Wight Crusader v Maricardo v Aerobat

[kc]

The Wight Crusader is a great Keith Humber design from Radio Modeller November 1988

Very similar in looks to the Maricardo or to the David Boddington Aerobat. I reckon the Wight Crusader is far better than the Aerobat. I built both and know which gave me the more satisfying flights!

The Wight Crusader is really a good plan built substitute for a Wot4 with a similar blunt thick airfoil. Better looking too.

What a pity this plan is not availble from any plan serviice and never has been.( just a pull out two colour plan from RM).

. . I wonder if David Ashby would consider re-publishing the classic Wight Crusader if supplied with a good copy of the plan.......

[Piers Bowlan]

kc, I bought a copy of the Wight Crusader plan off eBay following your recommendation, as I was intrigued. Yes it looks like a lightweight quick build, with a thick, blunt, wing section. Is yours still airworthy and did you do an electric conversion or stick with IC? It would be interesting to hear if anyone else remembers building and flying one. My plan is pretty much pristine, so if David was interested I could send it to him. What it would need KC is a build article if it were republished.

[Nigel R]

Piers you have a copy of the aerobat plan? Would you mind paying a couple of key measurements?

Wing chord, trailing edge to tailplane leading edge, and tail plane chord/ span.

I only have a very low res photo of the plan so all the measurements I have are very rough. I'm interested mainly due to prior discussion on the short moment arm and wanted to know just how short it was!

Many thanks

[Peter Christy]

I'm very puzzled about all this reference to a short moment arm on the Aerobat! I recall ours being a delight to fly - no problems with either take-offs or landings, certainly no tendency to ground-loop.

As I said in an earlier post, I built it as an advanced trainer for my son, who was only about 8 or 9 at the time. Neither of us had the slightest problem with its handling - in fact, like most Boddo designs, it was a very pleasant little model in all respects!

--

Pete

[kc]

My Wight Crusader was powered by an Enya 40SS plain bearing and went superbly for about 500 flights until an engine cut required an immediate dead stick landing - this would have been no problem except that a cyclist came unseen from behind the flightline speeding right across the landing area and a collision looked certain so i elected to turn the opposite way with no airspeed. The inevitable result.was the plane spun in and the cyclist veered the other way anyway! The first and only time a cyclist ever appeared!

Result was a broken wing spar and much fuselage damage. If it had not been so oil soaked I would have patched it up. It is still sitting in the garage tempting me to repair it......

If the wing had been intact i would have repaired it but it's better to build from scratch in the circumstances......

My plane was built with a sidewinder engine on an engine mount instead of engine bearers. Worked well and so would an electric version. I suggest a hatch combined with the cockpit would be easier to make than separate parts. My plan carries the pencil note " check height of F6 " and it seems about 5mm short. I built the wing in one piece with 48 inch ramin spars 1/4 sq instead of the 1/8 by 1/2 spruce. Unfortunately I reinforced the top spar with a tapered 1/4 sq doubler but not the bottom spar. Inevitably the bottom spar broke in the crash. Perhaps if the top had not been strengthened it might have bent a little and saved the bottom spar too....... Either reinforce both the same ( well almost ) or none is the lesson learnt. Ramin does tend to 'explode' when really forced, maybe spruce less so. Of course my plane was built in the 1990's when Ramin was easily availble in B&Q. Now it's an endangered species or something.

I still have the original magazine plan with article. PM me if you want a scanned copy. But to republish surely RCME would prefer you to do an update article for electric Piers!

I don't think anybody will be disappointed if they build a Wight Crusader, the thick blunt wing and generous proportions almost guarantee a good flier if built straight and reasonably light. Wing and tailplane almost on the thrustline and good side area all help.

[kc]

Aerobat

dimensions from an original free plan

chord 232mm including aileron

trailing edge to tailplan LE 320mm to rudder hinge line 430mm   ( that's what it measures - doesnt quite tie up with tailplane size on the other drawing!)

tailplane is a complex shape 505mm at elevator line by 115mm at centre but 80mm at tips. Elevator 42mm at centr but 30,mm at tips.

Edited By kc on 14/11/2017 17:49:54

[Piers Bowlan]

Yes I have the Aerobat plan Nigel.

Wing Chord=232mm. Wing TE - Tailplane LE=320mm. Tailplane chorde 115mm. Tailplane span=505mm.

