DaleJEckart

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Hello peeps...

Long time r/c'er deciding to test the waters. I have a couple of questions though...

1) Why do guys use dope/fabric instead of iron-on fabric for the same size planes we in RC use IOF on? WHY is weight that important?
I am about to finish my SIg Akromaster and am planning to cover it with IOF (if I were a betting man I would bet the farm I will crash it LOL),
besides, I live in an apartment and we have single-digit weather, so spray painting is not a viable option.

2) I have an OS 20 FP RN that I am going to use with the carb locked wide open - does anybody else do this? I'm thinking no need to buy a C/L engine if I can have an r/c engine and swap it out into an r/c plane if need be. Am I way off base on this?

Thanks in advance, I'm sure I will have more in short order LOL

Dale

Clean

I cover with plastic all the time. I have a couple of planes that are nothing but plastic, they're made out of Coroplast. But these aren't competitive stunters. One I use for balloon bust and it is awesome at that, might actually be a better starting plane for you then a SIG akromaster.

Weight is not important in a control line plane, it's CRITICAL. It is only slightly more important to an indoor Free Flight model. If you're just going to go out and sling a rock on a string around in a circle, well, weight isn't so bad. But weight will slow you down if you want to go fast, weight will help break things if you plan on arriving hard and weight will eliminate your ability to turn fast when you need to turn fast.It's not so apparant in RC where we can put a bigger engine on it.

the Akromaster is a bit nose heavy with a 15 on it, it's better with an old Cox style .09 or .15 on it. I Have an old Steal fin Fox on mine sans muffler and it's nose heavy. You OS 20? wow. It will go around the circle, you might want to put the prop on backwards but as a trainer, ehhhhh. Here's a quick link to the BustaHor thread I had on Spadworld. I use a 25 Thunder Tiger on it. Locking he throttle forward is fine on an RC engine. A little more performance can be had with a venturi instead of a sleeve but that's not necessary just yet. I built this to kind of resemble an old guillows trainer. It works quite well really and WOW it's 6 years old. Hangin in my garage ready to go kill another balloon.

Don't use too much fuel. An ounce will get you plenty dizzy right now.

skylark-flier

1) Why do guys use dope/fabric instead of iron-on fabric for the same size planes we in RC use IOF on? ...

I always heard that the plastics "don't hang onto the air like dope & fabric" - that's the old wives tale going back to my childhood (a long long long time ago). However, I've had dozens of CL planes covered with dope & fabric, and a dozen or so covered with monokote - and I've never really noticed any difference.

Clean's 100% right on all his points too. That .20 is going to be heavy in the nose - watch your balance! You want the Akromaster CG just about dead on the spar. Also, while it's perfectly fine to lock the throttle full open, you also want to adjust the needle just a bit rich. It'll help keep that engine a bit cooler. The rule-of-thumb I learned back in the 1950s was to run the engine right up to the top and then back it off about 1/8-1/4 turn. You want it just a bit richer than you would in a RC plane. A weak prop, 8x4, 8x3 will also help keep your speed down.

Now, let an old geezer give you just a bit of a heads-up on flying her. GEEZER ALERT!!! I learned this with my first CL plane in 1955. You're planning to fly in the spring? GREAT!!! Right now, TODAY, pick a spot in the yard and hold your arm out straight in front of you. Turn yourself around counterclockwise so you're making a full circle every 8-10 seconds. Do this for 3 minute periods, nonstop. When you can do that without getting even a little bit dizzy, start extending the time. When you're up to 8 minutes you're good to go - you'll have zero problems with flying and getting dizzy.

...(if I were a betting man I would bet the farm I will crash it LOL)...

