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dick sarpolus 50 caliber

Old 05-02-2013, 11:27 AM
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carlgrover
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Default dick sarpolus 50 caliber

Anybody know anything about this plane? How it flies? Building, ect? I'm looking for a home for a pair of K&B .28s

thanks

Carl
Old 05-02-2013, 03:03 PM
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MrMulligan
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Default RE: dick sarpolus 50 caliber

This originated as an article in Flying Models magazine about 30 years ago. It is a large aircraft and he flew it with piped .40's. I remember it was very fast and flew great. It seems to me that I have that magazine her somewhere and I will look for it if you want it. Let me know. This was the inspiration for my first twin, a Midwest Twin Stick with OS .25's. Dick was a big help setting this up.
Old 05-02-2013, 05:26 PM
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A6TEXAN
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Default RE: dick sarpolus 50 caliber

I have been wanting to build this twin for some time as well. cool looking aircraft. i hope someone who has built it chimes in here.
Old 05-02-2013, 05:48 PM
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carlgrover
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Default RE: dick sarpolus 50 caliber

The 50 caliber flies on .25s and was featured in Model Airplane News, September 1980. The one you are thinking of with .40s may be the larger version, also by Dick Sarpolus. I forget what that one was called but I would like to see the article on it if you have it.

Thanks,

carl
Old 05-02-2013, 07:38 PM
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MrMulligan
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Default RE: dick sarpolus 50 caliber

I'll look for it tomorrow.
Old 05-02-2013, 09:07 PM
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Default RE: dick sarpolus 50 caliber

The big one is the Magnum 80. Mine has two ST 45's (Magnum 90?). I also have the plans for the 50 Caliber.
The 50 Caliber is designed as a foam wing model. The Magnum 80 is of conventional rib wing construction.
The 50 could easily be built up by using the root and tip templates and stacking the appropriate number of
rib blanks and sanding to shape.

The Big Apple is basically the same plane as the Magnum 80 with a different nose shape and tail feathers. I built the
Big Apple also. Power is six MDS 18's.

Have not flown either one yet.

Tony
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Old 05-02-2013, 09:26 PM
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Default RE: dick sarpolus 50 caliber

Below is link to another short thead including picture of my 50 caliber. It is a really nice plane to fly and quite simple to build. My plane was powered with pair of ASP .25 which are not too reliable and so most of landings were done with single engine. Big fin and rudder makes engine out situations easy to handle and with one .25 running it could maintain level flight and even climb if not turning at same time.

http://www.rcuniverse.com/forum/m_11...m.htm#11307450
Old 05-03-2013, 05:35 PM
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A6TEXAN
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Default RE: dick sarpolus 50 caliber

NOFAMC, that is 2 great looking planes. I must say you have some fantastic modeling skills ! i may steal part of the trim scheme on the Magnum 90. lol. that 6 engine aircraft is flat out awesome looking ! Whats the chance of me purchasing a copy of the 50 caliber plans ? the only avaliable plans service that we have access to for them stinks from what i have read here on RCU. thanks for posting those great pics.
Old 05-03-2013, 10:16 PM
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Default RE: dick sarpolus 50 caliber

A6TEXAN,

I will see if I can find the plans this weekend. I will get back to you

Tony

PS; thanks for the compliments.
Old 05-04-2013, 01:55 PM
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Default RE: dick sarpolus 50 caliber

The 50 Cal was the junior version of the Magnum 80. If it flies as well the Mag 80 it will be a great flier. You will need 2 very clean running .25's to make it right.

I built several Mag. 80's right after it came out in FM. The first was power by K&B 40's. I wore both of them out in less than one season. I replaced them with K&B 40 with pumps. These were very good when they both ran right but there were many days that I spent all day trying to get them to run together and didn't get a flight in. A pilot error created one of the most spectacular high speed crashes I've ever had. I didn't salvage a single part from this one. Basically I just kicked dirt over the holes in the ground and walked away.

I then went to K&B 6.5 as shown in the article. I did tuned pipes then added pumps. This plane was spectacular for the day. The best radar speed recorded was 125 mph but it actually was faster and the radar wouldn't lock on. I built 2 more of these and managed to wear out the original motors and blew up 2 more. I was a top fuel drag racer at the time so nitro was in my blood and the motors. haha

These are the best flying twins I have ever seen. I'd love to build a giant version with G-62's some day.

Good luck on your build.
Old 05-04-2013, 03:19 PM
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carlgrover
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Default RE: dick sarpolus 50 caliber

I was hoping the 50 caliber was a built up wing instead of foam. I don't know if I could build the wing built up as a twin or not. Never done that before. Making ribs would be easy enough but I don't know how I would tackle the engine nacelles.


carl
Old 05-04-2013, 10:21 PM
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Default RE: dick sarpolus 50 caliber

A6TEXAN,

I can't seem to find my plans for the 50 Caliber.

I don't know what you have read on RCU about Model Airplane News Plans Service, but I have had great service from them
for years. Never a problem, and fast shipping.

The plans for the Magnum 80 came from Flying Models.

