Highplains
Well-Known Member
At that size, Robart almost makes retracts that would fit.
Help Support Homebuilt Aircraft & Kit Plane Forum:
Congratulations Finn !!! Please allow all of us to continue being "part" of this by being involved in the ongoing discussion, progress report, and cheering section.
The first question is... what specific type of flying are you wanting to do with it?
IMHO give up now on the idea of a soaring motorglider... the MONI will not be doing very much soaring in Iowa without a major redesign (extending the wings to 36+ foot span).
If your goal is to fly on minimum power and achieve absolute maximum miles per gallon, then build the 27 foot stock length wings and a small block V-twin with fuel injection and electronic ignition.
If you are looking for something sporty and maneuverable that has a little more aerobatic capability to boot, then look at 4 feet less span.
If you want a hotrod with a little Habanero pepper, then 18-20 feet and a 40-45HP 2-stroke is worth looking into.
Monnett and company found that 16 foot span (as it sits now in the EAA museum) was not enough, and was needlessly tricky to deal with.
The first question is... what specific type of flying are you wanting to do with it?
IMHO give up now on the idea of a soaring motorglider... the MONI will not be doing very much soaring in Iowa without a major redesign (extending the wings to 36+ foot span).
If your goal is to fly on minimum power and achieve absolute maximum miles per gallon, then build the 27 foot stock length wings and a small block V-twin with fuel injection and electronic ignition.
If you are looking for something sporty and maneuverable that has a little more aerobatic capability to boot, then look at 4 feet less span.
If you want a hotrod with a little Habanero pepper, then 18-20 feet and a 40-45HP 2-stroke is worth looking into.
Monnett and company found that 16 foot span (as it sits now in the EAA museum) was not enough, and was needlessly tricky to deal with.
Last edited:
What he said
Be sure you have the updated plans, with the riveted wing instructions. They are available via monimotorglider groups.io Group
The engine that Victor Bravo is suggesting doesn't exist as a commercial product, at least not in the weight (less than 70# FWF) that you'll need. TiPi has some suggestions, the 38 series Briggs in particular - you MAY be able to get the special bits from the SD-1 people in Czechoslovakia B&S 49-series (810cm3/49ci) - TiPi's conversion for aircraft use
Kohler has a single cylinder horizontal EFI engine that probably doesn't have quite enough horsepower, then both they and Briggs have EFI V-twins that are too heavy.
Another way to go would be to start with a Harbor Freight Predator 670 or a DuroMax 713cc There is a new V-Twin on the market - DuroMax 713cc for some discussion of that. There are other discussions of prop adapters, ignitions, etc, search for them.
You MIGHT be able to get 70 lbs FWF with one of these (comparable in displacement to the previously mentioned Briggs 38 Series), which would require a little bit of Weight and Balance adjustment vice the original KFM 107. Which you should mount on the wall...
I have a Kohler in a closet, and at test stand a-building. By the time you get the airframe done, I might have some results to share <frowning>.
Kiwi303
Well-Known Member
3W-684i B4 – 3W Modellmotoren
3w-modellmotoren.de
Expensive but light. 16Kg/35lb and 44kw/59Hp.
You'd need a small diameter prop turning fast for the speed it goes, but on a motorglider that should be achievable.
TFF
Well-Known Member
Popped up on my YouTube today
billyvray
Well-Known Member
In a similar vein, I would present also the ZDZ engines (4 cyl 420cc and 500 cc) available with electric start and 1:2.7 reduction.
www.zdz.eu
37 pounds (17 kg) and 50hp...$6k range
ZDZ 500B4-JSR
ZDZ 500B4-JSR ENGINE WITH ELECTRIC STARTER AND BELT REDUCTION GEAR Very powerful, very light and compact, super low vibration level and easy to cool...
37 pounds (17 kg) and 50hp...$6k range3W-684i B4 – 3W Modellmotoren
Expensive but light. 16Kg/35lb and 44kw/59Hp.
You'd need a small diameter prop turning fast for the speed it goes, but on a motorglider that should be achievable.
Speaking of different motors to use.
This Honda has a forged crank and integrated cylinder and heads just like your favorite traditional aviation motors.
www.sprayerdepot.com
This Honda has a forged crank and integrated cylinder and heads just like your favorite traditional aviation motors.
