Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
July 13, 2020, 09:33:31 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 2 3 4 [5]   Go Down
Print
Author Topic: Another Gowen LPP  (Read 10919 times)
0 Members and 1 Guest are viewing this topic.
AC01010
Bronze Member
***

Kudos: 0
Offline Offline

United States United States

Posts: 14



Ignore
« Reply #100 on: July 16, 2019, 05:03:45 PM »

The rest of the photos.

Interesting. I will definitely take a look at this. Thank you!
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #101 on: June 23, 2020, 05:26:04 PM »

An Update in the ABQ team:

As most know, three of my kids won Nationals at SO last June, and all three went on to build F1D's. All three made the US team, but worlds is on hold due to Pandemic. Hopefully next March (2021) we get to fly.

Meanwhile, I need to keep building for the future! I had 9 parents, siblings, and other SO team members build P18's form Laser Cut planes, and they had a great time with them. Now we are building 9 new Gowen Carbon Pennies on my kitchen table! Two are prior team members (F1D experienced), three are Dad's of the F1D team, and 4 are younger siblings that will be moving on to F1D for the 2022 cycle.

So far the Gowen plane has proven straightforward to build. Two are complete, and several are close. Both completed planes came in up to 100 mg under weight, using Sig balsa, so not bad.

Only change we did compared to prior builds is we greatly thinned 3M77 with TCE, and brushed it on, rather than spraying. We found this to be substantially lighter on the F1D's, so incorporated it here.

In addition, the MS is 285 high instead of 250. The original batch we made at 250, using 6.1# wood, and they came out substantially lighter than Bill's numbers, and I judged them too flexible. Instead of going to heavier wood, we went a little taller, and the MS's performed great. The MS assembly with boom is still a slight bit lighter than Bill's plan, but it works well.

Once we open up and get a flying site, I'll get a group photo of the entire build! I think we are at 14 LPP's now, about 10 F1D's, and 9 P18's, as well as a handful of Scraps.

Chuck
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #102 on: June 24, 2020, 10:06:18 AM »

Thanks for the update chuck. I would love to see a photo of the finjshed models. I had problems in guaranteeing a good glue joint from the leading and trailing edges to the tip fences. What are your experiences of this?
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #103 on: June 24, 2020, 10:18:38 AM »

I think I noted earlier, we wrap these joints with 2 turns of thread and a drop of ca, after initial drop of ca. After this we trim the carbon right up to the thread.

Chuck
Logged
Olbill
Titanium Member
*******

Kudos: 69
Offline Offline

United States United States

Posts: 2,581



Ignore
« Reply #104 on: June 25, 2020, 12:31:10 AM »

Several years ago I started building the wings with the outermost rib set a little bit in from the end of the spars. Then I put the tip plates inside the spars. That gives a pretty strong joint.
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #105 on: June 25, 2020, 06:27:12 PM »

Thanks gents. I inset the tip rib and bound and applied fresh cyano. My joints were a little hit and miss. I think caused by the parts not properly touching.
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #106 on: June 25, 2020, 06:51:13 PM »

We inset as Bill describes, and also wrap with thread. Perhaps because newbies building, but it makes a very strong joint.

Chuck
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #107 on: June 25, 2020, 07:50:14 PM »

Hi Chuck. Any details of the propellers you guys use will also be appreciated.
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #108 on: June 25, 2020, 08:03:16 PM »

We are using a bass spar, 1/16 square, 6 inches long, set on diagonal. We sand it to about 0.045" thick excerpt about 1/8"around the hub. The two sides are sanded parallel to the blade, so 90 degrees from each other.

Blades are scaled up slightly from Ikara flaring prop, and are 100% flaring (no trailing edge). Blades are 6# 1/32 wood, c grain, sanded to 0.025, the formed on Don S's LPP form 3-d printed. I believe they are 20" pitch, 6% camber, set to 45 degrees at 4 inches radius.

First two planes in this build came in about 100 mg under weight.

