Author Topic: Profile building techniques? (Read 7382 times)

Matt Brown · « **on:** December 28, 2023, 03:58:15 PM »

I’m planning to build a profile fuse to use with an extra SV11 arf wing and tail. Just curious if there are any newer techniques beyond just a slab of balsa. I’ve built a lot of RC profiles with balsa sticks and sheeted as well as just the sticks with a 1/2” fiberglass tube full length of the fuselage. That method not useable as tube can’t pass through the wing without a lot of headaches. It will be built for electric power and using a similar front end design as the Brodak profile electric conversion kits. I just have to make my own since Brodak doesn’t offer a kit for .60 size profiles.

Thanks, Matt

Dan Berry · « **Reply #1 on:** December 28, 2023, 04:34:52 PM »

Get one of Don Hutchinson's profile warbird plans and emulate his structure.

Matt Brown · « **Reply #2 on:** December 28, 2023, 05:01:52 PM »

I think I have his whole collection. I’ll have a look!

Matt

Ken Culbertson · « **Reply #3 on:** December 28, 2023, 08:42:01 PM »

This one is both light and strong. I took advantage of the maximum width of 3/4". I used 5lb 1/8" for the sides and 1/2" for the framing. Today I would use 7-8lb 1/16 for the sides. Motor mount was from Tom Morris, now Okie Air. 1/16" ply to the wing highpoint. Thick soft 1/2" cheek doublers again to the wing high point. Lots of room to carve out homes for the various electric components.

Ken

Motorman · « **Reply #4 on:** December 28, 2023, 08:49:18 PM »

Is it going to be a big wide profile of a modern stunt ship or just a low profile stick going back?

If it's the big one then 1/2" sq. balsa top and bottom with 3/16 x 1/2 balsa sticks in a Warren truss pattern with 1/16" balsa on both sides.

If it's a small stick then just sand into an oval cross section.

In either case take some Dave brown CF laminate and cut it in half length wise for some 5/16 wide strips. Glue it to both sides of the fuselage in a big X patteren. You want the CF to cross at the mid point between wing and stab and on center height wise if possible.

This solves both problems of bending and twisting. This will give you the lightest strongest profile fuselage of your dreams and be ugly as hell. Enjoy.

MM

Dennis Toth · « **Reply #5 on:** December 29, 2023, 06:41:34 AM »

Matt,
The truss system that Ken showed is very strong. If you can use 1/64" plywood in place of the 1/16" balsa sides, it weights just about the same but makes the fuse very rigid. Tom Morris used this type of construction on the profiles he did and it is great.

Best, DennisT

Ken Culbertson · « **Reply #6 on:** December 29, 2023, 07:05:20 AM »

Quote from: Dennis Toth on December 29, 2023, 06:41:34 AM

Matt,
The truss system that Ken showed is very strong. If you can use 1/64" plywood in place of the 1/16" balsa sides, it weights just about the same but makes the fuse very rigid. Tom Morris used this type of construction on the profiles he did and it is great.

Best, DennisT

if you use the 1/64" plywood make sure your credit score is good. You seen the prices lately! Still the best option.

Ken

Lauri Malila · « **Reply #7 on:** December 29, 2023, 08:49:23 AM »

Would it be better to order it straight from the factory..?
a sheet of 1. quality 23,40 Euro's. L

Dave_Trible · « **Reply #8 on:** December 29, 2023, 02:05:12 PM »

Really large profiles are especially rough in one respect. I have three here now that all have a major problem. Larger engines create much more vibration and foam the fuel no matter what you do. We have used everything from ST .51s to Merco, K&B and Enya 60s with no real success. Either from takeoff or at best, when the tank gets about half full the rascals all take off into wild screams and screw you into the ground. I'm of the opinion there is just too much mass moving around in that large engine for a profile. We've also fiberglassed the fuselages with little improvements. I will not put upholstery polish in my fuel.....We have tried a dozen different props and rpms as well. The planes fly very well-if I could get the engine issues resolved. I'm to believe that something using an LA .46 is just about the practical size limit to get acceptable engine runs. This also something that is going to run normally in a scream so if the fuel foamed you might not tell the difference anyway. An engine that cycles up and down may actually make it worse. In the future we will max out profiles for .35-40s

Dave

Matt Brown · « **Reply #9 on:** December 29, 2023, 02:09:08 PM »

Quote from: Dave_Trible on December 29, 2023, 02:05:12 PM

Really large profiles are especially rough in one respect. I have three here now that all have a major problem. Larger engines create much more vibration and foam the fuel no matter what you do. We have used everything from ST .51s to Merco, K&B and Enya 60s with no real success. Either from takeoff or at best, when the tank gets about half full the rascals all take off into wild screams and screw you into the ground. I'm of the opinion there is just too much mass moving around in that large engine for a profile. We've also fiberglassed the fuselages with little improvements. I will not put upholstery polish in my fuel.....We have tried a dozen different props and rpms as well. The planes fly very well-if I could get the engine issues resolved. I'm to believe that something using an LA .46 is just about the practical size limit to get acceptable engine runs. This also something that is going to run normally in a scream so if the fuel foamed you might not tell the difference anyway. An engine that cycles up and down may actually make it worse. In the future we will max out profiles for .35-40s

Dave

These problems all go away with electric power which is my plan for this. I may find new problems with electric power but I don’t think anything major.

Matt

Dave_Trible · « **Reply #10 on:** December 29, 2023, 02:47:59 PM »

Yes that should solve that.

Dave

Fred Underwood · « **Reply #11 on:** December 29, 2023, 09:06:10 PM »

As you originally suggested, a front with a box similar to Brodak conversion kits works well. The aft portion seems plenty stiff for full size if you sheet with 1/64 ply on the sides. Be ware, most "1/64" is now metric and a few thousands over 1/64 with a corresponting weight increase. 1/64 is about 0.0156 and most of my new 1/64 is 0.019 -0.020 which is significantly more weight percentage wise. I use a center truss fuse similar to what Ken showed above, behind the wing. Use about 7/16 then the 1/64 x 2 will leave just enough room for finish and not exceed 3/4". The box can be large wnough to house the timer, esc, and battery and then front or rear mount motor. The nose needs to be long enough to help the CG balance from the plywood.

This was about 685 squares and 66 oz with aver 3000 flights.
https://stunthanger.com/smf/gettin-all-amp'ed-up!/old-dog-new-trics-old-plane-new-rogerio-fiorotti-timer/

This about 720 squares and 68 oz and unstimely early demise.
https://stunthanger.com/smf/gettin-all-amp'ed-up!/another-dog-another-'tric-fiorotti-v4-4-timer-with-accelerometer/

and below about 666 squares and 63 oz and over 1000 flights.

Author Topic: Profile building techniques? (Read 7382 times)

Matt Brown

Profile building techniques?

Dan Berry

Re: Profile building techniques?

Matt Brown

Re: Profile building techniques?

Ken Culbertson

Re: Profile building techniques?

Motorman

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Dennis Toth

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Ken Culbertson

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Lauri Malila

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Dave_Trible

Re: Profile building techniques?

Matt Brown

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Dave_Trible

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Fred Underwood

Re: Profile building techniques?