Excaliber

I have heard that the Excaliber is a fine flying machine. It could be used in Classic, Profile 40 and PA. This would be ideal for me in those contests that provide all three events since I can only take one model with me when I fly in the Lancair 360 to a contest.

Last summer I flew to Witchita for an event and was introduced to the black asphalt circle thanks to the Witchita winds. My new twister left a white stripe on the asphalt from 1/2 inch of my canopy and vertical stab.

Witchita, Woodland, CA and perhaps Salt Lake City would be good events to fly to from Bremerton, WA.

What experience have you guys had with an Excaliber, preferred engine, weight etc.? I must make a removeable aft fuselage behind the trailing edge. This has been done on a twister and a Primary Force with about .5 to .75 oz penalty.

Question. What whould you recommend for powerplant and other ideas
to build such an airplane.

Thanks for your input.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler.

Here is a photo of one at the recent VSC. A nice utility stunt machine in Monokote, it did a good job of contending with the late afternoon wind in Tucson.

My X used an FP40 with a tongue muffler. The plane does tend to build nose heavy, so I'd keep that in mind when selecting an engine. It's a farly big ship, too, so go with a 40 (maybe LA 46?) instead of a 35. Leonard is preparing me a TT 42, that may also be a good choice.

Construction - choose wood for fuse carefully: The fuse aft of the wing is very shallow and prone to twisting. Covering it with .5oz fiberglass with the weave running at a 45 degree angle to the grain would also be wise.

The nose construction with 1/2" balsa doublers is strong and looks cool. The metal tank recesses into the outboard doubler. Go one better and recess it into the fuse core as well. This centers the tank behind the enginne (when viewed from above) and will help to give a more predictable engine run.

There is a third version, unpublished, that was a kit in the mid-70s. I think Dixon has plans to that one. Features a thicker, more moderen airfoil than the '67 FM version.

You'll like the X

LAST EDITED ON Apr-01-03 AT 04:29 PM (CDT)
 
> ... It's a fairly big ship, too, so go with a 40 (maybe LA 46?)
>instead of a 35. Leonard is preparing me a TT 42, that may also be
>a good choice.
>
The one I built had just an OS Max-S and balanced nicely with it, with *more than enough power* for anything. My Excalibur would've been just fine with an "average" Fox 35 Stunt, I'm sure! By that time in my own maturing building style, I used a 1/4" thick sheet empennage on any stunters that didn't already use wood that thick or thicker. I did add a long, tall dorsal fin to my Excalibur (so if I built another that way, I'd want to hunt up any photographs for validation of fidelity points, if I could find some from back in '68 when I built it).

>Construction - choose wood for fuse carefully: The fuse aft
>of the wing is very shallow and prone to twisting. Covering
>it with .5oz fiberglass with the weave running at a 45
>degree angle to the grain would also be wise.
>
That trick, or some strips of carbon fiber tape for stiffening, is a good strategy for any long-tailed profile design.

>The nose construction with 1/2" balsa doublers is strong and
>looks cool. The metal tank recesses into the outboard
>doubler. Go one better and recess it into the fuse core as
>well. This centers the tank behind the enginne (when viewed
>from above) and will help to give a more predictable engine
>run.
>
>There is a third version, unpublished, that was a kit in the
>mid-70s. I think Dixon has plans to that one. Features a
>thicker, more moderen airfoil than the '67 FM version.
>
AFAIK, M&P's kit (Mathis' own kit company) was the 1973 version with C-tube wing. If there was a "third" version, I never heard of it. And I was never familiar with any OTHER kit of an Excalibur other than the M & P, before Walter created his.

.
Kiwi

>
>Here is a photo of one at the recent VSC. A nice utility
>stunt machine in Monokote, it did a good job of contending
>with the late afternoon wind in Tucson.
This is Dave Ek's "Ek'sCalibur". He alternates LA 40 and LA 46, using the 46 at the VSC. We practised in some really wild turbulence one afternoon and I had doubts that my Oriental was going to survive. I feared Dave might lose his Excalibur and cautioned him accordingly. He flew the entire pattern- no sweat! He allowed me to fly it the last day and it pulls harder than any ship I've ever flown, including my overweight SVII when it winds up in loops. Although pretty heavy, it never stalls so those spars must be turbulating after all. best regards,

>I have heard that the Excaliber is a fine flying machine.
>It could be used in Classic, Profile 40 and PA.

Dick Mathis had two versions of the Excaliber. The first was published in Flying Models, May 67. The second was in Flying Models, Sep 73.

Either one is a good flying aircraft as were any of Dick Mathis' airplanes. Excaliber II would not be Classic Legal.

