Thread Tools
Oct 16, 2019, 07:30 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by RDJeff
I'm actually looking for a home for my 3750, and it'll probably handle a bit bigger plane. I'm thinking 120" might be the sweet spot. My head hurts!
I had to look that engine up. I think you're right and more like 120 to 140" span and keep the weight down by using the truss style fuselage construction and classic full size wing construction with two spar runs and a good number of ribs. With that style of build it should be possible to keep even the larger size down to just a bit over 20 lbs and have a good performer and model that doesn't mind slowing down. Then pick the right sort of lower camber airfoil and tune the CG location and it would laugh at all but the worst winds.

Mind you by the time you do all that I'm sort of thinking that something scale inspired might be nice too.
Sign up now
to remove ads between posts
Oct 16, 2019, 08:07 PM
Registered User
Thread OP
Quote:
Originally Posted by Azoic
Hmmmm 1/3rd scale Spacewalker ,eh??....I have an unused 320 Pegasus in it's box.....the PERFECT motor.....you build the airframe, I will give you the motor. All it would cost you is the $3500AUD postage.....
I really appreciate the offer Azo, but that is about $3,400 AUD over my budget!
Oct 16, 2019, 08:20 PM
Registered User
Thread OP
I totally agree with you Bruce. I've been looking at some of the Hostetler kits for the Cessna 170 or 185, they'd fit the bill, but then where would be the fun of experimenting on my own? I also have plenty of scale kits in the queue already, so there's that.

BTW, did you find any info on the 3750? Mine had no paperwork, and I've only found vague references to it's existence.
Oct 17, 2019, 02:51 AM
B for Bruce
BMatthews's Avatar
Only the displacement. And one of the hits was your previous thread here on RCG. I didn't go deep though. I just wanted to see how big a displacement it was.

You planning in using it as a glow engine though? That's a lot of fuel cost and oil on the model. A friend of mine that got big into the big scale stuff often waxed poetic about how he could tear off a small corner of a paper towel and wipe away the small dainty dribble of oil that he got with his spark engines running 50:1 gasoline. With something that big on glow I'm sort of thinking a half roll of paper towels per session....

His pep talks convinced me that if I do go bigger than a .60 ever it WILL be gas and spark just for this reason. But I may have drank the Kool Aid on this one already....
Oct 17, 2019, 12:23 PM
Registered User
Thread OP
I'm amazed at how little information is available on the 3750! I do plan on running it as a glow engine. I mix my own with zero nitro, so the cost isn't terrible, especially considering I only get to fly a limited number of days every year. Careful placement of the muffler outlet helps to keep the oil off the plane, and if I go through a few paper towels, so be it.
Oct 17, 2019, 05:24 PM
N = R* fp ne fl fi f
Azoic's Avatar
The secret to glow IS the oil......the more the model has on it, the sleeker it is, the FASTER it will fly.....

All I can find on the motor is that they were initially a G3250, either bored, stroked, or both to the larger displacement. Below is an OLD ebay listing for one, it shows what LOOKS like it might be a factory sticker stating it's a G3750, but handwritten beside that in red pen is "built from a G3250" so unless anyone can say anything better, it looks like they were at best, a limited special factory run. None of the paperwork I have has anything. They all go from smallest sizes to the G3250 then the G4500, there is nothing about anything in between. I would have asked Les Mizen, but he died on me....he was Mr ST in Australia for years....

https://www.ebay.com/itm/SuperTigre-...p2047675.l2557
Oct 17, 2019, 07:20 PM
Registered User
Thread OP
I had to pop the head off mine to measure it, and it is indeed bored and stroked.
Oct 17, 2019, 08:32 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by RDJeff
I'm amazed at how little information is available on the 3750! I do plan on running it as a glow engine. I mix my own with zero nitro, so the cost isn't terrible, especially considering I only get to fly a limited number of days every year. Careful placement of the muffler outlet helps to keep the oil off the plane, and if I go through a few paper towels, so be it.
Yeah, that sort of thing happens. Some maker thinks something will take off like gangbusters and find that it ends up being a bump in the road and don't make many.

I'm in the same boat with my old OS75FS. It's a bored and stroked open rocker engine I've had for something like 40 years now. It grew out of the old original first OS four stroke .60 and was quickly superseded by the FS line with the enclosed valve gear. Not much out there about my engine as it was only in production for a year or at most two.
Oct 18, 2019, 02:20 AM
N = R* fp ne fl fi f
Azoic's Avatar
Last time I saw one those Open Rocker .60's it was in a boat, with a very nice, but complex water cooling setup. Worked really well in a scale lake cruiser from the 1920's. I have a .30 open rocker on my desk. It's never seen fuel. It's just for lookin' at.....
Can't help with the manual for the modified one, but here's the original if you want it.
Oct 26, 2019, 01:13 PM
Registered User
Thread OP
I'm still doing my research on this plane. I'm thinking of calling it the Super Tiger to go with the Super Tigre engine. Or maybe the Ten Foot Tiger. We'll see.

I know I'm going to have to add an extension to my bench in order to frame up the fuselage, and I'm looking into a way to make the tail section detachable for storage and transport.

I've run some calculations on the engine, and using a 22 x 12 prop at 6500 rpm, the 3750 will produce 27 pounds of thrust, and deliver a 74 mph top speed. That sounds do-able, as my weight estimate is 20-24 lbs.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Target wing loading for an indoor sport flier? imacflier Modeling Science 19 Aug 18, 2017 10:04 AM
Help! Looking for a Micro 120 size heli for scale indoors flier cap231ex Micro Helis 10 Feb 19, 2017 07:14 PM
Discussion Scaling up powerplants for scaled up foamies b-29er Foamies (Scratchbuilt) 3 Jun 15, 2016 11:28 AM
Question Any advantage in using idle-up for scale/sport flying? Uncle Gravity Beginner Training Area (Heli-Electric) 19 Sep 12, 2013 05:36 PM
?First Brushless for sport flier, ..confused No Step Power Systems 18 Dec 01, 2006 11:41 PM