Chuck
Logged
Olbill
Titanium Member
*******

Kudos: 69
Offline Offline

United States United States

Posts: 2,581



Ignore
« Reply #109 on: June 26, 2020, 05:24:46 PM »

The worst problem I've had over the years is the tip ribs breaking. When that happens the camber increases at the tips and screws up the airfoil. The best fix I've found is to put in another rib against the broken one. All the schemes I've tried to prevent the breakage have been pretty unsuccessful.
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #110 on: July 06, 2020, 09:31:54 AM »

This post is an aid to myself to note down how some of my many variations of propellers worked. I made too many to test and lost track of them over time. I periodically end up measuring their pitch because i have lost track.

I had a session in late in 2019 where I was getting consistent times and so I performed a comparison of propellers with differing number of carbon rods on the hub. Their pitch were changed relative to the baseline 4 Rod and 22" pitch; to compensate for the increase in flair when rods were eliminated. I aimed to use the same launch torque for each prop.

I used a single partial motor without resting between flights under a approximately 25' ceiling.
1.93g/m 5.5" Loopx 0.535g with 0.986g spacer (stint)

The following flights were made before the motor broke:

#16, 2 Rod, 17.5" pitch
Wind to.680 turns, 56g.cm, back off 40 turns & launch at 26.5g.cm
Climb to 22' in 2m0s
? Landing turns
3m34s, ?RPM

#16B, 3 Rod 20" pitch
Wind to 710 turns 54g.cm, back off 63 turns & launch 25.0g.cm
Climb to 15' in 1m30s
180 Landing Turns
3m0s, 216 RPM

#12, 4 Rod, 22" pitch
Wind to 720 Turns 56g.cm, back off 43 turns & launch 26.3g.cm
Climb to 18' in 2m0s
140 Landing Turns
3m32s, 192 RPM

I judged that the 4 rod and 2 rod props were of very similar performance and that I had backed off the pitch appropriately on the 2 rod prop to match the 4 rod performance. When using the same motor they exhibited similar maximum height and time to climb and were within 1% duration.

The 3 Rod propeller was launched at a 6% lower torque, didn't climb as high, peaked earlier and landed with 16% less duration. This may be more due to the lower launch torque than due to differences in the prop, but the RPM was higher. Perhaps I should increase the pitch half and inch or an inch to reduce it somewhat and hopefully increase duration. This was the propeller that I used in the velodrome competition which gave disapointing performance. I hadn't tested it properly before the competition.

Bearing in mind that i don't have a statistically significant number of flights to confidently compare. But, I was supprised that the 2 and 4 rod props gave such time to climb, max heights and duration. It realy does not seem to make much difference whether a 4 rod, 22" pitch prop or a 2 rod 17.5" pitch prop is used (when using the same motor of certain characterisitics).
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #111 on: July 06, 2020, 10:13:12 AM »

Piecost

Thank you for posting your data. Definitely interesting.

You mention that perhaps the 3 rod prop needs a different static pitch. It is then also possible the other two matched out of coincidence, and adjusting static pitch there will find an optimum where one is better than the other

Many variables!

Chuck
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #112 on: July 06, 2020, 11:46:54 AM »

Yes, you are probably right. It does seem that lots of different propellers have a similar performance. I tried Bills blade shape and my own and didn't see a massive difference. But, I may not have followed his design very well in reproducing the twist and camber.

The thing that is bothering me is the lack of consistancy in duration between flights. This model is the only one of the few classes that I fly with such a problem.

 I wondered if different launch speeds caused the propeller to flair different amounts each time. So, i started releasing the model with zero forward speed to guarantee consistancy. I have noticed an improvement yet.

I also wondered if bunches were causing a reduction in effective turns on some flights. This is more likely. I have started noting down how bunchy the motor is after winding. I believe that the LPP uses the longest motor relative to motor stick length of my models. If this is the case then I may be able to releive the problem emplying a shorter, fatter motor. I presume it should be combined with a higher pitched prop. More props!

It has been so long that i have flown that i have kind of forgotton what i did and can look back on it with some detachment.

Logged
Olbill
Titanium Member
*******

Kudos: 69
Offline Offline

United States United States

Posts: 2,581



Ignore
« Reply #113 on: July 06, 2020, 12:10:14 PM »

I assume you are using sleeves on both ends of your LPP motors. If not that would be a good place to start.