Honda iGX800 25 HP Engine (Electric Start)
**Currently on backorder**The 25 HP Honda Engine is made to provide power effectively and efficiently. With a net power output of 24.9 hp and a net torque of 40.2 lbs, this engine from Honda gets the job done every time. It has an electric starter to make it convenient and safe to operate. It's...
www.sprayerdepot.com
Heavier than other alternatives in that size range. No performance parts available, as they are for the Kohler and Predator engines, and to a lesser extent, the Briggs. But certainly higher quality than the Predator/Duromax, which are Clones of this engine. TiPi goes over this in his thread.Speaking of different motors to use.
This Honda has a forged crank and integrated cylinder and heads just like your favorite traditional aviation motors.
Honda iGX800 25 HP Engine (Electric Start)
**Currently on backorder**The 25 HP Honda Engine is made to provide power effectively and efficiently. With a net power output of 24.9 hp and a net torque of 40.2 lbs, this engine from Honda gets the job done every time. It has an electric starter to make it convenient and safe to operate. It's...
I must give a very hearty shout out to the seller of this kit. He let me use his (new) shop to build a framework out of 2x4 left over from the construction of his house to hold the spars and ailerons up above the pickup using his tools. He made sure I didn't dehydrate myself in the desert climate and just did an outstanding job of hosting a weary traveler getting me safely and securely back on the road.
I traveled just under 3000 miles in just over three days to buy this kit. Worth every moment to get it, and to see some stunningly beautiful parts of the US I hadn't see in years.
The only assembly of this kit that I've found to far are some tailwheel brackets. Nothing else. Plenty of (over)writing on the plans, but with the cashe of them at the groups.io I can got to a print shop and have a more sterile set printed to host MY (over)writing.
Cheers!
I traveled just under 3000 miles in just over three days to buy this kit. Worth every moment to get it, and to see some stunningly beautiful parts of the US I hadn't see in years.
The only assembly of this kit that I've found to far are some tailwheel brackets. Nothing else. Plenty of (over)writing on the plans, but with the cashe of them at the groups.io I can got to a print shop and have a more sterile set printed to host MY (over)writing.
Cheers!
No work, but plenty of homework completed so far.
The easiest of the homework is watching the Mike Arnold tapes on how he made the AR5 so fast, 55hp Rotax into 213mph (and saw plenty of places for improvements on the Moni). Mike didn't publish plans, but does spell out how he built it and what airfoil sections he used.
He gives you the reference books he used at the end. Pried my wallet open and bought a copy of Fluid Dynamic Drag (Koerner, self published) that was previously owned by an honest to gawd NASA rocket scientist. Very interesting read and understandable why a copy runs for good money.
In looking through the airfoils, I notice something about the NACA 23012 versus the 64-XXX is that the 23012 doesn't have the tendency to pitch down at nearly any angle of attach, where the 64-XXX tends to up and down the chart. Should I take this as the 23012 doesn't make the tailfins work as hard? More than willing to be corrected on this or any other point.
One thing missing from my plans and what I don't see on the on-line plans is any information about the In Wing spoilers. Anyone?
The easiest of the homework is watching the Mike Arnold tapes on how he made the AR5 so fast, 55hp Rotax into 213mph (and saw plenty of places for improvements on the Moni). Mike didn't publish plans, but does spell out how he built it and what airfoil sections he used.
In looking through the airfoils, I notice something about the NACA 23012 versus the 64-XXX is that the 23012 doesn't have the tendency to pitch down at nearly any angle of attach, where the 64-XXX tends to up and down the chart. Should I take this as the 23012 doesn't make the tailfins work as hard? More than willing to be corrected on this or any other point.
One thing missing from my plans and what I don't see on the on-line plans is any information about the In Wing spoilers. Anyone?
Bill-Higdon
Well-Known Member
Probably ask on monimotorglider groups.io Group
A caution: Every Modification From The Plans, No Matter How Small, Will Cost You 100 Hours of Thinking/Building. I learned this from a friend who spent 8000 hours building the world's nicest Glasair III.
You already have a challenge Firewall Forward, either retaining the original, completely unsupported, crappy starter, two stroke engine, or coming up with Something Else. If you want to complete and fly this project in any reasonable amount of time (like, your remaining lifespan <grinning>), resist the urge to modify, adopting only those changes Monnett/INAV promulgated or the Moni IO.Groups documents (riveting the wings vice bonding being the most important).