I will defer to others regarding powerplant recommendations.

I've never seen a bad flying Excalibur. I'm sure there must be one out there, but I haven't seen it.

I fly one here in Salt Lake City at 4300 feet. I've also flown it at Denver, where it flies pretty much the same as here. Same thing for flying in Oregon and California.

Be sure to build the first version, with the pointy, skinny airfoil, with turbulators. Don't be afraid of the airfoil as the turbulators work and the plane hasn't shown even a hint of stalling anywhere in the pattern.

Because of the lack of plywood in construction, and the low parts count, the plane will easily build to a great wing loading. Mine wieghs in at 37 oz's with an OS .35S. Bob Demkov, the guy who built the FireCat/74 glider that was shown at VSC, flew his for the first tme today. Flies just like mine, maybe better. It weighsd 33 oz's with a Johnson .35.

The plane is a real triple threat design as it indeed can be flown in Classic, P-40, and PAMPA classes, and do well.

I particulary like the OS .35S for power, coupled to a 9 X 6 grish three blade prop. A McCoy .35, Johnson, or Fox, if you can tame the burp, would also be great. A Brodak or double Star 40, also fine. The plane could also use a smaller engine such as a 20 or 25 in the high rev, low pitch mode, but be careful that you don't put a heavy engine up front, as there's not a lot of structure aft to balance a slug of an engine.

Go for it, you'll like it.

I'm wondering why everything is spinning around?

Ed Culver had a really nice one of those painted up in Navy markings at the october Charlotte contest. He used an FP 40 with tongue muffler. The plane was not fully trimmed out at the contest, but looked like it flew pretty good. There are some pictures of it on this forum posted around august of last year. I believe Ed used the Walter Umland kit for his, I'm not sure which design Walter used for kitting purposes.
A guy here in Richmond has one he scratch built with the OS 35S, it flies very well, but he had too much fun with it because the rod bearing wore out on the 35S....

As far as I know Walter Umland makes a kit of this plane I cannot remember his website address But I know that he makes a nice kit!

I'm almost sure Walter Umland is selling a kit. (I think the spelling is 'Excalibur'..)

Be aware that there are at least two versions of the model. The original model, published with plans and a construction article by Dick Mathis is definitely Classic legal. I'm not sure the later (kit) is absolutely legal, due to its date.

The original model has a fuselage which is less tall on the aft portion.

The wing construction of this model is interesting, with multiple top and bottom spars on the leading edge, instead of planking. The nose construction does not use plywood doublers, but has thick balsa doublers.

It's a very good flyer.

I believe the Coyote is sort of a "sister" design, with at least some of the same construction features. The Coyote looks "blockier", less interesting in shape to my eye. Ted Fancher had a superb example of the Coyote a few years ago at VSC.

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"Never judge a book by its movie." -J.W. Eagan

The Coyote has no flaps. The Excalibur has flaps.

I just finished a Primary Force with an OSLA25. I flew one of those powerplants on a Ringmaster from a fellow modeler. Very gutsy motor. Stronger than a Fox 35. It appears to be light weight. Would that be a respectable motor for the Excaliber with respect to power and weight?

I bought the plans from Tom Dixon for the Excaliber. It was indicated that it was the Classic legal version. I assume the above post referencing turbulators means that the forward spars are slightly raised above the ribs. interesting concept.

Bob Smiley

As I recall, the multiple spars were not specifically intended to be turbulators (they are flush with the airfoil as I recall), but I believe Mathis suggested in his article that they "might act like turbulators".

Whatever, it's a darned good flyer.

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"Is not is? Not is not is, not is not. Is is is.."

LAST EDITED ON Mar-31-03 AT 09:09 PM (CDT)
 
It looks like Bob is set to build from plans, but for the record, Walter Umland's kit is for the Classic legal version. Ed Culver's model is shown on Walter's website. http://www.builtrightflyright.net/standard_kit_range.htm I have one of the first batch, and am trying to decide between a Tower .40/Mac's Muffler or Magnum XL .36AII (PTG's favorite). For a profile, I'd consider using the Tom Morris hardware for a 2 piece wing, instead of a 2 piece fuselage. Definitely use more engine than an LA .25, especially for high altitude or windy places.

