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Thorp Speed Tips From Tom Hunter
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Author:  leewwalton [ Fri Nov 08, 2013 10:45 am ]
Post subject:  Thorp Speed Tips From Tom Hunter
I'm posting this on behalf of Tom Hunter ...

From: Tom Hunter
Where: Somewhere in Thailand
Subject: Thorp postings re: ways to go faster in a Thorp.

I notice that a number of Thorp owners are questioning ways to go faster In a Thorp.

The following is a review of the various steps I made in that pursuit.

1. Complete new wet wing using the Lyle Trusty wing as a model. Lyle lent me his master rib profile and I used it to make the tooling necessary to make a new wing. This entailed making all new ribs since the entire profile is different than the front and rear ribs in either the original Thorp wing or the modified Sunderland wing. By making the center inner D section wet, the total fuel load was increased to 52 gal.

a. The skins were modified so that they covered the aileron and flap "gaps" on the bottom surface of the wing. It was with a certain trepidation that I did that to the flaps since it would seem that the Fowler functionality would be diminished if you add these gap seals. I was very pleased to discover that the flaps were still extremely effective.

b. The main spar to skin joint was " adjusted" so that there is no disruption in air flow. You can check to see if your wing has a "bump" span wise at the main spar to skin joint. This is common with the Thorp structure if the builder did not take steps to eliminate it in construction. The reason for removing this bump is to reduce the drag of the wing.

c. Wing tips that "blend" into the modified airfoil.

d. The entire top of the wing and the bottom to the spar filled and blended so that there is no distortion when the wing is "at rest". Due to the light structure of the Thorp wing, one wonders when flying and noticing the continual deformation of the outboard panels how worth while the time and labor of rivet filling is in a practical sense.

e. Roll trim tab within aileron. The straightness of any wing can be intuitively verified by the amount of roll trim needed to maintain a wings level attitude at cruise speed. However, if you are still relying on the adjustable left flap for roll trim, you are tossing away some cruise speed due to extra drag with a flap partially deployed. Note, in my "new" wing, the flap was reflexed in relationship to its T.E. position on the standard or Sunderland wing.

f. Custom wrap around wing to fuselage fairing. This was added after the plane was flown. No measurable increase in cruise could be noted. It is possible that in some unusual attitudes that fairing could have positive benefits other than cosmetic.

That is about the sum of the changes to the wing.

2. Fuselage:

The side skins were changed to .032. Care was taken to achieve a smooth intersection between the windscreen and the canopy. I was fortunate to enlist the talent of a former Lockheed experimental shop worker who had worked on the P-80 (T-33) canopy fit and made the assembly line changes to solve in field issues. It took approx. 3 months of work to complete the fit of the canopy.

Fit of windshield. It is probably true that the best fit of windscreen is putting the glass UNDER the upturned lip on the forward skin. However, for ease of removal this was not done. It was deemed that quick removal of the windscreen would be of benefit in maintenance of instrument panel.

The fuselage rivets were filled back to the pilot station. A few words on body filler and the Thorp. I used only the best quality auto body filler. While several people informed me that it would crack and break off,
(especially on the wing) no such thing occurred. Of course if you do not follow good practices in application your results may vary.

The leaf spring and tail wheel were changed to a Trusty designed rod spring. The Aviation Products 6 inch tail wheel was faired in a split tail wheel pant with the general profile of the pressure recovery RV style main wheel pants. A number of these small pants are flying on T-18's and RV's.

The main wheel pants on the T-18 were originally from Rudy Adler. I worked on them to eliminate any surface waviness. The brake fairings were old parts as well. Eventually I made new female molds for slightly larger brake fairings so I could house Cleveland 500X 5 Heavy duty wheels and brakes. These fairings are made in a two part mold and are formed with no seam. The builder adds the split so that the fairings can be fit very tightly to your pants (if your pants are the original profile). Since the plane was tested both without and with the wheel pants and brake fairings comparable speeds could be determined. These fairings were originally molded with Carbon Fiber, but that was changed since Carbon Fiber is so difficult to cut and fit.


Since I was never pleased with my internal induction system to the IO-320, I designed a new system to take advantage of Ram Air as well as create a direct induction path to the Servo with a High Capacity Filter. The result of that effort can be seen flying on Jonathan Levi's T-18 as well as several T-18's in Australia and an RV-7 in San Diego. I happily noted an increase in inches of mercury and less "stumbling" of the engine on approaches.




Summary:

Reducing drag on the T-18 can give you long term rewards. It can allow you to cruise the same speed at less horsepower thus allowing your motor to work less and effectively extend its life span. Also, lowering drag can allow you to cruise climb at a higher speed. It will also allow your decent to land to be at a lower throttle setting and higher speed.

I still supply fiberglass parts for the following applications:

!. Tail wheel pant for the Aviation Products 6 inch tail wheel.

2. Brake Fairings manufactured in fiberglass.

3. Air scoop for an injected 0-290. 320 or 360 Lycoming.

4. Drop tanks to extend your range with an additional 10 gals of fuel. See Vimeo video: http://vimeo.com/2985919

I can be reached at thunter007007@yahoo.com or 805-769-2047 my Skype number.
Author:  Ryan Allen [ Fri Nov 08, 2013 3:34 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
I had been flying without my brake fairings, wing cuffs and pretty good sized openings around my exhaust pipes. I was seeing about 149kts IAS and about 4000 msl at about 2500rpm and 21-22"MP.