You already have a challenge Firewall Forward, either retaining the original, completely unsupported, crappy starter, two stroke engine, or coming up with Something Else. If you want to complete and fly this project in any reasonable amount of time (like, your remaining lifespan <grinning>), resist the urge to modify, adopting only those changes Monnett/INAV promulgated or the Moni IO.Groups documents (riveting the wings vice bonding being the most important).
Understand project creep completely. I have the legal documents she made me sign to prove it.
Plan on riveting. If I glue, I'd as soon just build fiberglass wings with known methods.
A big blank is any information on building the spoilers into the wings, there isn't information in the IO.Groups treasure trove that I saw, so any trail of crumps leading there would be appreciated. And putting a gear reduction on the KFM motor, which sounds like it was a fix that worked.
Simpler the better in my book.
Plan on riveting. If I glue, I'd as soon just build fiberglass wings with known methods.
A big blank is any information on building the spoilers into the wings, there isn't information in the IO.Groups treasure trove that I saw, so any trail of crumps leading there would be appreciated. And putting a gear reduction on the KFM motor, which sounds like it was a fix that worked.
Simpler the better in my book.
You want to buy a KFM with a reduction drive? Or keep your money in your pocket and trade us something for it? Our EAA chapter owns a KFM 107 ER and has no use for it. We do have a use for lots of other stuff. Interested?
Bill-Higdon
Well-Known Member
Did you ask on the group if anyone had the info?
RE Spoilers, from monimotorglider groups.io Group
Tony Bingelis has some sketches in "The Sportplane Builder" you could use as a start to build your own if it comes to that.
There were never plans for the spoilers themselves, only instructions for installing them.
Tony Bingelis has some sketches in "The Sportplane Builder" you could use as a start to build your own if it comes to that.
Copy the spoilers on the Monerai, the 1-26, or the Pilatus B-4, and you'll be fine.
I owned a Moni. These airplanes have a structural flaw in the fuselage at the spar carry through.
The Germans required a big u shaped doubler around the cutout to return some semblance of bending continuity in the fuselage. I designed a removable longeron strap and structural bottom skin for mine.
Some have a short piece of tubing in the corner of the gap cover in hopes of propping the longerons apart. Not terribly effective, barely better than nothing.
A look at unmodified Moni's reveals buckles of the side skins ranging from minor to severe.
The cockpit floor is not stout enough. I installed 1/4 inch marine ply floor boards stiff enough to beam the loads to the longerons and the central tunnel.
I added sailboat cable covers over the rudder cables in the cockpit to stop chafing at the bend in the first fairlead at the aft end of the cockpit.
The wing ribs are barely wide enough to rivet, if the rivets are installed at the bend tangency, and then the edge distance is marginal. As attractive as bonding seems, it's a lot of work to get it right, and the joints are still subjected to peel loads. In humid environments corrosion working it's way under the bond line is a concern to watch. Use rivets, a 3/32nd inch diameter rivet is better than nothing.
The airplane Incorporates some good ideas, and some that need to be refined or flatly corrected. I traded mine for two rifles and a stock.
The Germans required a big u shaped doubler around the cutout to return some semblance of bending continuity in the fuselage. I designed a removable longeron strap and structural bottom skin for mine.
Some have a short piece of tubing in the corner of the gap cover in hopes of propping the longerons apart. Not terribly effective, barely better than nothing.
A look at unmodified Moni's reveals buckles of the side skins ranging from minor to severe.
The cockpit floor is not stout enough. I installed 1/4 inch marine ply floor boards stiff enough to beam the loads to the longerons and the central tunnel.
I added sailboat cable covers over the rudder cables in the cockpit to stop chafing at the bend in the first fairlead at the aft end of the cockpit.
The wing ribs are barely wide enough to rivet, if the rivets are installed at the bend tangency, and then the edge distance is marginal. As attractive as bonding seems, it's a lot of work to get it right, and the joints are still subjected to peel loads. In humid environments corrosion working it's way under the bond line is a concern to watch. Use rivets, a 3/32nd inch diameter rivet is better than nothing.
The airplane Incorporates some good ideas, and some that need to be refined or flatly corrected. I traded mine for two rifles and a stock.
Thank you very much for this candid, experience based assessment.
