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Old Oct 17, 2014, 11:11 AM
Registered User
Joined Oct 2014
7 Posts
Hi Matt,

First of all congratulations for all your hard work. It's been quite lovely to follow this thread.
I do come a little late to the party, but I am entering the boat modeling hobby just now, so I had a couple questions (probably more will come, if you don't mind) on your Who-Doggy.

You say you coated your foam. But I am not sure with what. At one point you mention PVA glue and water, but I think you also put some resin, is that right? What kind and how many coats?

Second question.. how strong did the hull become? I am planning to make a sailboat.. would such a hull keep a drop keel with ballast or would that be too much?

Thanks again for your work!
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Old Oct 17, 2014, 08:15 PM
Resistance is futile
circuitfxr's Avatar
United States, FL, Wildwood
Joined Jul 2005
1,118 Posts
Welcome to RC boats! Thanks for your kind words. To answer your question about sealing the foam board... I used clear polyurethane spray paint after sealing the edges with thinned white glue. Please note that you cannot use the spray poly on the foam directly. I used it on the paper covering of the foam board.

I considered making a sailboat with this method at one time also. The issues that caused me to change my mind are these:

1. The weight and side forces involved with the keel will most likely be too strong for the strength of the foam board. The only solution I can think of is to coat the inside AND the outside of the foam board with a minimum of 3 coats of epoxy to add the required strength. Additional support around the keel mounting area can be achieved by epoxying some wood to the area surrounding the mount.

2. A similar situation will occur with the main mast for the mainsail. During a full billow from strong wind, a significant amount of side force will be applied to the mast. This force will be transferred to the deck where the mast is mounted. The foam board will need to be greatly reinforced to handle this leveraged force.
A suggestion that may work for the mast would be to allow the mast to completely penetrate the hull and become seated on a flange mounted to the top of the keel.
Another consideration is the rigging. Most sailboats have rigging lines that attach to the mast and are then attached to the deck to help hold the mast straight under heavy load times. The connection points on the deck will need to be securely attached and have some reinforcing also. A modified version of the rigging ring I used on the cabin top of the Who Doggy may be the way to go. That rigging eye is actually pushed through the foam board and glued into place. It is not just glue on top.

3. I have started using a "folding technique" with the foam board material that will give a more watertight and solid structure for the hull construction. You can see this method in my new thread here in Dock Talk. The title of the new build thread is "EDF powered foam board Hydro-Cat". The construction method I used for the Hydro's sponsons is VERY similar to a sailboat hull design. please check it out as it may give you some good ideas.
Please feel free to contact me with any further questions. circuitfxr@yahoo.com
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Old Oct 17, 2014, 10:55 PM
Po' boys does w/ Po'boys ways
United States, NC, Charlotte
Joined Feb 2011
590 Posts
Welcome Tony!

Hey Matt ,I hope you don't mind my butting in here!,.. Yes,Tony foam is more cost effectitive/flexable/unsinkable/and simular build qualities, aspects as balsa,..however you do need to consider the use and "modifify" as nessesary here. SEE my elc. drive boat build of a 'V' hull,which is ongoing, to see the probs n soulutions I've had with this ,my First build ever!..http://www.rcgroups.com/forums/showthread.php?t=2013981 As a heads up in what to expect or look out for in you project.By ALL MEANS, I am not disscourrageing you from trying it, we all learn here from one another!!Try it ,..IF it FAILS misserabley you can always repurpose the gear in another build and have learned a few things on the way as I am doing!!,....Good luck n WELCOME to the famliy!!....HEE-HE-hee-he-hee!!!!,.....Tim...
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Old Oct 20, 2014, 06:33 AM
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Joined Oct 2014
7 Posts
Thank you both for the kind welcome!
Unfortunately for the next month or so I'll be quite busy between work and family so updates will be far and in between, but I'll do my best.

I was afraid foam may not be able to withstand all those forces.
Since I would have to do several coating passes anyway, maybe I would be better off fiberglass coating the deck and the hull?

I'll keep reading a bit.

Thanks for the advices so far!
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