I built one in '67-'68 for an OS .35S. My flying buddies also built them, one with a Fox .35 and other a McCoy .40. I flew the McCoy version, and maybe the Fox version. The McCoy powered model was the best. The original had 1/8" thick tail surfaces, which are very floppy. I built my model with 3/16" or 1/4" stab and elevators, and a torsion bar (R~C style) LG. There is a picture of it in one of the first issues of Model Builder magazine, issue #3, I think. The one issue I would warn about is the recessed engine may not be quite legal for P.40 rules. I was thinking about making small removable panels to make it P.40 legal, and with them installed, Classic legal. It hacks me off that P.40 would not allow a Classic legal profile. Steve

Walter produces an excellent kit, but I believe his version may not be classic legal. In the mid 70's there was a hobby shop in Fort Worth called the Hobby Market. They are no longer in business, but at that time they produced an Excalibur kit. I had this kit, and this one had a wing that was much thicker in airfoil than the original 60's version. I built the original version when it first appeared. I still had my set of plans from the 60's version so it was easy to see the difference. If Walter's version is the one with the thicker wing, then I would expect some questions about being classic legal.

The Hobby Market version also had a thicker stab and elevator. Everything else was pretty much the same, but since there is a difference in airfoil, this may disqualify it from being classic legal.

LAST EDITED ON Apr-01-03 AT 01:25 PM (CDT)
 
I know that Walt was concerned about his kit being Classic legal. He contacted me asking about the one I had built, which was a Hobby Market kit. I seem to recall sending Walt a copy of the Mathis article and plans.

(I just looked at the photo of the one on Walt's web site. The aft fuselage looks slender enough in height to me to be the legal one.)

The one I built (Hobby Market kit) did have the multiple top and bottom spars. I seem to remember the kit having very heavy leading and trailing edge pieces, which I did not use for my model.

The other problem I had with my model was that the fuselage sheet had warped badly, in an unusual way. The TE of the stab cutout was quite a bit out from level, so that the AOA of the stab was negative (very noticeable, AFTER I had finished and flown the model). This induced the very unpleasant flight characteristic of wanting to tighten inside loops, with a reduction of line tension.

After the misalignment was pointed out to me, it stuck out like a sore thumb! I cut the stab off, filled the stab slot, and cut a new (aligned) slot in the fuselage sheet. When fitted with a new stab, the ship suddently flew very well.

I actually flew this ship at VSC, although at the time I did not realize that it was technically illegal for Classic. Tony Drago photographed it, and asked me if he could use the photo on a kit he was considering producing at the time. I don't think he ever actually produced that kit.

I cut out and started a second copy of my Excalibur, which I ended up giving to Doug Carson. He finished and flew it at Toronto, some of the Canadians here probably remember seeing it.

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"A clear conscience is a continual Christmas" - Benjamin Franklin

There indeed are two versions of the Excalibur. I have the plans for both of them. The first version is classic legal has the skinnier, pointier, airfoil, with the high point at about 50% of the chord. It also does not have a sheeted leading edge, instead it uses 1/8" sq balsa spars ahead of the main spar. These seem to work as turbulators, even though they are flush with the ribs. Don't be afraid of using the first version as the wing works very well. it flies better than it should, given our love of thick, blunt airfoils. I've never seen one stall in a turn.

Both versions share almost identical shapes, fuselage, wing, stab-elevator, and rudder. The main difference is the airfoil. The later version, the one kitted at one time. Uses what appears to be a NACA 4 digit airfoil and utilizes a sheeted leading edge. The second version also uses a thicker stab, whereas the first version calls fo 1/8" balsa.

1/8" balsa, of 10+ pound weight could be used, I've always opted for 3/16" 6-8 pound stock. It allows for a more secure elevator horn mounting.

I would highly recommend modern torsion arm gear mounts, a small departure from the original, but worth the effort, as they will aloow gear changes from hard surface to grass gear, and hold up better.

Add a tip weight box, corrected geometry on the flap horn, and adjustable leadouts, and you'll have a very competitive flying plane.

About the skinny aft section. I selected 8-10 pound wood for the fuse. I figured that the stiffer, harder, wood would resist profile twisting without having to resort to fiberglassing the aft section. It seems to be working well for me. I also felt that I could get away with using heavier, stiffer wood in some areas as the parts count for this design is very low. Mine came in at 37 oz's ready to fly. They can be lighter, my buddies came in at 33 oz's. I believe that anywhere up to 42 oz's will be fine for the power it was designed for.

Speaking of power. Overpowering the plane with a larger engine might be counter productive. The larger engines add more weight forward which means adding more weight aft to balance. Believe me, a nice running OS .35S is plenty of power, period. more will not necessarily make it better. I wouldn't worry about removing the .35S from mine and bolting in an OS .20fp or LA. I'm confident that propped right, the smaller engine will have no problem flying the planethrough the pattern. Keep the engine light weight means a lighter airplane without needing to add dead weight aft to balance.

