Anyone have any suggestions I can pass to him on the best thing to use? He's looking at about 300-600lbs of thrust needed and any extra weight from the motor, will be more power needed to lift it.

MyYz400

Not that i really know the first thing about aeroplanes or blimps.
but if he doesn't want to pay much and it needs to be small how about a motorbike engine? I'm sure you can find an engine from a wrecked superbike for the same as the v8. and then your talking high revving 150-200 bhp in a small size/lightweight.

Lawn chair + weather balloons + leaf blower + bb gun

Oh wait, it's been done...

Thats what I've been telling him!!!! But he wants something he can take his GF in... I'm sorry but if I was dating someone who'd want me to fly thousands of feet into the air on some shoe-string-budget craft, I might want to find someone a little less adventurous.

im not sure what you consider heavy, but in v8 terms a ls1 is by no means heavy, it tips the scales at just over 350 pounds while an iron block weighs 200 lbs more. They can also be built to run at sustained rpms for a very long time, they are in many boats. Power to weight probably one of the best motors. Just wanted to clear that up not saying it is a good choice for a blimp. Why on earth would you want to make a homemade blimp? Lol life insurance before beginnning building is probably advised

Good stuff, looking forward to reading more about what your friend does

A water cooled V8 is going to be way too much weight to be practical.

There have been a fair number of DIY airplane kits that used automotive engines, but the almost exclusively use the old air-cooled VW engines. They're only 36-40HP, but they're reasonably lightweight, because they don't need a radiator or cooling jacket, which saves up a lot more of hte payload budget for things that you might want to carry on your aircraft. Also, the low power output isn't a problem for most usage, and also means that you have to carry less fuel. Fuel weighs more than you think that it does...

If I had to use a water-cooled engine, I'd still stick with something of 4cyl or less. Power doesn't matter as much as weight does, a lot of aircraft with reasonable performance have signifigantly less than 100 horsepower. 60-80 horsepower will still get a 4 passenger aircraft well over 100mph, and some very streamlined models will do more than 120mph with less than 50hp.

Remember, the more power you produce, the more heat your cooling system has to be able to get rid of, and the more fuel you'll need.

Seriously, look for the lightest engine that you can find, and worry less about how much power that it puts out.

There are a number of companies which are supplying air-cooled VW blocks for homebuilt aircraft engines, and I think that these are likely to be the best overall option.

Another very lightweight engine would be the 1.1L Mazda rotary. This is a water-cooled engine, so there's a bit more weight to them, but they'll put out quite a bit more power for the small gain in weight.

Of course if you want something that *will* do aerobatics, and be able to do things like fly straight up, then you'll need a lot more power, and that can be done.

Personally, I think that the boxer engine configuration from a Subaru would make for a very nice powerplant for higher power operation.

Sounds like this cat will be eligible for the Darwin Award....soon.

Regards,
Hal

Doing a bit of reading and GM smallblock V8s seem to be in use for some high performance applications, like 3/4 scale WWII replica planes, which need a lot of power to do what they do.

There are a lot of companies which seem to be selling the VW blocks, modified for homebuilt aircraft use. They're reasonably inexpensive for what they are, and ought to work well for the application.