I measured in mm this time and the Maricardo Wing TE to Tailplane LE is 380mm and .85% of that is 323mm so (embarrassingly) the RM Aerobat does have pretty much the same proportions as the Maricardo after all, according to my measurements. . I also measured from the wing TE to the stern post and the Maricardo is 535mm so 85% of that is 455mm. The Aerobat is actually 430mm so is 25mm or an inch shorter here (not a lot).

So sorry about that chaps, duff gen there, I should blame it on not wearing the right specs or my age or something.

There is nothing for it but for us all to build one and compare notes!

[Piers Bowlan]

You beat me to it kc.

What is the weight of your Wight Crusader kc or I expect you have taken all the gear out of it now? Sorry to hear about it's unfortunate demise. A lecky conversion would be logical but I have an ASP 61 which might be suitable? But, I have to add, not for a while as I have a house move pending, then three models to finish! 

 

Edited By Piers Bowlan on 14/11/2017 19:02:50

[Nigel R]

Gentlemen, many thanks for the numbers. From that it does appear to have a fairly standard fuselage length given the wing size. Food for thought.

[kc]

I am pretty sure my Wight Crusader would have weighed about 4 and quarter pounds with the quite light Enya 40SS. Maybe an ounce or so either way. Having learnt from my RM trainer which weighed about 5 pounds with an OS25 Max needing 6 oz of lead! Ever since for the last 30 years I have been very careful about selecting a light but stiff piece of balsa for the tailplane, rudder & fin. Most of my 40 size models have been built to 4 pound to 4.25 pounds. Makes all the difference in flight! Low wing loading makes the difference between getting away with a rash move instead of crashing. The blunt thick wing also helps by reducing any speed as it hurtles downward after a mistake.

An ASP 61 2 stroke would be way too much, a 61 4 stroke might be about right for the Crusader, but electric would be the way to go now. You need to decide on the engine early on if you build as per the plan with beech engine bearers ( to get the spacing correct or to eliminate them and make room for the Lipo )

The lack of the 25mm in the Aerobat tail moment possibly makes it more of a handful than the Maricardo or Crusader. Putting in an extra 25mm to an Aerobat might be worthwhile if you must build one.

[onetenor]

May I suggest Obeche (if still available ) for spars .Also stick to the given sizes for them .This is as important as material.

[onetenor]

May I suggest Obeche (if still available ) for spars .Also stick to the given sizes for them .This is as important as material.

[Nigel Grant 1]

Interesting thread KC. I think it would be great to see a model like the Wight Crusader in the RCME. Surely its in a similar vein to the retro models that Shaun is putting in. I doubt a full build article would be needed. Just a bit of history and a few comments about modern options such as electric. Lets hope the Ashby's pick this up. Any chance of a photo of the plane or even of the plan spread out in the meantime?

[Piers Bowlan]

kc, I should have clarified that I was referring to a ASP61 four stroke (I am allergic to the sound of two strokes). You are probably right, electric would make more sense and at that weight 500W might be enough, so a 4S setup would work. Like you, I would eliminate the beech engine bearers in any event and if going for the FS option would mount the engine inverted, as per the plan, as I like the cowl arrangement.

Keeping the back end light is always a priority and I see the design features a simple skid as per Peter Millers designs. I have not used Obeche for spars or indeed Cyparis which has been suggested in previous threads. Cyparis is a type of cedar and is very straight grained like spruce, which it is why spruce is commonly used in light aircraft construction. The spar construction looks strong and light, it is just a matter of whether you can get hold of the 1/2 x 1/8in strip for the upper and lower members, I can't see that 1/4 x 1/4 would be inferior however and it would weigh the same.

Would I build an RM Aerobat? I haven't done so for the last thirty three years but never say never... It is probably on my build list somewhere!

[Nigel R]

"Ever since for the last 30 years I have been very careful about selecting a light but stiff piece of balsa for the tailplane, rudder & fin. "

wise words!

I favour 1/8 frame with 1/16 sheet, a little more work I'll grant but easy to ensure it stays flat and you can afford to be less choosy about the wood stock.

kc I'm guessing the Wight Crusader had a low aspect ratio wing, vs Aerobat / Maricardo?

"Obeche (if still available ) for spars"

Slec sell obeche (and basswood).

I've always used hard balsa of a suitable size without problem, the key point being the words "suitable size". Mind you, a D box or a full skin imparts a lot of strength to a wing (s/a the average foam wing).