I finally got around to I reinstalling my brake caliper cuffs, wing/fuselage cuffs and tightened up the open areas around the exhaust pipes where they exit the bottom cowl. And for good measure I tried to align the gear and wheel fairings. I was at just under red line when I was downwind, so I backed off the throttle. I got out a little ways and was seeing 161kts IAS at about 4000msl, 2500rpm and 21"MP. I think the fairings/exhaust work gave me the extra 11 knots. I was glad to see it. I backed off to about 2450rpm (not much change in MP that I recall now that I'm typing this) and was seeing about 157kts IAS.

The plane was flying at about 1455 pounds when I got these numbers and OAT was about 54 degrees F. I am happy with these numbers. Should I be going faster or is this about average for a fixed pitch 0-360?
Author:  jrevens [ Fri Nov 08, 2013 9:25 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
What was your TAS, Ryan? Indicated airspeeds will usually vary a surprising amount among homebuilts such as Thorps, with all kinds of different pitot/static assemblies & systems mounted in many different locations.
Author:  Rich Brazell [ Fri Nov 08, 2013 11:04 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
John is right . TAS ? Break out the EA-6B . I have found that I average around 20 mph over IAS to = TAS . Based upon my 40 year old high tech EA-6B ! ??? My main goal in flying is how fast I fly over the ground ! ;) My fastest GS was 698 kts ! BOOM ! OH MY ! ;) No not in the Thorp .



RB O:-)

Faster and Higher
Author:  fytrplt [ Sat Nov 09, 2013 6:30 am ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Mach 2.0 here briefly in a Phantom II. My 180 HP T-18C averages 165 KTAS on trips, however I have seen 214 MPH IAS flat out at 1000' MSL. I do not have a bunch of speed mods.
Author:  James Grahn [ Sat Nov 09, 2013 10:49 am ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
I never got the Phantom that fast, but I did take an Eagle to 736 KCAS at 100 ft!
So Rich, is your EA6B related to an E-6B?
My Thorp is quite slo. Can't tell you TAS since I don't have Temp read out. But the fastest I've seen is 166KCAS in level flight. We can't get below about 2500ft here in Vegas
Cubes
Author:  Ryan Allen [ Sat Nov 09, 2013 1:20 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
I can't say that I specifically recall what my TAS was reading, but I believe it was about 167-169 knots. I will certainly look at that more closely the next time and report back. By the way, my gain was 12 knots (161-149), not 11 knots like I said earlier......I don't want to short myself any speed....

It may take me 30 minutes to figure out how to work my E6B again Rich. I gonna break it out though and see what I get.
Author:  Ryan Allen [ Mon Nov 11, 2013 1:57 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Hey John, I flew again today and I am showing 168 knots TAS. I think I'm OK with that. I have to say I am please with my plane now that I have the new engine and got it all faired up.
Author:  SHIPCHIEF [ Mon Nov 11, 2013 4:11 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
'Feisty' has 125 Big Bad O-290 HP, and tops out about 150 Kts @ 4000 MSL. It' slower down lower.
Maybe it's faster up higher?
It has a Ted Hendrickson 68x68 prop, and turns about 2650 RPM. I go most everywhere at full throttle, what the heck?
Over-all, I think it performs well. It does not have brake fairings, the back of the canopy is kind of high, like the builder was trying to get all the head room possible, and that works for me. I fly off a grass strip, grass and gravel find their way into the wheel fairings as it is. I worry that brake fairings could lead to jamming the brakes. I already had a gentle ground loop from a bound brake, so I give up a little speed for some presumed safety.
Author:  Rich Brazell [ Mon Nov 11, 2013 5:40 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Cubes: You caught me ! E-6B . Been a few days since I had it out to do a few math problems ! ??? I still have my slide rule from AOCS boot camp and could never work that either ! :o The only thing that saved me was the $60.00 HP hand held calculator my Mom bought me to take to boot camp . A hand held calculator that solved math problems was big News back in 1976 ! 8)

RB O:-)
Author:  dan [ Mon Nov 11, 2013 9:55 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
E6b? Couldn't use it, had to have an electronic one, haven't seen it in 5 yrs. Dan
Author:  Rich Brazell [ Mon Nov 11, 2013 10:15 pm ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Time, speed, distance . Must be getting close to the next T-18 fly in ? ??? Speaking of...I still plan to fly up to KMHV this Saturday for the "Plane Crazy" fly in . WX permitting . Runs 0900-1300 . For the folks in the valley I think it is less than an hour ? For us SOCAL SAN dudes about 1 hour . Still putting together the "Fun and Cheap" SOCAL fly in events list . Stay patient .

RB O:-)

Higher and faster
Author:  James Grahn [ Tue Nov 12, 2013 1:27 am ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Just trying to make sure you were not jamming the computer! I will not be at the flyin this weekend as I will be in PTV.
Cubes
Author:  dan [ Tue Nov 12, 2013 9:18 am ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
Ira and myself are planning on attending also Rich,weather permitting. Cubs are you heading that way from PTV or are you stopping at KMHV on the way in...........Lou, you up for this one?? Tony?? Dan
Author:  James Grahn [ Tue Nov 12, 2013 10:34 am ]
Post subject:  Re: Thorp Speed Tips From Tom Hunter
I am not going at all, Dan. I'm going to work on the Thunderbucket!
Cubes
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