My comment to the question about this design being legal for Profile 40. You've got to be kidding. This plane is a profile, with thicker doublers. The engine is entirely exposed. You can see the exposed mounting lugs that are recessed to the motor mounts. The tank is exposed though also recessed. I would ask that those who would exclude this design, or it's stable mate, the "Coyote" should re-think their position.

The Excalibur is one of the best flying classic profiles ever. But, it's not because of the nose treatment.

I'm wondering why everything is spinning around?

>
>Speaking of power. Overpowering the plane with a larger
>engine might be counter productive. The larger engines add
>more weight forward which means adding more weight aft to
>balance. Believe me, a nice running OS .35S is plenty of
>power, period. more will not necessarily make it better.

I'm wondering if a Brodak .40 might not be a good engine for my Walter Umland Excalibur kit?

Thoughts?

A closer look at Walt's site (and reading) I conclude his kit is the Hobby Warehouse version.. (technically not legal for Classic). He states that he includes a reproduction of the H.W. plans, so I assume that is the version he kitted.

Also the model he shows has carved block wing tips. The original has built up tips (I don't suppose this would make it illegal for Classic in itself, however.)

I don't believe the H.W. kit had carved block wing tips, for whatever that is worth.

Build it. Enjoy it. It's a darn good airplane.

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"Stand still and silently watch the world go by - and it will."

>I'm wondering if a Brodak .40 might not be a good engine for
>my Walter Umland Excalibur kit?
>
>Thoughts?

It's the right weight, and offers great power for its' size, runs in a 4-2-4 on a decent prop. It looks like a winner to me.

I'm wondering why everything is spinning around?

LAST EDITED ON Apr-01-03 AT 07:57 AM (CDT)
 
>Definitely use more engine than an LA .25, especially for
>high altitude or windy places.
>
With zero time using big props on any LA's, I can't make comparisons to using a lot of old 35's swinging big props, but I can say that my several Asian Rim BB 25 Schneurle engines swinging small props very fast are stronger than a majority of the pre-1970 engines used for combat, such as the pre-PDP G21-35's I owned, and any Fox before a Mark III Combat Special. The bushing 25's are somewhat less powerful, and I've done some flying with those as well, but all high rpm stuff.

I believe that with a prop intended to let an FP 25 really rev up, at least to its power peak, one of those out-powers anything from the slower-revving field of old engines smaller than a 45. An LA isn't really the same kind of engine, though. Probably fully equal to any slow-revvers up to a 35. I think it likely that a sub-40 Ounce plane the Excalibur's size would not tax an LA 25 to the extent that it will reach the limit of a Fox 35's power range.

> ... The one issue I would warn about is the recessed engine may not
>be quite legal for P.40 rules. I was thinking about making small
>removable panels to make it P.40 legal, and with them installed,
>Classic legal. It hacks me off that P.40 would not allow a Classic
>legal profile. Steve

My view: the P-40 event's rules should NOT be construed to restrain Exacliburs or Coyotes from competing. If necessary, the rules should have a specific exclusion in regard to the Mathis style profile nose structure and the semi-recess around the engine in the inboard balsa doubler.

.
Kiwi

It never occurred to me that the nose construction might make the Excalibur technically illegal for P40 competition.

I agree with Kiwi, that feature SHOULDN'T. It is clearly a profile ship.

(But I suppose a Fancher Imitation might have a similar problem?)

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""Scattered showers my foot." - Noah

3.2. Doublers or triplers and cheek cowls are allowed including faired spinners, but the fuselage must meet the “profile” definition of 3/4" thickness by the trailing edge of the wing/flap hinge line, and the engine must be fully exposed from lugs to plug.

The above is a copy/paste from our PNW P.40 regs, which are new and to my knowledge, we have never had a contest under these rulz. I expect this line was mostly taken from some other version of P.40 or the AMA definition of profile. The last line bothers me, regarding the Excalibur. I asked Dave Gardner, our esteemed PA ED at the NWCLR, and he didn't see a problem, but I see it a bit iffy, and not because I want to. I want it to be ok per plans, but the lugs aren't fully exposed. Anyway, we are not having P.40 at the NWCLR (I asked).

Regarding the engine size...my model was a bit tailheavy with the OS .35S, Veco NN Spinner and nylon prop. I don't know what the total weight was. The one with the McCoy balanced best and had a better tank/engine run. These were before mufflers, of couse. Having seen Bob fly for a year, I really think he (like me) would prefer plenty of umph on the nose. Steve

Fellas, Thanks for the great input to date. I am under the impression that the OSLA25 being light might require some tail lead and that it may have sufficient ommph to do the job if revved up. I also have an OSLA40 to put on the front end. Given these two choices what is your recommendation?