I'd be willing to bet that same farm you won't. You know how to fly RC, you know about climb & dive already. Limit your elevator travel to minimum (1/4" up and down) and you'll have little to zero problems. That reminds me - 2ND GEEZER ALERT!!!! Adjust your handle so that when you're holding your arm straight out and pointing at the plane the elevator is totally level. In the "old days" that was called "zeroing". To control a CL plane (especially for beginners), you hold your arm this way while flying - handle is straight up and down, "up" line at the top, "down" line at the bottom. If you want to climb you lift your arm a little above the plane, as you see it from the center of the circle. If you want to descend you drop your arm a little below the plane. You don't move your wrist. This gives you near precision control of the plane. Once you've got a half-dozen flights in, you can relax that a bit and still be OK. But for those first flights you're going to want all the "docileness" you can get.

One final item. CL planes normally don't glide like RC ones do. She's going to come down a bit faster than you're used to. Keep her speed up when the engine quits - just hold her level and let her drop naturally, flaring right before she touches down. You'll be just fine with her.

My Akromaster - 30 yrs old and still ticking with her original Fox .15 with 8x6 prop:

JohnBuckner

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High Dale welcome to the wonderful and not so dizzy world of controlline. To answer in short you are not alone in using Monocoat on ukies and it is perfectly acceptable to use throttled engines with the the throttle arm fixed and some cases like me in my wheelchair I use throttled engines with RC.

The pics are all current and flying airplanes of mine, all covered with monocoat and the two larger I use the throttles in flight but the little Ringmaster Junior A simple newspaper rubber band does fine when strategically wrapped around the throttle arm and the idle screws.

One thought on CG for first timers CG over the spar is to far aft and things will go far better for you is you keep it near the leading edge (yes leading edge). Also keep the line spacing close at the handle.

John

DaleJEckart

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So what you are saying is that flying while dizzy is actually a BAD thing?

DaleJEckart

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88mwpKYJohn. I had that exact same CG issue with my long-departed Sig Wonder. Built it just a hair nose-heavy at Plans CG (spar)... I lost control right away and within about 15 seconds (the time it took one of the hotshot 3-D guys to notice what was going on and get to me to help) I was about a quarter mile away, out of control, and almost out of sight. Recentered her on the tip of the LE and she was all good

aspeed

My Wonder was balanced on the spar when I got it. It was quite a handful. I am guessing that is the reason I got such a good deal at the swap meet. I followed the instructions which I found online, and it was still a fair bit behind the leading edge, but ahead of the spar for sure. It flies very well. I still got it and it is right up on the list of favourite planes. Just after the Twist. Control line stuff is normally a bit more noseheavy than RC, and the leadouts should end up behind that somewhat. A bit more power is normal too, as well as tipweight.

JohnBuckner

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Here is the rubber band technique using a simple newspaper band. Will stay on a surprisingly long time and when it does rot off only takes seconds to replace.

Another old school misconception is to fly controlline you must have a controlline tank and it has to be uniflow. What is uniflow? I don,t know either and there are as many different versions as there are controlline flyers you ask. In any case even if you are successful with it, often it involves much experimentation.

Instead just plain old cluck tank every one is use to works perfectly well with most airplanes. In my Magician and the Nobeler I use bubbleless tanks borrowed from my pylon days which work extrememly well with no experimentation but ordinary clunk types work great also.

John

skylark-flier

Well, no - as long as you don't mind losing a plane every other flight or so.

When I learned to fly CL I learned that if I was dizzy I wasn't in control - either of myself or my plane. That usually resulted in the plane digging a new hole in the lawn, and another trip to the LHC to get a new one. Hence, the self-training.

I'm like Jack Benny, I hate spending unnecessary $$$$. Actually he hated spending ANY $$$$.

Oh, yeah. Jack Benny was an old time (1950's) radio & TV personality, had his own shows, and was TOTALLY reputed to be the person responsible for inventing copper wire. He and Rochester (his sidekick) both found the same penny and the resulting tug-o-war created copper wire.

Yeah, he was THAT much of a tightwad.

I mentioned the above because I know that most all y'all are nowhere even close to my "seniority". That was a geezer-alert.