Even with sleeves you will have bunching problems. There will always be wasted turns at the rear but the real killer is getting a big CG shift late in the flight. Since my front hookup eliminates snags at the front I usually try to move as many of the knots to the front as possible before launch.
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #114 on: July 06, 2020, 02:45:16 PM »

Hill Bill,

I bought some heatshrink and put it in my flight box but never tried it. I should give it a go. Hopefully it will work with reverse S hooks on the prop

I started to move away from long heavy motors. Perhaps this will help getting the most from them.

Thanks
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #115 on: July 06, 2020, 03:23:03 PM »

Piecost:

My kids have had consistent and good flights with 1.5g rubber. When we pushed it to 20" lengths, at 2-2.5g, the results were not as consistent, with or without sleeves (we use reverse S hooks).

With 1.5g loops (to be consistent with F1M), their flights are highly repeatable.

BUT, we are not in Bill's territory yet.

We are running about 6 minutes in a Cat 1 site (26' at center, less at edges), and I also got around 6.5 minutes at Colo Springs in March. At our local Cat 1 site, most of the kids reached right at 6 minutes virtually every flight. Brett also was putting up times around 6-6:10, so I think we are doing OK. Our site is over 1 mile high. Our flights at this facility have all been with 1.5g of rubber, typically in the 37-42 cm loop length, depending on pitch and prop design. And, yes, with quite a variety of prop pitches, stiffnesses and RPM's, we are quite consistent in our max times.

It is that next increment, from doing "well" to doing "Bill", that is a stretch!

Chuck

But they sure have fun trying to beat each other
Logged
Olbill
Titanium Member
*******

Kudos: 69
Offline Offline

United States United States

Posts: 2,581



Ignore
« Reply #116 on: July 06, 2020, 04:01:01 PM »

For LPP and A6 I use an oval hook so that the front sleeve can go over the o-ring and the hook. In the rear the sleeve goes against the rear hook with the knot in front of the sleeve to hold it in place. These days I'm using a fairly large diameter plastic straw in the rear b/c it's lighter than heat shrink tubing and it doesn't trap the turns as bad as the heat shrink tubing that's in the picture.

My motors nearly always range from 20" to 22" in length and from 2.3 to 2.8g (5/99 or 3/02) for any ceiling height.



Attached files Thumbnail(s):
Re: Another Gowen LPP
Re: Another Gowen LPP
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #117 on: July 06, 2020, 07:47:14 PM »

Thanks for the detailed.photos Bill. I will have to give it a go and see if i can get the maximum potential out of longer and heavier motors. I am supprised that the plastic straw does not damage the rubber.

I think that my winding technique could do with refinement to minimise bunching. I stretch to about 5x resting length.to about half torque before comming in. But i always seem in a rush in competions rather than winding carefully.

 It has been so long since inhave flown indoors I may not remember what to do.
Logged
ceandra
Silver Member
****

Kudos: 11
Offline Offline

United States United States

Posts: 240



Ignore
« Reply #118 on: July 08, 2020, 01:00:53 AM »

Just finished a build session with Monet's family. She built another carbon penny too. Hers came in 310mg under weight¡ This is using the same wood that she built her original 1.5 years ago, right at weight. Shows how much she had learned about managing glue weight, since glue has to be the only difference. She had also weighed and recorded every piece and every step, per her f1d practice.

Hoping we can get a flying session in early August. Should have 12 carbon penny flyers with 14 planes!

Chuck
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #119 on: July 08, 2020, 05:36:51 AM »

Good job!
Logged
piecost
Gold Member
*****

Kudos: 9
Offline Offline

United Kingdom United Kingdom

Posts: 488

Topic starter


Ignore
« Reply #120 on: July 08, 2020, 05:55:59 AM »

I make a point of finishing the motor stick last so that i employ any weight saved on other parts in extra meat on the stick. I also ballast propellers, if nessesary, to match a target weight. This ensures that they are interchangable and will not affect the trim if swapping propellers.
Logged
Pages: 1 2 3 4 [5]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!