Go Back  RCU Forums > RC Boats > RC Airboats
Reload this Page >

New Builder/First Air Boat

Notices
RC Airboats Discuss R/C Airboats here!

New Builder/First Air Boat

Old 03-13-2017, 06:03 PM
  #101  
NEW222
 
Join Date: Sep 2004
Location: OAKBANK, MB, CANADA
Posts: 361
Likes: 0
Received 1 Like on 1 Post
Default

Looks very good. I unfortunately did not fiberglass mine. Just a good sealing inside the hull, and a few good coats on the outside. I do not know how much of a difference in strength overall between glassing and non-glassing.
Old 03-14-2017, 12:15 AM
  #102  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Fiberglass helps keep the hull from flexing too much. It's well worth the hassle. I typically only glass seams and joints inside the hull (small scraps) and the bottom. I use resin only on the top - no cloth. It saves weight a bit and doesn't (hasn't so far anyway) sacrificed strength. Only do one layer of cloth. Just build up a couple 2-3 coats of resin on top of the cloth. 3 coats if you're thinning your resin (similar viscosity to polyurethane finish) or 2 coats if using a finishing resin straight up. On the bottom after final curing and ready for final assembly - sand the bottom with 240-400 grit sandpaper. It should help speed the boat up overall.

Last edited by 1QwkSport2.5r; 03-14-2017 at 12:18 AM.
Old 03-14-2017, 01:07 AM
  #103  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Thats helpful to know. the main reason we ended glassing the top was to strengthen the joints, some of which were not perfect.

My next effort is the engine mount. Earlier it was suggested to make this movable to allow for CG adjustment. Would anyone have photos of how yours was built so i dont have to reinvent the wheel?
Old 03-14-2017, 05:04 AM
  #104  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Originally Posted by trapper7
Thats helpful to know. the main reason we ended glassing the top was to strengthen the joints, some of which were not perfect.

My next effort is the engine mount. Earlier it was suggested to make this movable to allow for CG adjustment. Would anyone have photos of how yours was built so i dont have to reinvent the wheel?

Look here: http://www.rcuniverse.com/forum/rc-a...0-90-size.html Post #8 you can see how I slotted the engine mount. Just an idea that works for me.
Old 03-14-2017, 06:20 AM
  #105  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Had a quick look. Seems like a simple solution. Do you want the engine level with the deck ( ie thrust pulling straight or pulling nose down at all?).
Old 03-14-2017, 06:28 AM
  #106  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Originally Posted by trapper7
Had a quick look. Seems like a simple solution. Do you want the engine level with the deck ( ie thrust pulling straight or pulling nose down at all?).

I always set my thrust line (prop) to be parallel to the waters surface on plane - which most often is parallel to the keel/bottom for a flat bottom boat. I always play with the CG to get the boat to run true before messing with the pitch of the engine. A good starting point is having the bow hang at about a 20 degree angle lower than the transom when you hold the boat up by the tips of the prop.
Old 03-15-2017, 11:24 AM
  #107  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

How much clearance do you give for the prop; prop tip to deck?
Old 03-15-2017, 03:09 PM
  #108  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Originally Posted by trapper7
How much clearance do you give for the prop; prop tip to deck?

I give it 1/8" minimum. Probably not more than 1/2" so the CG doesnt get too high.
Old 03-15-2017, 04:59 PM
  #109  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks, thats about what we have. Bolted on the mount tonight...
Attached Thumbnails Click image for larger version

Name:	6.2.jpg
Views:	185
Size:	1.06 MB
ID:	2205475   Click image for larger version

