I am currently building a V-Max and have begun thinking about engine options. I believe the V-Max would typically call for a 1600cc VW engine. However, I am curious if anyone has ever tried anything larger, what considerations come into play and at what size this becomes a problem. The weight penalty from moving up in size seems low, for the most part. From what I gather thus far, the larger concern would be stress on the air frame from a higher HP rating. Curious what other folks experience is with this. including some comparisons below from the Hummel engine website.
From Hummel Engines: 50 HP at 3600 R.P.M. – 4 Cylinders – 140 lbs. (Slick Magneto w/New Case, Hand start 1600 cc) - $5,100.00 60 HP at 3600 R.P.M. – 4 Cylinders – 145 lbs. (Slick Magneto w/New Case, Hand start 1835 cc) - $5,300.00 65 HP at 3600 R.P.M. _ 4 Cylinders _ 145 lbs. (Slick Magneto w/New Case, Hand start 1915 cc - $5,325.00 76 HP at 3600 R.P.M. – 4 Cylinders – 147 lbs. (Slick Magneto w/New Case, Hand start 2180 cc) - $7,200.00
To add a little more to this - I am not trying to build a 'beast' of an aircraft. More likely, I am wondering if a good deal pops up for a 1915cc VW, should I completely avoid it.
I fitted a 60 -65 hp engine MZ202) to my Eros. I modified the engine mount from the as drawn plans for a Rotax 503, but nothing else. There didn't appear to be any problems in 2 years of flying, and I certainly appreciated the extra power for super short takeoff & a climb rate of over 1000 fpm.
Thanks, guys. I'm thinking the VW 1915 cc would not be a huge deal. I have some time before I pull the trigger on an engine so I'll probably keep doing some more research.
Sharing a link to all my build videos and photos below:
These engines are too heavy for such a small plane. There are better option on the market, with almost the same power, with half of the VW weight. Furthermore, the work on these engines to make them aeronautical are huge. Better think about stationary engines, such as B & S, 438cc (single cyl) that is the model I use in my Himax, or the heavier 2 cyl 638cc, which is also a good option. You just need to remove the RPM governor, instal a 2.5/1 belt reduction, and, if you want to make it safer, a new stronger valve rocker arm, which is readily available in the market. My engine, complete, with propeller, belt reduction, and silencer, weight only 66 pounds. Think well!
Thanks for the input. That is really interesting! Just out of curiosity, I would like to learn more about that Briggs and Stratton option. Is there a forum or anywhere online that details how to transform those B&S engines you mentioned?
I have seen a few of these flying with a full VW online. When you say these engines are too heavy for these planes, are you referring to ALL the full VW engines I listed? What makes these too heavy? Does it make even the modified V-Max air frame more susceptible to damage or negatively impact the handling characteristics, etc.
I am building the V-Max, not a part 103 ultralight, so it is my understanding the Mini-Max plans, especially the fuselage, are built around accommodating that engine. Are you saying the weight of these engines is too much for the V-Max model, or Ultralight version?
Anyone out there reading this thread that have flown both Mini-Max planes? V-Max and it's lighter smaller engine versions? If so what are your thoughts.
I have not flown a V-MAX but MiniMAX did the engineering years ago, drew and sells plans and kits, so I'd feel safe with the full VW. People have been putting 447 and 503 Rotax engines on MiniMAXs for years and the 503 is basically the same HP as the full VW. I personally would be more comfortable any day behind a direct drive 4-cylinder 4-stroke VW than a 2-cylinder 2-stroke or any engine that required a reduction unit. The big difference in the V-MAX construction to handle more weight and more speed is in the wing spars and design. The fuselage strength on the MiniMAX runs through the entire plane line-up with very few differences between the lightest designs and the heaviest and fastest.
I'm just beginning construction of a 2-place side by side plane similar to a HiMAX. The designer borrowed a lot of MiniMAX methods and materials including basically a copy of the wing rib design. My plan is to use the robust structure of the V-MAX wing spars, compression and anti drag ribs in my build. It's a much more robust spar and wing in general than what the plans call out for in the plans for the plane I'm building. The gross weight of what I'm building is comparable to the V-MAX.