Hey John (Buckner)!! Good to see you here!!!! Yeah, y'er right and I was wrong. CG, especially for a newby, should be farther forward. I was thinking of my own planes (and experience/years of flying). My bad, definitely.

wnewbury

Don't fly in the wind. If you do fly in the wind, start your takeoff down wind.

Bob Mears

Lots of us use the iron on. Go with what you like. The pro/stunt guys prefer non plastic just because of aesthetics. And an airplane with dope and silk or silkspan, will be a stiffer wing that the plastic coverings. Nothing wrong with using your rc engine and block it open. Your carrying the unnecessary carb weight, but thats not too big of a deal. Your sport flying right? Anything goes !

Bob Jablonski

I have a Ackromaster. kinda ugly due to age (26 years) I covered it with plastic film, and have an OS .15 C/L engine on the nose.I am probably going to build a replacement this winter.
Mr. Bob
Countyline Hobbies
Grovertown, IN.
574-540-1123
[email protected]
www.countylinehobbies.com

tony0707

i flew control line combat ,with a modified Flight Streek ,for about 5 years
When i started ,i used silk span and aerogloss clear dope ,to cover the open bays in the wing,as that was the way it was done ( late1950's )
The film covering came much later ,which i have been using from the day it came out
The silk span and dope are a good deal more durable than the film covering
Film is lighter
The silk is so strong ,when you crash you have a bag of balsa
A lighter airframe will accelerate and decelerate more quickly , which equals more performance
Performance is Always --Power to weight Ratio
Use the smaller handle ,for a quicker elevator response
Launch with the elevator in the neutral position ,for a few feet for the airframe to pick up some air speed then ,apply your control
We would always land on the belly ,after running out of fuel ,and had a few laps ,to bleed off speed and touch down
If you watch the plane ,and not the senery, the plane is moving with you ,you will not get dizzy
I designed my plane to have one more wing bay to the inside of the circle ,than the outside wing
This allowed the plane to fly more level ,than angled and allowed me to put a 4 oz fuel tank in the wing on the CG ( fuel use does not effect the CG ,in that location )
The nose of the Flight Streek is short and the design will only lets you put a 2 oz tank ,in the profile planes nose
I make the profile fuse --an airfoil ( like the wing ) by rounding the ouside edges of the profile fuse ,which makes the plane want to pull to the outside of the circle ,thus keeping the control lines tighter
The fuse with that design ,creates lift (pull ) in this case to the outside of the circle
Use the largest control horn ,and be sure it is secure with hardwood ,for those times when --the lines slack --,and will TUG ,on the lines , recover if you can
Otherwise it will pull the wing apart ,as the horn comes out the wing tip
Increased the size of the wing tips ,using the same shape ,as it stabilized the airframe some
I went to using the flexible leads ,out of the wing as they are easier to live with than the solid metal ,that get cought on everything
The engine needs to be shimmed ,about 2 degrees to pull to the outside of the circle
Set up the elevator to give you as much movement as is possible
The large control horn and the small control handle will slow the controls movement thru its travel curve
I was about 16 years old and flying with two neighborhood friends ,when i came up with the above designs
One of the boys went on to win a major combat event ,and i honestly , almost always beat him when we flew locally
My favorite engine in those years ,was Johnson 35
The engine would start on the first, bump on compression
This was my amazing education regarding handiling a glo engines , which took me into flying two cycle glo for 23 years ,with a great track record in RC ( my trainner was as good as one gets )
I cut out a grove in the front bottom of the profile fuse ,and glued a piece of -hanger wire -into it ,as the nose of many planes of the day would snap off ,at the leading edge , until that was done (never came off again ,during regular flights ) acts like a landing skid ,but hidden in the balsa

vertical grimmace

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You can always count on the CL guys to give you lots of info!

I will throw in my 2 cents. I would not be too concerned about chasing weight right now. I just got a Sig Akromaster kit, and If I were worried about the weight, I would have to replace all of the wood in the kit! I would cover with a plastic film because it is more durable. You want to learn how to fly and not fixing holes in Silkspan!

