bfanger
Member
I finally decided to start building something instead of just researching airplanes on the internet. I've decided on the CH 701 purely due to budget and the length of my back yard (980 ft @ 5450 MSL). Now I'm in the process of working out my time line and budget. The VW engine is my obvious choice since it is the basis of my previous, less than successful, attempts at flight...
Never built one but have had extensive experience keeping them going. Mostly because we just used stock motors and replaced them when they finally died. This also means I have a few cases and left over parts which should keep the cost down.
From the internet, one would believe that its is not possible to fly on anything less than a zero time rotax 912. I have found a few examples of flying 701's with VW power and seem to claim that it works but is not the best and with any VW cooling is an issue. This means it is possible so I know it works but before I spend the money to make it happen I'd like to be a little more sure its not going to be a complete waste of money.
My plan-
1915 VW
New crank and rotating assembly
A belted prop reduction spinning a 2 blade 72" prop
Diehl case with the alternator
That's the fairly common part, the big problem I face is density altitude. The solution I see is a turbo. From the automotive stand point almost any turbo works ok as long as it spools and doesn't surge. I could imagine that the same is not true of aircraft turbos. Does anyone have any experience with sizing a turbo for an aircraft engine? My guess is for a "stol" plane a smaller turbo with a waste gate to get everything spinning and to still build some boost in cruise. At take off it would be on the waste gate for a boost limit of about 10 psi. Running 6.5:1 compression and 100LL I think that it should be OK without an intercooler. My best estimate is about 100 HP(120@ SL) at 4500 RPM for takeoff which would be about that of a rotax. I'm not expecting a 150 ft takeoff but 500 ft with one person/1000 lb gross. Am I at least in the ballpark here?
As for the continuous power, am I right to assume that it would be the max that can be cooled and at or below about 4000 RPM? My cooling strategy begins with the traditional air cooled baffles and some cowl experimenting. It seems that the only problem is cooling the heads. To accomplish this I'm thinking a second oil pump that circulates oil through the cooler and sprays the oil in the heads as a pseudo liquid cooling system. I have heard it mentioned but has anybody actually done this and have results as to the effectiveness? In theory enough mass flow of oil should be able to remove the heat and no I have not had time to do any calculations.
As a final note does anyone have any actual experience with the Great Plains reduction drive or any other belted reduction drive for the VW?
Never built one but have had extensive experience keeping them going. Mostly because we just used stock motors and replaced them when they finally died. This also means I have a few cases and left over parts which should keep the cost down.
From the internet, one would believe that its is not possible to fly on anything less than a zero time rotax 912. I have found a few examples of flying 701's with VW power and seem to claim that it works but is not the best and with any VW cooling is an issue. This means it is possible so I know it works but before I spend the money to make it happen I'd like to be a little more sure its not going to be a complete waste of money.
My plan-
1915 VW
New crank and rotating assembly
A belted prop reduction spinning a 2 blade 72" prop
Diehl case with the alternator
That's the fairly common part, the big problem I face is density altitude. The solution I see is a turbo. From the automotive stand point almost any turbo works ok as long as it spools and doesn't surge. I could imagine that the same is not true of aircraft turbos. Does anyone have any experience with sizing a turbo for an aircraft engine? My guess is for a "stol" plane a smaller turbo with a waste gate to get everything spinning and to still build some boost in cruise. At take off it would be on the waste gate for a boost limit of about 10 psi. Running 6.5:1 compression and 100LL I think that it should be OK without an intercooler. My best estimate is about 100 HP(120@ SL) at 4500 RPM for takeoff which would be about that of a rotax. I'm not expecting a 150 ft takeoff but 500 ft with one person/1000 lb gross. Am I at least in the ballpark here?
As for the continuous power, am I right to assume that it would be the max that can be cooled and at or below about 4000 RPM? My cooling strategy begins with the traditional air cooled baffles and some cowl experimenting. It seems that the only problem is cooling the heads. To accomplish this I'm thinking a second oil pump that circulates oil through the cooler and sprays the oil in the heads as a pseudo liquid cooling system. I have heard it mentioned but has anybody actually done this and have results as to the effectiveness? In theory enough mass flow of oil should be able to remove the heat and no I have not had time to do any calculations.
As a final note does anyone have any actual experience with the Great Plains reduction drive or any other belted reduction drive for the VW?