Now....the choice of what HP VW to chose....I'll leave that up to you but the V-MAX specs say 50 HP so I think that would be a very good place to be. In the last few days I looked at Great Plains VW engine kits for self assembly. No disrespect to Scott Casler and Hummel Engines, but if the prices online at Great Plains are current, they are substantially less money, but you do have to assemble the engine.
I have started on a RagWing Ragabond 2-place. Comparing the RagWing plans to the MiniMAX 1550 V-MAX plans, I plan to borrow the spar construction methods of the 1550 as it seems the spars are more robust than what is called out on the Ragabond plans.
Plan would be a VW. I'm curious...what is ISTR? No, I haven't flown a Ragwing. I have a couple posts on a Ragwing Facebook group hoping to find a Ragabond builder who can fill in some "blanks" in the plans to build the 2-seat Ragabond vs the 1-seat version.
I fly a Vmax with a 1600cc VW with slick mag. I weigh 180lbs and my plane weighs 405 empty. She has never felt low on power and will make 90mph wide open in level flight at 3500rpm. I dont think you could go wrong with the 1835 or 1915 but with the 1915 you will definitely have to make sure you dont bust the VNE.
Chris
Remember, in aviation death sentences are administered by the laws of physics, not the FAA.
BlueMax....thank you so much for your post. I would have a lot of questions for you but I'll just start out with a couple, and I'll say "Thank You" in advance if you have time to reply.
I still haven't decided 100% that I'm going to pursue building a HiMAX on steroids/V-MAX/Ragabond hybrid plane but I was thinking of using the V-MAX wing spar design, compression and anti-drag rib arrangements but adding one wing bay and also increasing the lengths of the center spar reinforcement members between the spar caps. With a 40" wide fuselage I would end up at a 29' wingspan with no wing tips. Is yours the "normal" 26.5' V-MAX wingspan? Do you know an approximate rate of climb you see? You must have been pretty careful building as 405# empty weight sounds great!
I feel I will have to make a build direction decision soon since I'm at wing rib #17 now, so other building will need to follow soon! My other thought is a 103 legal MiniMAX but using a 2A042 military surplus engine. My first MiniMAX beat the Part 103 weight limit with an empty weight of 246# and I'm sure I have enough weight saving ideas to keep it under 254# again even with the slightly heavier 4-stroke, 2-cylinder engine.
Would you perhaps have any photos of your VW engine and it's mounting? Are you driving the prop off of the VW's flywheel or pulley end? I'm guessing the Slick mag is mounted on the firewall side of the engine? About what is the distance from the firewall to the end of the prop pulley? Did you build your own engine or buy one built from ????
I estimate the plane I have in mind would weigh about 800 - 820# gross weight with 8 to 10 gallons of fuel split between 2 wing tanks, and a total weight of my good friend pilot and me as passenger(co-pilot) at 325-ish pounds. I can see it being for short flights around the area of the base airport and the occasional Saturday morning breakfast run to another nearby airport.
Lynn the ragabond/pt2s wing spar already looks strong enough.1x3/4 spar cap vs 3/4 sq spar cap for v max.there is a top doubler also for both spars plus wood block packing similiar to v max but 15" vs 30" long.both wings look almost similiar.there is video of ragabond flying with jabiru 2200cc engine so looks like vw2180 should be suitable though probably nose heavy.an engine like viking 90 hp mitsubishi based engine may also be considered.
Thanks for the post. Good point about the wing spar cap size, but I do believe the Ragabond plans call for 1/8" shear web instead of the V-MAX 1.5MM, so that would cancel out some of the weight differences. Reason for being drawn to the V-MAX spars is also because of extending the wing by one bay on each side, plus the higher gross weight I expect compared to the V-MAX. The V-MAX spar design seems to better place material and strength in the right areas.
The Ragabond plans also suggest extending the rear of the fuselage by 20" for "heavier engines" and that would suggest engines heavier than a 503 Rotax. That's one of the problems with the Ragabond plans, there are a lot of blanks that need to be filled in rather than there being any firm directions. There's also probably reason to extend the fuselage length to work with a longer wingspan to maintain rudder and elevator authority, but again by just how much?
I need to continue to study the plans side-by-side but since I'm not an engineer it's still a bit of guessing. I also like the MiniMAX tail construction more than the Ragabond design, so I need to compare square footage of the 2 designs. I just want to be sure I'm not building a 2-place yard dart! I have a couple airplane design books so I may have to try working through some of the calculations. My head hurts already.
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