The biggest key to success, is understanding your engine, so that you can get a good engine run. When I first started CL, the the I could not figure out was how to get a good engine run from the beginning of the flight until the end without it running away lean.

So, I recommend you get a Uniflow vented tank, in the appropriate size. That will be one of the most important things you do, to get good runs.

tony0707

Your flight will only be as good as your engine performs
Assuming it is a complete flight ,from start to finish ,and Dirt is not involved in any way
Enjoy

tony0707

Silk ( not silkspan) was the covering to use , before film coverings came on the sceen
i used Monocoat when it first came out and we used a household, iron to apply it
It is stronger than film ,but that has to do , with how much Dope was applied to fill the weave
Stronger than the films ,but more work and Smell from Dope

GallopingGhostler

Nothing wrong with plastic film, good for sport aircraft. You'll go through a couple aircraft learning. Once you have experience, you'll know how weight affects performance. When it is time to compete, you can go to a lighter finish, some even use iron on Coverite Coverlite.

Dale, that OS .20FP-RN should be good enough for a 42 inch span Ringmaster, Flite Streak or Sky-ray. Many use an RC engine and just wire the throttle wide open. Later on if you want, there are a few out there in the CL cottage industry with NOS parts, others who make venturis with CL NVA's available for your FP.

sigrun

Hi Dale. Read this. I logged in today for the first time in an veritable age and saw your post. That link should answer all your Akromaster questions. Using an R/C carb with the throttle wired open is fine, but, an O.S. 20 FP is A. too heavy, and B. overpowered for an Akromaster. The model was originally designed to fly well on a modest powered .15in² without a muffler, e.g. Fox 15 or baffle piston ported O.S. 15 III, and it does if you get the weight and balance right. Even a Schnuerle ported O.S. 15 FP-S flies it like a rocket and has power in excess. The primary thing to keep in mind is that Akromaster is a tight squeeze on maximum permissible weight for good aerobatic performance because of its wing, and that extra couple of ounces of the O.S. 20 FP RN and its muffler up front will kill its aerobatic performance. OTOH if all you want to do is turn in circles and get dizzy, it'll be fine.

The Akromaster was a truly legendary design by the late Mike Gretz intended to perform well on the modest power of a Fox .15 or O.S. Max III .15. Hence the smallish wing area for a model annotated as suitable for a .15. The Akromaster's weight restriction to perform well is a function of its wing area and its aerofoil. On the Akromaster that's a modest 250in² and although aerofoiled, of relatively shallow section. Compare that with the Peacemaker's 300in² and much deeper aerofoil section and you should get the picture. If you end up with too high a wing loading, it won't matter how much power you have up front, it'll fly like a train. If you want it to fly right, build it light with a lightweight .15in² plain bearing motor up front throwing an 8x4 on 52' x .012 or .015 lines. It files very well on either of those lightweight O.S. engines I mentioned with muffler fitted if you keep the build weight down per my linked guide. An O.S. LA .15 with lightweight muffler will be OK too. And covering the wings with plastic film, e.g. Monokote, is lighter and definitely the way to go. GL. Have fun.

GallopingGhostler

sigrun, missed the part about Acromaster. I put an OS .15FP-S on a 30 inch span 200 square inch Ringmaster Jr, was too much engine even on 60 foot lines, got under 4 second laps. Plus it was nose heavy. Better engine for these sizes in more modern sport Schneurle is an OS .10FP or .10LA. If noise is not a problem, can run them without muffler.

sigrun

Hi GallopingGhostler

I've used the O.S. 10 FP-S in a Mini-Peacemaker on 42' lines. That is roughly about the same size but of slightly less wing area as a Flite Streak Jnr. where it'd probably work similarly well. It's undeniably a very 'go' motor for a .10 but I wouldn't choose it for the Akromaster in preference to its .15 sibling, and I say that as someone who tends to avoid overpowering models whether R/C or C/L. The .10 has the same Schnuerle ported run characteristics as the .15 FP-S and weighs similiarly. An Akromaster would fly on it, but from experience the .15FP-S is undeniably a better choice between the two if wanting to acrobat it hard, especially per schedule. On the .15FP-S the Akro will enjoy full line tension overhead at top of circle through sustained manoevre on 52' wire.