I have started cutting out parts.

The plans are Hobby market drawn by Dick Mathis 12/31/76 and have a narrow tail, built up wingtips, 1/4 inch thick Horizontal stab and elevators, multiple spars on the leading edge with 1/64th inch rise above ribs, The airfoil does look thick but I was under the impression that this plan set is Classic legal.

Bob Smiley

LAST EDITED ON Apr-02-03 AT 02:19 PM (CDT)
 
>Fellas, Thanks for the great input to date. I am under the
>impression that the OSLA25 being light might require some
>tail lead

No-No! Just right as is.

Both of the Excalibur prototypes were designed around engines in the 6 to 7 ounce range, which is where the LA 25 fits. If there was a 5 Ounce engine powerful enough, you might then need lead in the NOSE.

>and that it may have sufficient ommph to do the job if (when) revved
>up. I also have an OSLA40 to put on the front end.

That's the one heavy enough it probably calls for lead weight in the TAIL.
>

.
Kiwi

>Fellas, Thanks for the great input to date. I am under the
>impression that the OSLA25 being light might require some
>tail lead and that it may have sufficient ommph to do the
>job if revved up. I also have an OSLA40 to put on the front
>end. Given these two choices what is your recommendation?
>
>I have started cutting out parts.
>
>The plans are Hobby market drawn by Dick Mathis 12/31/76 and
>have a narrow tail, built up wingtips, 1/4 inch thick
>Horizontal stab and elevators, multiple spars on the leading
>edge with 1/64th inch rise above ribs, The airfoil does look
>thick but I was under the impression that this plan set is
>Classic legal.
>
>Bob Smiley

Well Bob, you'll enjoy your Excalibur. You'll also be suprized at the low parts count.

As for the 2 engines you mentioned, I would suggest the lightest engine that will develop enough power. I will say that given the choices of only modern engines, I would opt for the Brodak 40 myself, but the La .25 with a 10 X 3 or 4 APC should work fine.

As for the plans you're building from, The date on the plans tell the tale. The cutoff date for Classic is the end of 1969. Now. the later plane is a fine flier, and will serve you well, but you might get hit with a loss of fidelity points at some contests.

Bewst wishes,

I'm wondering why everything is spinning around?

LAST EDITED ON Apr-03-03 AT 01:17 AM (CDT)
 
I got out my Walter Umland kit of the Excalibur and unrolled the plans for the first time. They say Hobby Market, but also shows adjustable leadouts, so the plans have obviously been modified by Walter. Wing shows overlapped center sheeting (all ribs identical, not undercut), and is per the '67 Flying Models plans in all ways, tho I didn't check the thickness of the flaps, stab, elevators, etc. It has multiple LE spars. The completed model and bare framework photos all appear to be the model built by Ed Culver, and it has been somewhat customized. The front section of the wingtips is carved block, and the center sheeting ahead of the spar was extended to the LG location. There is no question that the plans and kit Walter sells is Classic Legal. I believe I have both FM issues, and will dig them out. The Classic legal version also has wing mounted LG, while the later design has fuselage mounted gear (of aluminum, I think). When I built mine in '67/'68, I undercut the center ribs so the sheeting was flush, so would feel ok with doing it again. Steve

I just pulled out my articles on this plane. I did a rereading of both articles and found some answers to a couple of "questions" that were asked about the Excaliber 1. It seems that the prototype was powered with a McCoy .40 and a suggested weight of 30-35 oz. In the article Dick Mathis does state that carved tips would be easier to cover than the built up tips, and to relocate the landing gear 1/2" forward if you fly off of grass.
"As I have it set up on the plans, the "Excaliber"is in full competition dress. It has flaps on the wing, 45 degree control surface movement, a semi-pressurized tank, landing gear in the wing for good ground handling, and a colorful trim scheme using japanese tissue and clear dope only. For sport flying, I think the trim scheme would still be good, because it only takes an hour or so to do, but the flaps can be glued solid on the wing and not change the performance too much. Control movement can be desensitized merely by changing control horn holes, and the landing gear can be mounted on the fuselage conventionally, if you are still having trouble with hard landings and crashes."
"The center planking is not inlayed flush with the wing surface, but on top of it, for extra strength. If care is used to feather its edges no one will notice and it will look fine." The original was completely covered in tissue with tissue trim, etc.
For control movement, 45 degrees each way and a forward cg location. Mr. Mathis then states that when you get used to it, you can move the cg back further- but no more than 1 inch aft.
Dick Mathis had some intertaining ideas when it came to models. The Citabria is on the to do list along with Tear along if I ever refind that article.
Later,
Ron

Ron