Name:	6.3.jpg
Views:	161
Size:	1.05 MB
ID:	2205476  
Old 03-16-2017, 03:10 AM
  #110  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Looks good. A couple cautions - if the aluminum angle you're using is 1/16" thick, it will crack. Also, with how far the engine is "hanging off" the engine mount, you may encounter lots of vibration and as such foamy fuel and a hard needle valve to hold onto. Ideally you want the engine to not overhang the edge of the pylons much if possible.
Old 03-16-2017, 10:42 AM
  #111  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for the feedback-the aluminum appears to be 1/16" so I guess we will consider what to do there. For pylon/engine position it would be easy to slide the engine mount further back. With engine and boat we are at 5 lbs.
Old 03-16-2017, 11:55 AM
  #112  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Originally Posted by trapper7
Thanks for the feedback-the aluminum appears to be 1/16" so I guess we will consider what to do there. For pylon/engine position it would be easy to slide the engine mount further back. With engine and boat we are at 5 lbs.

Yeah, I would step the aluminum up to 1/8" which will add some weight, but I assure you it's worth it. My little .35 on my SI3 mini cracked the 1/16" aluminum within 6-7 tanks of fuel. If your prop is out of balance, it could happen sooner. I suggest being better safe than sorry.

5lbs is great. Hopefully it doesn't get too much heavier once fully rigged. A .40 will be good for reasonable performance up to about 6.5lbs. Above that, you might need to step it up to a .60.
Old 03-18-2017, 12:36 PM
  #113  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

So, we redid the angle with 1/8th. Nothing like doing something twice! Would you have any input on servo configurations? i was thinking to have them towards the front of the servo compartment as i fugured the cables need to flex due to the servo arm radial movement.
Old 03-19-2017, 01:50 AM
  #114  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

this is roughly how i am thinking to position the servo, the 2nd would be to the left of this one.
Attached Thumbnails Click image for larger version

Name:	6.4.jpg
Views:	153
Size:	1.14 MB
ID:	2206077  
Old 03-19-2017, 03:26 AM
  #115  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

You have the right idea. Just give yourself enough room in case you need a longer servo arm for a longer throw.
Attached Thumbnails Click image for larger version

Name:	IMG_6423.JPG
Views:	31
Size:	1.40 MB
ID:	2206080  
Old 03-19-2017, 03:19 PM
  #116  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Well, it turns out the boat weight is less than i calculated! So we may have a better shot at good performance. Worked for three solid hours today!
Old 03-22-2017, 04:33 PM
  #117  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

progress!
Attached Thumbnails Click image for larger version

Name:	6.5.jpg
Views:	137
Size:	1.12 MB
ID:	2206615  
Old 03-24-2017, 05:38 AM
  #118  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Oh dear...our last batch of epoxy is not drying well at all. its been a day and a half and still tacky! Any advice welcome. (guess poor mix ratio or not mixed long enough)
Old 03-24-2017, 06:50 AM
  #119  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

Originally Posted by trapper7
Oh dear...our last batch of epoxy is not drying well at all. its been a day and a half and still tacky! Any advice welcome. (guess poor mix ratio or not mixed long enough)

You could try hitting it with a hair dryer or heat gun, but you will probably need to take a wetted rag (with methanol or acetone) and remove as much of the tacky epoxy as you can. Epoxy will not cure if you don't use enough hardener or mix it well enough. If it was mixed well and in the proper ratio, it may just be not warm enough. Generally, you want epoxy to cure at 70F or warmer. Try heating it good and see if that gets it to set up better.

By the way the boat looks good. Your air rudders may be too big, but it won't hurt to try it as it is.
Old 03-24-2017, 10:19 AM
  #120  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks, i picked up some acetone (heat made no difference. I read somewhere that rudders can be too small so i figured to shoot big and we can make smaller ones if needed (easily lifted off the pins)!