Today the O.S. LA 15 would be a good alternative choice to the .15 FP-S IMO, but O.S. don't make the LA-S any more TMK? IDK if the port timing of the R/C throttle version is the same as the C/L version was, but it seems to me with the dearth of options, as a .15 IC engine still purchaseable NIB today, the O.S. LA 15 combined with an LA-S C/L venturi and N/V sourced from a vendor selling stale stock on eBay or an aftermarket venturi (specialist item - Brodak?) and N/V assembly is the best off the shelf alternative in 2016. Fortunately I don't have to address that issue as I still own X4 NIB O.S. .15 MAX (final version baffle piston) C/L motors and a similar number of O.S. .15 FP-S' among others, one still NIB as memory serves. I've used the larger .40 and .46 LA series in R/C and they are reliable powerful motors in their PB class in with a singular negative caveat. Their ABN P&Ls wear out far too quickly in R/C use. Most people never noitice that today for a myriad of reasons, and it would take years of regular C/L use for that. But R/C pro training running them quite literally for several hours every day, that evidenced itself very quickly. But I digress.

I've built my share of Akromasters and Peacemakers over the years. I truly do love both models. Both build to about the same weight, but the Peacemaker has the advantage of a higher lift aerofoil and an additional 20% wing area over the Akromaster. I traced the parts of the Akromaster years ago so I have 'plans'. I've built four (three for myself) assembled from actual SIG kits over the years and double that many again scratch built from hand selected wood. ('Once upon a time' I used them and Peacemakers to fly an event called .15 slow combat).

I concur that the O.S. 15 FP-S isn't the ideal engine for a SIG Akromaster. It was fine for my purpose, but it does fly it faster than ideal and with typical Schnuerled characteristic. The ideal engine IME for an Akromaster is a baffle ported O.S. 15 Max (or earlier 15 Max III) or similar Fox, ideally without a muffler. But the model will perform well with a .15 MAX (or .15 FP-S) with muffler if built light and right. The baffle ported iron pistoned steel cylindered Enya .15s of similar vintage whether IIII or IV are just too heavy for the Akromaster IMO. If using an ENYA (& I love ENYA engines), to carry that extra weight with ease, the more generous wing area and section of either a Peacemaker or (Modelhob) Smousen are just a smarter choice.

IME the Akromaster weighs relatively heavy-ish for its 250in² wing area, very much so if built from kit wood with a skill level expected of the kit's target buyer and covered with fabric, doped and painted.To end up with a light one requires critical wood and hardware selection, judicious use of glue, especially epoxy, and wings covered with plastic film. The fuselage and empennage can be fuelproofed in various ways from plastic film through spray or brush paint or just a coat of polyurethane clear over a couple of lightweight coats of sealing dope.

If coming in on those target weights mentioned in the "read this" link in my previous post, an Akro will fly aerobatics beautifully turning responsively and with ease. Remember TOW (wet) will be 2oz heavier than dry, so this needs to be taken into consideration or it will fly like a train until that fuel is burnt off and it's time to land. The suggested target weight can be achieved if scratch built. From the kit wood it's 'pot luck', and can prove impossible without substitution. My first SIG Banshee kit was the same as was Twister etc. Truth is, the Akromaster is a really nice model to fly, but is less weight bloat tolerant and is more difficult to achieve a build with it at a weight where it is a no brainer to achieve uncompromised aerobatic performance. The Peacemaker is easily turned out at the same or less weight with more area and generous section, and so is more tolerant of those extra couple of ounces whether added by engine choice, glue or finishing.

To reiterate, I really really love SIG's Akromaster as you can probably tell, but IME it needs to be built light, balanced right, and adequately powered by a light weight engine to achieve a standard of aerobatic capability meeting my expectation/standard and of which it is capable.