Tony
Old 05-09-2013, 04:50 PM
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Default RE: dick sarpolus 50 caliber

Thanks for looking for NOFAMC. once again those are some GREAT lookin planes. Ill check out M.A.N. plans service.
maybe its the other plans service i hear such bad things about.
Old 05-09-2013, 10:21 PM
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Default RE: dick sarpolus 50 caliber

A6TEXAN,

I think the bad you here is for RCM Plans service. It is located here in Gold Beach, Oregon.
They have always been slow in shipping plans, but I always got what I ordered. There is a
post on the Classic Pattern Forum titled, (RCM Plans Service Sucks).
Seems they may have sorted out their problems.

Again, sorry I could not find my plans for the 50 Caliber.

Tony
Old 05-10-2017, 08:37 PM
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Default 50 Caliber CAD

Hi Fellas,

I thought some of you might be interested in a project I'm working on at the moment. I'm re-designing Sarpolus' Fifty Caliber in CAD (now 50 Caliber) with a few mods of my own liking. Wing is built up (no foam core wing) and developed in 3D software with a variable airfoil. I've also added an airfoiled 10% stab and made some cosmetic changes to the vertical (rudder is slightly larger too). Retracts too have been added. The model is being developed for either glow or electric power and parts for either power plant will be included with an eventual laser cut kit I'll be offering.

I've designed the planforms, lofted the wing and stab ribs (a couple of minor tweaks to the wing remain to better accommodate either power source) and am moving on to fuse and nacelle formers. The model will hopefully be a touch lighter using thinner sides and top and more formers and plates. I thought about the option of bolting the nacelles to the wing effectively allowing one to have two models in one! By building all four nacelles and installing support equipment, one could fly glow during the summer, swap out the nacelles, and fly electric in winter! In the end though, a wing specific to the power plants makes more sense and most builders will want to choose either electric or glow. A 7-8 channel radio is expected with two servos per control (2 x elevator/2 x aileron/2 x rudder, steering/2 x throttle)

Anyone build a 50 Cal as of late? Any further thoughts on this model or my mods, please do chime in!

Cheers, David
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Old 05-11-2017, 03:28 AM
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Nice cad work up! Great way to see what you are building ahead of time. I have access to SolidWorks 2016. I've been around SW since irs beginning along with Autocad mechanical desktop and Inventor.

Anyway your Fifty Cal should be a great flyer. The Magnum 80's that I built and flew were really ahead of their time. Nobody flew twins back then. I even won an unlimited pylon event with the last one. The retracts were a huge factor in cleaning the plane up. Again very few flew retracts except the pattern guys.

your electric idea is cool. No having cylinders ans exhaust pipes should clean it up even more.

just a thought. I'd really consider adding flaps to help slow down landings. I used a speed brake/flap arrangement. The flaps went down and a spoiler went up. Aerodynamically I think this provided lift while creating drag and stalling the inner wing. I'm no aero expert and truth be told I copied this design off another plane. It worked very well as the Magnum 80 could easily be landed on our 160 foot paved runways.
Old 05-11-2017, 04:14 AM
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Originally Posted by bentwings View Post
Nice cad work up! Great way to see what you are building ahead of time. I have access to SolidWorks 2016. I've been around SW since irs beginning along with Autocad mechanical desktop and Inventor.

Anyway your Fifty Cal should be a great flyer. The Magnum 80's that I built and flew were really ahead of their time. Nobody flew twins back then. I even won an unlimited pylon event with the last one. The retracts were a huge factor in cleaning the plane up. Again very few flew retracts except the pattern guys.
Thanks for the reply and positive comments bentwings! I have seen your Magnum 80's in other threads - very nice work! There is an active Magnum 80 thread on the classic pattern forum on RCG that I recently revived. Please join in.

I had heard good things about Sarpolus' twins so they seemed like a good project to undertake. The smaller 50 Cal seemed like the logical first step although I admit I like the lines of his later Big Apple (BA) a little better. I was considering doing a "50 Caliber Apple" using the 50 wing and stab planform and the BA fuse but after looking at it the moments didn't look right. The BA will be a separate project but developed along the same lines as the 50 Cal here. Retracts, electric option, flaps, spoilers and so on.

your electric idea is cool. Not having cylinders ans exhaust pipes should clean it up even more.
Indeed. Can't claim any originality though as there are plenty of electric twins but few with pattern lines and retracts. In truth, I want to see for myself what, if any, is the to and fro about counter rotators. I'll build an electric and a glow wing with the former having counter rotators and the latter a pair of standard CCW turning props. 9x6's on both using EF1 motors and probably a pair of NV25 engines (formerly Norvel) as I have them on the shelf. I suspect the EF1's will put out plenty more Watts than the NV25's but it'll be interesting to hear them both and see how they each perform in flight. Some Wizard type quarter wave pipes should work on the 25's if I can find some. Or..., maybe a pair of NR 28RE engines!

just a thought. I'd really consider adding flaps to help slow down landings. I used a speed brake/flap arrangement. The flaps went down and a spoiler went up. Aerodynamically I think this provided lift while creating drag and stalling the inner wing. I'm no aero expert and truth be told I copied this design off another plane. It worked very well as the Magnum 80 could easily be landed on our 160 foot paved runways.
That does sound like a good idea and was wondering about them myself given Dick used them on the BA. I plan on doing the BA with plug-in wings so I was working a pair of servos per panel into the design. I kept the smaller 50 Cal single piece wing so adding a central flap/spoiler servo on torque rods should be straight forward. I only need to sort out clearance issues as I have little of it above the wing with radio gear and the 4s5K LiPo (for the e-version) in that area. But..., I might just have enough for the servo to be mounted inverted in the wing pan leaving a clean center wing. Thanks for the tip!

