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Engine size confusion

Old 12-15-2018, 10:50 AM
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left seat
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Default Engine size confusion

I has recently built a Lanier 1/4 scale Taylorcraft and put it on floats. The engine I installed was a DLE 35. Owing to the wide cowel the 35 fit like a dream with little to no alterations. Originally I had purchased a Zenoah G26 but I was advised that since I would be flying off floats the G26 would be a little low on hp so I went up to the DLE 35. On the maiden flight the 35 had plenty of power and she took off with little throttle. On the second curciut something went horribly wrong. And due to a catastropic mechanical malfunction, something siezed up and didn't respond to commands and she spiralled into the water totally distroyed. As one can imagine this loss was devastating. After retrieving the wreck I salvaged what I could. Now I would buy another Taylorcraft but Lanier is no longer in buisness so I bought a Sig 1/4 scale cub. The problem I have now is the DLE 35 is too long and moving the firewall back won't solve the cowel issue since the cowel was made for a specific engine length. So, I have the Zenoah which is almost the correct length but it is so wide I would have to cut away an awful lot of the coweling in order to make it fit. Plus it is fairly underpowered, from what I have been told, and I've been working on the fuse but have to stop because I'm not sure which way to go. I might have to bite the bullet and buy a new engine. This sucks because both engines are new and I would like to stick to gasoline for fuel because of the low cost of operation. Any modification suggestions or perhaps new engine suggestions ( gas engine that would fit with no modification ) would be greatly appreciated
Old 12-15-2018, 01:28 PM
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s3nfo
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Good friend of mine has a 1/4 Cub on floats and fly's it with an old, tired G23 and it fly's scale, but well. I had a 1/4 Cub which was all scaled up for competition with a full body pilot and all the works and at 17 lbs I flew it at half throttle most of the time, including scale take-off (land only, not floats) on a DLE-20. People have gotten so power happy over the last several years.

Sucks about the cowl though, I'd probably get a smaller engine just to avoid cutting the cowl up too much.
Old 12-16-2018, 05:48 AM
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ahicks
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Just get a Super Cub cowl for it.
Old 12-16-2018, 10:06 AM
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I'm not sure what the problem is here. I've had / have a number of CUBS with various size engines. It is not uncommon to have to move the firewall to accommodate modern engines in an airplane like the SIG CUB as it is an older design from 40 years ago. Times and engines change over the years. The CUB cowl is actually quite large and will accommodate a wide variety of engine sizes but in many cases, YES, you will have to move the firewall back. You may have to make a new firewall to fit the new location. Not difficult ..... just lay the engine you plan to use on the plan sheet in its desired location. Project the back of the motor mount to the plans and that is your new firewall location. As far as cowl cutting, it is minimal with any of the rear intake engines. My last CUB has a DLE35 and the only cowl cutting is to allow for cooling airflow, exhaust exit and the very top front of the cylinder head and spark plug. No cutting on the cowl sides at all, just bottom, most of which doesn't show at all on the ground. Engines like the DLE 30 with a wrap around Pitts muffler easily fit completely within the cowl with only the plug and exhaust stacks sticking below the cowl line. A DLE20 with Pitts muffler fits even better. I flew a Hanger 9 100" CUB for years with a DLE30 and it easily fit in the under 1/4 size cowl. Be a modeler .... adapt and overcome! You can change the airframe structure any way you have to. You will have to extend the sheeting on the front of the fuselage to the same length shown on the plans so it will overhang the new firewall location which is very common on many airplanes. My old Hanger 9 CUB and Great Planes CUB were both done this way. Oh yes, I mention DLE engines only because I know how they fit. Any similar engines will fit the same. Side intake engines like Zenoah will require a cutout in the side of the cowl for carb air intake and perhaps carb clearance.

On some later SIG kits like the Spacewalker, they included plan drawings that showed multiple engine types and firewall locations. They stated the firewall location would depend on the engine used. Too bad they didn't do the same with the CUB. As popular as the CUB is, it would be nice if the whole kit was updated for more modern construction techniques, engines, etc. and in general, bring it into this century.

For the guy who doesn't like big engines, I like the newer, light weight 20 -35 engines in a CUB because they give you options. You can use a scale like and sized prop that smaller engines don't allow and the larger engine balances the plane nicely.You have plenty of power to get out of trouble or to just play around with but you can also throttle back to just above idle and cruise around scale like when you want to. You don't have to use the power but it is there when you need or want it. You don't have these options with a too small engine. Of course if you are a person that treats the throttle stick like it is an on - off toggle switch, these may not be for you! In years past, I've seen way too many underpowered CUBs get into trouble, stall and crash when a bit more power in a critical situation would have saved the plane. Just like the full scale CUB that seems so innocent, beyond ground loops, the stall / spin / crash is the most common destroyer of airframes.
Old 12-16-2018, 05:38 PM
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ahicks
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Nice note Truckracer.
Old 12-18-2018, 04:57 AM
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Originally Posted by ahicks
Nice note Truckracer.
Ditto that.

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