By way of similar example, with SIG closing down their production line of C/L kits, I bought up an example of all the remaining kits I could find. These included an Akromaster, a Skyray 35, a Banshee, a Twister and a Super Chipmunk. I like profile C/L as you can probably guess.

For the Skyray .35, I really didn't have a suitable engine and I didn't want to overpower it. Ideal contemporary power would have been a .20~.25FP-S or LA-S. I didn't want it to go like a rocket, but fly per the Brett Buck package suggestion, so I powered it with an ABC TBR ASP .21A., a much lower capacity than the box suggested .35 but about the right power output for the model propped with a Bolly 9x4.5 or APC 9x4 to competently fly the schedule. When I get around to putting the Banshee together -I've built & flown one one before fitted with a Fox .35, I'll be using something contemporary, Fox light and less than .35in² up the front end, probably with a nose mod this time.

sigrun

P.S. Just surfing about to bring myself up to speed. I've not run one myself, but reading the spec and reviews, as an OOTB alternavie to reconfiguring an R/C LA, Brodak's .15 seems the obvious sub for an O.S. 15FP-S. CNC'd bushed bearing Schnuerled AAC with a C/L venturi. Should work as well in an Akromaster.

paw080

Hi Sigrun, I wish to say You're absolutely right about building the Akromaster as light as possible. My first Akromaster was built

about 20 years ago, and I used a Yin Yan 2.5cc diesel(4.5oz engine). The ready to fly weight is 17.5 ozs; placing it in the

mini-elephant category. It fly's okay on 52'x .015" lines, but it really is easier to fly the full stunt pattern with 55' lines.

The same engine flew a Dumas Tomahawk(330 sq") much, much better on the same 55' x .015" lines. This led me

to build a from plans version with a really careful selection of wood, covering and light weight foam wheels. I even reduced

the nose length to accommodate the smaller fuel tank required for my engine choice, an MP-Jet 1.0cc diesel. The ready to fly

weight, sans fuel, is 11.2 ozs. The wing is covered with the long discontinued clear Micafilm; I wish I could find more of that

covering .

This model fly's like a slow combat ship. I fly it on 44' X .008" lines. This configuration is a lot of fun to fly.

Best of luck

Tony

GallopingGhostler

Just some data, according to OS docs without silencer, the .15FP weighs 142 grams (5.01 oz), 0.41 bhp at 17,000 rpm. .20FP weighs 193 grams (6.81 oz), 0.5 bhp at 15,000 rpm. Powerful yes, but heavy buggers compared with old Fox .15X at 3.6 oz, 0.22 hp at 16,000rpm. .20FP weighs almost an ounce more than my McCoy .19 Red Head, which is a heavy bugger. Regarding Micafilm, really loved the stuff, lightweight, tough but strong, but alas it is no longer sold.

sigrun

Hi again GallopingGhostler. I never owned or ran one, but was the venerable Fox 15X truly only 'rated' at .22 hp? Almost half the claimed output of the venerable O.S. MAX-15 does seem to me rather 'conservative' for approximately the same in³ capacity. O.S. was 2.49in³ (spec).