BTW, would you have a digital copy of the Mag 80 plans I could take a look at? I'm set on developing the BA as I do like it's lines but looking at all available info is always helpful. When the plans are complete (or perhaps the model) I should drop Dick a line to get his thoughts. I hear he's still active in the hobby! What a great contributor he's been. Countless great designs.

David

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Old 05-11-2017, 04:39 AM
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BTW,

since you guys have first hand experience with these sport pattern twins, what if any issues did you come across with the amount of mass off the model's centroid? With the glow versions, only 6 oz of fuel in nacelle tanks plus the engines are present but the electric model would increase that weight considerably if individual LiPo's were located in the nacelle's. Several have built electric Duelist's with batteries in the nacelles but I haven't heard of any issues related to roll performance of the model with such large amounts of weight off center axis.

I do want the model to perform well in pattern or at least to its maximum potential (or the pilot's in my case...) so I went with a single fuse mounted LiPo. Hopefully I won't run into Eddy current issues with the slightly longer battery to ESC leads. I've tried to optimize that as best possible and should only require a ~3" extension power Y to the ESC's

TIA, David.
Old 05-11-2017, 03:58 PM
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The Big Apple was the second generation of the twin .40s. It was very similar but had a tapered leading edge and straight trailing edge. I'm not sure exactly why but I know from my own experience with a number of pattern planes the straight trailing edge rolled much better, and snapped nicer. I actually have considered building a giant scale version of the BA with DLE 55 rear exhaust motors and tuned pipes....ever the hotrodder. 110-120" wing. I probably would build a couple of different span outer wing panels to try.

I never did get to build the BA. I had all the parts cut out and two K&B 7.5 ducted fan motors with pipes and we moved. My engineering career was getting a jump start and I had to concentrate on it. At some point I sold it as a builder kit. I do have plans some place but not in CAD. I think it would have had all the M 80 good points plus some others. I had planned on full gear doors and longer gear legs.

one issue the M80 had was the nose gear leg was too springy. I made a number of them but never really fixed it. The 7.5's liked a bit larger prop with more pitch. These were hard to get and rather expensive in the day. I often used a dozen or more props and a pair of glow plugs per flight. It was funny about fuel. A gallon of glow fuel lasted many guys a couple weeks. I could go through a couple gallons of 30% a day. The field was only a couple blocks away so I flew several days a week plus Sat and Sun weather permitting. I was one of the few that had a spare battery pack as well as a quick charger. Somewhere I have a single picture of me and my oldest son at a big meet. The M80 is partly covered as it was raining and I was getting ready to fly a repaired DB. As I recall it was a challenge to see who was the hardest core flyer. My son says we won but I don't remember.

i don't think you will have balance problems. I'd be more concerned about weight. As with most models the heavier they get relative to wing area the faster they land. Flaps again. Oh yes please don't use flapsrons. On our warbirds we use a little up aileron plus washout. This prevents early tip stall when landing. As your plane gets heavier using flaps it will land Corsair style....think carrier landing.

Last edited by bentwings; 05-11-2017 at 04:00 PM.
Old 03-09-2018, 09:01 AM
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Kinda resurrecting this thread... I picked up a bare 50 Caliber airframe at a swap meet the other week. Wondering if someone could let me know where the CG range is?

Thanks!
Old 03-09-2018, 10:26 AM
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My plans show it to be 4" from the leading edge at the fuse side. I was just looking at the plans in the last couple of dsys. I always wanted to build it. I got plans in the mid 80's and stared cut out parts but never started the assembly. I think I'll make it one of my next builds . Keep us updated on your progress. What state is the air frame in?
Old 03-10-2018, 12:05 PM
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Originally Posted by CF105 View Post
Kinda resurrecting this thread... I picked up a bare 50 Caliber airframe at a swap meet the other week. Wondering if someone could let me know where the CG range is?

Thanks!
Glad you brought this thread back to life!

I've been unable to yet get my re-design cut but will do so before the Summer. Work has prevented me from all the fun stuff!

I'll check my plans this evening for CG but I believe AJ is correct.

Do post some pictures of your airframe. It would be great to see yours come together if you are planning to finish it! AJ, you too!

David
Old 03-14-2018, 08:26 AM
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Thanks guys! The airframe looks pretty good. It’s used, but the previous owner stripped it of all the gear. The canopy/hatch is missing, but making a replacement is simple enough. I’m strictly an electric flyer, so it’ll get a pair of Power 25’s or so. The covering needs some tightening up, but seems in good shape and I like the scheme. I’ll try to post some pics later.

Also thinking I’ll 3D print some cowls for the motors.

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