The boat has been quite a project! Never anticipated it to be so much work, but in a way its all custom so not surprising. If we make another that one will be a lot easier from what we learned on this one.
Old 03-24-2017, 11:15 AM
  #121  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Though we are not ready yet, I am wondering what paint is good for the boat? (My son is VERY keen to paint it!)
Attached Thumbnails Click image for larger version

Name:	6.6.jpg
Views:	146
Size:	266.4 KB
ID:	2206805  
Old 03-24-2017, 11:52 AM
  #122  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

I believe automotive paints will adhere to epoxy provided its abraded well and cleaned extremely well. I don't paint my models, so I cannot say for sure.
Old 03-25-2017, 09:27 PM
  #123  
NEW222
 
Join Date: Sep 2004
Location: OAKBANK, MB, CANADA
Posts: 361
Likes: 0
Received 1 Like on 1 Post
Default

Looking better and better. A couple of things from a newbie here. I built mine as per the plans and I do indeed need to increase the size of my rudders and was thinking of similar to what you have, as my turning was not the best in my opinion. Also, as per the suggestion, automotive paints will stick to epoxy, just make sure to 'rough' it up, but that goes for any surfaces to be painted with automotive paint. This also applies to most paints. By roughing up the surface, you will give the paint something to 'bite' into. Paint will also stick to non sanded and or shiny surfaces, but the adhesion will not be anywhere as good. Also, heed the advice of a good cleaning before paint.
Old 03-26-2017, 02:38 AM
  #124  
trapper7
Senior Member
Thread Starter
 
Join Date: Feb 2017
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks. I noticed a few builds that had trouble with small rudders so we went big, and these should be easy to make smaller if need be as they just unhook. Years ago i build a speed boat and the local boat builder said rustoleum would be fine so thats what we used and it seemed fine. But I see many differing opinions out there on what to use on models. I do know a local auto body shop and perhaps he would be willing to airbrush primer and top coat.

amazing the amount of hours in this build!
Old 03-26-2017, 11:51 AM
  #125  
1QwkSport2.5r
 
1QwkSport2.5r's Avatar
 
Join Date: Oct 2006
Location: Cottage Grove, MN
Posts: 10,409
Received 76 Likes on 69 Posts
Default

The only problem you could run into is whether the paint is chemically compatible with epoxy. Generally speaking, 2-component finishes are compatible with other 2-component paints. 2-component means the material uses a catalyst/crosslinker/hardener. There are limits to this however - polyester resin is 2-component, but will not adhere to epoxy and vice versa. I know for a fact that commercial 2-component waterborne polyurethane will stick to epoxy as does oil based polyurethane.. but epoxy won't stick to polyurethane. Some automotive paints are urethane based and others are lacquer based. I think it fair to say that a urethane paint will be a "slam dunk" whereas lacquer may not. You would need to do some test spots to determine adhesion before painting the whole thing. At minimum, use scotchbrite to break the sheen of the epoxy to aid adhesion. Better yet, use some 220-320 grit abrasive (sandpaper) to break the sheen. A quality finish/paint should adhere provided the substrate is adequately abraded. I may be making a mountain from a mole hill, but I'd hate for someone to have their paint peel.

As for the rudders - I haven't found a huge benefit from the height of the rudders as much as depth. Meaning a rudder that is wider (protrudes farther off the back of the boat) will provide more positive control than a narrower but taller rudder. If you read my thread about my SI3 flat bottom boat, you will see the "evolution" of my rudders on that boat starting with the rudders the plans outlined and the two revisions I made to improve steering control and response. Post #43 http://www.rcuniverse.com/forum/rc-a...-bottom-2.html

You don't expressly need to have your rudders' height match the height of the propwash. 1/2-2/3 of the propwash is totally good provided the width of the rudder is adequate. Do test your initial rudders first though - if it doesn't respond quickly or turn sharply, you will need to adjust the throw and/or the size of the rudders.

Besides building a strong hull, your rudders need to perform A-1 perfect. It's a real PITA if your boat don't turn for crap and she gets stuck in the weeds requiring going for a swim or canoe ride to recover it. I learned the hard way a time or two.

Last edited by 1QwkSport2.5r; 03-26-2017 at 12:01 PM.

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.