For comparison the O.S. MAX-15 weighed in at just 114g (4.02oz) sans silencer (reading per the O.S. supplied in box instruction sheet spec here in front of me) claiming an output of .48PS (1PS = approx equiv 1HP) at 17,000RPM as max practical vs achievable 19,000RPM. I do find that alleged .48PS (HP) claim 'ambitious', but that's what it states here on the document. It's O.S. 15FP-S successor weighed a tad more at 130g (4.6oz) sans silencer, but makes no maximum PS claim. Both figures per their respective O.S. box supplied instruction sheets right here in front of me. Your heavier weight lesser power spec mentioned above is undoubtedly for the 15FP R/C carb fitted variant with effective lesser venturi diameter and thus power restrictive. e.g. .41PS figure. The Schnuerle ported 15FP-S is more powerful than the baffle piston ported MAX-15 in real world application IME, although the two engines have different run characteristics. The O.S. MAX-15 was successor to the venerable and revered MAX-15 III which had been around since I was a teenager - which is a long time ago now. IDK if improvments or changes were made to the induction and transfer ports size or timing between the MAX-15 and MAX-15 III variants, but AFAIK it was identical much the same except with a fully cast crankase including the cylinder casing external finning rather than the steel cylinder case finning. The MAX-15 and MAX 15 III both ran the same band on muffler design, although the III could run the earlier bolt on variants in common with the 19 III which was obsoleted circa 1971. The FPS runs a bolt on of contemporary design. I CBF getting up to weigh them right now, but at a guess, either article of additional 'ironmongery' adds an impost of about 2oz up front.

The ARF industry has a lot to answer for. Like most Coverite products, Micafilm was a great covering in class.

Hi paw080. Yes, the Akro is a fantastic design with the prerequisite one meets a weight restriction the limitation of its area, section and optimum CG. Undeniably they will fly heavier, and quite fast in a straight line with stability and penetration in windy conditions as any model with a high wing loading will, but they won't perform contiguous aerobatics to well -if at all IME.

Yin Yang aka Silver Swallow AFAIK? I had and ran a Silver Swallow 1.5cc diesel. 1.47 on the outside of the box, 1.49 on the instruction leaflet. Chinglish as was the wont of the day. <laughs> Still have it stored in its original box. Was an absolute ball tearer out of the box, ...for all of about 90 minutes running! Rubbish Chinese metallurgy of the era saw it life expired prematurely to so worn, it was unstartable no matter how much I increased the ether content. Shame. Delivered phenominal power and RPM for a PB diesel, would tune easily and hold it well during its short service life. A very good friend and my vintage combat pal (since deceased) had one as well as a couple of its PB 2.5cc siblings.

Years ago now, I put one of my 2.5cc P.A.W. TBR (vintage combat) diesels in my heaviest Akromaster after it aerobated like a B-24 on a 15FP-S due to its weight bloat. Can't recall now whether it was 20 or 22oz wet TOW with the muffled FP-S as memory serves, either way too heavy by far the consequence of SIG kit wood plus too much dope and decoration, which reminded me that's 5 not 4 Akromasters I have bult from SIG Kit wood. On the P.A.W. TBR .15in³ diesel all I can say is WOW! Way overpowered, and way too fast. The 2.5cc TBR diesels provided so much power and the increased speed so much lift (coeff L=½RhoV²S) that it would aerobat, but the manoeuvres were so open due to the speed and increased turn radius imposed by the wing loading that flying the pattern with it was too difficult for me on 52' lines even with younger reflexes. I never tried it, but I reckon it would have maintained good line tension of 60' lines with that P.A.W. TBR up front, and of course, being much quieter than a glow, even though the motors themselves were heavier per se, they didn't require mufflers and so equalising out on W&B and AUW with the muffler fitted FP-S. Still no answer to building light and powering right for the design.

I reckon a scaled down Akro would fly well on an O.S. .10 glow or .09 diesel. Full marks to you for getting its RTF dry weight down to 11.2oz! Impressive! Well done. At that weight, experience informs me that it'd perform well on a powerful 1.5cc glow or 1.5cc diesel. I've not owned or run an MP-Jet 1.0cc diesel. Is it PB BR or TBR?

vertical grimmace

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After reading all of the info in this thread, I think that when I build my Akromaster, I may scratch the whole thing from new wood. I think it might be a good idea to truss build the fuselage with sticks and just sheet it over with thin balsa to save weight. All of the wood in my kit feels like a brick. I bet I could cut half of the weight out of it by scratching the whole thing.

One of the things I do not like about some of the old CL kits, is that they do not have full sized plans. I know you can just copy the existing parts, but it is always nice to have good accurate full sized plans, to use for duplicating the parts.