[Piers Bowlan]

Edited By Piers Bowlan on 15/11/2017 09:56:43

[Piers Bowlan]

The aspect ratios are quite similar:-

White Crusader 52/10.5in = 4.95

Maricado 56/11in = 5.09

RM Aerobat 48/9.12in = 5.3

It might also depend to a small degree of the dimensions of the TE stock you use and how you finish the wing tips. Basically, if you want to adhere rigidly to the plans.

Incidentally the ribs of the Wight Crusader are just 1/16th thick and the wing is fully sheeted, again with 1/16th balsa.

 

Edited By Piers Bowlan on 15/11/2017 10:27:17

[Nigel R]

Nice one Piers. I remember that one now. Perhaps a little more involved a build than the other two?

[Piers Bowlan]

It must have been before I started buying RM. I still have the 'Superplans' for the Aeronica C3, Flying Flea and Jodel 112, another on my 'build list' by Keith Humber.

Yes, a little more involved but not a complex build by any means. I see the engine is offset three degrees, did you incorporate that kc? Most of the designs don't seem to have any side thrust these days.

PM sent by the way Nigel.

[kc]

Nigel, I would estimate the Maricardo is a bit more work than the others due to built up tailplane and fuselage 1/4 sq framework. But not much in it except that the Aerobat is so much tighter around the servos and needs more ingenuity to avoid aileron rods hitting elevator servo.

If using a commercial engine mount or electric ( instead of engine bearers ) then the work is very similar. I used a plastic SLEC round engine mount without any sidethrust on my Crusader. And my crusader wing was not fully sheeted but used capstrips for the outer part of the wing in the normal way. This possibly saved a few ounces and about 5 pounds worth of balsa.

[Nigel R]

kc, yes, having seen the Maricardo plan now (its been on aerofred for some while) it does have a more involved structure with sheet AND 1/4sq sides. It appears typical of the "slightly overbuilt" approach of the period.

"Incidentally the ribs of the Wight Crusader are just 1/16th thick and the wing is fully sheeted, again with 1/16th balsa."

Excellent method in my opinion! And easy to do with the parallel chord wing. Saves all that messing about with cap strips and TE sheeting and centre sheeting...

I'm very tempted to do an RM Aerobat after the RM Trainer is complete, as it would use the same set of batteries and similar ESC/motor. After this discussion the designs look much of a muchness in terms of aerodynamics and moments and suchlike. The smaller radio bay is a non-issue if you use two micro servos in the wing (which I would). If the weight is kept to around 3lbs then it would have a nice low wing loading and correspondingly pleasant flight characteristics. Much the same I think as the Wight Crusader at around 4.25lb. The key is keeping down to 3lbs.

 

Edited By Nigel R on 23/11/2017 12:24:46

[kc]

Well it may " look much of a muchness in terms of aerodynamics " etc but my Aerobat didn't fly as well as the Wight Crusader! Mine dropped into a sudden spin and wouldn't come out - just as someone else said his Aerobat did ( earlier in this thread) Of course I accept it was pilot error in my case but other designs don't do this so easily in my experience. It may be that the low mounted tailplane is the problem. Some designs fly well, some don't without being visually that different. Nobody really knows why - it's all a matter of proportions and compromise.

There are loads of better designs than the Aerobat - a Kwik Fli or Flea fli scaled to 48 inch or whatwever you need would be a better idea.

[Peter Christy]

Good Grief! Our Aerobat would only spin when told to, and would recover instantly when the sticks were released! (Unlike a certain swept-wing design I once had that would snap-roll and spin if you were only slightly over enthusiastic with the elevator!)

Are you sure you had the CofG correct? As I said earlier, ours was extremely well behaved, and a pleasure to fly, like most of Boddo's designs. It was also tough enough to survive landings in some of the (rough!) fields we had at the time. Both my son and I were quite upset at its demise through a NiCad failure. I didn't build another one at the time, as he had moved on to helicopters, but in the light of this thread, I'm tempted to build another, just to see if its a case of rose-tinted glasses or not!

--

Pete

[kc]

The CG would havebeen spot on as it was test flown by a great pilot. My aerobat did 200 flights in 1987 to 91 but was just not in the same league as the Wot4 i built two months later, so I am confident in saying there are better models than the Aerobat. But build one and find out for yourself!

[Nigel Grant 1]

I found this thread when I was looking up info about the RM Aerobat. Only a couple of days earlier I had seen that the Wight Crusader plan and article had appeared on Outerzone, Wight Crusader , if any one is interested. Looks a similar build to the Ruhig Tigre that has been discussed on here in earlier times, which is also on Outerzone. Thick symmetrical wing and relatively light build.