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mast location fuselage length and stab pitch

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tahoedirk
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mast location fuselage length and stab pitch

Postby tahoedirk » Wed Jun 14, 2017 6:19 pm

I have been pulling my hair out!

I thought I had the perfect combination. Why did I shorten my fuselage by an inch then?

My new 2 piece foils have moments of silent brilliance but that's it, moments. I made 2 , changed the mast location on both. I changed the pitch on one and they are both better but I'm looking for perfect!

I decided to back up a bit. I just made a long fuselage with unlimited mounting options.for mast and wings.. I should be able to try any combo of wings, pitch and placements. If I nail it I can make another mold for the foil half. I also made a new set of foils with very accurate profiles (for me).

Does any one have any experience messing around with mast location, tenths of degrees or fuse length or mounting wings on both the top and bottom of the fuse?

Dirk
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plummet
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Re: mast location fuselage length and stab pitch

Postby plummet » Wed Jun 14, 2017 8:05 pm

No I don't. But why not make your wings adjustable in the first instance? then when the perfect pitch is discovered for that configuration make a fixed set.
At least make the rear adjustable.

I'm also coming to the conclusion that different styles of riding require a different AOA of the rear wing relative to the front.
I'm still fluffing around with the pitch on my stab. I started off with 2 Deg. But that was way to loose for learning. Cranked it up to 3.2 deg. Which made it stable as hell. Now 8 months on I've backed it off to 2.8 deg to get a compromise between stability and maneuverability.

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mopman365
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Re: mast location fuselage length and stab pitch

Postby mopman365 » Thu Jun 15, 2017 7:37 am

plummet wrote:
Wed Jun 14, 2017 8:05 pm
I'm still fluffing around with the pitch on my stab. I started off with 2 Deg. But that was way to loose for learning. Cranked it up to 3.2 deg. Which made it stable as hell. Now 8 months on I've backed it off to 2.8 deg to get a compromise between stability and maneuverability.
No answers either, just more questions: how do you guys measure relative pitch angles so accurately!?

plummet
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Re: mast location fuselage length and stab pitch

Postby plummet » Thu Jun 15, 2017 10:04 am

phpBB [video]

GrantL
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Re: mast location fuselage length and stab pitch

Postby GrantL » Sat Jun 17, 2017 3:44 am

plummet wrote:
Thu Jun 15, 2017 10:04 am
phpBB [video]
I have some thoughts and experiences with measuring wing angles as in video. Even though this method works I do have issues with repeatibity. I have a set of calipers machine ground at 45deg.even with these it is very difficult to measure left and right side of front wing and obtain the same zero angle. I always get an error of +/-0.2deg If your front wing is not perfect left and right you need to use an average value. Also to consider if the wing has washout along trailing edge.
If you consider the same factors on the stabiliser then your margin of error could be doubled.

To reduce the above errors I use a jig to measure the angle. I have perfect profiles of wing and stabiliser on jig. I can easily set stabiliser angle on foil. It is very easy and accurate to measure angle with a vernier protractor, which will measure to 1min accuracy.
wing protractor.pdf
(20.9 KiB) Downloaded 45 times

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Peter_Frank
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Re: mast location fuselage length and stab pitch

Postby Peter_Frank » Sat Jun 17, 2017 10:26 am

Indeed, not only washout influences, but also AR and particularly if different wing profiles they have different zero lift angles (the negative AOA necessary to have zero lift for cambered wings), which means they should have different angles if you want the board/fuselage at a given angle or horizontal.

But I can not see how it makes sense to "measure" to obtain a given angle precisely ?
As a thumb-rule when building and for the first flights on the water, so you are not way off, yes, but later you will simply trim the stab to find what works for you, right ?

8) PF

tahoedirk
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Re: mast location fuselage length and stab pitch

Postby tahoedirk » Sun Jun 18, 2017 4:48 pm

1497800610595.jpg
20170618_082945.jpg
Cool jig.
Yes the Wixey or phone app is off by some tenths for sure.
Yes these numbers are just guidelines. The true test is on the water , somewhere between 1.5 and 5 degrees for me.
I am trying to nail a non adjustable design for consistency and production. I guess I am going to put a piece of steel with adjustment screws on my mold for the pitch. I think the mold must be too flexible for identical results
With difficulty I lengthened this foil in the picture by 1.5 inches, i can't wait to try it
I hope my new low tech super adjustable fuselage and a few shims will provide some answers and more insight.

plummet
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Re: mast location fuselage length and stab pitch

Postby plummet » Sun Jun 18, 2017 10:05 pm

Why not make the tail adjustable and then go about adjusting pitch until you find then perfect angle? Then make the fixed wing fuse?


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